Quantum Field Theory & Gravity
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begin? What is its large scale structure and evolution? How can gravity be unified with quantum mechanics and the Standard Model? Quantum Field Theory, Gravity & Cosmology There...
Quantum Field Theory & Gravity
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quantum Field Theory & Gravity Quantum Field Theory & Gravity Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email Bruce Carlsten (505) 667-5657 Email Quantum Field Theory and Gravity at Los Alamos The HEP effort at Los Alamos in this area is actively pursing a number of questions in this area. What is the final state of complete gravitational collapse? What happens at the event horizon? What is dark energy? How did the
Renormalized linear kinetic theory as derived from quantum field...
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Renormalized linear kinetic theory as derived from quantum field theory: A novel ... Citation Details In-Document Search Title: Renormalized linear kinetic theory as derived ...
Quantum simulation of quantum field theory using continuous variables
Marshall, Kevin; Pooser, Raphael C.; Siopsis, George; Weedbrook, Christian
2015-12-14
Much progress has been made in the field of quantum computing using continuous variables over the last couple of years. This includes the generation of extremely large entangled cluster states (10,000 modes, in fact) as well as a fault tolerant architecture. This has lead to the point that continuous-variable quantum computing can indeed be thought of as a viable alternative for universal quantum computing. With that in mind, we present a new algorithm for continuous-variable quantum computers which gives an exponential speedup over the best known classical methods. Specifically, this relates to efficiently calculating the scattering amplitudes in scalar bosonic quantum field theory, a problem that is known to be hard using a classical computer. Thus, we give an experimental implementation based on cluster states that is feasible with today's technology.
Quantum simulation of quantum field theory using continuous variables
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Marshall, Kevin; Pooser, Raphael C.; Siopsis, George; Weedbrook, Christian
2015-12-14
Much progress has been made in the field of quantum computing using continuous variables over the last couple of years. This includes the generation of extremely large entangled cluster states (10,000 modes, in fact) as well as a fault tolerant architecture. This has lead to the point that continuous-variable quantum computing can indeed be thought of as a viable alternative for universal quantum computing. With that in mind, we present a new algorithm for continuous-variable quantum computers which gives an exponential speedup over the best known classical methods. Specifically, this relates to efficiently calculating the scattering amplitudes in scalar bosonicmore » quantum field theory, a problem that is known to be hard using a classical computer. Thus, we give an experimental implementation based on cluster states that is feasible with today's technology.« less
Renormalized linear kinetic theory as derived from quantum field theory: A
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novel diagrammatic method for computing transport coefficients (Journal Article) | SciTech Connect Renormalized linear kinetic theory as derived from quantum field theory: A novel diagrammatic method for computing transport coefficients Citation Details In-Document Search Title: Renormalized linear kinetic theory as derived from quantum field theory: A novel diagrammatic method for computing transport coefficients We propose a novel diagrammatic method for computing transport coefficients in
Multi-time wave functions for quantum field theory
Petrat, Sren; Tumulka, Roderich
2014-06-15
Multi-time wave functions such as ?(t{sub 1},x{sub 1},,t{sub N},x{sub N}) have one time variable t{sub j} for each particle. This type of wave function arises as a relativistic generalization of the wave function ?(t,x{sub 1},,x{sub N}) of non-relativistic quantum mechanics. We show here how a quantum field theory can be formulated in terms of multi-time wave functions. We mainly consider a particular quantum field theory that features particle creation and annihilation. Starting from the particleposition representation of state vectors in Fock space, we introduce multi-time wave functions with a variable number of time variables, set up multi-time evolution equations, and show that they are consistent. Moreover, we discuss the relation of the multi-time wave function to two other representations, the TomonagaSchwinger representation and the Heisenberg picture in terms of operator-valued fields on spacetime. In a certain sense and under natural assumptions, we find that all three representations are equivalent; yet, we point out that the multi-time formulation has several technical and conceptual advantages. -- Highlights: Multi-time wave functions are manifestly Lorentz-covariant objects. We develop consistent multi-time equations with interaction for quantum field theory. We discuss in detail a particular model with particle creation and annihilation. We show how multi-time wave functions are related to the TomonagaSchwinger approach. We show that they have a simple representation in terms of operator valued fields.
Matter-enhanced transition probabilities in quantum field theory
Ishikawa, Kenzo Tobita, Yutaka
2014-05-15
The relativistic quantum field theory is the unique theory that combines the relativity and quantum theory and is invariant under the Poincar transformation. The ground state, vacuum, is singlet and one particle states are transformed as elements of irreducible representation of the group. The covariant one particles are momentum eigenstates expressed by plane waves and extended in space. Although the S-matrix defined with initial and final states of these states hold the symmetries and are applied to isolated states, out-going states for the amplitude of the event that they are detected at a finite-time interval T in experiments are expressed by microscopic states that they interact with, and are surrounded by matters in detectors and are not plane waves. These matter-induced effects modify the probabilities observed in realistic situations. The transition amplitudes and probabilities of the events are studied with the S-matrix, S[T], that satisfies the boundary condition at T. Using S[T], the finite-size corrections of the form of 1/T are found. The corrections to Fermis golden rule become larger than the original values in some situations for light particles. They break Lorentz invariance even in high energy region of short de Broglie wave lengths. -- Highlights: S-matrix S[T] for the finite-time interval in relativistic field theory. S[T] satisfies the boundary condition and gives correction of 1/T . The large corrections for light particles breaks Lorentz invariance. The corrections have implications to neutrino experiments.
Ordinary versus PT-symmetric Φ³ quantum field theory
Bender, Carl M.; Branchina, Vincenzo; Messina, Emanuele
2012-04-02
A quantum-mechanical theory is PT-symmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PT-symmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observed in laboratory experiments. This paper focuses on the properties of a PT-symmetric igΦ³ quantum field theory. This quantum field theory is the analog of the PT-symmetric quantum-mechanical theory described by the Hamiltonian H=p²+ix³, whose eigenvalues have been rigorously shown to be all real. This paper compares the renormalization group properties of a conventional Hermitian gΦ³ quantum field theory with those of the PT-symmetric igΦ³ quantum field theory. It is shown that while the conventional gΦ³ theory in d=6 dimensions is asymptotically free, the igΦ³ theory is like a gΦ⁴ theory in d=4 dimensions; it is energetically stable, perturbatively renormalizable, and trivial.
Ordinary versus PT-symmetric Φ³ quantum field theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Bender, Carl M.; Branchina, Vincenzo; Messina, Emanuele
2012-04-02
A quantum-mechanical theory is PT-symmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PT-symmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observed in laboratory experiments. This paper focuses on the properties of a PT-symmetric igΦ³ quantum field theory. This quantum fieldmore » theory is the analog of the PT-symmetric quantum-mechanical theory described by the Hamiltonian H=p²+ix³, whose eigenvalues have been rigorously shown to be all real. This paper compares the renormalization group properties of a conventional Hermitian gΦ³ quantum field theory with those of the PT-symmetric igΦ³ quantum field theory. It is shown that while the conventional gΦ³ theory in d=6 dimensions is asymptotically free, the igΦ³ theory is like a gΦ⁴ theory in d=4 dimensions; it is energetically stable, perturbatively renormalizable, and trivial.« less
Gerber, U.; Wiese, U.-J.; Hofmann, C. P.; Kaempfer, F.
2010-02-01
We consider a microscopic model for a doped quantum ferromagnet as a test case for the systematic low-energy effective field theory for magnons and holes, which is constructed in complete analogy to the case of quantum antiferromagnets. In contrast to antiferromagnets, for which the effective field theory approach can be tested only numerically, in the ferromagnetic case, both the microscopic and the effective theory can be solved analytically. In this way, the low-energy parameters of the effective theory are determined exactly by matching to the underlying microscopic model. The low-energy behavior at half-filling as well as in the single- and two-hole sectors is described exactly by the systematic low-energy effective field theory. In particular, for weakly bound two-hole states the effective field theory even works beyond perturbation theory. This lends strong support to the quantitative success of the systematic low-energy effective field theory method not only in the ferromagnetic but also in the physically most interesting antiferromagnetic case.
Time-reversal symmetry breaking and the field theory of quantum chaos
Simons, B.D. [Cavendish Laboratory, Madingley Road, Cambridge, CB3 0HE (United Kingdom)] [Cavendish Laboratory, Madingley Road, Cambridge, CB3 0HE (United Kingdom); Agam, O. [NEC Research Institute, 4 Independence Way, Princeton, New Jersey 08540 (United States)] [NEC Research Institute, 4 Independence Way, Princeton, New Jersey 08540 (United States); Andreev, A.V. [Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)] [Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)
1997-04-01
Recent studies have shown that the quantum statistical properties of systems which are chaotic in their classical limit can be expressed in terms of an effective field theory. Within this description, spectral properties are determined by low energy relaxation modes of the classical evolution operator. It is in the interaction of these modes that quantum interference effects are encoded. In this paper we review this general approach and discuss how the theory is modified to account for time-reversal symmetry breaking. To keep our discussion general, we will also briefly describe how the theory is modified by the presence of an additional discrete symmetry such as inversion. Throughout, parallels are drawn between quantum chaotic systems and the properties of weakly disordered conductors. {copyright} {ital 1997 American Institute of Physics.}
Ab-Initio Hamiltonian Approach to Light Nuclei And to Quantum Field Theory
Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Shirokov, A.M.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Ng, E.G.; Yang, C.; Sosonkina, M.; /Ames Lab
2012-06-22
Nuclear structure physics is on the threshold of confronting several long-standing problems such as the origin of shell structure from basic nucleon-nucleon and three-nucleon interactions. At the same time those interactions are being developed with increasing contact to QCD, the underlying theory of the strong interactions, using effective field theory. The motivation is clear - QCD offers the promise of great predictive power spanning phenomena on multiple scales from quarks and gluons to nuclear structure. However, new tools that involve non-perturbative methods are required to build bridges from one scale to the next. We present an overview of recent theoretical and computational progress with a Hamiltonian approach to build these bridges and provide illustrative results for the nuclear structure of light nuclei and quantum field theory.
One-loop calculations in quantum field theory: from Feynman diagrams to unitarity cuts
Ellis, R. Keith; Kunszt, Zoltan; Melnikov, Kirill; Zanderighi, Giulia
2012-09-01
The success of the experimental program at the Tevatron re-inforced the idea that precision physics at hadron colliders is desirable and, indeed, possible. The Tevatron data strongly suggests that one-loop computations in QCD describe hard scattering well. Extrapolating this observation to the LHC, we conclude that knowledge of many short-distance processes at next-to-leading order may be required to describe the physics of hard scattering. While the field of one-loop computations is quite mature, parton multiplicities in hard LHC events are so high that traditional computational techniques become inefficient. Recently new approaches based on unitarity have been developed for calculating one-loop scattering amplitudes in quantum field theory. These methods are especially suitable for the description of multi-particle processes in QCD and are amenable to numerical implementations. We present a systematic pedagogical description of both conceptual and technical aspects of the new methods.
Kelly, Aaron; Markland, Thomas E.; Brackbill, Nora
2015-03-07
In this article, we show how Ehrenfest mean field theory can be made both a more accurate and efficient method to treat nonadiabatic quantum dynamics by combining it with the generalized quantum master equation framework. The resulting mean field generalized quantum master equation (MF-GQME) approach is a non-perturbative and non-Markovian theory to treat open quantum systems without any restrictions on the form of the Hamiltonian that it can be applied to. By studying relaxation dynamics in a wide range of dynamical regimes, typical of charge and energy transfer, we show that MF-GQME provides a much higher accuracy than a direct application of mean field theory. In addition, these increases in accuracy are accompanied by computational speed-ups of between one and two orders of magnitude that become larger as the system becomes more nonadiabatic. This combination of quantum-classical theory and master equation techniques thus makes it possible to obtain the accuracy of much more computationally expensive approaches at a cost lower than even mean field dynamics, providing the ability to treat the quantum dynamics of atomistic condensed phase systems for long times.
Twisted conformal symmetry in noncommutative two-dimensional quantum field theory
Lizzi, Fedele; Vitale, Patrizia; Vaidya, Sachindeo
2006-06-15
By twisting the commutation relations between creation and annihilation operators, we show that quantum conformal invariance can be implemented in the 2-d Moyal plane. This is an explicit realization of an infinite dimensional symmetry as a quantum algebra.
Quantum field theory in the presence of a medium: Green's function expansions
Kheirandish, Fardin; Salimi, Shahriar
2011-12-15
Starting from a Lagrangian and using functional-integration techniques, series expansions of Green's function of a real scalar field and electromagnetic field, in the presence of a medium, are obtained. The parameter of expansion in these series is the susceptibility function of the medium. Relativistic and nonrelativistic Langevin-type equations are derived. Series expansions for Lifshitz energy in finite temperature and for an arbitrary matter distribution are derived. Covariant formulations for both scalar and electromagnetic fields are introduced. Two illustrative examples are given.
Vukmirovic, Nenad; Wang, Lin-Wang
2009-11-10
This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.
An effective field theory for collinear and soft gluons: Heavy...
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An effective field theory for collinear and soft gluons: Heavy to light decays Citation ... Subject: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM ...
Driven Morse oscillator: Classical chaos, quantum theory, and photodissociation
Goggin, M.E.; Milonni, P.W.
1988-02-01
We compare the classical and quantum theories of a Morse oscillator driven by a sinusoidal field, focusing attention on multiple-photon excitation and dissociation. In both the classical and quantum theories the threshold field strength for dissociation may be estimated fairly accurately on the basis of classical resonance overlap, and the classical and quantum results for the threshold are in good agreement except near higher-order classical resonances and quantum multiphoton resonances. We discuss the possibility of ''quantum chaos'' in such driven molecular systems and use the Morse oscillator to test the manifestations of classical resonance overlap suggested semiclassically.
Prequantum Classical Statistical Field Theory: Fundamentals
Khrennikov, Andrei
2011-03-28
We present fundamentals of a prequantum model with hidden variables of the classical field type. In some sense this is the comeback of classical wave mechanics. Our approach also can be considered as incorporation of quantum mechanics into classical signal theory. All quantum averages (including correlations of entangled systems) can be represented as classical signal averages and correlations.
Pastore, S.; Wiringa, Robert B.; Pieper, Steven C.; Schiavilla, Rocco
2014-08-01
We report quantum Monte Carlo calculations of electromagnetic transitions in $^8$Be. The realistic Argonne $v_{18}$ two-nucleon and Illinois-7 three-nucleon potentials are used to generate the ground state and nine excited states, with energies that are in excellent agreement with experiment. A dozen $M1$ and eight $E2$ transition matrix elements between these states are then evaluated. The $E2$ matrix elements are computed only in impulse approximation, with those transitions from broad resonant states requiring special treatment. The $M1$ matrix elements include two-body meson-exchange currents derived from chiral effective field theory, which typically contribute 20--30\\% of the total expectation value. Many of the transitions are between isospin-mixed states; the calculations are performed for isospin-pure states and then combined with the empirical mixing coefficients to compare to experiment. In general, we find that transitions between states that have the same dominant spatial symmetry are in decent agreement with experiment, but those transitions between different spatial symmetries are often significantly underpredicted.
Vector field theories in cosmology
Tartaglia, A.; Radicella, N.
2007-10-15
Recently proposed theories based on the cosmic presence of a vectorial field are compared and contrasted. In particular the so-called Einstein aether theory is discussed in parallel with a recent proposal of a strained space-time theory (cosmic defect theory). We show that the latter fits reasonably well the cosmic observed data with only one, or at most two, adjustable parameters, while other vector theories use much more. The Newtonian limits are also compared. Finally we show that the cosmic defect theory may be considered as a special case of the aether theories, corresponding to a more compact and consistent paradigm.
Effective Field Theory of Fractional Quantized Hall Nematics (Journal
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Article) | SciTech Connect Effective Field Theory of Fractional Quantized Hall Nematics Citation Details In-Document Search Title: Effective Field Theory of Fractional Quantized Hall Nematics We present a Landau-Ginzburg theory for a fractional quantized Hall nematic state and the transition to it from an isotropic fractional quantum Hall state. This justifies Lifshitz-Chern-Simons theory - which is shown to be its dual - on a more microscopic basis and enables us to compute a ground state
Double field theory inspired cosmology
Wu, Houwen; Yang, Haitang E-mail: hyanga@scu.edu.cn
2014-07-01
Double field theory proposes a generalized spacetime action possessing manifest T-duality on the level of component fields. We calculate the cosmological solutions of double field theory with vanishing Kalb-Ramond field. It turns out that double field theory provides a more consistent way to construct cosmological solutions than the standard string cosmology. We construct solutions for vanishing and non-vanishing symmetry preserving dilaton potentials. The solutions assemble the pre- and post-big bang evolutions in one single line element. Our results show a smooth evolution from an anisotropic early stage to an isotropic phase without any special initial conditions in contrast to previous models. In addition, we demonstrate that the contraction of the dual space automatically leads to both an inflation phase and a decelerated expansion of the ordinary space during different evolution stages.
Quantum fields in toroidal topology
Khanna, F.C.; Malbouisson, A.P.C.; Santana, A.E.
2011-10-15
The standard representation of c*-algebra is used to describe fields in compactified space-time dimensions characterized by topologies of the type {Gamma}{sub D}{sup d}=(S{sup 1}){sup d}xM{sup D-d}. The modular operator is generalized to introduce representations of isometry groups. The Poincare symmetry is analyzed and then we construct the modular representation by using linear transformations in the field modes, similar to the Bogoliubov transformation. This provides a mechanism for compactification of the Minkowski space-time, which follows as a generalization of the Fourier integral representation of the propagator at finite temperature. An important result is that the 2x2 representation of the real-time formalism is not needed. The end result on calculating observables is described as a condensate in the ground state. We initially analyze the free Klein-Gordon and Dirac fields, and then formulate non-abelian gauge theories in {Gamma}{sub D}{sup d}. Using the S-matrix, the decay of particles is calculated in order to show the effect of the compactification. - Highlights: > C*-algebra is used to describe fields in compactified space-time dimensions. > The space-time is characterized by toroidal topologies. > Representations of the Poincare group are studied by using the modular operator. > We derive non-abelian gauge theories in compactified regions of space-time. > We show the compactification effect in the decay of particles using the S-matrix.
Finite field-dependent symmetries in perturbative quantum gravity
Upadhyay, Sudhaker
2014-01-15
In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear CurciFerrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using BatalinVilkovisky (BV) formulation. -- Highlights: The perturbative quantum gravity is treated as gauge theory. BRST and anti-BRST transformations are developed in linear and non-linear gauges. BRST transformation is generalized by making it finite and field dependent. Connection between linear and non-linear gauges is established. Using BV formulation the results are established at quantum level also.
From Entropic Dynamics to Quantum Theory
Caticha, Ariel
2009-12-08
Non-relativistic quantum theory is derived from information codified into an appropriate statistical model. The basic assumption is that there is an irreducible uncertainty in the location of particles so that the configuration space is a statistical manifold. The dynamics then follows from a principle of inference, the method of Maximum Entropy. The concept of time is introduced as a convenient way to keep track of change. The resulting theory resembles both Nelson's stochastic mechanics and general relativity. The statistical manifold is a dynamical entity: its geometry determines the evolution of the probability distribution which, in its turn, reacts back and determines the evolution of the geometry. There is a new quantum version of the equivalence principle: 'osmotic' mass equals inertial mass. Mass and the phase of the wave function are explained as features of purely statistical origin.
Quantum emitters dynamically coupled to a quantum field
Acevedo, O. L.; Quiroga, L.; Rodrguez, F. J.; Johnson, N. F.
2013-12-04
We study theoretically the dynamical response of a set of solid-state quantum emitters arbitrarily coupled to a single-mode microcavity system. Ramping the matter-field coupling strength in round trips, we quantify the hysteresis or irreversible quantum dynamics. The matter-field system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity. Here we extend this model to address non-equilibrium situations. Analyzing the systems quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We also explore signatures of the crossing of the critical points on the radiation subsystem by monitoring its Wigner function; then, the subsystem can exhibit the emergence of non-classicality and complexity.
Nonlocal microscopic theory of quantum friction between parallel metallic slabs
Despoja, Vito
2011-05-15
We present a new derivation of the friction force between two metallic slabs moving with constant relative parallel velocity, based on T=0 quantum-field theory formalism. By including a fully nonlocal description of dynamically screened electron fluctuations in the slab, and avoiding the usual matching-condition procedure, we generalize previous expressions for the friction force, to which our results reduce in the local limit. Analyzing the friction force calculated in the two local models and in the nonlocal theory, we show that for physically relevant velocities local theories using the plasmon and Drude models of dielectric response are inappropriate to describe friction, which is due to excitation of low-energy electron-hole pairs, which are properly included in nonlocal theory. We also show that inclusion of dissipation in the nonlocal electronic response has negligible influence on friction.
Vortex operators in gauge field theories
Polchinski, J.
1980-07-01
Several related aspects of the 't Hooft vortex operator are studied. The current picture of the vacuum of quantum chromodynamics, the idea of dual field theories, and the idea of the vortex operator are reviewed first. The Abelian vortex operator written in terms of elementary fields and the calculation of its Green's functions are considered. A two-dimensional solvable model of a Dirac string is presented. The expression of the Green's functions more neatly in terms of Wu and Yang's geometrical idea of sections is addressed. The renormalization of the Green's functions of two kinds of Abelian looplike operators, the Wilson loop and the vortex operator, is studied; for both operators only an overall multiplicative renormalization is needed. In the case of the vortex this involves a surprising cancellation. Next, the dependence of the Green's functions of the Wilson and 't Hooft operators on the nature of the vacuum is discussed. The cluster properties of the Green's functions are emphasized. It is seen that the vortex operator in a massive Abelian theory always has surface-like clustering. The form of Green's functions in terms of Feynman graphs is the same in Higgs and symmetric phases; the difference appears in the sum over all tadpole trees. Finally, systems having fields in the fundamental representation are considered. When these fields enter only weakly into the dynamics, a vortex-like operator is anticipated. Any such operator can no longer be local looplike, but must have commutators at long range. A U(1) lattice gauge theory with two matter fields, one singly charged (fundamental) and one doubly charged (adjoint), is examined. When the fundamental field is weakly coupled, the expected phase transitions are found. When it is strongly coupled, the operator still appears to be a good order parameter, a discontinuous change in its behavior leads to a new phase transition. 18 figures.
Maxwell-Garnett effective medium theory: Quantum nonlocal effects
Moradi, Afshin
2015-04-15
We develop the Maxwell-Garnett theory for the effective medium approximation of composite materials with metallic nanoparticles by taking into account the quantum spatial dispersion effects in dielectric response of nanoparticles. We derive a quantum nonlocal generalization of the standard Maxwell-Garnett formula, by means the linearized quantum hydrodynamic theory in conjunction with the Poisson equation as well as the appropriate additional quantum boundary conditions.
Two-dimensional lattice gauge theories with superconducting quantum circuits
Marcos, D.; Widmer, P.; Rico, E.; Hafezi, M.; Rabl, P.; Wiese, U.-J.; Zoller, P.
2014-12-15
A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability.
Quantum theory and Einstein's general relativity
v. Borzeszkowski, H.; Treder, H.
1982-11-01
We dicusss the meaning and prove the accordance of general relativity, wave mechanics, and the quantization of Einstein's gravitation equations themselves. Firstly, we have the problem of the influence of gravitational fields on the de Broglie waves, which influence is in accordance with Einstein's weak principle of equivalence and the limitation of measurements given by Heisenberg's uncertainty relations. Secondly, the quantization of the gravitational fields is a ''quantization of geometry.'' However, classical and quantum gravitation have the same physical meaning according to limitations of measurements given by Einstein's strong principle of equivalence and the Heisenberg uncertainties for the mechanics of test bodies.
Travel Funding for Quantum Theory and Symmetries 6
Das, Sumit R.; Shapere, Alfred D.
2009-07-01
This is the proceedings volume of the 6th International Symposium on Quantum Theory and Symmetries (QTS6), held in Lexington KY, 20-25 July 2009.
The effective field theory of dark energy
Gubitosi, Giulia; Vernizzi, Filippo; Piazza, Federico E-mail: fpiazza@apc.univ-paris7.fr
2013-02-01
We propose a universal description of dark energy and modified gravity that includes all single-field models. By extending a formalism previously applied to inflation, we consider the metric universally coupled to matter fields and we write in terms of it the most general unitary gauge action consistent with the residual unbroken symmetries of spatial diffeomorphisms. Our action is particularly suited for cosmological perturbation theory: the background evolution depends on only three operators. All other operators start at least at quadratic order in the perturbations and their effects can be studied independently and systematically. In particular, we focus on the properties of a few operators which appear in non-minimally coupled scalar-tensor gravity and galileon theories. In this context, we study the mixing between gravity and the scalar degree of freedom. We assess the quantum and classical stability, derive the speed of sound of fluctuations and the renormalization of the Newton constant. The scalar can always be de-mixed from gravity at quadratic order in the perturbations, but not necessarily through a conformal rescaling of the metric. We show how to express covariant field-operators in our formalism and give several explicit examples of dark energy and modified gravity models in our language. Finally, we discuss the relation with the covariant EFT methods recently appeared in the literature.
Twisting all the way: From classical mechanics to quantum fields
Aschieri, Paolo
2008-01-15
We discuss the effects that a noncommutative geometry induced by a Drinfeld twist has on physical theories. We systematically deform all products and symmetries of the theory. We discuss noncommutative classical mechanics, in particular its deformed Poisson bracket and hence time evolution and symmetries. The twisting is then extended to classical fields, and then to the main interest of this work: quantum fields. This leads to a geometric formulation of quantization on noncommutative space-time, i.e., we establish a noncommutative correspondence principle from *-Poisson brackets to * commutators. In particular commutation relations among creation and annihilation operators are deduced.
Resonant Perturbation Theory of Decoherence and Relaxation of Quantum Bits
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Merkli, M.; Berman, G. P.; Sigal, I. M.
2010-01-01
We describe our recenmore » t results on the resonant perturbation theory of decoherence and relaxation for quantum systems with many qubits. The approach represents a rigorous analysis of the phenomenon of decoherence and relaxation for general N -level systems coupled to reservoirs of bosonic fields. We derive a representation of the reduced dynamics valid for all times t ≥ 0 and for small but fixed interaction strength. Our approach does not involve master equation approximations and applies to a wide variety of systems which are not explicitly solvable.« less
Optimal quantum control in nanostructures: Theory and application to a
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generic three-level system (Journal Article) | SciTech Connect Optimal quantum control in nanostructures: Theory and application to a generic three-level system Citation Details In-Document Search Title: Optimal quantum control in nanostructures: Theory and application to a generic three-level system Coherent carrier control in quantum nanostructures is studied within the framework of optimal control. We develop a general solution scheme for the optimization of an external control (e.g.,
Quantum cryptography for security challenges to be topic of Frontiers...
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has authored more than 150 scientific papers on quantum field theory, the foundations of quantum mechanics, quantum cryptography and quantum computation. He has held distinguished...
MIT-CTP/4229 Effective Field Theory
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Field Theory of Fractional Quantized Hall Nematics Michael Mulligan, 1 Chetan Nayak, 2 and Shamit Kachru 3 1 Center for Theoretical Physics, MIT, Cambridge, MA 02139, USA 2...
Integrable perturbations of conformal field theories and Yetter-Drinfeld modules
Bücher, David; Runkel, Ingo
2014-11-15
In this paper we relate a problem in representation theory — the study of Yetter-Drinfeld modules over certain braided Hopf algebras — to a problem in two-dimensional quantum field theory, namely, the identification of integrable perturbations of a conformal field theory. A prescription that parallels Lusztig's construction allows one to read off the quantum group governing the integrable symmetry. As an example, we illustrate how the quantum group for the loop algebra of sl(2) appears in the integrable structure of the perturbed uncompactified and compactified free boson.
Microscopic theory of quantum anomalous Hall effect in graphene (Journal
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Article) | SciTech Connect Microscopic theory of quantum anomalous Hall effect in graphene Citation Details In-Document Search Title: Microscopic theory of quantum anomalous Hall effect in graphene Authors: Qiao, Zhenhua ; Jiang, Hua ; Li, Xiao ; Yao, Yugui ; Niu, Qian Publication Date: 2012-03-27 OSTI Identifier: 1098600 Type: Publisher's Accepted Manuscript Journal Name: Physical Review B Additional Journal Information: Journal Volume: 85; Journal Issue: 11; Journal ID: ISSN 1098-0121
Statistical theory of Coulomb blockade oscillations: Quantum chaos in quantum dots
Jalabert, R.A.; Stone, A.D.; Alhassid, Y. (Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06511 (United States))
1992-06-08
We develop a statistical theory of the amplitude of Coulomb blockade oscillations in semiconductor quantum dots based on the hypothesis that chaotic dynamics in the dot potential leads to behavior described by random-matrix theory. Breaking time-reversal symmetry is predicted to cause an experimentally observable change in the distribution of amplitudes. The theory is tested numerically and good agreement is found.
Quantum Theory for Cold Avalanche Ionization in Solids
Deng, H. X.; Zu, X. T.; Xiang, X.; Sun, K.
2010-09-10
A theory of photon-assisted impact ionization in solids is presented. Our theory makes a quantum description of the new impact ionization--cold avalanche ionization recently reported by P. P. Rajeev, M. Gertsvolf, P. B. Corkum, and D. M. Rayner [Phys. Rev. Lett. 102, 083001 (2009)]. The present theory agrees with the experiments and can be reduced to the traditional impact ionization expression in the absence of a laser.
Theory Of Alkyl Terminated Silicon Quantum Dots
Reboredo, F; Galli, G
2004-08-19
We have carried out a series of ab-initio calculations to investigate changes in the optical properties of Si quantum dots as a function of surface passivation. In particular, we have compared hydrogen passivated dots with those having alkyl groups at the surface. We find that, while on clusters with reconstructed surfaces a complete alkyl passivation is possible, steric repulsion prevents full passivation of Si dots with unreconstructed surfaces. In addition, our calculations show that steric repulsion may have a dominant effect in determining the surface structure, and eventually the stability of alkyl passivated clusters, with results dependent on the length of the carbon chain. Alkyl passivation weakly affects optical gaps of silicon quantum dots, while it substantially decreases ionization potentials and electron affinities and affect their excited state properties. On the basis of our results we propose that alkyl terminated quantum dots may be size selected taking advantage of the change in ionization potential as a function of the cluster size.
General Embedded Brane Effective Field Theories
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Goon, Garrett L.; Hinterbichler, Kurt; Trodden, Mark
2011-06-10
We presented a new general class of four-dimensional effective field theories with interesting global symmetry groups, which may prove relevant to the cosmology of both the early and late universe.
Hamiltonian Light-front Field Theory Within an AdS/QCD Basis
Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Sternberg, P.; Ng, E.G.; Yang, C.; /LBL, Berkeley
2009-12-16
Non-perturbative Hamiltonian light-front quantum field theory presents opportunities and challenges that bridge particle physics and nuclear physics. Fundamental theories, such as Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED) offer the promise of great predictive power spanning phenomena on all scales from the microscopic to cosmic scales, but new tools that do not rely exclusively on perturbation theory are required to make connection from one scale to the next. We outline recent theoretical and computational progress to build these bridges and provide illustrative results for nuclear structure and quantum field theory. As our framework we choose light-front gauge and a basis function representation with two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall AdS/QCD model obtained from light-front holography.
The Theory of Quantized Fields. II
DOE R&D Accomplishments [OSTI]
Schwinger, J.
1951-01-01
The arguments leading to the formulation of the Action Principle for a general field are presented. In association with the complete reduction of all numerical matrices into symmetrical and anti-symmetrical parts, the general field is decomposed into two sets, which are identified with Bose-Einstein and Fermi-Dirac fields. The spin restriction on the two kinds of fields is inferred from the time reflection invariance requirement. The consistency of the theory is verified in terms of a criterion involving the various generators of infinitesimal transformations. Following a discussion of charged fields, the electromagnetic field is introduced to satisfy the postulate of general gauge invariance. As an aspect of the latter, it is recognized that the electromagnetic field and charged fields are not kinematically independent. After a discussion of the field-strength commutation relations, the independent dynamical variable of the electromagnetic field are exhibited in terms of a special gauge.
Bilinear covariants and spinor fields duality in quantum Clifford algebras
Ab?amowicz, Rafa?; Gonalves, Icaro; Rocha, Roldo da
2014-10-15
Classification of quantum spinor fields according to quantum bilinear covariants is introduced in a context of quantum Clifford algebras on Minkowski spacetime. Once the bilinear covariants are expressed in terms of algebraic spinor fields, the duality between spinor and quantum spinor fields can be discussed. Thus, by endowing the underlying spacetime with an arbitrary bilinear form with an antisymmetric part in addition to a symmetric spacetime metric, quantum algebraic spinor fields and deformed bilinear covariants can be constructed. They are thus compared to the classical (non quantum) ones. Classes of quantum spinor fields classes are introduced and compared with Lounesto's spinor field classification. A physical interpretation of the deformed parts and the underlying Z-grading is proposed. The existence of an arbitrary bilinear form endowing the spacetime already has been explored in the literature in the context of quantum gravity [S. W. Hawking, The unpredictability of quantum gravity, Commun. Math. Phys. 87, 395 (1982)]. Here, it is shown further to play a prominent role in the structure of Dirac, Weyl, and Majorana spinor fields, besides the most general flagpoles and flag-dipoles. We introduce a new duality between the standard and the quantum spinor fields, by showing that when Clifford algebras over vector spaces endowed with an arbitrary bilinear form are taken into account, a mixture among the classes does occur. Consequently, novel features regarding the spinor fields can be derived.
Open quantum systems and random matrix theory
Mulhall, Declan
2014-10-15
A simple model for open quantum systems is analyzed with RMT. The system is coupled to the continuum in a minimal way. In this paper we see the effect of opening the system on the level statistics, in particular the level spacing, width distribution and Δ{sub 3}(L) statistic are examined as a function of the strength of this coupling. The usual super-radiant state is observed, and it is seen that as it is formed, the level spacing and Δ{sub 3}(L) statistic exhibit the signatures of missed levels.
Category of trees in representation theory of quantum algebras
Moskaliuk, N. M.; Moskaliuk, S. S.
2013-10-15
New applications of categorical methods are connected with new additional structures on categories. One of such structures in representation theory of quantum algebras, the category of Kuznetsov-Smorodinsky-Vilenkin-Smirnov (KSVS) trees, is constructed, whose objects are finite rooted KSVS trees and morphisms generated by the transition from a KSVS tree to another one.
Alpha particles in effective field theory
Caniu, C.
2014-11-11
Using an effective field theory for alpha (?) particles at non-relativistic energies, we calculate the strong scattering amplitude modified by Coulomb corrections for a system of two ?s. For the strong interaction, we consider a momentum-dependent interaction which, in contrast to an energy dependent interaction alone [1], could be more useful in extending the theory to systems with more than two ? particles. We will present preliminary results of our EFT calculations for systems with two alpha particles.
Chiral effective field theory predictions for muon capture on...
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Journal Article: Chiral effective field theory predictions for muon capture on deuteron and 3He Citation Details In-Document Search Title: Chiral effective field theory...
Combined local-density and dynamical mean field theory calculations...
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field theory calculations for the compressed lanthanides Ce, Pr, and Nd Citation Details In-Document Search Title: Combined local-density and dynamical mean field theory ...
Effective Field Theory of Fractional Quantized Hall Nematics...
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Journal Article: Effective Field Theory of Fractional Quantized Hall Nematics Citation Details In-Document Search Title: Effective Field Theory of Fractional Quantized Hall ...
The Effective Field Theory of Multifield Inflation (Journal Article...
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The Effective Field Theory of Multifield Inflation Citation Details In-Document Search Title: The Effective Field Theory of Multifield Inflation Authors: Senatore, Leonardo ; ...
Effective field theory of fractional quantized Hall nematics...
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Effective field theory of fractional quantized Hall nematics Citation Details In-Document Search Title: Effective field theory of fractional quantized Hall nematics Authors: ...
The Effective Field Theory of Dark Matter Direct Detection (Journal...
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Effective Field Theory of Dark Matter Direct Detection Citation Details In-Document Search Title: The Effective Field Theory of Dark Matter Direct Detection You are accessing a...
The Effective Field Theory of Dark Matter Direct Detection (Journal...
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The Effective Field Theory of Dark Matter Direct Detection Citation Details In-Document Search Title: The Effective Field Theory of Dark Matter Direct Detection Authors: ...
The Effective Field Theory of Cosmological Large Scale Structures...
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The Effective Field Theory of Cosmological Large Scale Structures Citation Details In-Document Search Title: The Effective Field Theory of Cosmological Large Scale Structures...
Local Three-Nucleon Interaction from Chiral Effective Field Theory...
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Local Three-Nucleon Interaction from Chiral Effective Field Theory Citation Details In-Document Search Title: Local Three-Nucleon Interaction from Chiral Effective Field Theory ...
On classical and quantum dynamics of tachyon-like fields and their cosmological implications
Dimitrijević, Dragoljub D. Djordjević, Goran S. Milošević, Milan; Vulcanov, Dumitru
2014-11-24
We consider a class of tachyon-like potentials, motivated by string theory, D-brane dynamics and inflation theory in the context of classical and quantum mechanics. A formalism for describing dynamics of tachyon fields in spatially homogenous and one-dimensional - classical and quantum mechanical limit is proposed. A few models with concrete potentials are considered. Additionally, possibilities for p-adic and adelic generalization of these models are discussed. Classical actions and corresponding quantum propagators, in the Feynman path integral approach, are calculated in a form invariant on a change of the background number fields, i.e. on both archimedean and nonarchimedean spaces. Looking for a quantum origin of inflation, relevance of p-adic and adelic generalizations are briefly discussed.
Critical-field theory of the Kondo lattice model in two dimensions
Kim, Ki-Seok
2005-05-15
In the context of the U(1) slave-boson theory we derive a critical-field theory near the quantum-critical point of the Kondo lattice model in two spatial dimensions. First, we argue that strong gauge fluctuations in the U(1) slave-boson theory give rise to confinement between spinons and holons, thus causing 'neutralized' spinons in association with the slave-boson U(1) gauge field. Second, we show that critical fluctuations of Kondo singlets near the quantum-critical point result in a new U(1) gauge field. This emergent gauge field has nothing to do with the slave-boson U(1) gauge field. Third, we find that the slave-boson U(1) gauge field can be exactly integrated out in the low-energy limit. As a result we find a critical-field theory in terms of renormalized conduction electrons and neutralized spinons interacting via the new emergent U(1) gauge field. Based on this critical-field theory we obtain the temperature dependence of the specific heat and the imaginary part of the self-energy of the renormalized electrons. These quantities display non-Fermi-liquid behavior near the quantum-critical point.
Quantum tomography meets dynamical systems and bifurcations theory
Goyeneche, D.; Torre, A. C. de la
2014-06-01
A powerful tool for studying geometrical problems in Hilbert spaces is developed. We demonstrate the convergence and robustness of our method in every dimension by considering dynamical systems theory. This method provides numerical solutions to hard problems involving many coupled nonlinear equations in low and high dimensions (e.g., quantum tomography problem, existence and classification of Pauli partners, mutually unbiased bases, complex Hadamard matrices, equiangular tight frames, etc.). Additionally, this tool can be used to find analytical solutions and also to implicitly prove the existence of solutions. Here, we develop the theory for the quantum pure state tomography problem in finite dimensions but this approach is straightforwardly extended to the rest of the problems. We prove that solutions are always attractive fixed points of a nonlinear operator explicitly given. As an application, we show that the statistics collected from three random orthonormal bases is enough to reconstruct pure states from experimental (noisy) data in every dimension d ? 32.
[Research in two-dimensional critical phenomena and conformal field theory]. Final report
Not Available
1990-12-31
A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)
Instantaneous spatially local projective measurements are consistent in a relativistic quantum field
Lin, Shih-Yuin
2012-12-15
Suppose the postulate of measurement in quantum mechanics can be extended to quantum field theory; then a local projective measurement at some moment on an object locally coupled with a relativistic quantum field will result in a projection or collapse of the wavefunctional of the combined system defined on the whole time-slice associated with the very moment of the measurement, if the relevant degrees of freedom have nonzero correlations. This implies that the wavefunctionals in the same Hamiltonian system but defined in different reference frames would collapse on different time-slices passing through the same local event where the measurement was done. Are these post-measurement states consistent with each other? We illustrate that the quantum states of the Raine-Sciama-Grove detector-field system started with the same initial Gaussian state defined on the same initial time-slice, then collapsed by the measurements on the pointlike detectors on different time-slices in different frames, will evolve to the same state of the combined system up to a coordinate transformation when compared on the same final time-slice. Such consistency is guaranteed by the spatial locality of interactions and the general covariance in a relativistic system, together with the spatial locality of measurements and the linearity of quantum dynamics in its quantum theory. - Highlights: Black-Right-Pointing-Pointer Spatially local quantum measurements in detector-field models are studied. Black-Right-Pointing-Pointer Local quantum measurement collapses the wavefunctional on the whole time-slice. Black-Right-Pointing-Pointer In different frames wavefunctionals of a field would collapse on different time-slices. Black-Right-Pointing-Pointer States collapsed by the same measurement will be consistent on the same final slice.
Yb-based heavy fermion compounds and field tuned quantum chemistry...
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and field tuned quantum chemistry Citation Details In-Document Search Title: Yb-based heavy fermion compounds and field tuned quantum chemistry You are accessing a ...
Working Group Report: Lattice Field Theory
Blum, T.; et al.,
2013-10-22
This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.
Heavy Quarks, QCD, and Effective Field Theory (Technical Report...
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Heavy Quarks, QCD, and Effective Field Theory Citation Details In-Document Search Title: Heavy Quarks, QCD, and Effective Field Theory The research supported by this OJI award is ...
Heavy Quarks, QCD, and Effective Field Theory Thomas Mehen 72...
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Heavy Quarks, QCD, and Effective Field Theory Thomas Mehen 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS Heavy Quarks, Quarkonium,...
Theory of melting at high pressures: Amending density functional theory with quantum Monte Carlo
Shulenburger, L.; Desjarlais, M. P.; Mattsson, T. R.
2014-10-01
We present an improved first-principles description of melting under pressure based on thermodynamic integration comparing Density Functional Theory (DFT) and quantum Monte Carlo (QMC) treatments of the system. The method is applied to address the longstanding discrepancy between density functional theory (DFT) calculations and diamond anvil cell (DAC) experiments on the melting curve of xenon, a noble gas solid where van der Waals binding is challenging for traditional DFT methods. The calculations show excellent agreement with data below 20 GPa and that the high-pressure melt curve is well described by a Lindemann behavior up to at least 80 GPa, a finding in stark contrast to DAC data.
Semiclassical and quantum field theoretic bounds for traversable Lorentzian stringy wormholes
Nandi, Kamal Kanti; Zhang Yuanzhong; Kumar, K.B. Vijaya
2004-09-15
A lower bound on the size of a Lorentzian wormhole can be obtained by semiclassically introducing the Planck cutoff on the magnitude of tidal forces (Horowitz-Ross constraint). Also, an upper bound is provided by the quantum field theoretic constraint in the form of the Ford-Roman Quantum Inequality for massless minimally coupled scalar fields. To date, however, exact static solutions belonging to this scalar field theory have not been worked out to verify these bounds. To fill this gap, we examine the wormhole features of two examples from the Einstein frame description of the vacuum low energy string theory in four dimensions which is the same as the minimally coupled scalar field theory. Analyses in this paper support the conclusion of Ford and Roman that wormholes in this theory can have sizes that are indeed only a few order of magnitudes larger than the Planck scale. It is shown that the two types of bounds are also compatible. In the process, we point out a 'wormhole' analog of naked black holes.
Quantum theory of amplified spontaneous emission: scaling properties
Garrison, J.C.; Nathel, H.; Chiao, R.Y.
1988-07-01
We formulate a second-quantized theory of propagation in laser-active media and apply it to the description of amplified spontaneous emission for the case of homogeneously broadened three-level atoms in a rodlike geometry with arbitrary Fresnel number. The electromagnetic field is treated in paraxial approximation by an ad hoc quantization scheme, and spontaneous emission into off-axis modes is described by noise operator methods. We show by a scaling (dimensional) analysis how to derive the characteristic fields and lengths for superfluorescence and amplified spontaneous emission. The results show that dye media can be used as experimental analogs for x-ray lasers.
Boundary conformal field theory and tunneling of edge quasiparticles in
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non-Abelian topological states (Journal Article) | SciTech Connect Boundary conformal field theory and tunneling of edge quasiparticles in non-Abelian topological states Citation Details In-Document Search Title: Boundary conformal field theory and tunneling of edge quasiparticles in non-Abelian topological states We explain how (perturbed) boundary conformal field theory allows us to understand the tunneling of edge quasiparticles in non-Abelian topological states. The coupling between a
Dissipative Effects in the Effective Field Theory of Inflation (Journal
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Article) | SciTech Connect SciTech Connect Search Results Journal Article: Dissipative Effects in the Effective Field Theory of Inflation Citation Details In-Document Search Title: Dissipative Effects in the Effective Field Theory of Inflation We generalize the effective field theory of single clock inflation to include dissipative effects. Working in unitary gauge we couple a set of composite operators, {Omicron}{sub {mu}{nu}}..., in the effective action which is constrained solely by
Theory of melting at high pressures: Amending density functional theory with quantum Monte Carlo
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Shulenburger, L.; Desjarlais, M. P.; Mattsson, T. R.
2014-10-01
We present an improved first-principles description of melting under pressure based on thermodynamic integration comparing Density Functional Theory (DFT) and quantum Monte Carlo (QMC) treatments of the system. The method is applied to address the longstanding discrepancy between density functional theory (DFT) calculations and diamond anvil cell (DAC) experiments on the melting curve of xenon, a noble gas solid where van der Waals binding is challenging for traditional DFT methods. The calculations show excellent agreement with data below 20 GPa and that the high-pressure melt curve is well described by a Lindemann behavior up to at least 80 GPa, amore » finding in stark contrast to DAC data.« less
Local Three-Nucleon Interaction from Chiral Effective Field Theory...
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Journal Article: Local Three-Nucleon Interaction from Chiral Effective Field Theory Citation Details In-Document Search Title: Local Three-Nucleon Interaction from Chiral Effective ...
Warped Conformal Field Theory (Journal Article) | SciTech Connect
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Search Title: Warped Conformal Field Theory Authors: Detournay, Stephane ; Harvard U. ; Hartman, Thomas ; Princeton, Inst. Advanced Study ; Hofman, Diego M. ; Harvard...
Conformal field theories at nonzero temperature: Operator product...
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nonzero temperature: Operator product expansions, Monte Carlo, and holography Citation Details In-Document Search Title: Conformal field theories at nonzero temperature: Operator ...
Field-induced quantum criticality in YbAgGe
Bud'ko, S.; Canfield, P.
2008-01-01
YbAgGe is one of the very few stoichiometric, Yb-based, heavy fermion materials that exhibit field-induced quantum criticality. We will present an overview of thermodynamic and transport measurements in YbAgGe single crystals. Moderate magnetic field (45-90 kOe, depending on orientation) suppresses long range magnetic order, giving rise to non-Fermi-liquid behavior followed at higher field by a crossover to a heavy Fermi-liquid. Given the more accessible temperature and field scales, a non-Fermi liquid region rather than point for T {yields} 0 K may be detected.
Twisted noncommutative field theory with the Wick-Voros and Moyal products
Galluccio, Salvatore; Lizzi, Fedele; Vitale, Patrizia
2008-10-15
We present a comparison of the noncommutative field theories built using two different star products: Moyal and Wick-Voros (or normally ordered). For the latter we discuss both the classical and the quantum field theory in the quartic potential case and calculate the Green's functions up to one loop, for the two- and four-point cases. We compare the two theories in the context of the noncommutative geometry determined by a Drinfeld twist, and the comparison is made at the level of Green's functions and S matrix. We find that while the Green's functions are different for the two theories, the S matrix is the same in both cases and is different from the commutative case.
Relativistic field theory of neutron stars and their hyperon populations
Glendenning, N.K.
1986-01-01
The nuclear many-body problem is examined by means of the formulation of an effective relativistic field theory of interacting hadrons. A relativistic field theory of hadronic matter is especially appropriate for the description of hot or dense matter, because of the appearance of antiparticles and higher baryon resonances and because it automatically respects causality. 8 refs., 7 figs., 1 tab. (WRF)
Automatically generating Feynman rules for improved lattice field theories
Hart, A. . E-mail: a.hart@ed.ac.uk; Hippel, G.M. von; Horgan, R.R.; Storoni, L.C.
2005-10-10
Deriving the Feynman rules for lattice perturbation theory from actions and operators is complicated, especially when improvement terms are present. This physically important task is, however, suitable for automation. We describe a flexible algorithm for generating Feynman rules for a wide range of lattice field theories including gluons, relativistic fermions and heavy quarks. We also present an efficient implementation of this in a freely available, multi-platform programming language (PYTHON), optimised to deal with a wide class of lattice field theories.
The effective field theory of dark matter direct detection (Journal
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Article) | SciTech Connect The effective field theory of dark matter direct detection Citation Details In-Document Search Title: The effective field theory of dark matter direct detection We extend and explore the general non-relativistic effective theory of dark matter (DM) direct detection. We describe the basic non-relativistic building blocks of operators and discuss their symmetry properties, writing down all Galilean-invariant operators up to quadratic order in momentum transfer
Electric field geometries dominate quantum transport coupling in silicon nanoring
Lee, Tsung-Han E-mail: sfhu.hu@gmail.com; Hu, Shu-Fen E-mail: sfhu.hu@gmail.com
2014-03-28
Investigations on the relation between the geometries of silicon nanodevices and the quantum phenomenon they exhibit, such as the Aharonov–Bohm (AB) effect and the Coulomb blockade, were conducted. An arsenic doped silicon nanoring coupled with a nanowire by electron beam lithography was fabricated. At 1.47 K, Coulomb blockade oscillations were observed under modulation from the top gate voltage, and a periodic AB oscillation of ΔB = 0.178 T was estimated for a ring radius of 86 nm under a high sweeping magnetic field. Modulating the flat top gate and the pointed side gate was performed to cluster and separate the many electron quantum dots, which demonstrated that quantum confinement and interference effects coexisted in the doped silicon nanoring.
Effective field theory: A modern approach to anomalous couplings
Degrande, Cline; Centre for Particle Physics and Phenomenology , Universit Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve ; Greiner, Nicolas; Max-Planck-Institut fr Physik, Fhringer Ring 6, 80805 Mnchen ; Kilian, Wolfgang; University of Siegen, Fachbereich Physik, D-57068 Siegen ; Mattelaer, Olivier; Mebane, Harrison; Stelzer, Tim; Willenbrock, Scott; Zhang, Cen; Centre for Particle Physics and Phenomenology , Universit Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve
2013-08-15
We advocate an effective field theory approach to anomalous couplings. The effective field theory approach is the natural way to extend the standard model such that the gauge symmetries are respected. It is general enough to capture any physics beyond the standard model, yet also provides guidance as to the most likely place to see the effects of new physics. The effective field theory approach also clarifies that one need not be concerned with the violation of unitarity in scattering processes at high energy. We apply these ideas to pair production of electroweak vector bosons. -- Highlights: We discuss the advantages of effective field theories compared to anomalous couplings. We show that one need not be concerned with unitarity violation at high energy. We discuss the application of effective field theory to weak boson physics.
Not Available
1990-01-01
A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)
On the stability of the asymptotically free scalar field theories
Shalaby, A M.
2015-03-30
Asymptotic freedom plays a vital role in our understanding of the theory of particle interactions. To have this property, one has to resort to a Non-abelian gauge theory with the number of colors equal to or greater than three (QCD). However, recent studies have shown that simple scalar field theories can possess this interesting property. These theories have non-Hermitian effective field forms but their classical potentials are bounded from above. In this work, we shall address the stability of the vacua of the bounded from above (??{sup 4+n}) scalar field theories. Moreover, we shall cover the effect of the distribution of the Stokes wedges in the complex ?-plane on the features of the vacuum condensate within these theories.
Quantum mechanical force field for hydrogen fluoride with explicit electronic polarization
Mazack, Michael J. M.; Gao, Jiali
2014-05-28
The explicit polarization (X-Pol) theory is a fragment-based quantum chemical method that explicitly models the internal electronic polarization and intermolecular interactions of a chemical system. X-Pol theory provides a framework to construct a quantum mechanical force field, which we have extended to liquid hydrogen fluoride (HF) in this work. The parameterization, called XPHF, is built upon the same formalism introduced for the XP3P model of liquid water, which is based on the polarized molecular orbital (PMO) semiempirical quantum chemistry method and the dipole-preserving polarization consistent point charge model. We introduce a fluorine parameter set for PMO, and find good agreement for various gas-phase results of small HF clusters compared to experiments and ab initio calculations at the M06-2X/MG3S level of theory. In addition, the XPHF model shows reasonable agreement with experiments for a variety of structural and thermodynamic properties in the liquid state, including radial distribution functions, interaction energies, diffusion coefficients, and densities at various state points.
Killing vector fields and harmonic superfield theories
Groeger, Josua
2014-09-15
The harmonic action functional allows a natural generalisation to semi-Riemannian supergeometry, also referred to as harmonic, which resembles the supersymmetric sigma models studied in high energy physics. We show that Killing vector fields are infinitesimal supersymmetries of this harmonic action and prove three different Noether theorems in this context. En passant, we provide a homogeneous treatment of five characterisations of Killing vector fields on semi-Riemannian supermanifolds, thus filling a gap in the literature.
Combined local-density and dynamical mean field theory calculations...
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a combination of the local-density approximation (LDA) and dynamical mean field theory (DMFT), or LDA+DMFT. The 4f moment, spectra, and the total energy among other properties are ...
Effective field theory for spacetime symmetry breaking (Journal Article) |
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SciTech Connect SciTech Connect Search Results Journal Article: Effective field theory for spacetime symmetry breaking Citation Details In-Document Search This content will become publicly available on August 17, 2016 Title: Effective field theory for spacetime symmetry breaking Authors: Hidaka, Yoshimasa ; Noumi, Toshifumi ; Shiu, Gary Publication Date: 2015-08-18 OSTI Identifier: 1212121 Grant/Contract Number: HKUST4/CRF/13G; FG-02-95ER40896; 604213; 16304414 Type: Publisher's Accepted
The Effective Field Theory of Dark Matter Direct Detection (Journal
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Article) | SciTech Connect SciTech Connect Search Results Journal Article: The Effective Field Theory of Dark Matter Direct Detection Citation Details In-Document Search Title: The Effective Field Theory of Dark Matter Direct Detection Authors: Fitzpatrick, A.Liam ; /Stanford U., ITP ; Haxton, Wick ; /UC, Berkeley /LBL, Berkeley ; Katz, Emanuel ; /Stanford U., ITP /Boston U. /SLAC ; Lubbers, Nicholas ; Xu, Yiming ; /Boston U. Publication Date: 2013-04-02 OSTI Identifier: 1074218 Report
The Effective Field Theory of Multifield Inflation (Journal Article) |
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SciTech Connect SciTech Connect Search Results Journal Article: The Effective Field Theory of Multifield Inflation Citation Details In-Document Search Title: The Effective Field Theory of Multifield Inflation Authors: Senatore, Leonardo ; /Princeton, Inst. Advanced Study /Stanford U., Phys. Dept. /KIPAC, Menlo Park ; Zaldarriaga, Matias ; /Princeton, Inst. Advanced Study Publication Date: 2013-06-18 OSTI Identifier: 1084310 Report Number(s): SLAC-PUB-15598 arXiv:1009.2093 DOE Contract
Theory of the nucleus as applied to quantum chaos
Bunakov, V. E., E-mail: bunakov@VB13190.spb.edu [St. Petersburg State University, Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute (Russian Federation)
2014-12-15
A critical analysis of the present-day concept of chaos in quantum systems as nothing but a quantum signature of chaos in classical mechanics is given. It is proposed to specify a regular versus a chaotic behavior on the basis of symmetries of the system being considered and global integrals of motion that are associated with these symmetries in accordance with the Liouville-Arnold theorem rather than on the basis of the concept of Lyapunovs instability of trajectories. Numerical criteria of quantum chaos that follow from the proposed concept are analyzed.
Effective field theory and integrability in two-dimensional Mott transition
Bottesi, Federico L.; Zemba, Guillermo R.
2011-08-15
Highlights: > Mott transition in 2d lattice fermion model. > 3D integrability out of 2D. > Effective field theory for Mott transition in 2d. > Double Chern-Simons. > d-Density waves. - Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a quantum group symmetry as a consequence of a recently found solution of the Zamolodchikov tetrahedron equation. A projection (from three to two space-time dimensions) property of the solution is used to identify the symmetry of the model at the Mott critical point as U{sub q}(sl(2)-circumflex)xU{sub q}(sl(2)-circumflex), with deformation parameter q = -1. Based on this result, the low-energy effective field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the effective filed theory methods, we show that the Mott transition that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.
Quantum driven dissipative parametric oscillator in a blackbody radiation field
Pachn, Leonardo A.; Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 ; Brumer, Paul
2014-01-15
We consider the general open system problem of a charged quantum oscillator confined in a harmonic trap, whose frequency can be arbitrarily modulated in time, that interacts with both an incoherent quantized (blackbody) radiation field and with an arbitrary coherent laser field. We assume that the oscillator is initially in thermodynamic equilibrium with its environment, a non-factorized initial density matrix of the system and the environment, and that at t = 0 the modulation of the frequency, the coupling to the incoherent and the coherent radiation are switched on. The subsequent dynamics, induced by the presence of the blackbody radiation, the laser field, and the frequency modulation, is studied in the framework of the influence functional approach. This approach allows incorporating, in analytic closed formulae, the non-Markovian character of the oscillator-environment interaction at any temperature as well the non-Markovian character of the blackbody radiation and its zero-point fluctuations. Expressions for the time evolution of the covariance matrix elements of the quantum fluctuations and the reduced density-operator are obtained.
Quantum confinement in Si and Ge nanostructures: Theory and experiment
Barbagiovanni, Eric G.; Lockwood, David J.; Simpson, Peter J.; Goncharova, Lyudmila V.
2014-03-15
The role of quantum confinement (QC) in Si and Ge nanostructures (NSs) including quantum dots, quantum wires, and quantum wells is assessed under a wide variety of fabrication methods in terms of both their structural and optical properties. Structural properties include interface states, defect states in a matrix material, and stress, all of which alter the electronic states and hence the measured optical properties. We demonstrate how variations in the fabrication method lead to differences in the NS properties, where the most relevant parameters for each type of fabrication method are highlighted. Si embedded in, or layered between, SiO{sub 2}, and the role of the sub-oxide interface states embodies much of the discussion. Other matrix materials include Si{sub 3}N{sub 4} and Al{sub 2}O{sub 3}. Si NSs exhibit a complicated optical spectrum, because the coupling between the interface states and the confined carriers manifests with varying magnitude depending on the dimension of confinement. Ge NSs do not produce well-defined luminescence due to confined carriers, because of the strong influence from oxygen vacancy defect states. Variations in Si and Ge NS properties are considered in terms of different theoretical models of QC (effective mass approximation, tight binding method, and pseudopotential method). For each theoretical model, we discuss the treatment of the relevant experimental parameters.
Chiral Effective Field Theory in the $\\Delta$-resonance region
Vladimir Pascalutsa
2006-09-18
I discuss the problem of constructing an effective low-energy theory in the vicinity of a resonance or a bound state. The focus is on the example of the $\\Delta(1232)$, the lightest resonance in the nucleon sector. Recent developments of the chiral effective-field theory in the $\\Delta$-resonance region are briefly reviewed. I conclude with a comment on the merits of the manifestly covariant formulation of chiral EFT in the baryon sector.
Large field inflation models from higher-dimensional gauge theories
Furuuchi, Kazuyuki; Koyama, Yoji
2015-02-23
Motivated by the recent detection of B-mode polarization of CMB by BICEP2 which is possibly of primordial origin, we study large field inflation models which can be obtained from higher-dimensional gauge theories. The constraints from CMB observations on the gauge theory parameters are given, and their naturalness are discussed. Among the models analyzed, Dante’s Inferno model turns out to be the most preferred model in this framework.
Motion of small bodies in classical field theory
Gralla, Samuel E. [Enrico Fermi Institute and Department of Physics University of Chicago 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States)
2010-04-15
I show how prior work with R. Wald on geodesic motion in general relativity can be generalized to classical field theories of a metric and other tensor fields on four-dimensional spacetime that (1) are second-order and (2) follow from a diffeomorphism-covariant Lagrangian. The approach is to consider a one-parameter-family of solutions to the field equations satisfying certain assumptions designed to reflect the existence of a body whose size, mass, and various charges are simultaneously scaled to zero. (That such solutions exist places a further restriction on the class of theories to which our results apply.) Assumptions are made only on the spacetime region outside of the body, so that the results apply independent of the body's composition (and, e.g., black holes are allowed). The worldline 'left behind' by the shrinking, disappearing body is interpreted as its lowest-order motion. An equation for this worldline follows from the 'Bianchi identity' for the theory, without use of any properties of the field equations beyond their being second-order. The form of the force law for a theory therefore depends only on the ranks of its various tensor fields; the detailed properties of the field equations are relevant only for determining the charges for a particular body (which are the ''monopoles'' of its exterior fields in a suitable limiting sense). I explicitly derive the force law (and mass-evolution law) in the case of scalar and vector fields, and give the recipe in the higher-rank case. Note that the vector force law is quite complicated, simplifying to the Lorentz force law only in the presence of the Maxwell gauge symmetry. Example applications of the results are the motion of 'chameleon' bodies beyond the Newtonian limit, and the motion of bodies in (classical) non-Abelian gauge theory. I also make some comments on the role that scaling plays in the appearance of universality in the motion of bodies.
A field theory of piezoelectric media containing dislocations
Taupin, V. Fressengeas, C.; Ventura, P.; Lebyodkin, M.
2014-04-14
A field theory is proposed to extend the standard piezoelectric framework for linear elastic solids by accounting for the presence and motion of dislocation fields and assessing their impact on the piezoelectric properties. The proposed theory describes the incompatible lattice distortion and residual piezoelectric polarization fields induced by dislocation ensembles, as well as the dynamic evolution of these fields through dislocation motion driven by coupled electro-mechanical loading. It is suggested that (i) dislocation mobility may be enhanced or inhibited by the electric field, depending on the polarity of the latter, (ii) plasticity mediated by dislocation motion allows capturing long-term time-dependent properties of piezoelectric polarization. Due to the continuity of the proposed electro-mechanical framework, the stress/strain and polarization fields are smooth even in the dislocation core regions. The theory is applied to gallium nitride layers for validation. The piezoelectric polarization fields associated with bulk screw/edge dislocations are retrieved and surface potential modulations are predicted. The results are extended to dislocation loops.
Semianalytical quantum model for graphene field-effect transistors
Pugnaghi, Claudio; Grassi, Roberto Gnudi, Antonio; Di Lecce, Valerio; Gnani, Elena; Reggiani, Susanna; Baccarani, Giorgio
2014-09-21
We develop a semianalytical model for monolayer graphene field-effect transistors in the ballistic limit. Two types of devices are considered: in the first device, the source and drain regions are doped by charge transfer with Schottky contacts, while, in the second device, the source and drain regions are doped electrostatically by a back gate. The model captures two important effects that influence the operation of both devices: (i) the finite density of states in the source and drain regions, which limits the number of states available for transport and can be responsible for negative output differential resistance effects, and (ii) quantum tunneling across the potential steps at the source-channel and drain-channel interfaces. By comparison with a self-consistent non-equilibrium Green's function solver, we show that our model provides very accurate results for both types of devices, in the bias region of quasi-saturation as well as in that of negative differential resistance.
Kondo effect in coupled quantum dots under magnetic fields
Aono, Tomosuke; Eto, Mikio
2001-08-15
The Kondo effect in coupled quantum dots is investigated theoretically under magnetic fields. We show that the magnetoconductance (MC) illustrates the peak structures of Kondo resonant spectra. When the dot-dot tunneling coupling V{sub C} is smaller than the dot-lead coupling {Delta} (level broadening), Kondo resonant levels appear at the Fermi level (E{sub F}). The Zeeman splitting of the levels weakens the Kondo effect, which results in a negative MC. When V{sub C} is larger than {Delta}, the Kondo resonances form bonding and antibonding levels, located below and above E{sub F}, respectively. We observe a positive MC since the Zeeman splitting increases the overlap between the levels at E{sub F}. In the presence of antiferromagnetic spin coupling between the dots, the sign of the MC can change as a function of the gate voltage.
Quantum field theory of classically unstable Hamiltonian dynamics
Strauss, Y.; Horwitz, L. P.; Levitan, J.; Yahalom, A.
2015-07-15
We study a class of dynamical systems for which the motions can be described in terms of geodesics on a manifold (ordinary potential models can be cast into this form by means of a conformal map). It is rigorously proven that the geodesic deviation equation of Jacobi, constructed with a second covariant derivative, is unitarily equivalent to that of a parametric harmonic oscillator, and we study the second quantization of this oscillator. The excitations of the Fock space modes correspond to the emission and absorption of quanta into the dynamical medium, thus associating unstable behavior of the dynamical system with calculable fluctuations in an ensemble with possible thermodynamic consequences.
Curing the UV/IR mixing for field theories with translation-invariant star products
Tanasa, Adrian; Vitale, Patrizia
2010-03-15
The ultraviolet/infrared (UV/IR) mixing of noncommutative field theories has been recently shown to be a generic feature of translation-invariant associative products. In this paper we propose to take into account the quantum corrections of the model to modify in this way the noncommutative action. This idea was already used to cure the UV/IR mixing for theories on Moyal space. We show that in the present framework also, this proposal proves successful for curing the mixing. We achieve this task by explicit calculations of one and higher loops Feynman amplitudes. For the sake of completeness, we compute the form of the new action in the matrix base for the Wick-Voros product.
Symplectic quantum mechanics and Chern-Simons gauge theory. I
Jeffrey, Lisa C.
2013-05-15
In this article we describe the relation between the Chern-Simons gauge theory partition function and the partition function defined using the symplectic action functional as the Lagrangian. We show that the partition functions obtained using these two Lagrangians agree, and we identify the semiclassical formula for the partition function defined using the symplectic action functional.
Nuclear axial currents in chiral effective field theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Baroni, Alessandro; Girlanda, Luca; Pastore, Saori; Schiavilla, Rocco; Viviani, Michele
2016-01-11
Two-nucleon axial charge and current operators are derived in chiral effective field theory up to one loop. The derivation is based on time-ordered perturbation theory and accounts for cancellations between the contributions of irreducible diagrams and the contributions owing to nonstatic corrections from energy denominators of reducible diagrams. Ultraviolet divergencies associated with the loop corrections are isolated in dimensional regularization. The resulting axial current is finite and conserved in the chiral limit, while the axial charge requires renormalization. As a result, a complete set of contact terms for the axial charge up to the relevant order in the power countingmore » is constructed.« less
Einstein-aether theory with a Maxwell field: General formalism
Balakin, Alexander B.; Lemos, José P.S.
2014-11-15
We extend the Einstein-aether theory to include the Maxwell field in a nontrivial manner by taking into account its interaction with the time-like unit vector field characterizing the aether. We also include a generic matter term. We present a model with a Lagrangian that includes cross-terms linear and quadratic in the Maxwell tensor, linear and quadratic in the covariant derivative of the aether velocity four-vector, linear in its second covariant derivative and in the Riemann tensor. We decompose these terms with respect to the irreducible parts of the covariant derivative of the aether velocity, namely, the acceleration four-vector, the shear and vorticity tensors, and the expansion scalar. Furthermore, we discuss the influence of an aether non-uniform motion on the polarization and magnetization of the matter in such an aether environment, as well as on its dielectric and magnetic properties. The total self-consistent system of equations for the electromagnetic and the gravitational fields, and the dynamic equations for the unit vector aether field are obtained. Possible applications of this system are discussed. Based on the principles of effective field theories, we display in an appendix all the terms up to fourth order in derivative operators that can be considered in a Lagrangian that includes the metric, the electromagnetic and the aether fields.
Locally smeared operator product expansions in scalar field theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Monahan, Christopher; Orginos, Kostas
2015-04-01
We propose a new locally smeared operator product expansion to decompose non-local operators in terms of a basis of smeared operators. The smeared operator product expansion formally connects nonperturbative matrix elements determined numerically using lattice field theory to matrix elements of non-local operators in the continuum. These nonperturbative matrix elements do not suffer from power-divergent mixing on the lattice, which significantly complicates calculations of quantities such as the moments of parton distribution functions, provided the smearing scale is kept fixed in the continuum limit. The presence of this smearing scale complicates the connection to the Wilson coefficients of the standardmore » operator product expansion and requires the construction of a suitable formalism. We demonstrate the feasibility of our approach with examples in real scalar field theory.« less
The adhesion model as a field theory for cosmological clustering
Rigopoulos, Gerasimos
2015-01-01
The adhesion model has been proposed in the past as an improvement of the Zel'dovich approximation, providing a good description of the formation of the cosmic web. We recast the model as a field theory for cosmological large scale structure, adding a stochastic force to account for power generated from very short, highly non-linear scales that is uncorrelated with the initial power spectrum. The dynamics of this Stochastic Adhesion Model (SAM) is reminiscent of the well known Kardar-Parisi-Zhang equation with the difference that the viscosity and the noise spectrum are time dependent. Choosing the viscosity proportional to the growth factor D restricts the form of noise spectrum through a 1-loop renormalization argument. For this choice, the SAM field theory is renormalizable to one loop. We comment on the suitability of this model for describing the non-linear regime of the CDM power spectrum and its utility as a relatively simple approach to cosmological clustering.
I THE THEORY OF QUANTIZED FIELDS I11 J
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
" THE THEORY OF QUANTIZED FIELDS I11 J d i a n Schwinger i Harvard University Cambridge, Mass. I . 1 i DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process
Formation of current filaments and magnetic field generation in a quantum current-carrying plasma
Niknam, A. R.; Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M.
2013-09-15
The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.
Transient quantum coherent response to a partially coherent radiation field
Sadeq, Zaheen S.; Brumer, Paul
2014-02-21
The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal toy model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.
The effective field theory of cosmological large scale structures
Carrasco, John Joseph M.; Hertzberg, Mark P.; Senatore, Leonardo
2012-09-20
Large scale structure surveys will likely become the next leading cosmological probe. In our universe, matter perturbations are large on short distances and small at long scales, i.e. strongly coupled in the UV and weakly coupled in the IR. To make precise analytical predictions on large scales, we develop an effective field theory formulated in terms of an IR effective fluid characterized by several parameters, such as speed of sound and viscosity. These parameters, determined by the UV physics described by the Boltzmann equation, are measured from N-body simulations. We find that the speed of sound of the effective fluid is c^{2}_{s} ? 10^{6}c^{2} and that the viscosity contributions are of the same order. The fluid describes all the relevant physics at long scales k and permits a manifestly convergent perturbative expansion in the size of the matter perturbations ?(k) for all the observables. As an example, we calculate the correction to the power spectrum at order ?(k)^{4}. As a result, the predictions of the effective field theory are found to be in much better agreement with observation than standard cosmological perturbation theory, already reaching percent precision at this order up to a relatively short scale k ? 0.24h Mpc^{1}.
Khots, Boris; Khots, Dmitriy
2014-12-10
Certain results that have been predicted by Quantum Mechanics (QM) theory are not always supported by experiments. This defines a deep crisis in contemporary physics and, in particular, quantum mechanics. We believe that, in fact, the mathematical apparatus employed within today's physics is a possible reason. In particular, we consider the concept of infinity that exists in today's mathematics as the root cause of this problem. We have created Observer's Mathematics that offers an alternative to contemporary mathematics. This paper is an attempt to relay how Observer's Mathematics may explain some of the contradictions in QM theory results. We consider the Hamiltonian Mechanics, Newton equation, Schrodinger equation, two slit interference, wave-particle duality for single photons, uncertainty principle, Dirac equations for free electron in a setting of arithmetic, algebra, and topology provided by Observer's Mathematics (see www.mathrelativity.com). Certain results and communications pertaining to solution of these problems are provided.
Analytical results from the quantum theory of a single-emitter nanolaser
Larionov, Nikolay V.; Kolobov, Mikhail I.
2011-11-15
We provide analytical results obtained in the framework of the quantum theory for a single-emitter nanolaser: an incoherently pumped single two-level system interacting with a single-cavity mode of finite finesse. In the good-cavity limit we analytically calculate the linewidth of such a laser, its amplitude fluctuation spectrum, and the intracavity Mandel Q parameter. Our analytical results are in very good agreement with numerical simulations of the master equation.
Slowly Varying Dilaton Cosmologies and Their Field Theory Duals
Awad, Adel; Das, Sumit R.; Ghosh, Archisman; Oh, Jae-Hyuk; Trivedi, Sandip P.; /Tata Inst. /Stanford U., ITP /SLAC
2011-06-28
We consider a deformation of the AdS{sub 5} x S{sup 5} solution of IIB supergravity obtained by taking the boundary value of the dilaton to be time dependent. The time dependence is taken to be slowly varying on the AdS scale thereby introducing a small parameter {epsilon}. The boundary dilaton has a profile which asymptotes to a constant in the far past and future and attains a minimum value at intermediate times. We construct the sugra solution to first non-trivial order in {epsilon}, and find that it is smooth, horizon free, and asymptotically AdS{sub 5} x S{sup 5} in the far future. When the intermediate values of the dilaton becomes small enough the curvature becomes of order the string scale and the sugra approximation breaks down. The resulting dynamics is analysed in the dual SU(N) gauge theory on S{sup 3} with a time dependent coupling constant which varies slowly. When N{epsilon} << 1, we find that a quantum adiabatic approximation is applicable, and use it to argue that at late times the geometry becomes smooth AdS{sub 5} x S{sup 5} again. When N{epsilon} >> 1, we formulate a classical adiabatic perturbation theory based on coherent states which arises in the large N limit. For large values of the tHooft coupling this reproduces the supergravity results. For small 'tHooft coupling the coherent state calculations become involved and we cannot reach a definite conclusion. We argue that the final state should have a dual description which is mostly smooth AdS5 space with the possible presence of a small black hole.
Julian Schwinger and the Source Theory
Office of Scientific and Technical Information (OSTI)
of elementary particles". "The theoretical achievements of Schwinger and Richard Feynman in the late 1940s and early 1950s ignited a revolution in quantum field theory and ...
Large-density field theory, viscosity, and '$2k_F$' singularities...
Office of Scientific and Technical Information (OSTI)
Large-density field theory, viscosity, and '2kF' singularities from string duals Citation Details In-Document Search Title: Large-density field theory, viscosity, and '2kF' ...
The one-loop matter bispectrum in the Effective Field Theory...
Office of Scientific and Technical Information (OSTI)
the Effective Field Theory of Large Scale Structures Citation Details In-Document Search Title: The one-loop matter bispectrum in the Effective Field Theory of Large Scale ...
The IR-resummed Effective Field Theory of Large Scale Structures...
Office of Scientific and Technical Information (OSTI)
IR-resummed Effective Field Theory of Large Scale Structures Citation Details In-Document Search Title: The IR-resummed Effective Field Theory of Large Scale Structures We present a ...
Quantum aspects of a moving magnetic quadrupole moment interacting with an electric field
Fonseca, I. C.; Bakke, K.
2015-06-15
The quantum dynamics of a moving particle with a magnetic quadrupole moment that interacts with electric and magnetic fields is introduced. By dealing with the interaction between an electric field and the magnetic quadrupole moment, it is shown that an analogue of the Coulomb potential can be generated and bound state solutions can be obtained. Besides, the influence of the Coulomb-type potential on the harmonic oscillator is investigated, where bound state solutions to both repulsive and attractive Coulomb-type potentials are achieved and the arising of a quantum effect characterized by the dependence of the harmonic oscillator frequency on the quantum numbers of the system is discussed.
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Cimmarusti, A. D.; Yan, Z.; Patterson, B. D.; Corcos, L. P.; Orozco, L. A.; Deffner, S.
2015-06-11
We measure the quantum speed of the state evolution of the field in a weakly-driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment assisted speed-up is realized: the quantum speed of the state re-population in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms).
Dissipative Effects in the Effective Field Theory of Inflation...
Office of Scientific and Technical Information (OSTI)
Park; Zaldarriaga, Matias; Princeton, Inst. Advanced Study 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DEGREES OF FREEDOM; DETECTION; FRICTION; RESPONSE FUNCTIONS;...
Quantum rings of non-uniform thickness in magnetic field
Rodrguez-Prada, F. A.; Garca, L. F.; Mikhailov, I. D.
2014-05-15
We consider a model of crater-shaped quantum dot in form of a thin layer whose thickness linearly increases with the distance from the axis. We show that one-particle wave equation for the electron confined in such structure can be completely separated in the adiabatic limit when the quantum dot thickness is much smaller than its lateral dimension. Analytical solutions found for this model has been used as base functions for analysing the effect of non-homogeneity on the electronic spectrum in the framework of the exact diagonalization method.
Exact scattering matrix of graphs in magnetic field and quantum noise
Caudrelier, Vincent; Mintchev, Mihail; Ragoucy, Eric
2014-08-15
We consider arbitrary quantum wire networks modelled by finite, noncompact, connected quantum graphs in the presence of an external magnetic field. We find a general formula for the total scattering matrix of the network in terms of its local scattering properties and its metric structure. This is applied to a quantum ring with N external edges. Connecting the external edges of the ring to heat reservoirs, we study the quantum transport on the graph in ambient magnetic field. We consider two types of dynamics on the ring: the free Schrdinger and the free massless Dirac equations. For each case, a detailed study of the thermal noise is performed analytically. Interestingly enough, in presence of a magnetic field, the standard linear Johnson-Nyquist law for the low temperature behaviour of the thermal noise becomes nonlinear. The precise regime of validity of this effect is discussed and a typical signature of the underlying dynamics is observed.
Effective field theory of non-attractor inflation
Akhshik, Mohammad; Firouzjahi, Hassan; Jazayeri, Sadra
2015-07-29
We present the model-independent studies of non attractor inflation in the context of effective field theory (EFT) of inflation. Within the EFT approach two independent branches of non-attractor inflation solutions are discovered in which a near scale-invariant curvature perturbation power spectrum is generated from the interplay between the variation of sound speed and the second slow roll parameter η. The first branch captures and extends the previously studied models of non-attractor inflation in which the curvature perturbation is not frozen on super-horizon scales and the single field non-Gaussianity consistency condition is violated. We present the general expression for the amplitude of local-type non-Gaussianity in this branch. The second branch is new in which the curvature perturbation is frozen on super-horizon scales and the single field non-Gaussianity consistency condition does hold in the squeezed limit. Depending on the model parameters, the shape of bispectrum in this branch changes from an equilateral configuration to a folded configuration while the amplitude of non-Gaussianity is less than unity.
Time-dependent density functional theory quantum transport simulation in non-orthogonal basis
Kwok, Yan Ho; Xie, Hang; Yam, Chi Yung; Chen, Guan Hua; Zheng, Xiao
2013-12-14
Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining time-dependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.
Usefulness of effective field theory for boosted Higgs production
Dawson, S.; Lewis, I. M.; Zeng, Mao
2015-04-07
The Higgs + jet channel at the LHC is sensitive to the effects of new physics both in the total rate and in the transverse momentum distribution at high _{pT}. We examine the production process using an effective field theory (EFT) language and discussing the possibility of determining the nature of the underlying high-scale physics from boosted Higgs production. The effects of heavy color triplet scalars and top partner fermions with TeV scale masses are considered as examples and Higgs-gluon couplings of dimension-5 and dimension-7 are included in the EFT. As a byproduct of our study, we examine the region of validity of the EFT. Dimension-7 contributions in realistic new physics models give effects in the high _{pT} tail of the Higgs signal which are so tiny that they are likely to be unobservable.
Breaking discrete symmetries in the effective field theory of inflation
Cannone, Dario; Gong, Jinn-Ouk; Tasinato, Gianmassimo
2015-08-03
We study the phenomenon of discrete symmetry breaking during the inflationary epoch, using a model-independent approach based on the effective field theory of inflation. We work in a context where both time reparameterization symmetry and spatial diffeomorphism invariance can be broken during inflation. We determine the leading derivative operators in the quadratic action for fluctuations that break parity and time-reversal. Within suitable approximations, we study their consequences for the dynamics of linearized fluctuations. Both in the scalar and tensor sectors, we show that such operators can lead to new direction-dependent phases for the modes involved. They do not affect the power spectra, but can have consequences for higher correlation functions. Moreover, a small quadrupole contribution to the sound speed can be generated.
Dark matter effective field theory scattering in direct detection experiments
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; et al
2015-05-18
We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. Here. we demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. In conclusion, we discussmore » the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less
Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M.; Devereaux, T. P.
2015-02-01
Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstancesmore » be regarded as more complex than the physics of a spin-orbital chain.« less
Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets
Johnston, David C.
2015-02-27
In this study, a unified molecular field theory (MFT) is presented that applies to both collinear and planar noncollinear Heisenberg antiferromagnets (AFs) on the same footing. The spins in the system are assumed to be identical and crystallographically equivalent. This formulation allows calculations of the anisotropic magnetic susceptibility ? versus temperature T below the AF ordering temperature T_{N} to be carried out for arbitrary Heisenberg exchange interactions J_{ij} between arbitrary neighbors j of a given spin i without recourse to magnetic sublattices. The Weiss temperature ?_{p} in the Curie-Weiss law is written in terms of the J_{ij} values and T_{N} in terms of the J_{ij} values and an assumed AF structure. Other magnetic and thermal properties are then expressed in terms of quantities easily accessible from experiment as laws of corresponding states for a given spin S. For collinear ordering these properties are the reduced temperature t=T/T_{N}, the ratio f = ?_{p}/T_{N}, and S. For planar noncollinear helical or cycloidal ordering, an additional parameter is the wave vector of the helix or cycloid. The MFT is also applicable to AFs with other AF structures. The MFT predicts that ?(T ? T_{N}) of noncollinear 120 spin structures on triangular lattices is isotropic and independent of S and T and thus clarifies the origin of this universally observed behavior. The high-field magnetization and heat capacity for fields applied perpendicular to the ordering axis (collinear AFs) and ordering plane (planar noncollinear AFs) are also calculated and expressed for both types of AF structures as laws of corresponding states for a given S, and the reduced perpendicular field versus reduced temperature phase diagram is constructed.
Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Johnston, David C.
2015-02-27
In this study, a unified molecular field theory (MFT) is presented that applies to both collinear and planar noncollinear Heisenberg antiferromagnets (AFs) on the same footing. The spins in the system are assumed to be identical and crystallographically equivalent. This formulation allows calculations of the anisotropic magnetic susceptibility χ versus temperature T below the AF ordering temperature TN to be carried out for arbitrary Heisenberg exchange interactions Jij between arbitrary neighbors j of a given spin i without recourse to magnetic sublattices. The Weiss temperature θp in the Curie-Weiss law is written in terms of the Jij values and TNmore » in terms of the Jij values and an assumed AF structure. Other magnetic and thermal properties are then expressed in terms of quantities easily accessible from experiment as laws of corresponding states for a given spin S. For collinear ordering these properties are the reduced temperature t=T/TN, the ratio f = θp/TN, and S. For planar noncollinear helical or cycloidal ordering, an additional parameter is the wave vector of the helix or cycloid. The MFT is also applicable to AFs with other AF structures. The MFT predicts that χ(T ≤ TN) of noncollinear 120° spin structures on triangular lattices is isotropic and independent of S and T and thus clarifies the origin of this universally observed behavior. The high-field magnetization and heat capacity for fields applied perpendicular to the ordering axis (collinear AFs) and ordering plane (planar noncollinear AFs) are also calculated and expressed for both types of AF structures as laws of corresponding states for a given S, and the reduced perpendicular field versus reduced temperature phase diagram is constructed.« less
The effective field theory of inflation models with sharp features
Bartolo, Nicola; Cannone, Dario; Matarrese, Sabino E-mail: dario.cannone@pd.infn.it
2013-10-01
We describe models of single-field inflation with small and sharp step features in the potential (and sound speed) of the inflaton field, in the context of the Effective Field Theory of Inflation. This approach allows us to study the effects of features in the power-spectrum and in the bispectrum of curvature perturbations, from a model-independent point of view, by parametrizing the features directly with modified ''slow-roll'' parameters. We can obtain a self-consistent power-spectrum, together with enhanced non-Gaussianity, which grows with a quantity ? that parametrizes the sharpness of the step. With this treatment it is straightforward to generalize and include features in other coefficients of the effective action of the inflaton field fluctuations. Our conclusion in this case is that, excluding extrinsic curvature terms, the only interesting effects at the level of the bispectrum could arise from features in the first slow-roll parameter ? or in the speed of sound c{sub s}. Finally, we derive an upper bound on the parameter ? from the consistency of the perturbative expansion of the action for inflaton perturbations. This constraint can be used for an estimation of the signal-to-noise ratio, to show that the observable which is most sensitive to features is the power-spectrum. This conclusion would change if we consider the contemporary presence of a feature and a speed of sound c{sub s} < 1, as, in such a case, contributions from an oscillating folded configuration can potentially make the bispectrum the leading observable for feature models.
Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets
Johnston, David C.
2015-02-27
In this study, a unified molecular field theory (MFT) is presented that applies to both collinear and planar noncollinear Heisenberg antiferromagnets (AFs) on the same footing. The spins in the system are assumed to be identical and crystallographically equivalent. This formulation allows calculations of the anisotropic magnetic susceptibility χ versus temperature T below the AF ordering temperature T_{N} to be carried out for arbitrary Heisenberg exchange interactions J_{ij} between arbitrary neighbors j of a given spin i without recourse to magnetic sublattices. The Weiss temperature θ_{p} in the Curie-Weiss law is written in terms of the J_{ij} values and T_{N} in terms of the J_{ij} values and an assumed AF structure. Other magnetic and thermal properties are then expressed in terms of quantities easily accessible from experiment as laws of corresponding states for a given spin S. For collinear ordering these properties are the reduced temperature t=T/T_{N}, the ratio f = θ_{p}/T_{N}, and S. For planar noncollinear helical or cycloidal ordering, an additional parameter is the wave vector of the helix or cycloid. The MFT is also applicable to AFs with other AF structures. The MFT predicts that χ(T ≤ T_{N}) of noncollinear 120° spin structures on triangular lattices is isotropic and independent of S and T and thus clarifies the origin of this universally observed behavior. The high-field magnetization and heat capacity for fields applied perpendicular to the ordering axis (collinear AFs) and ordering plane (planar noncollinear AFs) are also calculated and expressed for both types of AF structures as laws of corresponding states for a given S, and the reduced perpendicular field versus reduced temperature phase diagram is constructed.
Tanizaki, Yuya; Koike, Takayuki
2014-12-15
Picard–Lefschetz theory is applied to path integrals of quantum mechanics, in order to compute real-time dynamics directly. After discussing basic properties of real-time path integrals on Lefschetz thimbles, we demonstrate its computational method in a concrete way by solving three simple examples of quantum mechanics. It is applied to quantum mechanics of a double-well potential, and quantum tunneling is discussed. We identify all of the complex saddle points of the classical action, and their properties are discussed in detail. However a big theoretical difficulty turns out to appear in rewriting the original path integral into a sum of path integrals on Lefschetz thimbles. We discuss generality of that problem and mention its importance. Real-time tunneling processes are shown to be described by those complex saddle points, and thus semi-classical description of real-time quantum tunneling becomes possible on solid ground if we could solve that problem. - Highlights: • Real-time path integral is studied based on Picard–Lefschetz theory. • Lucid demonstration is given through simple examples of quantum mechanics. • This technique is applied to quantum mechanics of the double-well potential. • Difficulty for practical applications is revealed, and we discuss its generality. • Quantum tunneling is shown to be closely related to complex classical solutions.
Electric field control of spin-resolved edge states in graphene quantum nanorings
Farghadan, R.; Saffarzadeh, A.
2014-05-07
The electric-field effect on the electronic and magnetic properties of triangular and hexagonal graphene quantum rings with zigzag edge termination is investigated by means of the single-band tight-binding Hamiltonian and the mean-field Hubbard model. It is shown how the electron and spin states in the nanoring structures can be manipulated by applying an electric field. We find different spin-depolarization behaviors with variation of electric field strength due to the dependence of spin densities on the shapes and edges of this kind of nanorings. In the case of triangular quantum rings, the magnetization on the inner and outer edges can be selectively tuned and the spin states depolarize gradually as the field strength is increased, while in the case of hexagonal nanorings, the transverse electric field reduces the magnetic moments on both inner and outer edges symmetrically and rapidly.
Quantum chaos of atoms in a resonator driven by an external resonant field
Berman, G.P.; Bulgakov, E.N.; Holm, D.D. (Center for Nonlinear Studies, MS-B258, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) Kirensky Institute of Physics, Research Educational Center for Nonlinear Processes at Krasnoyarsk Polytechnical Institute, Theoretical Department at Krasnoyarsk State University, 660036, Krasnoyarsk (Russian Federation) Theoretical Division, MS-B284, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))
1994-06-01
A system of [ital N] two-level atoms in a resonator is considered interacting with a resonant eigenmode field and with an external coherent field, with a frequency slightly different from the frequency of the atomic transition. A model Hamiltonian is constructed for describing the slow quantum dynamics of the system, and a set of closed [ital c]-number equations for time-dependent quantum expectation values is derived in the boson and spin coherent states. In the region of parameters for developed chaos in the semiclassical limit (when the radiation field is considered classically) we show that the semiclassical approximation is violated by quantum effects at the time scale [tau][sub [h bar
An effective field theory for collinear and soft gluons: Heavy to light
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decays (Journal Article) | SciTech Connect An effective field theory for collinear and soft gluons: Heavy to light decays Citation Details In-Document Search Title: An effective field theory for collinear and soft gluons: Heavy to light decays We construct the Lagrangian for an effective theory of highly energetic quarks with energy Q, interacting with collinear and soft gluons. This theory has two low energy scales, the transverse momentum of the collinear particles, p{sub {perpendicular}},
Heavy Quarks, QCD, and Effective Field Theory (Technical Report) | SciTech
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Connect Technical Report: Heavy Quarks, QCD, and Effective Field Theory Citation Details In-Document Search Title: Heavy Quarks, QCD, and Effective Field Theory The research supported by this OJI award is in the area of heavy quark and quarkonium production, especially the application Soft-Collinear E#11;ective Theory (SCET) to the hadronic production of quarkonia. SCET is an e#11;ffective theory which allows one to derive factorization theorems and perform all order resummations for QCD
Non-singular bounce scenarios in loop quantum cosmology and the effective field description
Cai, Yi-Fu; Wilson-Ewing, Edward E-mail: wilson-ewing@phys.lsu.edu
2014-03-01
A non-singular bouncing cosmology is generically obtained in loop quantum cosmology due to non-perturbative quantum gravity effects. A similar picture can be achieved in standard general relativity in the presence of a scalar field with a non-standard kinetic term such that at high energy densities the field evolves into a ghost condensate and causes a non-singular bounce. During the bouncing phase, the perturbations can be stabilized by introducing a Horndeski operator. Taking the matter content to be a dust field and an ekpyrotic scalar field, we compare the dynamics in loop quantum cosmology and in a non-singular bouncing effective field model with a non-standard kinetic term at both the background and perturbative levels. We find that these two settings share many important properties, including the result that they both generate scale-invariant scalar perturbations. This shows that some quantum gravity effects of the very early universe may be mimicked by effective field models.
Quantum Confinement Induced Oscillatory Electric Field on a Stepped...
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surface of the wedge-shaped Pb(111) films. The alternating electric field has significant influence on surface reactivity, leading to selective even- or odd-layer adsorption...
Giant Collective Spin-Orbit Field in a Quantum Well: Fine Structure of Spin
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Plasmons (Journal Article) | SciTech Connect Giant Collective Spin-Orbit Field in a Quantum Well: Fine Structure of Spin Plasmons Citation Details In-Document Search Title: Giant Collective Spin-Orbit Field in a Quantum Well: Fine Structure of Spin Plasmons Authors: Baboux, F. ; Perez, F. ; Ullrich, C. A. ; D'Amico, I. ; Gómez, J. ; Bernard, M. Publication Date: 2012-10-15 OSTI Identifier: 1101593 Type: Publisher's Accepted Manuscript Journal Name: Physical Review Letters Additional Journal
Large-density field theory, viscosity, and '$2k_F$' singularities...
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Title: Large-density field theory, viscosity, and '2kF' singularities from string duals Authors: Polchinski, Joseph ; Santa Barbara, KITP ; Silverstein, Eva ; Santa Barbara, ...
Chiral effective field theory predictions for muon capture on...
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calculated and precisely measured rates on sup 3He, a value for the induced pseudoscalar form factor is obtained in good agreement with the chiral perturbation theory prediction. ...
Quantum and Classical Description of H Atom Under Magnetic Field and Quadrupole Trap Potential
Mahecha, J. [Institute of Physics, University of Antioquia, AA 1226, Medellin (Colombia); LPMC, Institute of Physics, University Paul Verlaine, 1 Bv Arago, 57078 Metz Cedex 3 (France); Salas, J. P. [Area of Applied Physics, University of La Rioja, C/Madre de Dios 51, 26006, Logrono (Spain)
2006-12-01
A discussion regarding the energy levels spectrum of quantum systems whose classical analogous has states of chaotic motion is presented. The chaotic dynamics of the classical underlying system has its manifestation in the wave functions (in the form of 'scars') and in the energy levels (in the form of 'statistical repulsion' of the energy levels). The above mentioned signatures are named 'quantum chaos'. A typical study of quantum chaos requires finding accurate energy eigenvalues of highly excited states, to calculate the nearest neighbors spacing between levels, to perform the 'unfolding' of the spectrum in order to separate the fluctuations, and finally to find the probability distribution of the unfolded spectrum. This is exemplified by the hydrogen atom under uniform magnetic field and a quadrupole electric field.
Jahan K, Luhluh Boda, Aalu; Chatterjee, Ashok
2015-05-15
The problem of an exciton trapped in a three dimensional Gaussian quantum dot is studied in the presence of an external magnetic field. A variational method is employed to obtain the ground state energy of the exciton as a function of the quantum dot size, the confinement strength and the magnetic field. It is also shown that the variation of the size of the exciton with the radius of the quantum dot.
Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.
Ovchinnikov, Yu. N.; Barone, A.; Varlamov, A. A.; Materials Science Division; Max-Planck Inst. for Physics of Complex Systems; Landau Inst. Theoretical Physics; Univ. di Napoli Federico II; Coherentia-INFM, CNR
2007-01-01
We study the phenomenon of macroscopic quantum tunneling (MQT) in small Josephson junctions (JJ) with an externally applied magnetic field. The latter results in the appearance of the Fraunhofer type modulation of the current density along the barrier. The problem of MQT for a pointlike JJ is reduced to the motion of the quantum particle in the washboard potential. In the case of a finite size JJ under consideration, this problem corresponds to a MQT in a potential which itself, besides the phase, depends on space variables. The general expression for the crossover temperature To between thermally activated and macroscopic quantum tunneling regimes and the escaping time {tau}{sub esc} have been calculated.
Effective field theory for a heavy Majorana fermion
Koepp, Karoline; Okui, Takemichi
2011-11-01
We formulate an effective theory for systems containing a heavy Majorana fermion, such as bound states of a long-lived gluino. This 'Majorana HQET' has the same degrees of freedom as the well-studied Dirac HQET. It respects an emergent U(1) symmetry despite the fundamental absence of a U(1) for Majorana fermions. Reparametrization invariance works identically in the two HQETs. Remarkably, while a Dirac HQET may or may not be charge conjugation symmetric, a charge conjugation symmetry emerges in all Majorana HQETs, potentially offering low energy probes to distinguish the two theories.
Saririan, K.
1997-05-01
In this thesis, the author presents some works in the direction of studying quantum effects in locally supersymmetric effective field theories that appear in the low energy limit of superstring theory. After reviewing the Kaehler covariant formulation of supergravity, he shows the calculation of the divergent one-loop contribution to the effective boson Lagrangian for supergravity, including the Yang-Mills sector and the helicity-odd operators that arise from integration over fermion fields. The only restriction is on the Yang-Mills kinetic energy normalization function, which is taken diagonal in gauge indices, as in models obtained from superstrings. He then presents the full result for the divergent one-loop contribution to the effective boson Lagrangian for supergravity coupled to chiral and Yang-Mills supermultiplets. He also considers the specific case of dilaton couplings in effective supergravity Lagrangians from superstrings, for which the one-loop result is considerably simplified. He studies gaugino condensation in the presence of an intermediate mass scale in the hidden sector. S-duality is imposed as an approximate symmetry of the effective supergravity theory. Furthermore, the author includes in the Kaehler potential the renormalization of the gauge coupling and the one-loop threshold corrections at the intermediate scale. It is shown that confinement is indeed achieved. Furthermore, a new running behavior of the dilaton arises which he attributes to S-duality. He also discusses the effects of the intermediate scale, and possible phenomenological implications of this model.
Magnetic field sensing beyond the standard quantum limit under the effect of decoherence
Matsuzaki, Yuichiro; Benjamin, Simon C.; Fitzsimons, Joseph
2011-07-15
Entangled states can potentially be used to outperform the standard quantum limit by which every classical sensor is bounded. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents an investigation of how a quantum sensor composed of many spins is affected by independent dephasing. We adopt general noise models including non-Markovian effects, and in these noise models the performance of the sensor depends crucially on the exposure time of the sensor to the field. We have found that, by choosing an appropriate exposure time within the non-Markovian time region, an entangled sensor does actually beat the standard quantum limit. Since independent dephasing is one of the most typical sources of noise in many systems, our results suggest a practical and scalable approach to beating the standard quantum limit.
The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown
Li, Yingjie; Go, David B.
2014-09-14
The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electronsa process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 ?m). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.
Quantum Theory of (H,H{Sub 2}) Scattering: Approximate Treatments of Reactive Scattering
DOE R&D Accomplishments [OSTI]
Tang, K. T.; Karplus, M.
1970-10-01
A quantum mechanical study is made of reactive scattering in the (H, H{sub 2}) system. The problem is formulated in terms of a form of the distorted-wave Born approximation (DWBA) suitable for collisions in which all particles have finite mass. For certain incident energies, differential and total cross sections, as well as other attributes of the reactive collisions, (e.g. reaction configuration), are determined. Two limiting models in the DWBA formulation are compared; in one, the molecule is unperturbed by the incoming atom and in the other, the molecule adiabatically follows the incoming atom. For thermal incident energies and semi-empirical interaction potential employed, the adiabatic model seems to be more appropriate. Since the DWBA method is too complicated for a general study of the (H, H{sub 2}) reaction, a much simpler approximation method, the “linear model” is developed. This model is very different in concept from treatments in which the three atoms are constrained to move on a line throughout the collision. The present model includes the full three-dimensional aspect of the collision and it is only the evaluation of the transition matrix element itself that is simplified. It is found that the linear model, when appropriately normalized, gives results in good agreement with that of the DWBA method. By application of this model, the energy dependence, rotational state of dependence and other properties of the total and differential reactions cross sections are determined. These results of the quantum mechanical treatment are compared with the classical calculation for the same potential surface. The most important result is that, in agreement with the classical treatment, the differential cross sections are strongly backward peaked at low energies and shifts in the forward direction as the energy increases. Finally, the implications of the present calculations for a theory of chemical kinetics are discussed.
Effective field theory for a heavy Higgs boson: A manifestly gauge-invariant approach
Nyffeler, A.; Schenk, A.
1996-02-01
For large values of the Higgs boson mass the low energy structure of the gauged linear {sigma} model in the spontaneously broken phase can adequately be described by an effective field theory. In this work we present a manifestly gauge-invariant technique to explicitly evaluate the corresponding effective Langrangian from the underlying theory. In order to demonstrate the application of this functional method, the effective field theory of the Abelian Higgs model is thoroughly analyzed. We stress that this technique does not rely on any particular property of the Abelian case. The application to the non-Abelian theory is outlined. {copyright} {ital 1996 The American Physical Society.}
Field effect in the quantum Hall regime of a high mobility graphene wire
Barraud, C., E-mail: cbarraud@phys.ethz.ch, E-mail: clement.barraud@univ-paris-diderot.fr; Choi, T.; Ihn, T.; Ensslin, K. [Solid State Physics Laboratory, ETH Zrich, CH-8093 Zrich (Switzerland); Butti, P.; Shorubalko, I. [Swiss Federal Laboratories of Materials Science and Technologies, EMPA Elect. Metrol. Reliabil. Lab., CH-8600 Dbendorf (Switzerland); Taniguchi, T.; Watanabe, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)
2014-08-21
In graphene-based electronic devices like in transistors, the field effect applied thanks to a gate electrode allows tuning the charge density in the graphene layer and passing continuously from the electron to the hole doped regime across the Dirac point. Homogeneous doping is crucial to understand electrical measurements and for the operation of future graphene-based electronic devices. However, recently theoretical and experimental studies highlighted the role of the electrostatic edge due to fringing electrostatic field lines at the graphene edges [P. Silvestrov and K. Efetov, Phys. Rev. B 77, 155436 (2008); F. T. Vasko and I. V. Zozoulenko, Appl. Phys. Lett. 97, 092115 (2010)]. This effect originates from the particular geometric design of the samples. A direct consequence is a charge accumulation at the graphene edges giving a value for the density, which deviates from the simple picture of a plate capacitor and also varies along the width of the graphene sample. Entering the quantum Hall regime would, in principle, allow probing this accumulation thanks to the extreme sensitivity of this quantum effect to charge density and the charge distribution. Moreover, the presence of an additional and counter-propagating edge channel has been predicted [P. Silvestrov and K. Efetov, Phys. Rev. B 77, 155436 (2008)] giving a fundamental aspect to this technological issue. In this article, we investigate this effect by tuning a high mobility graphene wire into the quantum Hall regime in which charge carriers probe the electrostatic potential at high magnetic field close to the edges. We observe a slight deviation to the linear shift of the quantum Hall plateaus with magnetic field and we study its evolution for different filling factors, which correspond to different probed regions in real space. We discuss the possible origins of this effect including an increase of the charge density towards the edges.
Das, Mukunda P.; Golden, Kenneth I.; Green, Frederick
2001-10-01
We study the problem of dynamical response and plasma mode dispersion in strongly coupled two-dimensional Coulomb fluids (2DCFs) in the weakly degenerate quantum domain. Adapting the nonlinear response function approach of Golden and Kalman [Phys. Rev. A 19, 2112 (1979)] to the 2DCF, we construct a self-consistent approximation scheme for the calculation of the density response functions and plasma mode dispersion at long wavelengths. The basic ingredients in the construction are (i) the first kinetic equation in the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, (ii) the velocity-average-approximation (VAA) hypothesis, (iii) the quadratic fluctuation-dissipation theorem, and (iv) the dynamical superposition approximation (DSA) closure hypothesis. The reliability of the VAA-DSA theory can be assessed by observing that the principal coupling correction to the 2D temperature-dependent Lindhard function is identified as being precisely the part of the third-frequency-moment sum-rule coefficient proportional to the potential energy.
Reliability of the Optimized Perturbation Theory for scalar fields at finite temperature
Farias, R. L.; Teixeira, D. L. Jr.; Ramos, R. O.
2013-03-25
The thermodynamics of a massless scalar field with a quartic interaction is studied up to third order in the Optimized Perturbation Theory (OPT) method. A comparison with other nonperturbative approaches is performed such that the reliability of OPT is accessed.
Physical meaning of gauge and super-gauge in general-relativistic field theories
Treder, H.
1985-05-01
The physical meaning of gauge groups in bimetrical, Riemannian, and Hermitian theories of gravitation is discussed. In Hermitian relativity, Einstein's A-invariance means a super-gauge group which characterizes the Einstein-Schroedinger equations as the only nondegenerate general-relativistic field theory.
Entanglement, avoided crossings, and quantum chaos in an Ising model with a tilted magnetic field
Karthik, J.; Sharma, Auditya; Lakshminarayan, Arul [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)
2007-02-15
We study a one-dimensional Ising model with a magnetic field and show that tilting the field induces a transition to quantum chaos. We explore the stationary states of this Hamiltonian to show the intimate connection between entanglement and avoided crossings. In general, entanglement gets exchanged between the states undergoing an avoided crossing with an overall enhancement of multipartite entanglement at the closest point of approach, simultaneously accompanied by diminishing two-body entanglement as measured by concurrence. We find that both for stationary as well as nonstationary states, nonintegrability leads to a destruction of two-body correlations and distributes entanglement more globally.
Magnetic field induced quantum phase transitions in the two-impurity Anderson model
Zhu, Lujun; Zhu, Jian - Xin
2010-11-17
In the two-impurity Anderson model, the inter-impurity spin exchange interaction favors a spin singlet state between two impurities leading to the localization of quasiparticles. We show that a local uniform magnetic field can delocalize the quasiparticies to restore the Kondo resonance. This transition is found to be continuous, accompanied by not only the divergence of the staggered (anti ferromagnetic) susceptibility, but also the divergence of the uniform spin susceptibility. This implies that the magnetic field induced quantum phase transitions in Kondo systems are in favor of the local critical type.
DOE Science Showcase - Effective field theories | OSTI, US Dept of Energy,
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Office of Scientific and Technical Information Effective field theories Effective field theories (EFTs) are types of approximations that contain the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale, while ignoring the substructure and the degrees of freedom at shorter distances or higher energies. The EFT method of approximation is widely used to analyze a myriad of phenomena in many different areas of high-energy physics, from the low-energy
Spinor matter in a particular 5-dimensional projective unified field theory
Schmutzer, E.
1985-05-01
After presenting the foundation and the basic equations of a new 5-dimensional projective unified field theory, the problem of incorporating spinor fields into this framework is investigated. Apart from Paulis method, we propose a new approach which leads to a consistent 5-dimensional spinor theory with a series of physical consequences (variability of the 4-dimensional ''rest mass,'' instability of 4-dimensional ''stationary states,'' etc.).
Auerbach, J.M.; Eimerl, D.; Milam, D.; Milonni, P.W.
1997-01-01
A theory is presented for the transfer of a perturbation of the electric field from the input to the output of a frequency converter. The transfer relationship for the field ripple is shown to depend on the plane-wave operating parameters of the converter. Predictions of the theory are shown to be in excellent agreement with full numerical simulations of doubling and tripling and experiments measuring ripple transfer in frequency doubling. {copyright} 1997 Optical Society of America
The one-loop matter bispectrum in the Effective Field Theory of Large Scale
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Structures (Journal Article) | SciTech Connect The one-loop matter bispectrum in the Effective Field Theory of Large Scale Structures Citation Details In-Document Search Title: The one-loop matter bispectrum in the Effective Field Theory of Large Scale Structures Authors: Angulo, Raul E. ; Foreman, Simon ; Schmittfull, Marcel ; Senatore, Leonardo Publication Date: 2015-10-01 OSTI Identifier: 1244649 DOE Contract Number: AC02-76SF00515 Resource Type: Journal Article Resource Relation: Journal
Dark matter effective field theory scattering in direct detection experiments
Schneck, K.; Cabrera, B.; Cerdeno, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Brandt, D.; Brink, P. L.; Bunker, R.; Caldwell, D. O.; Calkins, R.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, Priscilla B.; Daal, M.; Di Stefano, P. C.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, Jeter C.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D. M.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, W.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Saab, T.; Sadoulet, B.; Sander, J.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yang, X.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.
2015-05-01
We examine the consequences of the effective eld theory (EFT) of dark matter-nucleon scattering or current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral di*erences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.
Theory of multiphoton and tunnel ionization in a bichromatic field
Bagulov, D. S.; Kotelnikov, I. A.
2013-01-15
The imaginary-time method [6, 7] is used to calculate the multiphoton and tunnel ionization probabilities for atoms in a laser radiation field part of which is converted into the second harmonic. We assume that the first harmonic has a linear or elliptical polarization and the second harmonic is polarized linearly, with its polarization vector making an arbitrary angle with that of the first harmonic. The mean momentum of the photoelectrons knocked out from atoms is shown to depend on the phase shift between the first and second harmonics and their mutual polarization and to be identically equal to zero for a monochromatic field. An important difference between the case of elliptical polarization and the case of linear polarization of both harmonics is the absence of conditions under which the conditions for dominance of one of the two generation mechanisms considered here can be identified during the generation of terahertz radiation from the region of optical breakdown in a gas.
Kondo-type transport through a quantum dot under magnetic fields
Dong, Bing; Lei, X. L.
2001-06-15
In this paper, we investigate the Kondo correlation effects on linear and nonlinear transport in a quantum dot connected to reservoirs under finite magnetic fields, using the slave-boson mean field approach suggested by Kotliar and Ruckenstein [Phys. Rev. Lett. >57, 1362 (1986)]. A brief comparison between the present formulation and other slave-boson formulation is presented to justify this approach. The numerical results show that the linear conductance near electron-hole symmetry is suppressed by the application of the magnetic fields, but an anomalous enhancement is predicted in the nonsymmetry regime. The effect of external magnetic fields on the nonlinear differential conductances is discussed for the Kondo system. A significant reduction of the peak splitting is observed due to the strong Kondo correlation, which agrees well with experimental data.
Quantum nonlocal effects on optical properties of spherical nanoparticles
Moradi, Afshin
2015-02-15
To study the scattering of electromagnetic radiation by a spherical metallic nanoparticle with quantum spatial dispersion, we develop the standard nonlocal Mie theory by allowing for the excitation of the quantum longitudinal plasmon modes. To describe the quantum nonlocal effects, we use the quantum longitudinal dielectric function of the system. As in the standard Mie theory, the electromagnetic fields are expanded in terms of spherical vector wavefunctions. Then, the usual Maxwell boundary conditions are imposed plus the appropriate additional boundary conditions. Examples of calculated extinction spectra are presented, and it is found that the frequencies of the subsidiary peaks, due to quantum bulk plasmon excitations exhibit strong dependence on the quantum spatial dispersion.
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Amaral, Jose Jussi; Wan, Jacky; Rodarte, Andrea L.; Ferri, Christopher; Quint, Makiko T.; Pandolfi, Ronald J.; Scheibner, Michael; Hirst, Linda S.; Ghosh, Sayantani
2014-10-22
The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce ‘meta-materials’ has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small appliedmore » magnetic field (<100 mT). This magnetic field-driven brightening, ranging between a two- to three-fold peak intensity increase, is a truly cooperative effect: the LC phase transition creates the co-assemblies, the clustering of the MNPs produces LC re-orientation at atypical low external field, and this re-arrangement produces compaction of the clusters, resulting in the detection of increased QD emission. These results demonstrate a synergistic, reversible, and an all-optical process to detect magnetic fields and additionally, as the clusters are self-assembled in a fluid medium, they offer the possibility for these sensors to be used in broad ranging fluid-based applications.« less
Amaral, Jose Jussi; Wan, Jacky; Rodarte, Andrea L.; Ferri, Christopher; Quint, Makiko T.; Pandolfi, Ronald J.; Scheibner, Michael; Hirst, Linda S.; Ghosh, Sayantani
2014-10-22
The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce meta-materials has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small applied magnetic field (<100 mT). This magnetic field-driven brightening, ranging between a two- to three-fold peak intensity increase, is a truly cooperative effect: the LC phase transition creates the co-assemblies, the clustering of the MNPs produces LC re-orientation at atypical low external field, and this re-arrangement produces compaction of the clusters, resulting in the detection of increased QD emission. These results demonstrate a synergistic, reversible, and an all-optical process to detect magnetic fields and additionally, as the clusters are self-assembled in a fluid medium, they offer the possibility for these sensors to be used in broad ranging fluid-based applications.
Photodissociation in quantum chaotic systems: Random-matrix theory of cross-section fluctuations
Fyodorov, Y.V. [Fachbereich Physik, Universitaet-GH Essen, D-45117 Essen (Germany)] [Fachbereich Physik, Universitaet-GH Essen, D-45117 Essen (Germany); Alhassid, Y. [Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520 (United States)] [Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520 (United States)
1998-11-01
Using the random matrix description of open quantum chaotic systems we calculate in closed form the universal autocorrelation function and the probability distribution of the total photodissociation cross section in the regime of quantum chaos. {copyright} {ital 1998} {ital The American Physical Society}
Robustness of fractional quantum Hall states with dipolar atoms in artificial gauge fields
Grass, T.; Baranov, M. A.; Lewenstein, M.
2011-10-15
The robustness of fractional quantum Hall states is measured as the energy gap separating the Laughlin ground state from excitations. Using thermodynamic approximations for the correlation functions of the Laughlin state and the quasihole state, we evaluate the gap in a two-dimensional system of dipolar atoms exposed to an artificial gauge field. For Abelian fields, our results agree well with the results of exact diagonalization for small systems but indicate that the large value of the gap predicted [Phys. Rev. Lett. 94, 070404 (2005)] was overestimated. However, we are able to show that the small gap found in the Abelian scenario dramatically increases if we turn to non-Abelian fields squeezing the Landau levels.
AC transport in p-Ge/GeSi quantum well in high magnetic fields
Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.; Golub, L. E.; Tarasenko, S. A.; Suslov, A. V.; Mironov, O. A.; Kummer, M.; Känel, H. von
2014-08-20
The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shown that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.
Marunovic, Anja; Prokopec, Tomislav
2011-05-15
We calculate the one-loop graviton vacuum polarization induced by a massless, nonminimally coupled scalar field on Minkowski background. We make use of the Schwinger-Keldysh formalism, which allows us to study time dependent phenomena. As an application we compute the leading quantum correction to the Newtonian potential of a point particle. The novel aspect of the calculation is the use of the Schwinger-Keldysh formalism, within which we calculate the time transients induced by switching on the graviton-scalar coupling.
Naquin, Clint; Lee, Mark; Edwards, Hal; Mathur, Guru; Chatterjee, Tathagata; Maggio, Ken
2014-11-24
Introducing explicit quantum transport into Si transistors in a manner amenable to industrial fabrication has proven challenging. Hybrid field-effect/bipolar Si transistors fabricated on an industrial 45 nm process line are shown to demonstrate explicit quantum transport signatures. These transistors incorporate a lateral ion implantation-defined quantum well (QW) whose potential depth is controlled by a gate voltage (V{sub G}). Quantum transport in the form of negative differential transconductance (NDTC) is observed to temperatures >200 K. The NDTC is tied to a non-monotonic dependence of bipolar current gain on V{sub G} that reduces drain-source current through the QW. These devices establish the feasibility of exploiting quantum transport to transform the performance horizons of Si devices fabricated in an industrially scalable manner.
Tokman, M. D. [Institute of Applied Physics, RAS, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation)
2009-05-15
We discuss specific features of the electrodynamic characteristics of quantum systems within the framework of models that include a phenomenological description of the relaxation processes. As is shown by W. E. Lamb, Jr., R. R. Schlicher, and M. O. Scully [Phys. Rev. A 36, 2763 (1987)], the use of phenomenological relaxation operators, which adequately describe the attenuation of eigenvibrations of a quantum system, may lead to incorrect solutions in the presence of external electromagnetic fields determined by the vector potential for different resonance processes. This incorrectness can be eliminated by giving a gauge-invariant form to the relaxation operator. Lamb, Jr., et al. proposed the corresponding gauge-invariant modification for the Weisskopf-Wigner relaxation operator, which is introduced directly into the Schroedinger equation within the framework of the two-level approximation. In the present paper, this problem is studied for the von Neumann equation supplemented by a relaxation operator. First, we show that the solution of the equation for the density matrix with the relaxation operator correctly obtained ''from the first principles'' has properties that ensure gauge invariance for the observables. Second, we propose a common recipe for transformation of the phenomenological relaxation operator into the correct (gauge-invariant) form in the density-matrix equations for a multilevel system. Also, we discuss the methods of elimination of other inaccuracies (not related to the gauge-invariance problem) which arise if the electrodynamic response of a dissipative quantum system is calculated within the framework of simplified relaxation models (first of all, the model corresponding to constant relaxation rates of coherences in quantum transitions). Examples illustrating the correctness of the results obtained within the framework of the proposed methods in contrast to inaccuracy of the results of the standard calculation techniques are given.
Kushwaha, Manvir S.
2014-12-15
Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen to be forbidden. The spherical quantum dots have an edge over the strictly two-dimensional quantum dots in that the additional (magnetic) quantum number makes the physics richer (but complex). A deeper grasp of the Coulomb blockade, quantum coherence, and entanglement can lead to a better insight into promising applications involving lasers, detectors, storage devices, and quantum computing.
Unraveling the Structure of Hadrons with Effective Field Theories of QCD
Iain Stewart
2004-06-08
Effective Field theory is a powerful framework based on controlled expansions for problems with a natural separation of energy scales. This technique is particularly important for QCD, the theory of strong interactions, due to the vast diversity of phenomena that it describes. Stewart and collaborators have invented a new class of effective theories that can be used in processes with energetic hadrons. These Soft-Collinear Effective Theories provide a unified framework for describing hadronic processes which involve hard probes or the release of a large amount of energy. Many interesting issues about hadronic physics can be addressed with the soft-collinear effective theory. Examples include the size and shape of hadronic form factors, the universality of hadronic distribution functions for a plethora of processes, and the importance of subleading corrections at intermediate energy scales. Effective field theories allow these issues to be addressed using only the underlying symmetries and scales in QCD. Understanding these issues also has a direct impact on other areas of physics, such as on devising clean methods for the measurement of CP violation in the decay of B-mesons. Current progress on the soft-collinear effective theory and related methods is discussed in this report.
Elementary framework for cold field emission from quantum-confined, non-planar emitters
Patterson, A. A. Akinwande, A. I.
2015-05-07
For suitably small field emitters, the effects of quantum confinement at the emitter tip may have a significant impact on the emitter performance and total emitted current density (ECD). Since the geometry of a quantum system uniquely determines the magnitude and distribution of its energy levels, a framework for deriving ECD equations from cold field electron emitters of arbitrary geometry and dimensionality is developed. In the interest of obtaining semi-analytical ECD equations, the framework is recast in terms of plane wave solutions to the Schrdinger equation via the use of the Jeffreys-Wentzel-Kramers-Brillouin approximation. To demonstrate the framework's consistency with our previous work and its capabilities in treating emitters with non-planar geometries, ECD equations were derived for the normally unconfined cylindrical nanowire (CNW) and normally confined (NC) CNW emitter geometries. As a function of the emitter radius, the NC CNW emitter ECD profile displayed a strong dependence on the Fermi energy and had an average ECD that exceeded the Fowler-Nordheim equation for typical values of the Fermi energy due to closely spaced, singly degenerate energy levels (excluding electron spin), comparatively large electron supply values, and the lack of a transverse, zero-point energy. Such characteristics suggest that emitters with non-planar geometries may be ideal for emission from both an electron supply and electrostatics perspective.
Shot noise of charge current in a quantum dot responded by rotating and oscillating magnetic fields
Zhao, Hong-Kang Zou, Wei-Ke; Chen, Qiao
2014-09-07
We have investigated the shot noise and Fano factor of the dynamic spin-polarized quantum dot under the perturbations of a rotating magnetic field (RMF), and an oscillating magnetic field (OMF) by employing the non-equilibrium Green's function approach. The shot noise is enhanced from sub-Poissonian to super-Poissonian due to the application of RMF and OMF, and it is controlled sensitively by the tilt angle θ of RMF. The magnitude of shot noise increases as the photon energy ℏω of OMF increases, and its valley eventually is reversed to peaks as the photon energy is large enough. Double-peak structure of Fano factor is exhibited as the frequency of OMF increases to cover a large regime. The Zeeman energy μ{sub 0}B{sub 0} acts as an effective gate bias to exhibit resonant behavior, and novel peak emerges associated with the applied OMF.
Large-density field theory, viscosity, and '$2k_F$' singularities from
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string duals (Journal Article) | SciTech Connect Large-density field theory, viscosity, and '$2k_F$' singularities from string duals Citation Details In-Document Search Title: Large-density field theory, viscosity, and '$2k_F$' singularities from string duals Authors: Polchinski, Joseph ; /Santa Barbara, KITP ; Silverstein, Eva ; /Santa Barbara, KITP /Stanford U., Phys. Dept. /SLAC ; , Publication Date: 2013-10-28 OSTI Identifier: 1098113 Report Number(s): SLAC-PUB-14883 arXiv:1203.1015 DOE
Bruegger, C.; Kaempfer, F.; Wiese, U.-J.; Hofmann, C. P.; Pepe, M.
2007-01-01
Using the low-energy effective field theory for magnons and holes--the condensed matter analog of baryon chiral perturbation theory for pions and nucleons in QCD--we study different phases of doped antiferromagnets. We systematically investigate configurations of the staggered magnetization that provide a constant background field for doped holes. The most general configuration of this type is either constant itself or represents a spiral in the staggered magnetization. Depending on the values of the low-energy parameters, a homogeneous phase, a spiral phase, or an inhomogeneous phase is energetically favored. The reduction of the staggered magnetization upon doping is also investigated.
Combined local-density and dynamical mean field theory calculations for the
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compressed lanthanides Ce, Pr, and Nd (Journal Article) | SciTech Connect Journal Article: Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd Citation Details In-Document Search Title: Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd This paper reports calculations for compressed Ce (4f{sup 1}), Pr (4f{sup 2}), and Nd (4f{sup 3}) using a combination of the
Weakly interacting two-dimensional system of dipoles: Limitations of the mean-field theory
Astrakharchik, G. E.; Boronat, J.; Casulleras, J.; Kurbakov, I. L.; Lozovik, Yu. E.
2007-06-15
We consider a homogeneous two-dimensional Bose gas with repulsive dipole-dipole interactions. The ground-state equation of state, calculated using the diffusion Monte Carlo method, shows quantitative differences from the predictions of the commonly used Gross-Pitaevskii mean-field theory. The static structure factor, pair distribution function, and condensate fraction are calculated in a wide range of the gas parameter. Differences from mean-field theory are reflected in the frequency of the lowest ''breathing'' mode for harmonically trapped systems.
Theory of weak scattering of stochastic electromagnetic fields from deterministic and random media
Tong Zhisong; Korotkova, Olga
2010-09-15
The theory of scattering of scalar stochastic fields from deterministic and random media is generalized to the electromagnetic domain under the first-order Born approximation. The analysis allows for determining the changes in spectrum, coherence, and polarization of electromagnetic fields produced on their propagation from the source to the scattering volume, interaction with the scatterer, and propagation from the scatterer to the far field. An example of scattering of a field produced by a {delta}-correlated partially polarized source and scattered from a {delta}-correlated medium is provided.
Mueller, B.
1993-05-15
This report discusses research in the following topics: Hadron structure physics; relativistic heavy ion collisions; finite- temperature QCD; real-time lattice gauge theory; and studies in quantum field theory.
Lattice Quantum Chromodynamics
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Lattice Quantum Chromodynamics Lattice Quantum Chromodynamics QCD-BU.jpg Key Challenges: Although the QCD theory has been extensively tested at at high energies, at low energies or...
Strong field effects on binary systems in Einstein-aether theory
Foster, Brendan Z.
2007-10-15
'Einstein-aether' theory is a generally covariant theory of gravity containing a dynamical preferred frame. This article continues an examination of effects on the motion of binary pulsar systems in this theory, by incorporating effects due to strong fields in the vicinity of neutron star pulsars. These effects are included through an effective approach, by treating the compact bodies as point particles with nonstandard, velocity dependent interactions parametrized by dimensionless sensitivities. Effective post-Newtonian equations of motion for the bodies and the radiation damping rate are determined. More work is needed to calculate values of the sensitivities for a given fluid source; therefore, precise constraints on the theory's coupling constants cannot yet be stated. It is shown, however, that strong field effects will be negligible given current observational uncertainties if the dimensionless couplings are less than roughly 0.1 and two conditions that match the PPN parameters to those of pure general relativity are imposed. In this case, weak field results suffice. There then exists a one-parameter family of Einstein-aether theories with 'small-enough' couplings that passes all current observational tests. No conclusion can be reached for larger couplings until the sensitivities for a given source can be calculated.
Field theory and weak Euler-Lagrange equation for classical particle-field systems
Qin, Hong; Burby, Joshua W; Davidson, Ronald C
2014-10-01
It is commonly believed that energy-momentum conservation is the result of space-time symmetry. However, for classical particle-field systems, e.g., Klimontovich-Maxwell and Klimontovich- Poisson systems, such a connection hasn't been formally established. The difficulty is due to the fact that particles and the electromagnetic fields reside on different manifolds. To establish the connection, the standard Euler-Lagrange equation needs to be generalized to a weak form. Using this technique, energy-momentum conservation laws that are difficult to find otherwise can be systematically derived.
Coherent States and Spontaneous Symmetry Breaking in Light Front Scalar Field Theory
Vary, J.P.; Chakrabarti, D.; Harindranath, A.; Lloyd, R.; Martinovic, L.; Spence, J.R.; /Iowa State U.
2005-12-14
Recently developed nuclear many-body techniques provide novel results when applied to constituent quark models and to light-front scalar field theory. We show how spontaneous symmetry breaking arises and is consistent with a coherent state ansatz in a variational treatment. The kink and the kink-antikink topological features are identified and the onset of symmetry restoration is demonstrated.
Ions confined in spherical dielectric cavities modeled by a splitting field-theory
Lue, Leo; Linse, Per
2015-04-14
The properties of ions confined within spherical dielectric cavities are examined by a splitting field-theory and Monte Carlo simulations. Three types of cavities are considered: one possessing a uniform surface charge density, one with a uniform volume charge density, and one containing mobile ions. In all cases, mobile counterions are present within the dielectric sphere. The splitting theory is based on dividing the electrostatic interaction into long- and short-wavelength contributions and applying different approximations on the two contributions. The splitting theory works well for the case where the dielectric constant of the confining sphere is equal to or less than that of the medium external to the sphere. Nevertheless, by extending the theory with a virial expansion, the predictions are improved. However, when the dielectric constant of the confining sphere is greater than that of the medium outside the sphere, the splitting theory performs poorly, only qualitatively agreeing with the simulation data. In this case, the strong-coupling expansion does not seem to work well, and a modified mean-field theory where the counterions interact directly with only their own image charge gives improved predictions. The splitting theory works best for the system with a uniform surface charge density and worst for the system with a uniform volume charge density. Increasing the number of ions within the sphere, at a fixed radius, tends to increase the ion density near the surface of the sphere and leads to a depletion region in the sphere interior; however, varying the ion number does not lead to any qualitative changes in the performance of the splitting theory.
Kitaev models based on unitary quantum groupoids
Chang, Liang, E-mail: liangchang@math.tamu.edu [Department of Mathematics, Texas A and M University, College Station, Texas 77843-3368 (United States)] [Department of Mathematics, Texas A and M University, College Station, Texas 77843-3368 (United States)
2014-04-15
We establish a generalization of Kitaev models based on unitary quantum groupoids. In particular, when inputting a Kitaev-Kong quantum groupoid H{sub C}, we show that the ground state manifold of the generalized model is canonically isomorphic to that of the Levin-Wen model based on a unitary fusion category C. Therefore, the generalized Kitaev models provide realizations of the target space of the Turaev-Viro topological quantum field theory based on C.
Realising effective theories of tribrid inflation: are there effects from messenger fields?
Antusch, Stefan; Nolde, David
2015-09-22
Tribrid inflation is a variant of supersymmetric hybrid inflation in which the inflaton is a matter field (which can be charged under gauge symmetries) and inflation ends by a GUT-scale phase transition of a waterfall field. These features make tribrid inflation a promising framework for realising inflation with particularly close connections to particle physics. Superpotentials of tribrid inflation involve effective operators suppressed by some cutoff scale, which is often taken as the Planck scale. However, these operators may also be generated by integrating out messenger superfields with masses below the Planck scale, which is in fact quite common in GUT and/or flavour models. The values of the inflaton field during inflation can then lie above this mass scale, which means that for reliably calculating the model predictions one has to go beyond the effective theory description. We therefore discuss realisations of effective theories of tribrid inflation and specify in which cases effects from the messenger fields are expected, and under which conditions they can safely be neglected. In particular, we point out how to construct realisations where, despite the fact that the inflaton field values are above the messenger mass scale, the predictions for the observables are (to a good approximation) identical to the ones calculated in the effective theory treatment where the messenger mass scale is identified with the (apparent) cutoff scale.
The quantum equations of state of plasma under the influence of a weak magnetic field
Hussein, N. A.; Eisa, D. A.; Eldin, M. G.
2012-05-15
The aim of this paper is to calculate the magnetic quantum equations of state of plasma, the calculation is based on the magnetic binary Slater sum in the case of low density. We consider only the thermal equilibrium plasma in the case of n{lambda}{sub ab}{sup 3} Much-Less-Than 1, where {lambda}{sub ab}{sup 2}=( Planck-Constant-Over-Two-Pi {sup 2}/m{sub ab}KT) is the thermal De Broglie wave length between two particles. The formulas contain the contributions of the magnetic field effects. Using these results we compute the magnetization and the magnetic susceptibility. Our equation of state is compared with others.
The conformal window of deformed conformal field theories in the planar limit
Vecchi, Luca
2010-08-15
We discuss in the planar approximation the effect of double-trace deformations on conformal field theories. We show that this large class of models posses a conformal window describing a nontrivial flow between two fixed points of the renormalization group and reveal the presence of a resonance which we associate to the remnant of a dilaton pole. As the conformal window shrinks to zero measure, the theory undergoes a conformal phase transition separating a symmetric from a nonsymmetric phase. The recently conjectured strongly coupled branch of nonsupersymmetric, non-Abelian gauge theories with a large number of flavors is analyzed in light of these results, and a model for the strong branch is proposed. Some phenomenological implications in the context of unparticle physics are also emphasized.
Quantum work statistics of charged Dirac particles in time-dependent fields
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Deffner, Sebastian; Saxena, Avadh
2015-09-28
The quantum Jarzynski equality is an important theorem of modern quantum thermodynamics. We show that the Jarzynski equality readily generalizes to relativistic quantum mechanics described by the Dirac equation. After establishing the conceptual framework we solve a pedagogical, yet experimentally relevant, system analytically. As a main result we obtain the exact quantum work distributions for charged particles traveling through a time-dependent vector potential evolving under Schrödinger as well as under Dirac dynamics, and for which the Jarzynski equality is verified. Thus, special emphasis is put on the conceptual and technical subtleties arising from relativistic quantum mechanics.
Quantum work statistics of charged Dirac particles in time-dependent fields
Deffner, Sebastian; Saxena, Avadh
2015-09-28
The quantum Jarzynski equality is an important theorem of modern quantum thermodynamics. We show that the Jarzynski equality readily generalizes to relativistic quantum mechanics described by the Dirac equation. After establishing the conceptual framework we solve a pedagogical, yet experimentally relevant, system analytically. As a main result we obtain the exact quantum work distributions for charged particles traveling through a time-dependent vector potential evolving under Schrdinger as well as under Dirac dynamics, and for which the Jarzynski equality is verified. Thus, special emphasis is put on the conceptual and technical subtleties arising from relativistic quantum mechanics.
In the OSTI Collections: Effective Field Theories | OSTI, US Dept of
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Energy, Office of Scientific and Technical Information Effective Field Theories Dr. Watson computer sleuthing scientist. Article Acknowledgement: Dr. William N. Watson, Physicist DOE Office of Scientific and Technical Information Particles and nuclei Condensed matter Dark matter Cosmic inflation References Research Organizations Reports Available through OSTI's SciTech Connect Additional References Any set of objects will be attracted to each other by gravity. If the objects are electrically
Unified theory of exactly and quasiexactly solvable ''discrete'' quantum mechanics. I. Formalism
Odake, Satoru [Department of Physics, Shinshu University, Matsumoto 390-8621 (Japan); Sasaki, Ryu [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
2010-08-15
We present a simple recipe to construct exactly and quasiexactly solvable Hamiltonians in one-dimensional ''discrete'' quantum mechanics, in which the Schroedinger equation is a difference equation. It reproduces all the known ones whose eigenfunctions consist of the Askey scheme of hypergeometric orthogonal polynomials of a continuous or a discrete variable. The recipe also predicts several new ones. An essential role is played by the sinusoidal coordinate, which generates the closure relation and the Askey-Wilson algebra together with the Hamiltonian. The relationship between the closure relation and the Askey-Wilson algebra is clarified.
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Cotlet, Mircea; Huang, Yuan Zang; Chen, Jia -Shiang; Huidong Zang; Sutter, Eli A.; Sutter, Peter W.; Nam, Chang -Yong
2016-03-24
We report an improved photosensitivity in few-layer tin disulfide (SnS2) field-effect transistors(FETs) following doping with CdSe/ZnS core/shell quantum dots(QDs). The hybrid QD-SnS2 FET devices achieve more than 500% increase in the photocurrent response compared with the starting SnS2-only FET device and a spectral responsivity reaching over 650 A/W at 400 nm wavelength. The negligible electrical conductance in a control QD-only FET device suggests that the energy transfer between QDs and SnS2 is the main mechanism responsible for the sensitization effect, which is consistent with the strong spectral overlap between QDphotoluminescence and SnS2 optical absorption as well as the large nominalmore » donor-acceptor interspacing between QD core and SnS2. Furthermore, we also find enhanced charge carrier mobility in hybrid QD-SnS2 FETs which we attribute to a reduced contact Schottky barrier width due to an elevated background charge carrier density.« less
Charge state control in single InAs/GaAs quantum dots by external electric and magnetic fields
Tang, Jing; Cao, Shuo; Gao, Yunan; Sun, Yue; Jin, Kuijuan; Xu, Xiulai; Geng, Weidong; Williams, David A.
2014-07-28
We report a photoluminescence (PL) spectroscopy study of charge state control in single self-assembled InAs/GaAs quantum dots by applying electric and/or magnetic fields at 4.2?K. Neutral and charged exciton complexes were observed under applied bias voltages from ?0.5?V to 0.5?V by controlling the carrier tunneling. The highly negatively charged exciton emission becomes stronger with increasing pumping power, arising from the fact that electrons have a smaller effective mass than holes and are more easily captured by the quantum dots. The integrated PL intensity of negatively charged excitons is affected significantly by a magnetic field applied along the sample growth axis. This observation is explained by a reduction in the electron drift velocity caused by an applied magnetic field, which increases the probability of non-resonantly excited electrons being trapped by localized potentials at the wetting layer interface, and results in fewer electrons distributed in the quantum dots. The hole drift velocity is also affected by the magnetic field, but it is much weaker.
Noorian, Zainab; Eslami, Parvin; Javidan, Kurosh
2013-11-15
Interaction of a muon beam with hot dense QED plasma is investigated. Plasma system contains electrons and positrons with Fermi-Dirac distribution and Bose-Einstein distributed photons while the beam particles have nonthermal distribution. The energy loss of the beam particles during the interaction with plasma is calculated to complete leading order of interaction in terms of the QED coupling constant using thermal field theory approach. The screening effects of the plasma are computed consistently using resummation of perturbation theory with hard thermal loop approximation according to the Braaten-Pisarski method. Time evolution of the plasma characteristics and also plasma identifications during the interaction are investigated. Effects of the nonthermal parameter of the beam distribution on the energy exchange and the evolution of plasma-beam system are also explained.
Systematic low-energy effective field theory for electron-doped antiferromagnets
Bruegger, C.; Kaempfer, F.; Moser, M.; Wiese, U.-J.; Hofmann, C. P.; Pepe, M.
2007-06-01
In contrast to hole-doped systems which have hole pockets centered at ({+-}({pi}/2a),{+-}({pi}/2a)), in lightly electron-doped antiferromagnets the charged quasiparticles reside in momentum space pockets centered at (({pi}/a),0) or (0,({pi}/a)). This has important consequences for the corresponding low-energy effective field theory of magnons and electrons which is constructed in this paper. In particular, in contrast to the hole-doped case, the magnon-mediated forces between two electrons depend on the total momentum P-vector of the pair. For P-vector=0, the one-magnon exchange potential between two electrons at distance r is proportional to 1/r{sup 4}, while in the hole case, it has a 1/r{sup 2} dependence. The effective theory predicts that spiral phases are absent in electron-doped antiferromagnets.
Shafer, J.D.; Shepard, J.R.
1997-04-01
We derive an approximate renormalization group (RG) flow equation for the local effective potential of single-component {phi}{sup 4} field theory at finite temperature. Previous zero-temperature RG equations are recovered in the low- and high-temperature limits, in the latter case, via the phenomenon of dimensional reduction. We numerically solve our RG equations to obtain local effective potentials at finite temperature. These are found to be in excellent agreement with Monte Carlo results, especially when lattice artifacts are accounted for in the RG treatment. {copyright} {ital 1997} {ital The American Physical Society}
SCALING DEVIATIONS F O R NEUTRINO REACTIONS IN AYSMPTOTICALLY FREE FIELD THEORIES*
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
SCALING DEVIATIONS F O R NEUTRINO REACTIONS IN AYSMPTOTICALLY FREE FIELD THEORIES* A. ZeeYt F, Wilczek and S. B. Treiman /- / N O T I C E This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United Stater Atomic Energy Commhaion, nor any of their employees, nor M Y of their contractors, rubeontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the
Manifestations of quantum phase transitions in transport through nanosystems
Pustilnik, Michael
2014-08-28
The award led to several important new results in theory of interacting low-dimensional systems. The results are relevant for both traditional condensed matter systems, such as quantum wires and quantum spin chains, and for the relatively new field of ultra-cold atomic gases.
Nonlinear quantum electrodynamics in vacuum and plasmas
Brodin, Gert; Lundin, Joakim; Marklund, Mattias
2010-12-14
We consider high field physics due to quantum electrodynamics, in particular those that can be studied in the next generation of laser facilities. Effective field theories based on the Euler-Heisenberg Lagrangian are briefly reviewed, and examples involving plasma- and vacuum physics are given.
The Lagrangian-space Effective Field Theory of large scale structures
Porto, Rafael A.; Zaldarriaga, Matias; Senatore, Leonardo E-mail: senatore@stanford.edu
2014-05-01
We introduce a Lagrangian-space Effective Field Theory (LEFT) formalism for the study of cosmological large scale structures. Unlike the previous Eulerian-space construction, it is naturally formulated as an effective field theory of extended objects in Lagrangian space. In LEFT the resulting finite size effects are described using a multipole expansion parameterized by a set of time dependent coefficients and organized in powers of the ratio of the wavenumber of interest k over the non-linear scale k{sub NL}. The multipoles encode the effects of the short distance modes on the long-wavelength universe and absorb UV divergences when present. There are no IR divergences in LEFT. Some of the parameters that control the perturbative approach are not assumed to be small and can be automatically resummed. We present an illustrative one-loop calculation for a power law universe. We describe the dynamics both at the level of the equations of motion and through an action formalism.
Leary, A.; Wicha, A.; Harack, B.; Coish, W. A.; Hilke, M.; Yu, G.; Gupta, J. A.; Payette, C.; Austing, D. G.
2013-12-04
We outline the properties of the hyperfine-induced funnel structure observed in the two-electron spin blockade region of a weakly coupled vertical double quantum dot device. Hysteretic steps in the leakage current occur due to dynamic nuclear polarization when either the bias voltage or the magnetic field is swept up and down. When the bias voltage is swept, an intriguing ?3 mT wide cusp near 0 T appears in the down-sweep position, and when the magnetic field is swept, the current at 0 T can be switched from 'low' to 'high' as the bias is increased.
Cyclotron resonance in InAs/AlSb quantum wells in magnetic fields up to 45 T
Spirin, K. E. Krishtopenko, S. S.; Sadofyev, Yu. G.; Drachenko, O.; Helm, M.; Teppe, F.; Knap, W.; Gavrilenko, V. I.
2015-12-15
Electron cyclotron resonance in InAs/AlSb heterostructures with quantum wells of various widths in pulsed magnetic fields up to 45 T are investigated. Our experimental cyclotron energies are in satisfactory agreement with the results of theoretical calculations performed using the eight-band kp Hamiltonian. The shift of the cyclotron resonance (CR) line, which corresponds to the transition from the lowest Landau level to the low magnetic-field region, is found upon varying the electron concentration due to the negative persistent photoconductivity effect. It is shown that the observed shift of the CR lines is associated with the finite width of the density of states at the Landau levels.
Hadronic decays of the X(3872) to {chi}{sub cJ} in effective field theory
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(Journal Article) | SciTech Connect Hadronic decays of the X(3872) to {chi}{sub cJ} in effective field theory Citation Details In-Document Search Title: Hadronic decays of the X(3872) to {chi}{sub cJ} in effective field theory The decays of the X(3872) to P-wave quarkonia are calculated under the assumption that it is a shallow bound state of neutral charmed mesons. The X(3872) is described using an effective theory of nonrelativistic D mesons and pions (X-EFT). We calculate X(3872) decays
Solitary waves in nonlinear Dirac equation. From field theory to Dirac materials
Saxena, Avadh
2015-11-02
This report describes the implementation of nonlinear Dirac equations in the calculation of solitary waves. Conclusions and comments on quantum elasticity are also included.
Shakouri, Kh.; Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Vasilopoulos, P.; Vargiamidis, V. [Department of Physics, Concordia University, 7141 Sherbrooke Ouest Montral, Qubec H4B 1R6 (Canada); Hai, G.-Q. [Instituto de Fisica de So Carlos, Universidade de So Paulo, So Carlos, SP 13560-970 (Brazil)
2014-05-26
We study the commensurability oscillations in silicene subject to a perpendicular electric field E{sub z}, a weak magnetic field B, and a weak periodic potential V=V{sub 0}cos(Cy),C=2?/a{sub 0} with a{sub 0} its period. The field E{sub z} and/or the modulation lift the spin degeneracy of the Landau levels and lead to spin and valley resolved Weiss oscillations. The spin resolution is maximal when the field E{sub z} is replaced by a periodic one E{sub z}=E{sub 0}cos(Dy),D=2?/b{sub 0}, while the valley one is maximal for b{sub 0}?=?a{sub 0}. In certain ranges of B values, the current is fully spin or valley polarized. Additional quantum Hall conductivity plateaux arise due to spin and valley intra-Landau-level transitions.
Two-leg SU(2n) spin ladder: A low-energy effective field theory approach
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lecheminant, P.; Tsvelik, A. M.
2015-05-07
We present a field-theory analysis of a model of two SU(2n)-invariant magnetic chains coupled by a generic interaction preserving time reversal and inversion symmetry. Contrary to the SU(2)-invariant case the zero-temperature phase diagram of such two-leg spin ladder does not contain topological phases. Thus, only generalized Valence Bond Solid phases are stabilized when n > 1 with different wave vectors and ground-state degeneracies. In particular, we find a phase which is made of a cluster of 2n spins put in an SU(2n) singlet state. For n = 3, this cluster phase is relevant to ¹⁷³Yb ultracold atoms, with an emergentmore » SU(6) symmetry, loaded in a double-well optical lattice.« less
${{\\bar{d}} - {\\bar{u}}}$ Flavor Asymmetry in the Proton in Chiral Effective Field Theory
Salamu, Y.; Ji, Cheung-Ryong; Melnitchouk, Wally; Wang, P.
2015-09-01
The ${\\bar d - \\bar u}$ flavor asymmetry in the proton arising from pion loops is computed using chiral effective field theory. The calculation includes both nucleon and ? intermediate states, and uses both the fully relativistic and heavy baryon frameworks. The x dependence of ${\\bar d - \\bar u}$ extracted from the Fermilab E866 DrellYan data can be well reproduced in terms of a single transverse momentum cutoff parameter regulating the ultraviolet behavior of the loop integrals. In addition to the distribution at x > 0, corrections to the integrated asymmetry from zero momentum contributions are computed, which arise from pion rainbow and bubble diagrams at x = 0. These have not been accounted for in previous analyses, and can make important contributions to the lowest moment of ${\\bar d-\\bar u}$ .
Sudarshan, E.C.G.; Ne'eman, Y.
1980-01-01
A qualitative description is given of research in the following areas: particle physics in relativistic astrophysics and cosmology; phenomenology of weak and electromagnetic interactions; strong interaction physics and quark-parton physics; quantum mechanics, quantum field theory, and fundamental problems; and groups, gauges, and grand unified theories. Reports on this work have already been published, or will be, when it is completed. (RWR)
Improved convergence of chiral effective field theory for {sup 1}S{sub 0} of NN scattering
Long, Bingwei
2013-07-01
It is argued that the fine-tuning due to the unnaturally large, generalized effective range in the {sup 1}S{sub 0} channel of NN scattering must be incorporated in order for one to obtain satisfactory convergence for chiral effective field theory. Without the proposition of perturbative one-pion exchange, an effective field theory with the spin-0, isospin-1 dibaryon is developed to account for this fine-tuning, and is demonstrated up to O(Q) where the leading irreducible two-pion exchange arises. The approach shown in the paper results in rapid convergence of the {sup 1}S{sub 0} partial-wave amplitude.
Guan, Chun; Xing, Yunhui; Zhang, Chao; Ma, Zhongshui
2014-08-14
Due to quantum interference, light can transmit through dense atomic media, a phenomenon known as electromagnetically induced transparency (EIT). We propose that EIT is not limited to light transmission and there is an electronic analog where resonant transparency in charge transport in an opaque structure can be induced by electromagnetic radiation. A triple-quantum-dots system with Λ-type level structure is generally opaque due to the level in the center dot being significantly higher and therefore hopping from the left dot to the center dot is almost forbidden. We demonstrate that an electromagnetically induced electron transparency (EIET) in charge of transport can indeed occur in the Λ-type system. The direct evidence of EIET is that an electron can travel from the left dot to the right dot, while the center dot apparently becomes invisible. We analyze EIET and the related shot noise in both the zero and strong Coulomb blockade regimes. It is found that the EIET (position, height, and symmetry) can be tuned by several controllable parameters of the radiation fields, such as the Rabi frequencies and detuning frequencies. The result offers a transparency/opaque tuning technique in charge transport using interfering radiation fields.
Investigation of possible observable e ects in a proposed theory of physics
Freidan, Daniel
2015-03-31
The work supported by this grant produced rigorous mathematical results on what is possible in quantum field theory. Quantum field theory is the well-established mathematical language for fundamental particle physics, for critical phenomena in condensed matter physics, and for Physical Mathematics (the numerous branches of Mathematics that have benefitted from ideas, constructions, and conjectures imported from Theoretical Physics). Proving rigorous constraints on what is possible in quantum field theories thus guides the field, puts actual constraints on what is physically possible in physical or mathematical systems described by quantum field theories, and saves the community the effort of trying to do what is proved impossible. Results were obtained in two dimensional qft (describing, e.g., quantum circuits) and in higher dimensional qft. Rigorous bounds were derived on basic quantities in 2d conformal field theories, i.e., in 2d critical phenomena. Conformal field theories are the basic objects in quantum field theory, the scale invariant theories describing renormalization group fixed points from which all qfts flow. The first known lower bounds on the 2d boundary entropy were found. This is the entropy- information content- in junctions in critical quantum circuits. For dimensions d > 2, a no-go theorem was proved on the possibilities of Cauchy fields, which are the analogs of the holomorphic fields in d = 2 dimensions, which have had enormously useful applications in Physics and Mathematics over the last four decades. This closed o the possibility of finding analogously rich theories in dimensions above 2. The work of two postdoctoral research fellows was partially supported by this grant. Both have gone on to tenure track positions.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Benioff, Paul
2009-01-01
Tmore » his work is based on the field of reference frames based on quantum representations of real and complex numbers described in other work. Here frame domains are expanded to include space and time lattices. Strings of qukits are described as hybrid systems as they are both mathematical and physical systems. As mathematical systems they represent numbers. As physical systems in each frame the strings have a discrete Schrodinger dynamics on the lattices.he frame field has an iterative structure such that the contents of a stage j frame have images in a stage j - 1 (parent) frame. A discussion of parent frame images includes the proposal that points of stage j frame lattices have images as hybrid systems in parent frames.he resulting association of energy with images of lattice point locations, as hybrid systems states, is discussed. Representations and images of other physical systems in the different frames are also described.« less
Ensslin, Torsten A.; Frommert, Mona [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany)
2011-05-15
The optimal reconstruction of cosmic metric perturbations and other signals requires knowledge of their power spectra and other parameters. If these are not known a priori, they have to be measured simultaneously from the same data used for the signal reconstruction. We formulate the general problem of signal inference in the presence of unknown parameters within the framework of information field theory. To solve this, we develop a generic parameter-uncertainty renormalized estimation (PURE) technique. As a concrete application, we address the problem of reconstructing Gaussian signals with unknown power-spectrum with five different approaches: (i) separate maximum-a-posteriori power-spectrum measurement and subsequent reconstruction, (ii) maximum-a-posteriori reconstruction with marginalized power-spectrum, (iii) maximizing the joint posterior of signal and spectrum, (iv) guessing the spectrum from the variance in the Wiener-filter map, and (v) renormalization flow analysis of the field-theoretical problem providing the PURE filter. In all cases, the reconstruction can be described or approximated as Wiener-filter operations with assumed signal spectra derived from the data according to the same recipe, but with differing coefficients. All of these filters, except the renormalized one, exhibit a perception threshold in case of a Jeffreys prior for the unknown spectrum. Data modes with variance below this threshold do not affect the signal reconstruction at all. Filter (iv) seems to be similar to the so-called Karhune-Loeve and Feldman-Kaiser-Peacock estimators for galaxy power spectra used in cosmology, which therefore should also exhibit a marginal perception threshold if correctly implemented. We present statistical performance tests and show that the PURE filter is superior to the others, especially if the post-Wiener-filter corrections are included or in case an additional scale-independent spectral smoothness prior can be adopted.
Electromagnetic currents and magnetic moments in chiral effective field theory ({chi}EFT)
Pastore, S.; Girlanda, L.; Schiavilla, R.; Viviani, M.; Wiringa, R. B.
2009-09-15
A two-nucleon potential and consistent electromagnetic currents are derived in chiral effective field theory ({chi}EFT) at, respectively, Q{sup 2} (or N{sup 2}LO) and eQ (or N{sup 3}LO), where Q generically denotes the low-momentum scale and e is the electric charge. Dimensional regularization is used to renormalize the pion-loop corrections. A simple expression is derived for the magnetic dipole (M1) operator associated with pion loops, consisting of two terms, one of which is determined, uniquely, by the isospin-dependent part of the two-pion-exchange potential. This decomposition is also carried out for the M1 operator arising from contact currents, in which the unique term is determined by the contact potential. Finally, the low-energy constants entering the N{sup 2}LO potential are fixed by fits to the np S- and P-wave phase shifts up to 100 MeV laboratory energies.
Pop, N. Ilie, S.; Motapon, O.; Epée, M. D. Epée; Niyonzima, S.; Mezei, J. Zs.; Chakrabarti, K.; Schneider, I. F.
2014-11-24
The present work is aimed at performing the computation of cross sections and Maxwell rate coefficients in the framework of the stepwise version of the Multichannel Quantum Defect Theory (MQDT). Cross sections and rate coefficients suitable for the modelling of the kinetics of HD{sup +} and BeH{sup +} in fusion plasmas and in the stellar atmospheres are presented and discussed. A very good agreement is found between our results for rotational transitions for HD{sup +} and other computations, as well as with experiment.
Dynamics of ionisation and entanglement in the 'atom + quantum electromagnetic field' system
Sharapova, P R; Tikhonova, O V
2012-03-31
The dynamics of a model Rydberg atom in a strong nonclassical electromagnetic field is investigated. The field-induced transitions to the continuum involving different numbers of photons (with intermediate states in the discrete spectrum) are taken into account and the specific features of ionisation in 'squeezed' field states are considered in comparison with the case of classical light. A significant decrease in the ionisation rate is found, which is caused by the interference stabilisation of the atomic system. The entanglement of the atomic and field subsystems, the temporal dynamics of the correlations found, and the possibility of measuring them are analysed.
Crystal Field Disorder in the Quantum Spin Ice Ground State of Tb2Sn2 xTixO7
Gaulin, Bruce D.; Zhang, J.; Dahlberg, M. L.; Matthews, Maria J.; Bert, F.; Kermarrec, E.; Fritsch, Katharina; Granroth, Garrett E; Jiramongkolchai, P.; Amato, A.; Baines, C.; Cava, R. J.; Mendels, P.; Schiffer, P
2015-01-01
Spin ice physics marries that of hydrogen disorder in water ice, first discussed almost 60 years ago by Pauling, and that of low temperature magnetism on certain networks of connected tetrahedra. Recently the classical spin ice mag- nets Ho2Ti2O7 and Dy2Ti2O7 have shown an emergent artificial magneto- statics , which manifests itself as Coulombic spin correlations and excitations behaving as diffusive magnetic monopoles. The related pyrochlore magnet, Tb2Ti2O7, has been proposed as a quantum variant of spin ice, stabilized by 1 virtual excitations between the crystal field (CF) ground state doublet appro- priate to Tb3+, and its low lying excited state doublet. Isostructural Tb2Sn2O7 displays soft spin ice order, and its Tb3+ ground and excited CF eigenstates are known to differ relative to those of Tb2Ti2O7. We present a comprehensive study of Tb2Sn2 xTixO7 showing a novel, dynamic spin liquid state for all x other than the end members (0, 2). This state is the result of disorder in the low lying Tb3+ CF environments which de-stabilizes the mechanism by which quantum fluctuations contribute to ground state selection in Tb2Sn2 xTixO7.
Lincoln, Don
2014-10-24
The laws of quantum mechanics and relativity are quite perplexing however it is when the two theories are merged that things get really confusing. This combined theory predicts that empty space isnt empty at all its a seething and bubbling cauldron of matter and antimatter particles springing into existence before disappearing back into nothingness. Scientists call this complicated state of affairs quantum foam. In this video, Fermilabs Dr. Don Lincoln discusses this mind-bending idea and sketches some of the experiments that have convinced scientists that this crazy prediction is actually true.
Haeyrynen, Teppo; Oksanen, Jani; Tulkki, Jukka [Department of Biomedical Engineering and Computational Science, Aalto University School of Science and Technology, P. O. Box 12200, FI-00076 AALTO (Finland)
2011-01-15
We consider simultaneous dissipative and amplifying coupling of cavity fields to multiple two-state systems. We derive a master equation for optical field in a leaky cavity coupled to a reservoir through multiple two-state systems. In our previous works we have limited our study to systems where the reservoir either solely absorbs energy (detector setup) or adds energy (amplifying setup) to the cavity through a single two-state system. In this work we allow both interactions simultaneously and derive a reduced dynamic model for the optical field. We also generalize our model to cover the coupling of the field to several two state systems and discuss its connection to macroscopic interaction, e.g., in semiconductors. Our model includes four physical parameters: the field two-state system coupling {gamma}, the excitation and deexcitation couplings of the two-state system by the reservoir {lambda}{sub A} and {lambda}{sub D}, respectively, and the mirror losses of the cavity C. We solve the steady-state fields at different regimes of these physical parameters. Furthermore, we show that, depending on the parameters, our model can describe the operation of a detector, a light emitting diode, or a laser.
Chiral effective field theory analysis of hadronic parity violation in few-nucleon systems
Viviani, Michele; Baroni, Alessandro; Girlanda, Luca; Kievsky, Alejandro; Marcucci, Laura E.; Schiavilla, Rocco
2014-06-01
Background: Weak interactions between quarks induce a parity-violating (PV) component in the nucleonnucleon potential, whose effects are currently being studied in a number of experiments involving few-nucleon systems. In the present work, we reconsider the derivation of this PV component within a chiral effective field theory (chiEFT) framework. Purpose: The objectives of the present work are twofold. The first is to perform a detailed analysis of the PV nucleon-nucleon potential up to next-to-next-to-leading (N2LO) order in the chiral expansion, in particular, by determining the number of independent low-energy constants (LECs) at N2LO. The second objective is to investigate PV effects in a number of few-nucleon observables, including the #2; p-p longitudinal asymmetry, the neutron spin rotation in #2;n-p and #2;n-d scattering, and the longitudinal asymmetry in the {sup 3}He(#2;{vector n},p){sup 3}H chargeexchange reaction. Methods: The chiEFT PV potential includes one-pion-exchange, two-pion-exchange, and contact terms as well as 1/M (M being the nucleon mass) nonstatic corrections. Dimensional regularization is used to renormalize pion loops. The wave functions for the A = 2-4 nuclei are obtained by using strong two- and three-body potentials also derived, for consistency, from chiEFT. In the case of the A = 3-4 systems, the wave functions are computed by expanding on a hyperspherical harmonics functions basis. Results: We find that the PV potential at N2LO depends on six LECs: the pion-nucleon PV coupling constant h^1_pi and five parameters multiplying contact interactions. An estimate for the range of values of the various LECs is provided by using available experimental data, and these values are used to obtain predictions for the other PV observables. Conclusions: The chiEFT approach provides a very satisfactory framework to analyze PV effects in few-nucleon systems.
Generalised BRST symmetry and gaugeon formalism for perturbative quantum gravity: Novel observation
Upadhyay, Sudhaker
2014-05-15
In this paper the novel features of Yokoyama gaugeon formalism are stressed out for the theory of perturbative quantum gravity in the Einstein curved spacetime. The quantum gauge transformations for the theory of perturbative gravity are demonstrated in the framework of gaugeon formalism. These quantum gauge transformations lead to renormalised gauge parameter. Further, we analyse the BRST symmetric gaugeon formalism which embeds more acceptable KugoOjima subsidiary condition. Further, the BRST symmetry is made finite and field-dependent. Remarkably, the Jacobian of path integral under finite and field-dependent BRST symmetry amounts to the exact gaugeon action in the effective theory of perturbative quantum gravity. -- Highlights: We analyse the perturbative gravity in gaugeon formalism. The generalisation of BRST transformation is also studied in this context. Within the generalised BRST framework we found the exact gaugeon modes in the theory.
Gazit, D; Quaglioni, S; Navratil, P
2008-12-18
The chiral low-energy constants cD and cE are constrained by means of accurate ab initio calculations of the A = 3 binding energies and, for the first time, of the triton {beta} decay. We demonstrate that these low-energy observables allow a robust determination of the two undetermined constants. The consistency of the interactions and currents in chiral effective field theory is key to this remarkable result. The two- plus three-nucleon interactions from chiral effective field theory defined by properties of the A = 2 system and the present determination of c{sub D} and c{sub E} are successful in predicting properties of the A = 3, and 4 systems.
Mean-field analysis of quantum phase transitions in a periodic optical superlattice
Dhar, Arya; Singh, Manpreet; Pai, Ramesh V.; Das, B. P.
2011-09-15
We analyze the various phases exhibited by a system of ultracold bosons in a periodic optical superlattice using the mean-field decoupling approximation. We investigate for a wide range of commensurate and incommensurate densities. We find the gapless superfluid phase, the gapped Mott insulator phase, and gapped insulator phases with distinct density wave orders.
Electromagnetic field interactions with the human body: observed effects and theories
Raines, J.K.
1981-04-01
The effects of nonionizing electromagnetic (EM) field interactions with the human body were reported and human related studies were collected. Nonionizing EM fields are linked to cancer in humans in three different ways: cause, means of detection, and effective treatment. Bad and benign effects are expected from nonionizing EM fields and much more knowledge is necessary to properly categorize and qualify EM field characteristics. It is concluded that knowledge of the boundary between categories, largely dependent on field intensity, is vital to proper future use of EM radiation for any purpose and the protection of the individual from hazard.
Electrical resistivity as quantum chaos
Laughlin, R.B.
1987-08-01
The physics of quantum transport is re-examined as a problem in quantum chaos. It is proposed that the ''random potential'' in which electrons in dirty metals move is not random at all, but rather any potential inducing the electron motion to be chaotic. The Liapunov characteristic exponent of classical electron motion in this potential is identified with the collision rate l/tau appearing in Ohm's law. A field theory for chaotic systems, analogous to that used to describe dirty metals, is developed and used to investigate the quantum Sinai billiard problem. It is shown that a noninteracting degenerate electron gas moving in this potential exhibits Drude conductivity in the limit h-bar ..-->.. 0. 15 refs., 4 figs.
Quantum histories without contrary inferences
Losada, Marcelo; Laura, Roberto
2014-12-15
In the consistent histories formulation of quantum theory it was shown that it is possible to retrodict contrary properties. We show that this problem do not appear in our formalism of generalized contexts for quantum histories. - Highlights: We prove ordinary quantum mechanics has no contrary properties. Contrary properties in consistent histories are reviewed. We prove generalized contexts for quantum histories have no contrary properties.
Electromagnetic field interactions with the human body: observed effects and theories
Raines, J.K.
1981-04-01
The state of published knowledge about the effects of non-ionizing EM fields on humans is summarized. In addition to over 1000 written sources in-person meetings, telephone interviews and lecture tapes were used. It is indicated that there are good, bad and benign effects to be expected from non-ionizing EM fields and much more knowledge appears necessary to properly categorize and qualify EM field characteristics. Knowledge of the boundary between categories, perhaps largely dependent on field intensity, is vital to proper future use of EM radiaton for any purpose and the protection of the individual citizen from hazard.
Fan, Non Q.; Clarke, John
1993-01-01
A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced.
Fan, N.Q.; Clarke, J.
1993-10-19
A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced. 7 figures.
Berman, G.P. [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Bulgakov, E.N. [Kirensky Institute of Physics, 660036, Krasnoyarsk (Russia)] [Kirensky Institute of Physics, 660036, Krasnoyarsk (Russia); Campbell, D.K. [Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States)] [Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States); Krive, I.V. [Institute for Low Temperature Physics and Engineering, Ukrainian Academy of Sciences, 310164, Kharkov (Ukraine)] [Institute for Low Temperature Physics and Engineering, Ukrainian Academy of Sciences, 310164, Kharkov (Ukraine)
1997-10-01
We consider Aharonov-Bohm oscillations in a mesoscopic semiconductor ring threaded by both a constant magnetic flux and a time-dependent, resonant magnetic field with one or two frequencies. Working in the ballistic regime, we establish that the theory of {open_quotes}quantum nonlinear resonance{close_quotes} applies, and thus that this system represents a possible solid-state realization of {open_quotes}quantum nonlinear resonance{close_quotes} and {open_quotes}quantum chaos.{close_quotes} In particular, we investigate the behavior of the time-averaged electron energy at zero temperature in the regimes of (i) an isolated quantum nonlinear resonance and (ii) the transition to quantum chaos, when two quantum nonlinear resonances overlap. The time-averaged energy exhibits sharp resonant behavior as a function of the applied constant magnetic flux, and has a staircase dependence on the amplitude of the external time-dependent field. In the chaotic regime, the resonant behavior exhibits complex structure as a function of flux and frequency. We compare and contrast the quantum chaos expected in these mesoscopic {open_quotes}solid-state atoms{close_quotes} with that observed in Rydberg atoms in microwave fields, and discuss the prospects for experimental observation of the effects we predict. {copyright} {ital 1997} {ital The American Physical Society}
[Mathematics and string theory
Jaffe, A.; Yau, Shing-Tung.
1993-01-01
Work on this grant was centered on connections between non- commutative geometry and physics. Topics covered included: cyclic cohomology, non-commutative manifolds, index theory, reflection positivity, space quantization, quantum groups, number theory, etc.
Analytic cubic and quartic force fields using density-functional theory
Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth; Jonsson, Dan; High Performance Computing Group, University of TromsThe Arctic University of Norway, 9037 Troms ; Bast, Radovan; Ekstrm, Ulf; Helgaker, Trygve
2014-01-21
We present the first analytic implementation of cubic and quartic force constants at the level of KohnSham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchangecorrelation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and HartreeFock results. The HartreeFock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.
The Quantum Way of Sensing | Argonne Leadership Computing Facility
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
quantum optics and spintronics. He counts as a pioneer in the field of solid state spin quantum physics and has explored applications in photonics, spintronics, quantum computing ...
Naked singularities and quantum gravity
Harada, Tomohiro; Iguchi, Hideo; Nakao, Ken-ichi; Singh, T. P.; Tanaka, Takahiro; Vaz, Cenalo
2001-08-15
There are known models of spherical gravitational collapse in which the collapse ends in a naked shell-focusing singularity for some initial data. If a massless scalar field is quantized on the classical background provided by such a star, it is found that the outgoing quantum flux of the scalar field diverges in the approach to the Cauchy horizon. We argue that the semiclassical approximation (i.e., quantum field theory on a classical curved background) used in these analyses ceases to be valid about one Planck time before the epoch of naked singularity formation, because by then the curvature in the central region of the star reaches the Planck scale. It is shown that during the epoch in which the semiclassical approximation is valid, the total emitted energy is about one Planck unit, and is not divergent. We also argue that back reaction in this model does not become important so long as gravity can be treated classically. It follows that the further evolution of the star will be determined by quantum gravitational effects, and without invoking quantum gravity it is not possible to say whether the star radiates away on a short time scale or settles down into a black hole state.
Two-Yukawa fluid at a hard wall: Field theory treatment
Kravtsiv, I.; Patsahan, T.; Holovko, M.; Caprio, D. di
2015-05-21
We apply a field-theoretical approach to study the structure and thermodynamics of a two-Yukawa fluid confined by a hard wall. We derive mean field equations allowing for numerical evaluation of the density profile which is compared to analytical estimations. Beyond the mean field approximation, analytical expressions for the free energy, the pressure, and the correlation function are derived. Subsequently, contributions to the density profile and the adsorption coefficient due to Gaussian fluctuations are found. Both the mean field and the fluctuation terms of the density profile are shown to satisfy the contact theorem. We further use the contact theorem to improve the Gaussian approximation for the density profile based on a better approximation for the bulk pressure. The results obtained are compared to computer simulation data.
Giehler, M.; Wienold, M.; Schrottke, L.; Hey, R.; Grahn, H. T.; Pavlov, S. G.; Huebers, H.-W.; Winnerl, S.; Schneider, H.
2011-11-15
We investigate the effect of mid-infrared (MIR) pumping on the transport properties of GaAs/(Al,Ga)As terahertz (THz) quantum lasers (TQLs), which rely on quantum coherence effects of intersubband transitions. Aiming at THz lasing at elevated temperatures, we extend the concept of THz gain with and without population inversion of a single, MIR-pumped, electrically driven THz stage proposed by Waldmueller et al.[Phys. Rev. Lett. 99, 117401 (2007)] to an entire TQL. However, experiments using a CO{sub 2} as well as a free-electron laser and numerical simulations show that this resonant MIR pumping causes a negative differential conductivity (NDC) in addition to the NDC caused by sequential tunneling. Lasing of these TQLs is prevented by the formation of electric-field domains below the resonance field strength for gain of each single THz stage.
Multi-field inflation from holography
Garriga, Jaume; Urakawa, Yuko [Departament de Fsica Fonamental i Institut de Cincies del Cosmos, Universitat de Barcelona, Mart i Franqus 1, 08028 Barcelona (Spain); Skenderis, Kostas, E-mail: jaume.garriga@ub.edu, E-mail: K.Skenderis@soton.ac.uk, E-mail: urakawa.yuko@h.mbox.nagoya-u.ac.jp [STAG Research Centre and Mathematical Sciences, University of Southampton, Southampton SO17 1BJ (United Kingdom)
2015-01-01
We initiate the study of multi-field inflation using holography. Bulk light scalar fields correspond to nearly marginal operators in the boundary theory and the dual quantum field theory is a deformation of a CFT by such operators. We compute the power spectra of adiabatic and entropy perturbations in a simple model and find that the adiabatic curvature perturbation is not conserved in the presence of entropy perturbations but becomes conserved when the entropy perturbations are set to zero or the model is effectively a single scalar model, in agreement with expectations from cosmological perturbation theory.
Consistent interaction vertices in arbitrary topological BF theories
Bizdadea, C.; Cioroianu, E. M.; Saliu, S. O.; Sararu, S. C.; Stanciu-Oprean, L.
2013-11-13
Here we extend the previous results from [12] to the computation of all consistent self-interactions for topological BF theories with maximal field spectra in D =5,6,7,8 and present some partial results on possible generalizations on a space-time of arbitrary dimension D. For convenience, the deformation of the solution to the master equation in the context of the BRST-antifield formalism is used as a general method of constructing consistent interacting gauge field theories together with most of the standard hypotheses on quantum field theories on Minkowski space-times.
A Theory for the Comparative RF Surface Fields at Destructive Breakdown for Various Metels
Wilson, Perry; /SLAC
2006-03-20
By destructive breakdown we mean a breakdown event that results in surface melting over large areas on the iris tip region of an accelerator structure. The melting is the result of the formation of macroscopic areas of plasma in contact with the surface. The plasma bombards the surface with an intense ion current ({approx}10{sup 8} A/cm{sup 2}), which is equivalent to a pressure on the order of a thousand Atmospheres. A radial gradient in the pressure produces a ponderomotive force that causes molten copper to migrate away from the iris tip, resulting in a measurable change in the iris shape. This distortion in the iris shape in turn produces an error in the cell-to-cell phase shift of the accelerating wave with a consequent loss in synchronism with the electron beam and a reduction in the effective accelerating gradient. Assuming a long lifetime is desired for the structure, such breakdowns must be avoided or at least limited in number. The accelerating gradient at which these breakdowns begin to occur imposes, therefore, an absolute limit on an operationally attainable gradient. The destructive breakdown limit (DBL) on the accelerating gradient depends on a number of factors, such as the geometry of the irises and coupler, the accuracy of the cell-to-cell tuning (''field flatness''), and the properties of the metal used in the high E-field regions of the structure. In this note we consider only the question of the dependence of the DBL on the metal used in the high surface field areas of the structure. There are also various types of non-destructive breakdowns (NDB's) that occur during the ''processing'' period that, after the initial application of high power, is necessary to bring the gradient up to the desired operating level. During this period, as the input power and gradient are gradually increased, thousands of such NDB's occur. These breakdowns produce a collapse in the fields in the structure as energy stored in the fields is absorbed at the breakdown site. They are often marked by vacuum bursts and an increase in power reflected from the structure. The usual cause for NDB's during processing is the ''explosion'' of field emitters at sharp geometrical features on the metal surface. Exposed impurities in the metal surface can also produce NDB's as they are ''burned'' off by H-field heating or explosive field emission. The breakdown process can be roughly divided into four stages: (1) the formation of ''plasma spots'' at field emission sites, each spot leaving a crater-like footprint; (2) crater clustering, and the formation of areas with hundreds of overlapping craters; (3) surface melting in the region of a crater cluster; (4) the process after surface melting that leads to destructive breakdown.
Reid, J.-Ph.; Tanatar, Makariy; Daou, R.; Hu, Rongwei; Petrovic, C.; Taillefer, Louis
2014-01-23
The in-plane thermal conductivity kappa and electrical resistivity rho of the heavy-fermion metal YbRh2Si2 were measured down to 50 mK for magnetic fields H parallel and perpendicular to the tetragonal c axis, through the field-tuned quantum critical point H-c, at which antiferromagnetic order ends. The thermal and electrical resistivities, w L0T/kappa and rho, show a linear temperature dependence below 1 K, typical of the non-Fermi-liquid behavior found near antiferromagnetic quantum critical points, but this dependence does not persist down to T = 0. Below a characteristic temperature T-star similar or equal to 0.35 K, which depends weakly on H, w(T) and rho(T) both deviate downward and converge as T -> 0. We propose that T-star marks the onset of short-range magnetic correlations, persisting beyond H-c. By comparing samples of different purity, we conclude that the Wiedemann-Franz law holds in YbRh2Si2, even at H-c, implying that no fundamental breakdown of quasiparticle behavior occurs in this material. The overall phenomenology of heat and charge transport in YbRh2Si2 is similar to that observed in the heavy-fermion metal CeCoIn5, near its own field-tuned quantum critical point.
Dehghani, M. H.; Pakravan, J.; Hendi, S. H.
2006-11-15
We construct a class of charged rotating solutions in (n+1)-dimensional Maxwell-Brans-Dicke theory with flat horizon in the presence of a quadratic potential and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We find that these solutions can present black brane, with inner and outer event horizons, an extreme black brane or a naked singularity provided the parameters of the solutions are chosen suitably. We compute the finite Euclidean action through the use of counterterm method, and obtain the conserved and thermodynamic quantities by using the relation between the action and free energy in grand-canonical ensemble. We find that these quantities satisfy the first law of thermodynamics, and the entropy does not follow the area law.
Self-consistent field theory based molecular dynamics with linear system-size scaling
Richters, Dorothee; Khne, Thomas D.
2014-04-07
We present an improved field-theoretic approach to the grand-canonical potential suitable for linear scaling molecular dynamics simulations using forces from self-consistent electronic structure calculations. It is based on an exact decomposition of the grand canonical potential for independent fermions and does neither rely on the ability to localize the orbitals nor that the Hamilton operator is well-conditioned. Hence, this scheme enables highly accurate all-electron linear scaling calculations even for metallic systems. The inherent energy drift of Born-Oppenheimer molecular dynamics simulations, arising from an incomplete convergence of the self-consistent field cycle, is circumvented by means of a properly modified Langevin equation. The predictive power of the present approach is illustrated using the example of liquid methane under extreme conditions.
A mean field theory for the cold quark gluon plasma applied to stellar structure
Fogaca, D. A.; Navarra, F. S.; Franzon, B.; Horvath, J. E.
2013-03-25
An equation of state based on a mean-field approximation of QCD is used to describe the cold quark gluon plasma and also to study the structure of compact stars. We obtain stellar masses compatible with the pulsar PSR J1614-2230 that was determined to have a mass of (1.97 {+-} 0.04 M{sub Circled-Dot-Operator }), and the corresponding radius around 10-11 km.
Ian Balitsky
2010-09-01
I review the calculation of the next-to-leading order behavior of high-energy amplitudes in N=4 SYM and QCD using the operator expansion in Wilson lines.
Successive phase transitions and kink solutions in Φ⁸, Φ¹⁰, and Φ¹² field theories
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Khare, Avinash; Christov, Ivan C.; Saxena, Avadh
2014-08-27
We obtain exact solutions for kinks in Φ⁸, Φ¹⁰, and Φ¹² field theories with degenerate minima, which can describe a second-order phase transition followed by a first-order one, a succession of two first-order phase transitions and a second-order phase transition followed by two first-order phase transitions, respectively. Such phase transitions are known to occur in ferroelastic and ferroelectric crystals and in meson physics. In particular, we find that the higher-order field theories have kink solutions with algebraically-decaying tails and also asymmetric cases with mixed exponential-algebraic tail decay, unlike the lower-order Φ⁴ and Φ⁶ theories. Additionally, we construct distinct kinks withmore » equal energies in all three field theories considered, and we show the co-existence of up to three distinct kinks (for a Φ¹² potential with six degenerate minima). We also summarize phonon dispersion relations for these systems, showing that the higher-order field theories have specific cases in which only nonlinear phonons are allowed. For the Φ¹⁰ field theory, which is a quasi-exactly solvable (QES) model akin to Φ⁶, we are also able to obtain three analytical solutions for the classical free energy as well as the probability distribution function in the thermodynamic limit.« less
The General Theory of Relativity - F
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... The Evolution of Physics by Albert Einstein and Leopold Infeld Traces the main ideas of physics from Galileo to modern quantum theory in four chapters. Relativity theory, including ...
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09%2A en Ten-Year Site Plans (TYSP) http:nnsa.energy.govaboutusouroperationsinfopsinfopstysp
National Nuclear Security Administration (NNSA)
09%2A en Ten-Year Site Plans (TYSP) http:www.nnsa.energy.govaboutusouroperationsinfopsinfopstysp
Zhu, Laipan; Liu, Yu; Jiang, Chongyun; Yu, Jinling; Gao, Hansong; Ma, Hui; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai
2014-10-13
The spin polarization under low electric fields (?300?V/cm) at low temperatures has been studied in undoped InGaAs/AlGaAs multiple quantum well. The spin polarization was created by optical spin orientation using circularly polarized light and the inverse spin-Hall effect was employed to measure the spin polarization current. We observed an obvious spin depolarization especially at lower temperatures (80120?K). We ascribed the spin depolarization of the photoinduced electrons to the heating effect from the low electric fields (the low field regime 50300?V/cm). This spin depolarization due to the heating effect is sensitive to temperature and electric field, suggesting a wide range of potential applications and devices.
Sbruev, I. S.; Sbruev, S. B.
2010-10-15
The results of experiments with quantum wells on 3C-SiC/4H-SiC and 3C-SiC/6H-SiC heterojunctions obtained by various methods are reconsidered. Spontaneous polarizations, field strengths, and energies of local levels in quantum wells on 3C-SiC/NH-SiC heterojunctions were calculated within a unified model. The values obtained are in agreement with the results of all considered experiments. Heterojunction types are determined. Approximations for valence band offsets on heterojunctions between silicon carbide polytypes and the expression for calculating local levels in quantum wells on the 3C-SiC/NH-SiC heterojunction are presented. The spontaneous polarizations and field strengths induced by spontaneous polarization on 3C-SiC/4H-SiC and 3C-SiC/6H-SiC heterojunctions were calculated as 0.71 and 0.47 C/m{sup 2} and 0.825 and 0.55 MV/cm, respectively.
Volkn-Kacs, Sndor
2014-06-14
A theoretical method is proposed for the calculation of the photon counting probability distribution during a bin time. Two-state fluorescence and steady excitation are assumed. A key feature is a kinetic scheme that allows for an extensive class of stochastic waiting time distribution functions, including power laws, expanded as a sum of weighted decaying exponentials. The solution is analytic in certain conditions, and an exact and simple expression is found for the integral contribution of bright and dark states. As an application for power law kinetics, theoretical results are compared with experimental intensity histograms from a number of blinking CdSe/ZnS quantum dots. The histograms are consistent with distributions of intensity states around a bright and a dark maximum. A gap of states is also revealed in the more-or-less flat inter-peak region. The slope and to some extent the flatness of the inter-peak feature are found to be sensitive to the power-law exponents. Possible models consistent with these findings are discussed, such as the combination of multiple charging and fluctuating non-radiative channels or the multiple recombination center model. A fitting of the latter to experiment provides constraints on the interaction parameter between the recombination centers. Further extensions and applications of the photon counting theory are also discussed.
Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation
Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T.; Roy, Soumya Singha; Brown, Richard C. D.; Pileio, Giuseppe; Levitt, Malcolm H.
2015-01-28
Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T{sub 1}. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in {sup 13}CH{sub 3} groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.
Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.
2014-06-07
We report a study on the optical absorption coefficient associated to hydrogenic impurity interstate transitions in zinc-blende GaN quantum wires of cylindrical shape taking into account the effects of externally applied static electric and magnetic fields. The electron states emerge within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement and external field effects. The nonlinear optical absorption is calculated using a recently derived expression for the dielectric susceptibility, obtained via a nonperturbative solution of the density-matrix Bloch equation. Our results show that this treatment eliminates not only the intensity-dependent bleaching effect but also the change in sign of the nonlinear contribution due to the combined effect of asymmetric impurity location and the applied electric field.
The Wonders of Supersymmetry: From Quantum Mechanics, Topology, and Noise, to (maybe) the LHC
Poppitz, Erich [University of Toronto, Toronto, Ontario, Canada
2010-09-01
Supersymmetry, relating bosons and fermions was discovered almost 40 years ago in string theory and in quantum field theory, but the seeds of its 'miraculous' properties could have been seen already in quantum mechanics - which is also where it has found some of its more important applications. This talk introduces supersymmetry via the supersymmetric anharmonic oscillator. We shall see that this seemingly trivial example is sufficiently rich, allowing us to illustrate the uses of supersymmetric concepts in a variety of fields: mathematics, elementary particle physics, critical phenomena, and stochastic dynamics.
The promise of quantum simulation
Muller, Richard P.; Blume-Kohout, Robin
2015-07-21
In this study, quantum simulations promise to be one of the primary applications of quantum computers, should one be constructed. This article briefly summarizes the history of quantum simulation in light of the recent result of Wang and co-workers, demonstrating calculation of the ground and excited states for a HeH^{+} molecule, and concludes with a discussion of why this and other recent progress in the field suggest that quantum simulations of quantum chemistry have a bright future.
The promise of quantum simulation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Muller, Richard P.; Blume-Kohout, Robin
2015-07-21
In this study, quantum simulations promise to be one of the primary applications of quantum computers, should one be constructed. This article briefly summarizes the history of quantum simulation in light of the recent result of Wang and co-workers, demonstrating calculation of the ground and excited states for a HeH+ molecule, and concludes with a discussion of why this and other recent progress in the field suggest that quantum simulations of quantum chemistry have a bright future.
Suppression of quantum chaos in a quantum computer hardware
Lages, J.; Shepelyansky, D. L. [Laboratoire de Physique Theorique, UMR 5152 du CNRS, Universite Paul Sabatier, 31062 Toulouse Cedex 4 (France)
2006-08-15
We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.
Flavored quantum Boltzmann equations
Cirigliano, Vincenzo; Lee, Christopher; Ramsey-Musolf, Michael J.; Tulin, Sean [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 (United States); Center for Theoretical Physics, University of California, and Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California, 94720 (United States); Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin, 53706 (United States) and Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California, 91125 (United States); Theory Group, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada)
2010-05-15
We derive from first principles, using nonequilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading nontrivial order in ratios of relevant time scales, we study in detail a toy model for weak-scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a nontrivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.
Quantum chaos in compact lattice QED
Berg, B.A. [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States)] [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States); [Supercomputer Computations Research Institute, The Florida State University, Tallahassee, Florida 32306 (United States); Markum, H. [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria)] [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria); Pullirsch, R. [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States)] [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States); [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria)
1999-05-01
Complete eigenvalue spectra of the staggered Dirac operator in quenched 4D compact QED are studied on 8{sup 3}{times}4 and 8{sup 3}{times}6 lattices. We investigate the behavior of the nearest-neighbor spacing distribution P(s) as a measure of the fluctuation properties of the eigenvalues in the strong coupling and the Coulomb phase. In both phases we find agreement with the Wigner surmise of the unitary ensemble of random-matrix theory indicating quantum chaos. Combining this with previous results on QCD, we conjecture that quite generally the non-linear couplings of quantum field theories lead to a chaotic behavior of the eigenvalues of the Dirac operator. {copyright} {ital 1999} {ital The American Physical Society}
Stapp, Henry
2011-11-10
Robert Griffiths has recently addressed, within the framework of a consistent quantum theory (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his consistent quantum theory shows that the cited proof is valid within that restrictive framework. This necessary existence, within the consistent framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his consistent framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the vagaries that he cites do not upset the proof in question. It is show here in detail why the precise statement of this theorem justifies the specified application of CQT. It is also shown, in response to his challenge, why a putative proof of locality that he has proposed is not valid.
Banik, Sarmistha [BITS Pilani, Hyderabad Campus, Hyderabad-500078 (India); Hempel, Matthias [Departement Physik, Universitt Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Bandyopadhyay, Debades [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064 (India)
2014-10-01
We develop new hyperon equation of state (EoS) tables for core-collapse supernova simulations and neutron stars. These EoS tables are based on a density-dependent relativistic hadron field theory where baryon-baryon interaction is mediated by mesons, using the parameter set DD2 for nucleons. Furthermore, light and heavy nuclei along with interacting nucleons are treated in the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich which includes excluded volume effects. Of all possible hyperons, we consider only the contribution of ?s. We have developed two variants of hyperonic EoS tables: in the np?? case the repulsive hyperon-hyperon interaction mediated by the strange ? meson is taken into account, and in the np? case it is not. The EoS tables for the two cases encompass a wide range of densities (10{sup 12} to ?1 fm{sup 3}), temperatures (0.1 to 158.48 MeV), and proton fractions (0.01 to 0.60). The effects of ? hyperons on thermodynamic quantities such as free energy per baryon, pressure, or entropy per baryon are investigated and found to be significant at higher densities. The cold, ?-equilibrated EoS (with the crust included self-consistently) results in a 2.1 M {sub ?} maximum mass neutron star for the np?? case, whereas that for the np? case is 1.95 M {sub ?}. The np?? EoS represents the first supernova EoS table involving hyperons that is directly compatible with the recently measured 2 M {sub ?} neutron stars.
National Computational Infrastructure for Lattice Gauge Theory
Brower, Richard C.
2014-04-15
SciDAC-2 Project The Secret Life of Quarks: National Computational Infrastructure for Lattice Gauge Theory, from March 15, 2011 through March 14, 2012. The objective of this project is to construct the software needed to study quantum chromodynamics (QCD), the theory of the strong interactions of sub-atomic physics, and other strongly coupled gauge field theories anticipated to be of importance in the energy regime made accessible by the Large Hadron Collider (LHC). It builds upon the successful efforts of the SciDAC-1 project National Computational Infrastructure for Lattice Gauge Theory, in which a QCD Applications Programming Interface (QCD API) was developed that enables lattice gauge theorists to make effective use of a wide variety of massively parallel computers. This project serves the entire USQCD Collaboration, which consists of nearly all the high energy and nuclear physicists in the United States engaged in the numerical study of QCD and related strongly interacting quantum field theories. All software developed in it is publicly available, and can be downloaded from a link on the USQCD Collaboration web site, or directly from the github repositories with entrance linke http://usqcd-software.github.io
Baidus, N. V.; Belevskii, P. A.; Biriukov, A. A.; Vainberg, V. V.; Vinoslavskii, M. N.; Ikonnikov, A. V.; Zvonkov, B. N.; Pylypchuk, A. S.; Poroshin, V. N.
2010-11-15
It is shown that the far-infrared radiation of electrons in the selectively doped heterostructures with double tunnel-coupled quantum wells in high lateral electric fields strongly depends on the level of doping of the wells. At a high impurity concentration in a narrow well, higher than (1-2) x 10{sup 11} cm{sup -2}, the radiation is caused only by indirect intrasubband electron transitions. At a lower concentration, along with the indirect transitions, the direct intersubband transitions also contribute to the radiation. These transitions become possible in high electric fields due to the real-space electron transfer between the quantum wells.
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Quantum Institute Quantum Institute A new research frontier awaits! Our door is open and we thrive on mutually beneficial partnerships, collaborations that drive innovations and new technologies. Contact Leader Malcolm Boshier (505) 665-8892 Email Two of LANL's most successful quantum technology initiatives: quantum cryptography and the race for quantum computer The area of quantum information, science, and technology is rapidly evolving, with important applications in the areas of quantum
QUANTUM MECHANICS, GENERAL PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS...
Office of Scientific and Technical Information (OSTI)
of model atoms in fields Milonni, P.W. 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; OPTICAL MODELS; QUANTUM MECHANICS;...
Bruegger, C.; Kaempfer, F.; Moser, M.; Wiese, U.-J.; Pepe, M.
2006-12-01
Identifying the correct low-energy effective theory for magnons and holes in an antiferromagnet has remained an open problem for a long time. In analogy to the effective theory for pions and nucleons in QCD, based on a symmetry analysis of Hubbard and t-J-type models, we construct a systematic low-energy effective field theory for magnons and holes located inside pockets centered at lattice momenta ({+-}({pi}/2a),{+-}({pi}/2a)). The effective theory is based on a nonlinear realization of the spontaneously broken spin symmetry and makes model-independent universal predictions for the entire class of lightly doped antiferromagnetic precursors of high-temperature superconductors. The predictions of the effective theory are exact, order by order in a systematic low-energy expansion. We derive the one-magnon exchange potentials between two holes in an otherwise undoped system. Remarkably, in some cases the corresponding two-hole Schroedinger equations can even be solved analytically. The resulting bound states have d-wave characteristics. The ground state wave function of two holes residing in different hole pockets has a d{sub x{sup 2}-y{sup 2}}-like symmetry, while for two holes in the same pocket the symmetry resembles d{sub xy}.
Levi, Michele [Institut d'Astrophysique de Paris, Universit Pierre et Marie Curie, CNRS-UMR 7095, 98 bis Boulevard Arago, 75014 Paris (France); Steinhoff, Jan, E-mail: michele.levi@upmc.fr, E-mail: jan.steinhoff@ist.utl.pt [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2014-12-01
The next-to-next-to-leading order spin1-spin2 potential for an inspiralling binary, that is essential for accuracy to fourth post-Newtonian order, if both components in the binary are spinning rapidly, has been recently derived independently via the ADM Hamiltonian and the Effective Field Theory approaches, using different gauges and variables. Here we show the complete physical equivalence of the two results, thereby we first prove the equivalence of the ADM Hamiltonian and the Effective Field Theory approaches at next-to-next-to-leading order with the inclusion of spins. The main difficulty in the spinning sectors, which also prescribes the manner in which the comparison of the two results is tackled here, is the existence of redundant unphysical spin degrees of freedom, associated with the spin gauge choice of a point within the extended spinning object for its representative worldline. After gauge fixing and eliminating the unphysical degrees of freedom of the spin and its conjugate at the level of the action, we arrive at curved spacetime generalizations of the Newton-Wigner variables in closed form, which can also be used to obtain further Hamiltonians, based on an Effective Field Theory formulation and computation. Finally, we make use of our validated result to provide gauge invariant relations among the binding energy, angular momentum, and orbital frequency of an inspiralling binary with generic compact spinning components to fourth post-Newtonian order, including all known sectors up to date.
Vinolin, Ada; Peter, A. John
2014-04-24
Simultaneous effects of electric field and magnetic field on exciton binding energy as a function of dot radius in a cylindrical GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} strained quantum dot are investigated. The strain contribution includes the strong built-in electric field induced by the spontaneous and piezoelectric polarizations. Numerical calculations are performed using variational procedure within the single band effective mass approximation. Optical rectification in the GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} quantum dot is computed in the presence of electric and magnetic fields.
Burrola-Gándara, L. A. Santillan-Rodriguez, C. R.; Rivera-Gomez, F. J.; Saenz-Hernandez, R. J.; Botello-Zubiate, M. E.; Matutes-Aquino, J. A.
2015-05-07
Magnetocaloric materials with second order phase transition near the Curie temperature can be described by critical phenomena theory. In this theory, scaling, universality, and renormalization are key concepts from which several phase transition order criteria are derived. In this work, the rescaled universal curve, Banerjee and mean field theory criteria were used to make a comparison for several magnetocaloric materials including pure Gd, SmCo{sub 1.8}Fe{sub 0.2}, MnFeP{sub 0.46}As{sub 0.54}, and La{sub 0.7}Ca{sub 0.15}Sr{sub 0.15}MnO{sub 3}. Pure Gd, SmCo{sub 1.8}Fe{sub 0.2}, and La{sub 0.7}Ca{sub 0.15}Sr{sub 0.15}MnO{sub 3} present a collapse of the rescaled magnetic entropy change curves into a universal curve, which indicates a second order phase transition; applying Banerjee criterion to H/σ vs σ{sup 2} Arrot plots and the mean field theory relation |ΔS{sub M}| ∝ (μ{sub 0}H/T{sub c}){sup 2/3} for the same materials also determines a second order phase transition. However, in the MnFeP{sub 0.46}As{sub 0.54} sample, the Banerjee criterion applied to the H/σ vs σ{sup 2} Arrot plot indicates a first order magnetic phase transition, while the mean field theory prediction for a second order phase transition, |ΔS{sub M}| ∝ (μ{sub 0}H/T{sub c}){sup 2/3}, describes a second order behavior. Also, a mixture of first and second order behavior was indicated by the rescaled universal curve criterion. The diverse results obtained for each criterion in MnFeP{sub 0.46}As{sub 0.54} are apparently related to the magnetoelastic effect and to the simultaneous presence of weak and strong magnetism in Fe (3f) and Mn (3g) alternate atomic layers, respectively. The simultaneous application of the universal curve, the Banerjee and the mean field theory criteria has allowed a better understanding about the nature of the order of the phase transitions in different magnetocaloric materials.
QUANTUM MECHANICS WITHOUT STATISTICAL POSTULATES
G. GEIGER; ET AL
2000-11-01
The Bohmian formulation of quantum mechanics describes the measurement process in an intuitive way without a reduction postulate. Due to the chaotic motion of the hidden classical particle all statistical features of quantum mechanics during a sequence of repeated measurements can be derived in the framework of a deterministic single system theory.
Delande, D.; Gay, J.C.
1986-10-20
The transition to chaos in ''the hydrogen atom in a magnetic field'' is numerically studied and shown to lead to well-defined signature on the energy-level fluctuations. Upon an increase in the energy, the calculated statistics evolve from Poisson to Gaussian orthogonal ensemble according to the regular or chaotic character of the classical motion. Several methods are employed to test the generic nature of these distributions.
Fan, Wenjiang; Lawrie, Benjamin J.; Pooser, Raphael C.
2015-11-04
Surface plasmon resonance (SPR) sensors can reach the quantum noise limit of the optical readout field in various configurations. We demonstrate that two-mode intensity squeezed states produce a further enhancement in sensitivity compared with a classical optical readout when the quantum noise is used to transduce an SPR sensor signal in the Kretschmann configuration. The quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that with a classical optical readout in this configuration. Furthermore, the theoretical potential of this technique points to resolving particle concentrations with more accuracy than is possible via classical approaches to optical transduction.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Fan, Wenjiang; Lawrie, Benjamin J.; Pooser, Raphael C.
2015-11-04
Surface plasmon resonance (SPR) sensors can reach the quantum noise limit of the optical readout field in various configurations. We demonstrate that two-mode intensity squeezed states produce a further enhancement in sensitivity compared with a classical optical readout when the quantum noise is used to transduce an SPR sensor signal in the Kretschmann configuration. The quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that withmore » a classical optical readout in this configuration. Furthermore, the theoretical potential of this technique points to resolving particle concentrations with more accuracy than is possible via classical approaches to optical transduction.« less
A broken symmetry ontology: Quantum mechanics as a broken symmetry
Buschmann, J.E.
1988-01-01
The author proposes a new broken symmetry ontology to be used to analyze the quantum domain. This ontology is motivated and grounded in a critical epistemological analysis, and an analysis of the basic role of symmetry in physics. Concurrently, he is led to consider nonheterogeneous systems, whose logical state space contains equivalence relations not associated with the causal relation. This allows him to find a generalized principle of symmetry and a generalized symmetry-conservation formalisms. In particular, he clarifies the role of Noether's theorem in field theory. He shows how a broken symmetry ontology already operates in a description of the weak interactions. Finally, by showing how a broken symmetry ontology operates in the quantum domain, he accounts for the interpretational problem and the essential incompleteness of quantum mechanics. He proposes that the broken symmetry underlying this ontological domain is broken dilation invariance.
Quantum Criticality and Black Holes
Sachdev, Subir [Harvard University, Cambridge, Massachusetts, United States
2009-09-01
I will describe the behavior of a variety of condensed matter systems in the vicinity of zero temperature quantum phase transitions. There is a remarkable analogy between the hydrodynamics of such systems and the quantum theory of black holes. I will show how insights from this analogy have shed light on recent experiments on the cuprate high temperature superconductors. Studies of new materials and trapped ultracold atoms are yielding new quantum phases, with novel forms of quantum entanglement. Some materials are of technological importance: e.g. high temperature superconductors. Exact solutions via black hole mapping have yielded first exact results for transport coefficients in interacting many-body systems, and were valuable in determining general structure of hydrodynamics. Theory of VBS order and Nernst effect in cuprates. Tabletop 'laboratories for the entire universe': quantum mechanics of black holes, quark-gluon plasma, neutrons stars, and big-bang physics.
Kaprlov-?nsk, Petra Ruth; mydke, Jan; Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 ; Civi, Svatopluk
2013-09-14
Recently optimized exponentially tempered Gaussian basis sets [P. R. Kapralova-Zdanska and J. Smydke, J. Chem. Phys. 138, 024105 (2013)] are employed in quantitative simulations of helium absorption cross-sections and two-photon excitation yields of doubly excited resonances. Linearly polarized half-infinite and Gaussian laser pulses at wavelengths 3858 nm and large intensities up to 100 TW/cm{sup 2} are considered. The emphasis is laid on convergence of the results with respect to the quality of the Gaussian basis sets (typically limited by a number of partial waves, density, and spatial extent of the basis functions) as well as to the quality of the basis set of field-free states (typically limited by the maximum rotational quantum number and maximum excitation of the lower electron). Particular attention is paid to stability of the results with respect to varying complex scaling parameter. Moreover, the study of the dynamics is preceded by a thorough check of helium energies and oscillator strengths as they are obtained with the exponentially tempered Gaussian basis sets, being also compared with yet unpublished emission wavelengths measured in electric discharge experiments.
ASCR Workshop on Quantum Computing for Science
Aspuru-Guzik, Alan; Van Dam, Wim; Farhi, Edward; Gaitan, Frank; Humble, Travis; Jordan, Stephen; Landahl, Andrew J; Love, Peter; Lucas, Robert; Preskill, John; Muller, Richard P.; Svore, Krysta; Wiebe, Nathan; Williams, Carl
2015-06-01
This report details the findings of the DOE ASCR Workshop on Quantum Computing for Science that was organized to assess the viability of quantum computing technologies to meet the computational requirements of the DOE’s science and energy mission, and to identify the potential impact of quantum technologies. The workshop was held on February 17-18, 2015, in Bethesda, MD, to solicit input from members of the quantum computing community. The workshop considered models of quantum computation and programming environments, physical science applications relevant to DOE's science mission as well as quantum simulation, and applied mathematics topics including potential quantum algorithms for linear algebra, graph theory, and machine learning. This report summarizes these perspectives into an outlook on the opportunities for quantum computing to impact problems relevant to the DOE’s mission as well as the additional research required to bring quantum computing to the point where it can have such impact.
Thomas Weinacht
2011-08-05
Quantum control of light and matter is the quest to steer a physical process to a desirable outcome, employing constructive and destructive interference. Three basic questions address feasibility of quantum control: (1) The problem of controllability, does a control field exist for a preset initial and target state; (2) Synthesis, constructively finding the field that leads to the target; and (3) Optimal Control Theory - optimizing the field that carries out this task. These continue to be the fundamental theoretical questions to be addressed in the conference. How to realize control fields in the laboratory is an ongoing challenge. This task is very diverse viewing the emergence of control scenarios ranging from attoseconds to microseconds. How do the experimental observations reflect on the theoretical framework? The typical arena of quantum control is an open environment where much of the control is indirect. How are control scenarios realized in dissipative open systems? Can new control opportunities emerge? Can one null decoherence effects? An ideal setting for control is ultracold matter. The initial and final state can be defined more precisely. Coherent control unifies many fields of physical science. A lesson learned in one field can reflect on another. Currently quantum information processing has emerged as a primary target of control where the key issue is controlling quantum gate operation. Modern nonlinear spectroscopy has emerged as another primary field. The challenge is to unravel the dynamics of molecular systems undergoing strong interactions with the environment. Quantum optics where non-classical fields are to be generated and employed. Finally, coherent control is the basis for quantum engineering. These issues will be under the limelight of the Gordon conference on Quantum Control of Light and Matter.
Generalized Bogoliubov transformation for confined fields: Applications for the Casimir effect
Silva, J.C. da; Khanna, F.C.; Matos Neto, A.; Santana, A.E.
2002-11-01
The Bogoliubov transformation in thermofield dynamics, an operator formalism for the finite-temperature quantum field theory, is generalized to describe a field in arbitrary confined regions of space and time. Starting with the scalar field, the approach is extended to the electromagnetic field and the energy-momentum tensor is written via the Bogoliubov transformation. In this context, the Casimir effect is calculated for zero and nonzero temperature, and therefore it can be considered as a vacuum condensation effect of the electromagnetic field. This aspect opens an interesting perspective for using this procedure as an effective scheme for calculations in the studies of confined fields, including interacting fields.
Turbocharging Quantum Tomography.
Blume-Kohout, Robin J; Gamble, John King,; Nielsen, Erik; Maunz, Peter Lukas Wilhelm; Scholten, Travis L.; Rudinger, Kenneth Michael
2015-01-01
Quantum tomography is used to characterize quantum operations implemented in quantum information processing (QIP) hardware. Traditionally, state tomography has been used to characterize the quantum state prepared in an initialization procedure, while quantum process tomography is used to characterize dynamical operations on a QIP system. As such, tomography is critical to the development of QIP hardware (since it is necessary both for debugging and validating as-built devices, and its results are used to influence the next generation of devices). But tomography su %7C ers from several critical drawbacks. In this report, we present new research that resolves several of these flaws. We describe a new form of tomography called gate set tomography (GST), which unifies state and process tomography, avoids prior methods critical reliance on precalibrated operations that are not generally available, and can achieve unprecedented accuracies. We report on theory and experimental development of adaptive tomography protocols that achieve far higher fidelity in state reconstruction than non-adaptive methods. Finally, we present a new theoretical and experimental analysis of process tomography on multispin systems, and demonstrate how to more e %7C ectively detect and characterize quantum noise using carefully tailored ensembles of input states.
Wu, Wei; Wang, Jin
2014-09-14
We have established a general non-equilibrium thermodynamic formalism consistently applicable to both spatially homogeneous and, more importantly, spatially inhomogeneous systems, governed by the Langevin and Fokker-Planck stochastic dynamics with multiple state transition mechanisms, using the potential-flux landscape framework as a bridge connecting stochastic dynamics with non-equilibrium thermodynamics. A set of non-equilibrium thermodynamic equations, quantifying the relations of the non-equilibrium entropy, entropy flow, entropy production, and other thermodynamic quantities, together with their specific expressions, is constructed from a set of dynamical decomposition equations associated with the potential-flux landscape framework. The flux velocity plays a pivotal role on both the dynamic and thermodynamic levels. On the dynamic level, it represents a dynamic force breaking detailed balance, entailing the dynamical decomposition equations. On the thermodynamic level, it represents a thermodynamic force generating entropy production, manifested in the non-equilibrium thermodynamic equations. The Ornstein-Uhlenbeck process and more specific examples, the spatial stochastic neuronal model, in particular, are studied to test and illustrate the general theory. This theoretical framework is particularly suitable to study the non-equilibrium (thermo)dynamics of spatially inhomogeneous systems abundant in nature. This paper is the second of a series.
Surface plasmon oscillations on a quantum plasma half-space
Moradi, Afshin
2015-01-15
We investigate the propagation of surface electrostatic oscillations on a quantum plasma half-space, taking into account the quantum effects. We derive the quantum surface wave frequencies of the system, by means the quantum hydrodynamic theory in conjunction with the Poisson equation and applying the appropriate additional quantum boundary conditions. Numerical results show in the presence of the slow nonlocal variations, plasmon wave energies of the system are significantly modified and plasmonic oscillations with blue-shifted frequencies emerge.
Speck, Thomas; Menzel, Andreas M.; Bialké, Julian; Löwen, Hartmut
2015-06-14
Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with attractive interactions through a global effective free energy (motility-induced phase transition). Particular attention is paid to the square-gradient term necessary for the phase separation kinetics. We finally discuss results from numerical simulations corroborating the analytical results.
Leading order calculation of shear viscosity in hot quantum electrodyn...
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Subject: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACTION INTEGRAL; BOLTZMANN EQUATION; FERMIONS; FEYNMAN DIAGRAM; GAUGE INVARIANCE; INTEGRAL EQUATIONS; QUANTUM ...
The one and a half monopoles solution of the SU(2) YangMillsHiggs field theory
Teh, Rosy Ng, Ban-Loong; Wong, Khai-Ming
2014-04-15
Recently we have reported on the existence of finite energy SU(2) YangMillsHiggs particle of one-half topological charge. In this paper, we show that this one-half monopole can co-exist with a t HooftPolyakov monopole. The magnetic charge of the one-half monopole is of opposite sign to the magnetic charge of the t HooftPolyakov monopole. However the net magnetic charge of the configuration is zero due to the presence of a semi-infinite Dirac string along the positive z-axis that carries the other half of the magnetic monopole charge. The solution possesses gauge potentials that are singular along the z-axis, elsewhere they are regular. The total energy is found to increase with the strength of the Higgs field self-coupling constant ?. However the dipole separation and the magnetic dipole moment decrease with ?. This solution is non-BPS even in the BPS limit when the Higgs self-coupling constant vanishes. -- Highlights: This one-half monopole can co-exist with a t HooftPolyakov monopole. The magnetic charge of the one-half monopole and one monopole is of opposite sign. This solution is non-BPS. The net magnetic charge of the configuration is zero. This solution upon Cho decomposition is only singular along the negative z-axis.
Divergences of generalized quantum electrodynamics on the Lorenz gauge
Bufalo, R.; Pimentel, B. M.; Zambrano, G. E.
2013-03-25
In this paper we study the Generalized Quantum Electrodynamics (GQED4) on the Lorenz gauge condition and show that divergences are still present in the theory.
Scalable, High-Speed Measurement-Based Quantum Computer Using...
Office of Scientific and Technical Information (OSTI)
University of Toronto, Toronto, Ontario M5S 1A7 (Canada) 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CALCIUM IONS; INFORMATION THEORY; MULTI-PHOTON PROCESSES;...
Cox, Stephen J.; Michaelides, Angelos; Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ ; Towler, Michael D.; Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE ; Alf, Dario; Department of Earth Sciences, University College London Gower Street, London WC1E 6BT
2014-05-07
High quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested are sufficient to describe both the energetics and the structure of methane hydrate accurately, while the point charge force fields perform badly in their description of the cohesive energy but fair well for the dissociation energetics. By comparing to ice I{sub h}, we show that a good prediction of the volume and cohesive energies for the hydrate relies primarily on an accurate description of the hydrogen bonded water framework, but that to correctly predict stability of the hydrate with respect to dissociation to ice I{sub h} and methane gas, accuracy in the water-methane interaction is also required. Our results highlight the difficulty that density functional theory faces in describing both the hydrogen bonded water framework and the dispersion bound methane.
The Evolution of Soft Collinear Effective Theory
Lee, Christopher
2015-02-25
Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic jets in e^{+}e^{-}, lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used to factorize multi-scale cross sections in these processes into single-scale hard, collinear, and soft functions, and to evolve these through the renormalization group to resum large logarithms of ratios of the scales that appear in the QCD perturbative expansion, as well as to study properties of nonperturbative effects. We overview the elementary concepts of SCET and describe how they can be applied in high-energy and nuclear physics.
The Evolution of Soft Collinear Effective Theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lee, Christopher
2015-02-25
Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic jets in e+e-, lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used to factorize multi-scale cross sections in these processes into single-scale hard, collinear, and soft functions, and to evolve these through the renormalization group to resum large logarithms of ratios of the scales that appear in the QCD perturbativemore » expansion, as well as to study properties of nonperturbative effects. We overview the elementary concepts of SCET and describe how they can be applied in high-energy and nuclear physics.« less
Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells
Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-19
The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.
Finite groups and quantum physics
Kornyak, V. V.
2013-02-15
Concepts of quantum theory are considered from the constructive 'finite' point of view. The introduction of a continuum or other actual infinities in physics destroys constructiveness without any need for them in describing empirical observations. It is shown that quantum behavior is a natural consequence of symmetries of dynamical systems. The underlying reason is that it is impossible in principle to trace the identity of indistinguishable objects in their evolution-only information about invariant statements and values concerning such objects is available. General mathematical arguments indicate that any quantum dynamics is reducible to a sequence of permutations. Quantum phenomena, such as interference, arise in invariant subspaces of permutation representations of the symmetry group of a dynamical system. Observable quantities can be expressed in terms of permutation invariants. It is shown that nonconstructive number systems, such as complex numbers, are not needed for describing quantum phenomena. It is sufficient to employ cyclotomic numbers-a minimal extension of natural numbers that is appropriate for quantum mechanics. The use of finite groups in physics, which underlies the present approach, has an additional motivation. Numerous experiments and observations in the particle physics suggest the importance of finite groups of relatively small orders in some fundamental processes. The origin of these groups is unclear within the currently accepted theories-in particular, within the Standard Model.
Out-of-Equilibrium Kondo Effect in Double Quantum Dots
Aguado, Ramon; Langreth, David C.
2000-08-28
The out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime are studied theoretically by means of a two-impurity Anderson Hamiltonian with interimpurity hopping. The Hamiltonian is solved by means of a nonequilibrium generalization of the slave-boson mean-field theory. It is demonstrated that measurements of the differential conductance dI/dV , for appropriate values of voltages and tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kondo states of each dot. For large voltages and arbitrarily large interdot tunneling, there is a critical voltage above which the physical behavior of the system again resembles that of two decoupled quantum dots. (c) 2000 The American Physical Society.
Quantum superposition principle and gravitational collapse: Scattering times for spherical shells
Ambrus, M.; Hajicek, P.
2005-09-15
A quantum theory of spherically symmetric thin shells of null dust and their gravitational field is studied. In Nucl. Phys. B603, 555 (2001), it has been shown how superpositions of quantum states with different geometries can lead to a solution of the singularity problem and black hole information paradox: the shells bounce and re-expand and the evolution is unitary. The corresponding scattering times will be defined in the present paper. To this aim, a spherical mirror of radius R{sub m} is introduced. The classical formula for scattering times of the shell reflected from the mirror is extended to quantum theory. The scattering times and their spreads are calculated. They have a regular limit for R{sub m}{yields}0 and they reveal a resonance at E{sub m}=c{sup 4}R{sub m}/2G. Except for the resonance, they are roughly of the order of the time the light needs to cross the flat space distance between the observer and the mirror. Some ideas are discussed of how the construction of the quantum theory could be changed so that the scattering times become considerably longer.
Quantum Gravity corrections and entropy at the Planck time
Basilakos, Spyros; Vagenas, Elias C.; Das, Saurya E-mail: saurya.das@uleth.ca
2010-09-01
We investigate the effects of Quantum Gravity on the Planck era of the universe. In particular, using different versions of the Generalized Uncertainty Principle and under specific conditions we find that the main Planck quantities such as the Planck time, length, mass and energy become larger by a factor of order 10?10{sup 4} compared to those quantities which result from the Heisenberg Uncertainty Principle. However, we prove that the dimensionless entropy enclosed in the cosmological horizon at the Planck time remains unchanged. These results, though preliminary, indicate that we should anticipate modifications in the set-up of cosmology since changes in the Planck era will be inherited even to the late universe through the framework of Quantum Gravity (or Quantum Field Theory) which utilizes the Planck scale as a fundamental one. More importantly, these corrections will not affect the entropic content of the universe at the Planck time which is a crucial element for one of the basic principles of Quantum Gravity named Holographic Principle.
Identification of open quantum systems from observable time traces
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Zhang, Jun; Sarovar, Mohan
2015-05-27
Estimating the parameters that dictate the dynamics of a quantum system is an important task for quantum information processing and quantum metrology, as well as fundamental physics. In our paper we develop a method for parameter estimation for Markovian open quantum systems using a temporal record of measurements on the system. Furthermore, the method is based on system realization theory and is a generalization of our previous work on identification of Hamiltonian parameters.
Quantum-mechanical aspects of classically chaotic driven systems
Milonni, P.W.; Ackerhalt, J.R.; Goggin, M.E.
1987-01-01
This paper treats atoms and molecules in laser fields as periodically driven quantum systems. The paper concludes by determining that stochastic excitation is possible in quantum systems with quasiperiodic driving. 17 refs. (JDH)
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quantum ESPRESSOPWscf Quantum ESPRESSOPWscf Description Quantum ESPRESSO is an integrated suite of computer codes for electronic structure calculations and materials modeling at...
Regular and chaotic quantum dynamics in atom-diatom reactive collisions
Gevorkyan, A. S., E-mail: g_ashot@sci.a [IIAP/IAPP NAS of Armenia (Armenia); Bogdanov, A. V., E-mail: bogdanov@csa.r [Institute for High Performance Computing and Information Systems (Russian Federation); Nyman, G., E-mail: nyman@chem.gu.s [University of Gothenburg, Department of Chemistry (Sweden)
2008-05-15
A new microirreversible 3D theory of quantum multichannel scattering in the three-body system is developed. The quantum approach is constructed on the generating trajectory tubes which allow taking into account influence of classical nonintegrability of the dynamical quantum system. When the volume of classical chaos in phase space is larger than the quantum cell in the corresponding quantum system, quantum chaos is generated. The probability of quantum transitions is constructed for this case. The collinear collision of the Li + (FH) {sup {yields}}(LiF) + H system is used for numerical illustration of a system generating quantum (wave) chaos.
Inflation and dark energy from the Brans-Dicke theory
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek
2015-06-17
We consider the Brans-Dicke theory motivated by the f(R)=R+αR{sup n}−βR{sup 2−n} model to obtain a stable minimum of the Einstein frame scalar potential of the Brans-Dicke field. As a result we have obtained an inflationary scalar potential with non-zero value of residual vacuum energy, which may be a source of dark energy. In addition we discuss the probability of quantum tunnelling from the minimum of the potential. Our results can be easily consistent with PLANCK or BICEP2 data for appropriate choices of the value of n and ω.
Not Available
1992-12-01
The effort of the experimental group has been concentrated on the CERN ALEPH and FERMILAB D0 collider experiments and completion of two fixed target experiments. The BNL fixed target experiment 771 took the world`s largest sample of D(1285) and E/iota(1420) events, using pion, kaon and antiproton beams. Observing the following resonances: 0{sup {minus_plus}} [1280], 1{sup {plus}{plus}} [1280], 0{sup {minus_plus}} [1420], 0{sup {minus_plus}} [1470], 1{sup {plus_minus}} [1415]. The Fermilab fixed target experiment E711, dihadron production in pN interactions at 800 GeV, completed data reduction and analysis. The atomic weight dependence, when parameterized as {sigma}(A) = {sigma}{sub o}A{sup {alpha}}, yielded a value of {alpha} = 1.043 {plus_minus} 0.011 {plus_minus} .012. The cross section per nucleon and angular distributions was also measured as a function of two particle mass and agrees very well with QCD calculations. The D0 Fermilab Collider Experiment E740 began its first data taking run in April 1992. The CERN collider experiment ALEPH at LEP is presently taking more data. The Z mass and width, the couplings to the upper and lower components of the hadronic isospin doublet, forward-backward asymmetries of hadronic events, and measurements of the fragmentation process have been made. The effort of detector development for the SSC has substantially increased with particular emphasis on scintillators, both in fibers and plates. Work has continued on higher-order QCD calculations using the Monte Carlo technique developed previously. This year results for WW, ZZ, WZ, and {sub {gamma}{gamma}} production have been published. A method for incorporating parton showering in such calculations was developed and applied to W production. The multicanonical Monte Carlo algorithm has stood up to the promises anticipated; it was used in multicanonical simulations of first-order phase transitions and for spin glass systems.
Not Available
1992-01-01
The effort of the experimental group has been concentrated on the CERN ALEPH and FERMILAB D0 collider experiments and completion of two fixed target experiments. The BNL fixed target experiment 771 took the world's largest sample of D(1285) and E/iota(1420) events, using pion, kaon and antiproton beams. Observing the following resonances: 0[sup [minus plus
NON-EQUILIBRIUM DYNAMICS OF MANY-BODY QUANTUM SYSTEMS: FUNDAMENTALS AND NEW FRONTIER
DeMille, David; LeHur, Karyn
2013-11-27
Rapid progress in nanotechnology and naofabrication techniques has ushered in a new era of quantum transport experiments. This has in turn heightened the interest in theoretical understanding of nonequilibrium dynamics of strongly correlated quantum systems. This project has advanced the frontiers of understanding in this area along several fronts. For example, we showed that under certain conditions, quantum impurities out of equilibrium can be reformulated in terms of an effective equilibrium theory; this makes it possible to use the gamut of tools available for quantum systems in equilibrium. On a different front, we demonstrated that the elastic power of a transmitted microwave photon in circuit QED systems can exhibit a many-body Kondo resonance. We also showed that under many circumstances, bipartite fluctuations of particle number provide an effective tool for studying many-body physics—particularly the entanglement properties of a many-body system. This implies that it should be possible to measure many-body entanglement in relatively simple and tractable quantum systems. In addition, we studied charge relaxation in quantum RC circuits with a large number of conducting channels, and elucidated its relation to Kondo models in various regimes. We also extended our earlier work on the dynamics of driven and dissipative quantum spin-boson impurity systems, deriving a new formalism that makes it possible to compute the full spin density matrix and spin-spin correlation functions beyond the weak coupling limit. Finally, we provided a comprehensive analysis of the nonequilibrium transport near a quantum phase transition in the case of a spinless dissipative resonant-level model. This project supported the research of two Ph.D. students and two postdoctoral researchers, whose training will allow them to further advance the field in coming years.
Dynamics in the quantum/classical limit based on selective use of the quantum potential
Garashchuk, Sophya Dell’Angelo, David; Rassolov, Vitaly A.
2014-12-21
A classical limit of quantum dynamics can be defined by compensation of the quantum potential in the time-dependent Schrödinger equation. The quantum potential is a non-local quantity, defined in the trajectory-based form of the Schrödinger equation, due to Madelung, de Broglie, and Bohm, which formally generates the quantum-mechanical features in dynamics. Selective inclusion of the quantum potential for the degrees of freedom deemed “quantum,” defines a hybrid quantum/classical dynamics, appropriate for molecular systems comprised of light and heavy nuclei. The wavefunction is associated with all of the nuclei, and the Ehrenfest, or mean-field, averaging of the force acting on the classical degrees of freedom, typical of the mixed quantum/classical methods, is avoided. The hybrid approach is used to examine evolution of light/heavy systems in the harmonic and double-well potentials, using conventional grid-based and approximate quantum-trajectory time propagation. The approximate quantum force is defined on spatial domains, which removes unphysical coupling of the wavefunction fragments corresponding to distinct classical channels or configurations. The quantum potential, associated with the quantum particle, generates forces acting on both quantum and classical particles to describe the backreaction.
Quantum technology and its applications
Boshier, Malcolm; Berkeland, Dana; Govindan, Tr; Abo - Shaeer, Jamil
2010-12-10
Quantum states of matter can be exploited as high performance sensors for measuring time, gravity, rotation, and electromagnetic fields, and quantum states of light provide powerful new tools for imaging and communication. Much attention is being paid to the ultimate limits of this quantum technology. For example, it has already been shown that exotic quantum states can be used to measure or image with higher precision or higher resolution or lower radiated power than any conventional technologies, and proof-of-principle experiments demonstrating measurement precision below the standard quantum limit (shot noise) are just starting to appear. However, quantum technologies have another powerful advantage beyond pure sensing performance that may turn out to be more important in practical applications: the potential for building devices with lower size/weight/power (SWaP) and cost requirements than existing instruments. The organizers of Quantum Technology Applications Workshop (QTAW) have several goals: (1) Bring together sponsors, researchers, engineers and end users to help build a stronger quantum technology community; (2) Identify how quantum systems might improve the performance of practical devices in the near- to mid-term; and (3) Identify applications for which more long term investment is necessary to realize improved performance for realistic applications. To realize these goals, the QTAW II workshop included fifty scientists, engineers, managers and sponsors from academia, national laboratories, government and the private-sector. The agenda included twelve presentations, a panel discussion, several breaks for informal exchanges, and a written survey of participants. Topics included photon sources, optics and detectors, squeezed light, matter waves, atomic clocks and atom magnetometry. Corresponding applications included communication, imaging, optical interferometry, navigation, gravimetry, geodesy, biomagnetism, and explosives detection. Participants considered the physics and engineering of quantum and conventional technologies, and how quantum techniques could (or could not) overcome limitations of conventional systems. They identified several auxiliary technologies that needed to be further developed in order to make quantum technology more accessible. Much of the discussion also focused on specific applications of quantum technology and how to push the technology into broader communities, which would in turn identify new uses of the technology. Since our main interest is practical improvement of devices and techniques, we take a liberal definition of 'quantum technology': a system that utilizes preparation and measurement of a well-defined coherent quantum state. This nomenclature encompasses features broader than entanglement, squeezing or quantum correlations, which are often more difficult to utilize outside of a laboratory environment. Still, some applications discussed in the workshop do take advantage of these 'quantum-enhanced' features. They build on the more established quantum technologies that are amenable to manipulation at the quantum level, such as atom magnetometers and atomic clocks. Understanding and developing those technologies through traditional engineering will clarify where quantum-enhanced features can be used most effectively, in addition to providing end users with improved devices in the near-term.
Shortcuts to adiabaticity from linear response theory
Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian
2015-10-23
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts to adiabaticity for specific and very short driving times.
Shortcuts to adiabaticity from linear response theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian
2015-10-23
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts tomore » adiabaticity for specific and very short driving times.« less
Optical Abelian lattice gauge theories
Tagliacozzo, L.; Celi, A.; Zamora, A.; Lewenstein, M.; ICREA-Institucio Catalana de Recerca i Estudis Avancats, 08010 Barcelona
2013-03-15
We discuss a general framework for the realization of a family of Abelian lattice gauge theories, i.e., link models or gauge magnets, in optical lattices. We analyze the properties of these models that make them suitable for quantum simulations. Within this class, we study in detail the phases of a U(1)-invariant lattice gauge theory in 2+1 dimensions, originally proposed by P. Orland. By using exact diagonalization, we extract the low-energy states for small lattices, up to 4 Multiplication-Sign 4. We confirm that the model has two phases, with the confined entangled one characterized by strings wrapping around the whole lattice. We explain how to study larger lattices by using either tensor network techniques or digital quantum simulations with Rydberg atoms loaded in optical lattices, where we discuss in detail a protocol for the preparation of the ground-state. We propose two key experimental tests that can be used as smoking gun of the proper implementation of a gauge theory in optical lattices. These tests consist in verifying the absence of spontaneous (gauge) symmetry breaking of the ground-state and the presence of charge confinement. We also comment on the relation between standard compact U(1) lattice gauge theory and the model considered in this paper. - Highlights: Black-Right-Pointing-Pointer We study the quantum simulation of dynamical gauge theories in optical lattices. Black-Right-Pointing-Pointer We focus on digital simulation of abelian lattice gauge theory. Black-Right-Pointing-Pointer We rediscover and discuss the puzzling phase diagram of gauge magnets. Black-Right-Pointing-Pointer We detail the protocol for time evolution and ground-state preparation in any phase. Black-Right-Pointing-Pointer We provide two experimental tests to validate gauge theory quantum simulators.
Leading-order calculation of electric conductivity in hot quantum...
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Subject: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACTION INTEGRAL; CALCULATION METHODS; ELECTRIC CONDUCTIVITY; FEYNMAN DIAGRAM; GAUGE INVARIANCE; INTEGRAL EQUATIONS; QUANTUM ...
Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
He, Lianyi; Lu, Haifeng; Cao, Gaoqing; Hu, Hui; Liu, Xia -Ji
2015-08-14
We present a theoretical study of the ground state of the BCS-BEC crossover in dilute two-dimensional Fermi gases. While the mean-field theory provides a simple and analytical equation of state, the pressure is equal to that of a noninteracting Fermi gas in the entire BCS-BEC crossover, which is not consistent with the features of a weakly interacting Bose condensate in the BEC limit and a weakly interacting Fermi liquid in the BCS limit. The inadequacy of the two-dimensional mean-field theory indicates that the quantum fluctuations are much more pronounced than those in three dimensions. In this work, we show thatmore » the inclusion of the Gaussian quantum fluctuations naturally recovers the above features in both the BEC and the BCS limits. In the BEC limit, the missing logarithmic dependence on the boson chemical potential is recovered by the quantum fluctuations. Near the quantum phase transition from the vacuum to the BEC phase, we compare our equation of state with the known grand canonical equation of state of two-dimensional Bose gases and determine the ratio of the composite boson scattering length aB to the fermion scattering length a2D. We find aB ≃ 0.56a2D, in good agreement with the exact four-body calculation. As a result, we compare our equation of state in the BCS-BEC crossover with recent results from the quantum Monte Carlo simulations and the experimental measurements and find good agreements.« less
Discrete accidental symmetry for a particle in a constant magnetic field on a torus
Al-Hashimi, M.H. Wiese, U.-J.
2009-02-15
A classical particle in a constant magnetic field undergoes cyclotron motion on a circular orbit. At the quantum level, the fact that all classical orbits are closed gives rise to degeneracies in the spectrum. It is well-known that the spectrum of a charged particle in a constant magnetic field consists of infinitely degenerate Landau levels. Just as for the 1/r and r{sup 2} potentials, one thus expects some hidden accidental symmetry, in this case with infinite-dimensional representations. Indeed, the position of the center of the cyclotron circle plays the role of a Runge-Lenz vector. After identifying the corresponding accidental symmetry algebra, we re-analyze the system in a finite periodic volume. Interestingly, similar to the quantum mechanical breaking of CP invariance due to the {theta}-vacuum angle in non-Abelian gauge theories, quantum effects due to two self-adjoint extension parameters {theta}{sub x} and {theta}{sub y} explicitly break the continuous translation invariance of the classical theory. This reduces the symmetry to a discrete magnetic translation group and leads to finite degeneracy. Similar to a particle moving on a cone, a particle in a constant magnetic field shows a very peculiar realization of accidental symmetry in quantum mechanics.
Quantum cryptography over underground optical fibers
Hughes, R.J.; Luther, G.G.; Morgan, G.L.; Peterson, C.G.; Simmons, C.
1996-05-01
Quantum cryptography is an emerging technology in which two parties may simultaneously generated shared, secret cryptographic key material using the transmission of quantum states of light whose security is based on the inviolability of the laws of quantum mechanics. An adversary can neither successfully tap the key transmissions, nor evade detection, owing to Heisenberg`s uncertainty principle. In this paper the authors describe the theory of quantum cryptography, and the most recent results from their experimental system with which they are generating key material over 14-km of underground optical fiber. These results show that optical-fiber based quantum cryptography could allow secure, real-time key generation over ``open`` multi-km node-to-node optical fiber communications links between secure ``islands.``
Papp, E.; Micu, C.; Racolta, D.
2013-11-13
In this paper one deals with the theoretical derivation of energy bands and of related wavefunctions characterizing quasi 1D semiconductor heterostructures, such as InAs quantum wire models. Such models get characterized this time by equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions of dimensionless magnitude a under the influence of in-plane magnetic fields of magnitude B. We found that the orientations of the field can be selected by virtue of symmetry requirements. For this purpose one resorts to spin conservations, but alternative conditions providing sensible simplifications of the energy-band formula can be reasonably accounted for. Besides the wavenumber k relying on the 1D electron, one deals with the spin-like s=±1 factors in the front of the square root term of the energy. Having obtained the spinorial wavefunction, opens the way to the derivation of spin precession effects. For this purpose one resorts to the projections of the wavenumber operator on complementary spin states. Such projections are responsible for related displacements proceeding along the Ox-axis. This results in a 2D rotation matrix providing both the precession angle as well as the precession axis.
Gaddy, John; Heitmann, Tom; Montfrooij, Wouter
2014-05-07
The onset of ordering in quantum critical systems is characterized by a competition between the Kondo shielding of magnetic moments and the ordering of these moments. We show how a distribution of Kondo shielding temperaturesresulting from chemical dopingleads to critical behavior whose main characteristics are given by percolation physics. With the aid of Monte Carlo computer simulations, we are able to infer the low temperature part of the distribution of shielding temperatures in heavily doped quantum critical Ce(Ru{sub 0.24}Fe{sub 0.76}){sub 2}Ge{sub 2}. Based on this distribution, we show that the ordering dynamicssuch as the growth of the correlation length upon coolingcan be understood by the spawning of magnetic clusters. Our findings explain why the search for universal exponents in quantum critical systems has been unsuccessful: the underlying percolation network associated with the chemical doping of quantum critical systems has to be incorporated in the modeling of these quantum critical systems.
Bose-Einstein Condensation and Bose Glasses in an S = 1 Organo-metallic quantum magnet
Zapf, Vivien
2012-06-01
I will speak about Bose-Einstein condensation (BEC) in quantum magnets, in particular the compound NiCl2-4SC(NH2)2. Here a magnetic field-induced quantum phase transition to XY antiferromagnetism can be mapped onto BEC of the spins. The tuning parameter for BEC transition is the magnetic field rather than the temperature. Some interesting phenomena arise, for example the fact that the mass of the bosons that condense can be strongly renormalized by quantum fluctuations. I will discuss the utility of this mapping for both understanding the nature of the quantum magnetism and testing the thermodynamic limit of Bose-Einstein Condensation. Furthermore we can dope the system in a clean and controlled way to create the long sought-after Bose Glass transition, which is the bosonic analogy of Anderson localization. I will present experiments and simulations showing evidence for a new scaling exponent, which finally makes contact between theory and experiments. Thus we take a small step towards the difficult problem of understanding the effect of disorder on bosonic wave functions.
A quantum measure of the multiverse
Vilenkin, Alexander
2014-05-01
It has been recently suggested that probabilities of different events in the multiverse are given by the frequencies at which these events are encountered along the worldline of a geodesic observer (the ''watcher''). Here I discuss an extension of this probability measure to quantum theory. The proposed extension is gauge-invariant, as is the classical version of this measure. Observations of the watcher are described by a reduced density matrix, and the frequencies of events can be found using the decoherent histories formalism of Quantum Mechanics (adapted to open systems). The quantum watcher measure makes predictions in agreement with the standard Born rule of QM.
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Quantum Optics - Sandia Energy Energy Search Icon Sandia Home Locations Contact Us Employee Locator Energy & Climate Secure & Sustainable Energy Future Stationary Power Energy Conversion Efficiency Solar Energy Wind Energy Water Power Supercritical CO2 Geothermal Natural Gas Safety, Security & Resilience of the Energy Infrastructure Energy Storage Nuclear Power & Engineering Grid Modernization Battery Testing Nuclear Fuel Cycle Defense Waste Management Programs Advanced Nuclear
Volkova, E. A.; Popov, A. M. Tikhonova, O. V.
2013-03-15
The nonlinear polarization response of a quantum system modeling a silver atom in the field of high-intensity radiation in the IR and UV spectral ranges has been studied by direct numerical integration of a nonstationary Schroedinger equation. The domains of applicability of perturbation theory and polarization expansion in powers of the field intensity are determined. The contribution of excited atoms and electrons in a continuum to the atomic polarization response at the field frequency, which arises due to the radiation-induced excitation and photoionization processes, is analyzed. Features of the nonlinear response to an external field under conditions of atom stabilization are considered.
Engineering Light: Quantum Cascade Lasers
Claire Gmachl
2010-09-01
Quantum cascade lasers are ideal for environmental sensing and medical diagnostic applications. Gmachl discusses how these lasers work, and their applications, including their use as chemical trace gas sensors. As examples of these applications, she briefly presents results from her field campaign at the Beijing Olympics, and ongoing campaigns in Texas, Maryland, and Ghana.
Entanglement, Holography, and the Quantum Phases of Matter (Conference) |
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SciTech Connect SciTech Connect Search Results Conference: Entanglement, Holography, and the Quantum Phases of Matter Citation Details In-Document Search Title: Entanglement, Holography, and the Quantum Phases of Matter Electrons in many interesting materials, such as the high temperature superconductors, exhibit low energy states with complex varieties of quantum entanglement. I will describe how the methods of holography, drawn from string theory, have given us a new tool to describe such
Universality in dynamical formation of entanglement for quantum chaos
Kubotani, Hiroto; Toda, Mikito; Adachi, Satoshi [Institute of Physics, Faculty of Engineering, Kanagawa University, Yokohama 221-8686 (Japan); Department of Physics, Faculty of Science, Nara Women's University, Nara 630-8506 (Japan); Department of Physics, Faculty of Science, Tokyo Institute of Technology, Meguro 152-8550 (Japan)
2006-09-15
Dynamical formation of entanglement is studied for quantum chaotic biparticle systems. We find that statistical properties of the Schmidt eigenvalues for strong chaos are well described by the random matrix theory of the Laguerre unitary ensemble. This implies that entanglement formation for quantum chaos has universal properties, and does not depend on specific aspects of the systems.
An Effective Theory of Dirac Dark Matter Harnik, Roni; /Stanford...
Office of Scientific and Technical Information (OSTI)
Oregon U.; , 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ABUNDANCE; ANNIHILATION;...
Alpha Theory Maity, Debaprasad; /NCTS, Taipei /Taiwan, Natl....
Office of Scientific and Technical Information (OSTI)
Park SLAC 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; GALAXY CLUSTERS; MODIFICATIONS; PARITY; PHOTONS; PLASMA;...
Quantum Security for the Physical Layer
Humble, Travis S
2013-01-01
The physical layer describes how communication signals are encoded and transmitted across a channel. Physical security often requires either restricting access to the channel or performing periodic manual inspections. In this tutorial, we describe how the field of quantum communication offers new techniques for securing the physical layer. We describe the use of quantum seals as a unique way to test the integrity and authenticity of a communication channel and to provide security for the physical layer. We present the theoretical and physical underpinnings of quantum seals including the quantum optical encoding used at the transmitter and the test for non-locality used at the receiver. We describe how the envisioned quantum physical sublayer senses tampering and how coordination with higher protocol layers allow quantum seals to influence secure routing or tailor data management methods. We conclude by discussing challenges in the development of quantum seals, the overlap with existing quantum key distribution cryptographic services, and the relevance of a quantum physical sublayer to the future of communication security.
Koh, D., E-mail: dh.koh@utexas.edu, E-mail: Taewoo.Kim@sematech.org [Department of Electrical and Computer Engineering, Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States); SEMATECH, Inc., Albany, New York 12203 (United States); Kwon, H. M. [Department of Electronics Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Kim, T.-W., E-mail: dh.koh@utexas.edu, E-mail: Taewoo.Kim@sematech.org; Veksler, D.; Gilmer, D.; Kirsch, P. D. [SEMATECH, Inc., Albany, New York 12203 (United States); Kim, D.-H. [SEMATECH, Inc., Albany, New York 12203 (United States); GLOBALFOUNDRIES, Malta, New York 12020 (United States); Hudnall, Todd W. [Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, 78666 (United States); Bielawski, Christopher W. [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712 (United States); Maszara, W. [GLOBALFOUNDRIES, Santa Clara, California 95054 (United States); Banerjee, S. K. [Department of Electrical and Computer Engineering, Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States)
2014-04-21
In this study, we have fabricated nanometer-scale channel length quantum-well (QW) metal-oxide-semiconductor field effect transistors (MOSFETs) incorporating beryllium oxide (BeO) as an interfacial layer. BeO has high thermal stability, excellent electrical insulating characteristics, and a large band-gap, which make it an attractive candidate for use as a gate dielectric in making MOSFETs. BeO can also act as a good diffusion barrier to oxygen owing to its small atomic bonding length. In this work, we have fabricated In{sub 0.53}Ga{sub 0.47}As MOS capacitors with BeO and Al{sub 2}O{sub 3} and compared their electrical characteristics. As interface passivation layer, BeO/HfO{sub 2} bilayer gate stack presented effective oxide thickness less 1 nm. Furthermore, we have demonstrated In{sub 0.7}Ga{sub 0.3}As QW MOSFETs with a BeO/HfO{sub 2} dielectric, showing a sub-threshold slope of 100?mV/dec, and a transconductance (g{sub m,max}) of 1.1 mS/?m, while displaying low values of gate leakage current. These results highlight the potential of atomic layer deposited BeO for use as a gate dielectric or interface passivation layer for IIIV MOSFETs at the 7?nm technology node and/or beyond.
Photovoltaic Theory and Modeling - Energy Innovation Portal
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Photovoltaic Theory and Modeling Los Alamos National Laboratory Contact LANL About This Technology Effect of Ligands on semiconductor QD DOS (quantum chemistry calculations) Effect of Ligands on semiconductor QD DOS (quantum chemistry calculations) Technology Marketing SummaryThe scientists developing this capability welcome the opportunity to unite with industry and advance its potential.DescriptionAs the solar industry works to build the infrastructure necessary to make electricity from
Hamiltonian Light-Front Ffield Theory in a Basis Function Approach
Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Sternberg, P.; Ng, E.G.; Yang, C.
2009-05-15
Hamiltonian light-front quantum field theory constitutes a framework for the non-perturbative solution of invariant masses and correlated parton amplitudes of self-bound systems. By choosing the light-front gauge and adopting a basis function representation, we obtain a large, sparse, Hamiltonian matrix for mass eigenstates of gauge theories that is solvable by adapting the ab initio no-core methods of nuclear many-body theory. Full covariance is recovered in the continuum limit, the infinite matrix limit. There is considerable freedom in the choice of the orthonormal and complete set of basis functions with convenience and convergence rates providing key considerations. Here, we use a two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall AdS/QCD model obtained from light-front holography. We outline our approach, present illustrative features of some non-interacting systems in a cavity and discuss the computational challenges.
[Mathematics and string theory]. Progress report [August 1, 1992--July 31, 1993
Jaffe, A.; Yau, Shing-Tung
1993-07-01
Work on this grant was centered on connections between non- commutative geometry and physics. Topics covered included: cyclic cohomology, non-commutative manifolds, index theory, reflection positivity, space quantization, quantum groups, number theory, etc.
Quantum Fuel Systems Technologies Worldwide Inc Quantum Technologies...
Fuel Systems Technologies Worldwide Inc Quantum Technologies Jump to: navigation, search Name: Quantum Fuel Systems Technologies Worldwide Inc (Quantum Technologies) Place: Irvine,...
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Neutrino Theory Neutrino Theory Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email Bruce Carlsten (505) 667-5657 Email Neutrino Theory solar neutrino Figure 1: Impact of the solar neutrino mass splitting on collective oscillations of supernova neutrinos. Notice that while the strictly vanishing splitting gives the two-flavor result, even a tiny nonzero value qualitatively changes the answer. From [1]. Neutrino physics underwent
Sanfilippo, Antonio P.
2005-12-27
Graph theory is a branch of discrete combinatorial mathematics that studies the properties of graphs. The theory was pioneered by the Swiss mathematician Leonhard Euler in the 18th century, commenced its formal development during the second half of the 19th century, and has witnessed substantial growth during the last seventy years, with applications in areas as diverse as engineering, computer science, physics, sociology, chemistry and biology. Graph theory has also had a strong impact in computational linguistics by providing the foundations for the theory of features structures that has emerged as one of the most widely used frameworks for the representation of grammar formalisms.
Microscopic Theory of Nuclear Fission: Recent Highlights | Argonne...
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world, a predictive theory of fission should instead be based solely on quantum many-body methods and our best knowledge of nuclear forces. Today, there is a consensus that...
Barnes, Ted {F E }
2010-01-01
In this invited presentation, I review some recent developments in the theory of charmonium that appear likely to be of importance for future experimental studies in this field. The specific areas considered are double charmonium production. LQCD studies of charmonium, recent results for hadron loops, cc{bar} production cross sections at PANDA, charm molecules, and two recent developments, "charmiscelleny".
Reliable quantum communication over a quantum relay channel
Gyongyosi, Laszlo; Imre, Sandor
2014-12-04
We show that reliable quantum communication over an unreliable quantum relay channels is possible. The coding scheme combines the results on the superadditivity of quantum channels and the efficient quantum coding approaches.
Spectroscopic properties of colloidal indium phosphide quantum wires
Wang, Lin-Wang; Wang, Fudong; Yu, Heng; Li, Jingbo; Hang, Qingling; Zemlyanov, Dmitry; Gibbons, Patrick C.; Wang, Lin-Wang; Janes, David B.; Buhro, William E.
2008-07-11
Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence efficiencies through photochemical etching in the presence of HF result only in photochemical thinning or photo-oxidation, without a significant influence on quantum-wire photoluminescence. However, photo-oxidation produces residual dot and rod domains within the wires, which are luminescent. The results establish that the quantum-wire band gaps are weakly influenced by the nature of the surface passivation, and that colloidal quantum wires have intrinsically low photoluminescence efficiencies.
Primordial perturbations in Einstein-Aether and BPSH theories
Armendariz-Picon, Cristian; Sierra, Noela Fariña; Garriga, Jaume E-mail: noela@ffn.ub.es
2010-07-01
We study the primordial perturbations generated during a stage of single-field inflation in Einstein-aether theories. Quantum fluctuations of the inflaton and aether fields seed long wavelength adiabatic and isocurvature scalar perturbations, as well as transverse vector perturbations. Geometrically, the isocurvature mode is the potential for the velocity field of the aether with respect to matter. For a certain range of parameters, this mode may lead to a sizable random velocity of the aether within the observable universe. The adiabatic mode corresponds to curvature perturbations of co-moving slices (where matter is at rest). In contrast with the standard case, it has a non-vanishing anisotropic stress on large scales. Scalar and vector perturbations may leave significant imprints on the cosmic microwave background. We calculate their primordial spectra, analyze their contributions to the temperature anisotropies, and formulate some of the phenomenological constraints that follow from observations. These may be used to further tighten the existing limits on the parameters for this class of theories. The results for the scalar sector also apply to the extension of Hořava gravity recently proposed by Blas, Pujolàs and Sibiryakov.
Soft collinear effective theory for heavy WIMP annihilation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Bauer, Martin; Cohen, Timothy; Hill, Richard J.; Solon, Mikhail P.
2015-01-19
In a large class of models for Weakly Interacting Massive Particles (WIMPs), the WIMP mass M lies far above the weak scale mW. This work identifies universal Sudakov-type logarithms ~ ? log(2 M / mW) that spoil the naive convergence of perturbation theory for annihilation processes. An effective field theory (EFT) framework is presented, allowing the systematic resummation of these logarithms. Another impact of the large separation of scales is that a long-distance wavefunction distortion from electroweak boson exchange leads to observable modifications of the cross section. Careful accounting of momentum regions in the EFT allows the rigorous disentanglement ofmorethis so-called Sommerfeld enhancement from the short-distance hard annihilation process. The WIMP is described as a heavy-particle field, while the electroweak gauge bosons are treated as soft and collinear fields. Hard matching coefficients are computed at renormalization scale ? ~ 2 M , then evolved down to ? ~ mW, where electroweak symmetry breaking is incorporated and the matching onto the relevant quantum mechanical Hamiltonian is performed. The example of an SU(2)W triplet scalar dark matter candidate annihilating to line photons is used for concreteness, allowing the numerical exploration of the impact of next-to-leading order corrections and log resummation. For M ? 3 TeV, the resummed Sommerfeld enhanced cross section is reduced by a factor of ~ 3 with respect to the treelevel fixed order result.less
Andraka, Bohdan
2015-05-14
The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs?Sb??. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs?Sb?? are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense international controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.
Two-leg $\mathrm{SU}\left(2n\right)$ spin ladder: A low-energy effective field theory approach
Lecheminant, P.; Tsvelik, A. M.
2015-05-07
We present a field-theory analysis of a model of two SU(2n)-invariant magnetic chains coupled by a generic interaction preserving time reversal and inversion symmetry. Contrary to the SU(2)-invariant case the zero-temperature phase diagram of such two-leg spin ladder does not contain topological phases. Thus, only generalized Valence Bond Solid phases are stabilized when n > 1 with different wave vectors and ground-state degeneracies. In particular, we find a phase which is made of a cluster of 2n spins put in an SU(2n) singlet state. For n = 3, this cluster phase is relevant to ?Yb ultracold atoms, with an emergent SU(6) symmetry, loaded in a double-well optical lattice.
Kim, Inkoo; Lee, Yoon Sup
2014-10-28
We report the formulation and implementation of KRCASPT2, a two-component multi-configurational second-order perturbation theory based on Kramers restricted complete active space self-consistent field (KRCASSCF) reference function, in the framework of the spin-orbit relativistic effective core potential. The zeroth-order Hamiltonian is defined as the sum of nondiagonal one-electron operators with generalized two-component Fock matrix elements as scalar factors. The Kramers symmetry within the zeroth-order Hamiltonian is maintained via the use of a state-averaged density, allowing a consistent treatment of degenerate states. The explicit expressions are derived for the matrix elements of the zeroth-order Hamiltonian as well as for the perturbation vector. The use of a fully variational reference function and nondiagonal operators in relativistic multi-configurational perturbation theory is reported for the first time. A series of initial calculations are performed on the ionization potential and excitation energies of the atoms of the 6p-block; the results display a significant improvement over those from KRCASSCF, showing a closer agreement with experimental results. Accurate atomic properties of the superheavy elements of the 7p-block are also presented, and the electronic structures of the low-lying excited states are compared with those of their lighter homologues.
The breakdown of de Gennes Scaling in TbxEr1-xNi2B2C and its mean field theory explanation
Gao, Chunwang
2005-05-01
The Neel temperatures, T{sub N}, of Tb{sub x}Er{sub 1-x}Ni{sub 2}B{sub 2}C samples have been determined from the temperature dependence of magnetization measurements. A breakdown of the de Gennes scaling of T{sub N} with a clear turning point around x = 0.45 has been observed. The T{sub N} values of Tb{sub x}Er{sub 1-x}Ni{sub 2}B{sub 2}C do not change much within the range of O < x < 0.45 and then, for larger x they increase almost linearly with concentration until T{sub N} = 14.9K is reached for x = 1, TbNi{sub 2}B{sub 2}C. The clear change in the x-dependence of T{sub N} around x = 0.45 can be linked to a change in the local moment ordering direction from transverse to longitudinal, a change which is consistent with recent resonant X-ray scattering data. These features in T{sub N}(x) can be explained using a mean field model.
Selectivity in multiple quantum nuclear magnetic resonance
Warren, W.S.
1980-11-01
The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.
Correlated electron dynamics with time-dependent quantum Monte Carlo:
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Three-dimensional helium (Journal Article) | SciTech Connect Correlated electron dynamics with time-dependent quantum Monte Carlo: Three-dimensional helium Citation Details In-Document Search Title: Correlated electron dynamics with time-dependent quantum Monte Carlo: Three-dimensional helium Here the recently proposed time-dependent quantum Monte Carlo method is applied to three dimensional para- and ortho-helium atoms subjected to an external electromagnetic field with amplitude sufficient
Quantum stochastic thermodynamic on harmonic networks
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Deffner, Sebastian
2016-01-04
Fluctuation theorems are symmetry relations for the probability to observe an amount of entropy production in a finite-time process. In a recent paper Pigeon et al (2016 New. J. Phys. 18 013009) derived fluctuation theorems for harmonic networks by means of the large deviation theory. Furthermore, their novel approach is illustrated with various examples of experimentally relevant systems. As a main result, however, Pigeon et al provide new insight how to consistently formulate quantum stochastic thermodynamics, and provide new and robust tools for the study of the thermodynamics of quantum harmonic networks.
Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects
Urban, Jeffry Todd
2004-12-21
Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantum-mechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies.The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics. The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nuclei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically.The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy. The fifth chapter continues to extend the principles of multiple quantum NMR spectroscopy of quadrupolar nuclei to make analogies between experiments in NMR/nuclear quadrupolar resonance (NQR) and experiments in atomic/molecular optics (AMO). These analogies are made through the Hamiltonian and density operator formalism of angular momentum dynamics in the presence of electric and magnetic fields.The sixth chapter investigates the use of the macroscopic nuclear dipolar field to encode the NMR spectrum of an analyte nucleus indirectly in the magnetization of a sensor nucleus. This technique could potentially serve as an encoding module for the recently developed NMR remote detection experiment. The feasibility of using hyperpolarized xenon-129 gas as a sensor is discussed. This work also reports the use of an optical atomic magnetometer to detect the nuclear magnetization of Xe-129 gas, which has potential applicability as a detection module for NMR remote detection experiments.
Huang, Liang; Lai Yingcheng; Ferry, David K.; Goodnick, Stephen M.; Akis, Richard
2009-07-31
The concentrations of wave functions about classical periodic orbits, or quantum scars, are a fundamental phenomenon in physics. An open question is whether scarring can occur in relativistic quantum systems. To address this question, we investigate confinements made of graphene whose classical dynamics are chaotic and find unequivocal evidence of relativistic quantum scars. The scarred states can lead to strong conductance fluctuations in the corresponding open quantum dots via the mechanism of resonant transmission.
Quantum measurements of atoms using cavity QED
Dada, Adetunmise C.; Andersson, Erika [SUPA, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Jones, Martin L.; Kendon, Vivien M. [School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom); Everitt, Mark S. [School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom); National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda ku, Tokyo 101-8430 (Japan)
2011-04-15
Generalized quantum measurements are an important extension of projective or von Neumann measurements in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two nonstandard quantum measurements using cavity QED. The first measurement optimally and unambiguously distinguishes between two nonorthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionization detection of atoms and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurements have been realized only on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.
Geometric scalar theory of gravity
Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D.; Moschella, U. E-mail: eduhsb@cbpf.br E-mail: egoulart@cbpf.br E-mail: toniato@cbpf.br
2013-06-01
We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.
Sumpter, Bobby G; Sherrill, David; Sinnokrot, Mutasem O; Marshall, Michael S.; Hohenstein, Edward G.; Walker, Ross; Gould, Ian R
2009-01-01
Several popular force fields, namely, CHARMM, AMBER, OPLS-AA, and MM3, have been tested for their ability to reproduce highly accurate quantum mechani- cal potential energy curves for noncovalent interactions in the benzene dimer, the benzene-CH4 complex, and the benzene-H2S complex. All of the force fields are semi-quantitatively correct, but none of them is consistently reliable quantitatively. Re-optimization of Lennard-Jones parameters and symmetry-adapted perturbation theory analysis for the benzene dimer suggests that better agreement cannot be expected unless more flexible functional forms (particularly for the electrostatic contributions)are employed for the empirical force fields.
Scalable optical quantum computer
Manykin, E A; Mel'nichenko, E V [Institute for Superconductivity and Solid-State Physics, Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation)
2014-12-31
A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)
Quantum singularities in the BTZ spacetime
Pitelli, Joao Paulo M.; Letelier, Patricio S.
2008-06-15
The spinless Banados-Teiltelboim-Zanelli spacetime is considered in the quantum theory context. Specifically, we study the case of a negative mass parameter using quantum test particles obeying the Klein-Gordon and Dirac equations. We study if this classical singular spacetime, with a naked singularity at the origin, remains singular when tested with quantum particles. The need for additional information near the origin is confirmed for massive scalar particles and all of the possible boundary conditions necessary to turn the spatial portion of the wave operator self-adjoint are found. When tested by massless scalar particles or fermions, the singularity is ''healed'' and no extra boundary condition is needed. Near infinity, no boundary conditions are necessary.
Theory of antiferromagnetic superconductors
Machida, K.; Nokura, K.; Matsubara, T.
1980-09-01
In this paper a theory is presented of antiferromagnetic superconductors in which a spin-density wave (SDW) ordering with a wave vector Q may coexist with superconductivity. The effect of the antiferromagnetic molecular field h/sub Q/(T) on the Cooper pairing is studied, and it is shown that, below the magnetic transition temperature T/sub N/' the Bardeen-Cooper-Schruffer coupling parameter is reduced by a factor of (1-constsuch thatub Q/(T)epsilon/sub F/) due to the formation of energy gaps of SDW on the Fermi surface along Q and this reduction can explain the anomaly in the upper critical field H/sub c/2 just below T/sub N/ as observed in RMo/sub 6/S/sub 8/ (R=Gd, Tb, and Dy). Taking account of both the spin-orbit scattering and spin-fluctuation effect near T/sub N/ in addition to the effect of h/sub Q/(T), a theoretical calculation of the superconducting transition temperature T/sub c/ and H/sub c/2(T) is performed. Detailed quantitative comparisons between theory and experiments on H/sub c/2(T) are made with fairly good accord for the above three compounds. Some speculation is given to discuss the remaining descrepancies between theory and experiments and certain phenomena not yet explained by the theory.
A Leap Toward a 'Perfect' Quantum Metamaterial
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A Leap Toward a 'Perfect' Quantum Metamaterial
Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate
Anufriev, Roman; Chauvin, Nicolas Bru-Chevallier, Catherine; Khmissi, Hammadi; Naji, Khalid; Gendry, Michel; Patriarche, Gilles
2014-05-05
We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures.
Quantum Chemistry, and Eclectic Mix: From Silicon Carbide to Size Consistency
Jamie Marie Rintelman
2004-12-19
Chemistry is a field of great breadth and variety. It is this diversity that makes for both an interesting and challenging field. My interests have spanned three major areas of theoretical chemistry: applications, method development, and method evaluation. The topics presented in this thesis are as follows: (1) a multi-reference study of the geometries and relative energies of four atom silicon carbide clusters in the gas phase; (2) the reaction of acetylene on the Si(100)-(2x1) surface; (3) an improvement to the Effective Fragment Potential (EFP) solvent model to enable the study of reactions in both aqueous and nonaqueous solution; and (4) an evaluation of the size consistency of Multireference Perturbation Theory (MRPT). In the following section, the author briefly discusses two topics central to, and present throughout, this thesis: Multi-reference methods and Quantum Mechanics/Molecular Mechanics (QM/MM) methods.
Pseudospin symmetry and effective field theory
Ginocchio, J N
2008-01-01
Since pseudospin has been shown to be approximately conserved in nuclei, we investigate if there is an advantage in using the pseudospin operators as well as the spin operators in the description of the nucleon-nucleon interaction. We conclude that, indeed, there is an advantage.
Electron density magnification of the collective spin-orbit field...
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Electron density magnification of the collective spin-orbit field in quantum wells ... This content will become publicly available on September 27, 2016 Title: Electron density ...
High-Resolution Photocurrent Microscopy Using Near-FieldCathodolumine...
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High-Resolution Photocurrent Microscopy Using Near-Field Cathodoluminescence of Quantum Dots. Citation Details In-Document Search Title: High-Resolution Photocurrent Microscopy ...
Quantum transport, anomalous dephasing, and spin-orbit coupling in an open
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Connect Quantum chaos in Aharonov-Bohm oscillations Citation Details In-Document Search Title: Quantum chaos in Aharonov-Bohm oscillations Aharonov-Bohm oscillations in a mesoscopic ballistic ring are considered under the influence of a resonant magnetic field with one and two frequencies. The authors investigate the oscillations of the time-averaged electron energy at zero temperature in the regime of an isolated quantum nonlinear resonance and at the transition to quantum chaos, when two
Plasmon modes of metallic nanowires including quantum nonlocal effects
Moradi, Afshin
2015-03-15
The properties of electrostatic surface and bulk plasmon modes of cylindrical metallic nanowires are investigated, using the quantum hydrodynamic theory of plasmon excitation which allows an analytical study of quantum tunneling effects through the Bohm potential term. New dispersion relations are obtained for each type of mode and their differences with previous treatments based on the standard hydrodynamic model are analyzed in detail. Numerical results show by considering the quantum effects, as the value of wave number increases, the surface modes are slightly red-shifted first and then blue-shifted while the bulk modes are blue-shifted.
Group action in topos quantum physics
Flori, C.
2013-03-15
Topos theory has been suggested first by Isham and Butterfield, and then by Isham and Doering, as an alternative mathematical structure within which to formulate physical theories. In particular, it has been used to reformulate standard quantum mechanics in such a way that a novel type of logic is used to represent propositions. In this paper, we extend this formulation to include the notion of a group and group transformation in such a way that we overcome the problem of twisted presheaves. In order to implement this we need to change the type of topos involved, so as to render the notion of continuity of the group action meaningful.
Audenaert, Koenraad M. R.
2014-11-15
In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.
Heller, E.J. (Los Alamos National Lab., Albuquerque, NM); Davis, M.J.
1982-06-10
This paper reviews some of the opinions on quantum chaos put forth at the 1981 American Conference on Theoretical Chemistry and presents evidence to support the author's point of view. The degree of correspondence between classical and quantum onset and extent of chaos differs markedly according to the definition adopted for quantum chaos. At one extreme, a quantum generalization of the classical Kolmolgorov entropy which give zero entrophy for quantum systems with a discrete spectrum regardless of the classical properties, was a suitable foundation for the definition of quantum chaos. At the other, the quantum phase space definition shows generally excellent correspondence to the classical phase space measures. The authors preferred this approach. Another point of controversy is the question of whether the spectrum of energy levels (or its variation with some parameter of the Hamiltonian) is enough to characterize the quantum chaos (or lack of it), or whether more information is needed (i.e., eigenfunctions). The authors conclude that one does not want to rely upon eigenvalues alone to characterize the degree of chaos in the quantum dynamics.
Quantum filter of spin polarized states: Metal–dielectric–ferromagnetic/semiconductor device
Makarov, Vladimir I.; Khmelinskii, Igor
2014-02-01
Highlights: • Development of a new spintronics device. • Development of quantum spin polarized filters. • Development of theory of quantum spin polarized filter. - Abstract: Recently we proposed a model for the Quantum Spin-Polarized State Filter (QSPSF). The magnetic moments are transported selectively in this model, detached from the electric charge carriers. Thus, transfer of a spin-polarized state between two conductors was predicted in a system of two levels coupled by exchange interaction. The strength of the exchange interaction between the two conductive layers depends on the thickness of the dielectric layer separating them. External magnetic fields modulate spin-polarized state transfer, due to Zeeman level shift. Therefore, a linearly growing magnetic field generates a series of current peaks in a nearby coil. Thus, our spin-state filter should contain as least three nanolayers: (1) conductive or ferromagnetic; (2) dielectric; and (3) conductive or semiconductive. The spectrum of spin-polarized states generated by the filter device consists of a series of resonance peaks. In a simple case the number of lines equals S, the total spin angular momentum of discrete states in one of the coupled nanolayers. Presently we report spin-polarized state transport in metal–dielectric–ferromagnetic (MDF) and metal–dielectric–semiconductor (MDS) three-layer sandwich devices. The exchange-resonance spectra in such devices are quite specific, differing also from spectra observed earlier in other three-layer devices. The theoretical model is used to interpret the available experimental results. A detailed ab initio analysis of the magnetic-field dependence of the output magnetic moment averaged over the surface of the device was carried out. The model predicts the resonance structure of the signal, although at its present accuracy it cannot predict the positions of the spectral peaks.
Quantum physics and human values
Stapp, H.P.
1989-09-01
This report discusses the following concepts: the quantum conception of nature; the quantum conception of man; and the impact upon human values. (LSP).
Bilayer graphene quantum dot defined by topgates
Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W.
2014-06-21
We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.
Coherent Synchrotron Radiation: Theory and Simulations.
Novokhatski, Alexander; /SLAC
2012-03-29
The physics of coherent synchrotron radiation (CSR) emitted by ultra-relativistic electron bunches, known since the last century, has become increasingly important with the development of high peak current free electron lasers and shorter bunch lengths in storage rings. Coherent radiation can be described as a low frequency part of the familiar synchrotron radiation in bending magnets. As this part is independent of the electron energy, the fields of different electrons of a short bunch can be in phase and the total power of the radiation will be quadratic with the number of electrons. Naturally the frequency spectrum of the longitudinal electron distribution in a bunch is of the same importance as the overall electron bunch length. The interest in the utilization of high power radiation from the terahertz and far infrared region in the field of chemical, physical and biological processes has led synchrotron radiation facilities to pay more attention to the production of coherent radiation. Several laboratories have proposed the construction of a facility wholly dedicated to terahertz production using the coherent radiation in bending magnets initiated by the longitudinal instabilities in the ring. Existing synchrotron radiation facilities also consider such a possibility among their future plans. There is a beautiful introduction to CSR in the 'ICFA Beam Dynamics Newsletter' N 35 (Editor C. Biscari). In this paper we recall the basic properties of CSR from the theory and what new effects, we can get from the precise simulations of the coherent radiation using numerical solutions of Maxwell's equations. In particular, transverse variation of the particle energy loss in a bunch, discovered in these simulations, explains the slice emittance growth in bending magnets of the bunch compressors and transverse de-coherence in undulators. CSR may play same the role as the effect of quantum fluctuations of synchrotron radiation in damping rings. It can limit the minimum achievable emittance in the synchrotron light sources for short bunches.
High-Resolution Photocurrent Microscopy Using Near-Field
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Cathodoluminescence of Quantum Dots. (Journal Article) | SciTech Connect High-Resolution Photocurrent Microscopy Using Near-Field Cathodoluminescence of Quantum Dots. Citation Details In-Document Search Title: High-Resolution Photocurrent Microscopy Using Near-Field Cathodoluminescence of Quantum Dots. Abstract not provided. Authors: Talin, Albert Alec Publication Date: 2013-05-01 OSTI Identifier: 1145404 Report Number(s): SAND2013-4169J 453180 DOE Contract Number: DE-AC04-94AL85000 Resource
Jeff Neaton > DirectorTheory of Nanostructured Materials Facility...
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properties of materials with good accuracy from scratch, i.e., through solution of the quantum mechanics of a system of interacting electrons in a field of nuclei. In recent...
Quantum discord with weak measurements
Singh, Uttam Pati, Arun Kumar
2014-04-15
Weak measurements cause small change to quantum states, thereby opening up the possibility of new ways of manipulating and controlling quantum systems. We ask, can weak measurements reveal more quantum correlation in a composite quantum state? We prove that the weak measurement induced quantum discord, called as the super quantum discord, is always larger than the quantum discord captured by the strong measurement. Moreover, we prove the monotonicity of the super quantum discord as a function of the measurement strength and in the limit of strong projective measurement the super quantum discord becomes the normal quantum discord. We find that unlike the normal discord, for pure entangled states, the super quantum discord can exceed the quantum entanglement. Our results provide new insights on the nature of quantum correlation and suggest that the notion of quantum correlation is not only observer dependent but also depends on how weakly one perturbs the composite system. We illustrate the key results for pure as well as mixed entangled states. -- Highlights: Introduced the role of weak measurements in quantifying quantum correlation. We have introduced the notion of the super quantum discord (SQD). For pure entangled state, we show that the SQD exceeds the entanglement entropy. This shows that quantum correlation depends not only on observer but also on measurement strength.
Generalized contexts and consistent histories in quantum mechanics
Losada, Marcelo; Laura, Roberto
2014-05-15
We analyze a restriction of the theory of consistent histories by imposing that a valid description of a physical system must include quantum histories which satisfy the consistency conditions for all states. We prove that these conditions are equivalent to imposing the compatibility conditions of our formalism of generalized contexts. Moreover, we show that the theory of consistent histories with the consistency conditions for all states and the formalism of generalized context are equally useful representing expressions which involve properties at different times.
Soft collinear effective theory for heavy WIMP annihilation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Bauer, Martin; Cohen, Timothy; Hill, Richard J.; Solon, Mikhail P.
2015-01-19
In a large class of models for Weakly Interacting Massive Particles (WIMPs), the WIMP mass M lies far above the weak scale mW . This work identifies universal Sudakov-type logarithms ~ α log2(2 M/mW) that spoil the naive convergence of perturbation theory for annihilation processes. An effective field theory (EFT) framework is presented, allowing the systematic resummation of these logarithms. Another impact of the large separation of scales is that a long-distance wavefunction distortion from electroweak boson exchange leads to observable modifications of the cross section. Careful accounting of momentum regions in the EFT allows the rigorous disentanglement of thismore » so-called Sommerfeld enhancement from the short-distance hard annihilation process. In addition, the WIMP is described as a heavy-particle field, while the electroweak gauge bosons are treated as soft and collinear fields. Hard matching coefficients are computed at renormalization scale μ ~ 2 M , then evolved down to μ ~ mW , where electroweak symmetry breaking is incorporated and the matching onto the relevant quantum mechanical Hamiltonian is performed. The example of an SU(2)W triplet scalar dark matter candidate annihilating to line photons is used for concreteness, allowing the numerical exploration of the impact of next-to-leading order corrections and log resummation. As a result, for M ≃ 3 TeV, the resummed Sommerfeld enhanced cross section is reduced by a factor of ~ 3 with respect to the treelevel fixed order result.« less
Quantum states for quantum processes: A toy model for ammonia inversion spectra
Arteca, Gustavo A. [Departement de Chimie et Biochimie and Biomolecular Sciences Programme, Laurentian University, Ramsey Lake Road, Sudbury, Ontario, Canada P3E 2C6 (Canada); Department of Physical Chemistry, Uppsala University, A ring ngstroemlaboratoriet, Box 259, S-751 05 Uppsala (Sweden); Tapia, O. [Department of Physical Chemistry, Uppsala University, A ring ngstroemlaboratoriet, Box 259, S-751 05 Uppsala (Sweden)
2011-07-15
Chemical transformations are viewed here as quantum processes modulated by external fields, that is, as shifts in reactant to product amplitudes within a quantum state represented by a linear (coherent) superposition of electronuclear basis functions; their electronic quantum numbers identify the ''chemical species.'' This basis set can be mapped from attractors built from a unique electronic configurational space that is invariant with respect to the nuclear geometry. In turn, the quantum numbers that label these basis functions and the semiclassical potentials for the electronic attractors may be used to derive reaction coordinates to monitor progress as a function of the applied field. A generalization of Feynman's three-state model for the ammonia inversion process illustrates the scheme; to enforce symmetry for the entire inversion process model and ensure invariance with respect to nuclear configurations, the three attractors and their basis functions are computed with a grid of fixed floating Gaussian functions. The external-field modulation of the effective inversion barrier is discussed within this conceptual approach. This analysis brings the descriptions of chemical processes near modern technologies that employ molecules to encode information by means of confinement and external fields.
Direct measure of quantum correlation
Yu, Chang-shui [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Zhao, Haiqing [School of Science, Dalian Jiaotong University, Dalian 116028 (China)
2011-12-15
The quantumness of the correlation known as quantum correlation is usually measured by quantum discord. So far various quantum discords can be roughly understood as indirect measure by some special discrepancy of two quantities. We present a direct measure of quantum correlation by revealing the difference between the structures of classically and quantum correlated states. Our measure explicitly includes the contributions of the inseparability and local nonorthogonality of the eigenvectors of a density matrix. Besides its relatively easy computability, our measure can provide a unified understanding of quantum correlation of all the present versions.
Nexus: a modular workflow management system for quantum simulation codes
Krogel, Jaron T.
2015-08-24
The management of simulation workflows is a significant task for the individual computational researcher. Automation of the required tasks involved in simulation work can decrease the overall time to solution and reduce sources of human error. A new simulation workflow management system, Nexus, is presented to address these issues. Nexus is capable of automated job management on workstations and resources at several major supercomputing centers. Its modular design allows many quantum simulation codes to be supported within the same framework. Current support includes quantum Monte Carlo calculations with QMCPACK, density functional theory calculations with Quantum Espresso or VASP, and quantum chemical calculations with GAMESS. Users can compose workflows through a transparent, text-based interface, resembling the input file of a typical simulation code. A usage example is provided to illustrate the process.
On quantum Rnyi entropies: A new generalization and some properties
Mller-Lennert, Martin; Dupuis, Frdric; Szehr, Oleg; Fehr, Serge; Tomamichel, Marco
2013-12-15
The Rnyi entropies constitute a family of information measures that generalizes the well-known Shannon entropy, inheriting many of its properties. They appear in the form of unconditional and conditional entropies, relative entropies, or mutual information, and have found many applications in information theory and beyond. Various generalizations of Rnyi entropies to the quantum setting have been proposed, most prominently Petz's quasi-entropies and Renner's conditional min-, max-, and collision entropy. However, these quantum extensions are incompatible and thus unsatisfactory. We propose a new quantum generalization of the family of Rnyi entropies that contains the von Neumann entropy, min-entropy, collision entropy, and the max-entropy as special cases, thus encompassing most quantum entropies in use today. We show several natural properties for this definition, including data-processing inequalities, a duality relation, and an entropic uncertainty relation.
SU{sub {ital q}}(2) lattice gauge theory
Bimonte, G.; Stern, A.; Vitale, P.
1996-07-01
We reformulate the Hamiltonian approach to lattice gauge theories such that, at the classical level, the gauge group does not act canonically, but instead as a Poisson-Lie group. At the quantum level, the symmetry gets promoted to a quantum group gauge symmetry. The theory depends on two parameters: the deformation parameter {lambda} and the lattice spacing {ital a}. We show that the system of Kogut and Susskind is recovered when {lambda}{r_arrow}0, while QCD is recovered in the continuum limit (for any {lambda}). We, thus, have the possibility of having a two-parameter regularization of QCD. {copyright} {ital 1996 The American Physical Society.}
Dipole nano-laser: Theory and properties
Ghannam, T.
2014-03-31
In this paper we outline the main quantum properties of the system of nano-based laser called Dipole Nano-Laser emphasizing mainly on its ability to produce coherent light and for different configurations such as different embedding materials and subjecting it to an external classical electric field.
RKKY interaction in a chirally coupled double quantum dot system
Heine, A. W.; Tutuc, D.; Haug, R. J.; Zwicknagl, G.; Schuh, D.; Wegscheider, W.
2013-12-04
The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtained Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region.
Certifying the quantumness of a generalized coherent control scenario
Scholak, Torsten Brumer, Paul
2014-11-28
We consider the role of quantum mechanics in a specific coherent control scenario, designing a “coherent control interferometer” as the essential tool that links coherent control to quantum fundamentals. Building upon this allows us to rigorously display the genuinely quantum nature of a generalized weak-field coherent control scenario (utilizing 1 vs. 2 photon excitation) via a Bell-CHSH test. Specifically, we propose an implementation of “quantum delayed-choice” in a bichromatic alkali atom photoionization experiment. The experimenter can choose between two complementary situations, which are characterized by a random photoelectron spin polarization with particle-like behavior on the one hand, and by spin controllability and wave-like nature on the other. Because these two choices are conditioned coherently on states of the driving fields, it becomes physically unknowable, prior to measurement, whether there is control over the spin or not.
Castagnoli, G. )
1991-08-10
This paper reports that current conceptions of quantum mechanical computers inherit from conventional digital machines two apparently interacting features, machine imperfection and temporal development of the computational process. On account of machine imperfection, the process would become ideally reversible only in the limiting case of zero speed. Therefore the process is irreversible in practice and cannot be considered to be a fundamental quantum one. By giving up classical features and using a linear, reversible and non-sequential representation of the computational process - not realizable in classical machines - the process can be identified with the mathematical form of a quantum steady state. This form of steady quantum computation would seem to have an important bearing on the notion of cognition.
Values and the quantum conception of man
Stapp, H.P.
1995-06-01
Classical mechanics is based upon a mechanical picture of nature that is fundamentally incorrect. It has been replaced at the basic level by a radically different theory: quantum mechanics. This change entails an enormous shift in one`s basic conception of nature, one that can profoundly alter the scientific image of man himself. Self-image is the foundation of values, and the replacement of the mechanistic self-image derived from classical mechanics by one concordant with quantum mechanics may provide the foundation of a moral order better suited to today`s times, a self-image that endows human life with meaning, responsibility, and a deeper linkage to nature as a whole.
Hybrid Rotaxanes: Interlocked Structures for Quantum Computing...
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based on molecular magnets that may make them suitable as qubits for quantum computers. Chemistry Aids Quantum Computing Quantum bits or qubits are the fundamental...
Sandia Energy - 'Giant' Nanocrystal Quantum Dots
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'Giant' Nanocrystal Quantum Dots Home Energy Research EFRCs Solid-State Lighting Science EFRC 'Giant' Nanocrystal Quantum Dots 'Giant' Nanocrystal Quantum DotsTara...
Unimodular theory: A little pedagogical vision
Fernndez Cristbal, Jose Ma
2014-11-15
Under the generic designation of unimodular theory, two theoretical models of gravity are considered: the unimodular gravity and the TDiff theory. Our approach is primarily pedagogical. We aim to describe these models both from a geometric and a field-theoretical point of view. In addition, we explore connections with the cosmological-constant problem and outline some applications. We do not discuss the application of this theory to the quantization of gravity.
Quantum optics with single nanodiamonds flying over gold films: Towards a Robust quantum plasmonics
Mollet, O.; Drezet, A.; Huant, S.
2013-12-04
A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.
Towards a next theory of superconductivity
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Communications Office (505) 667-0471 Email "High magnetic-field measurements of doped copper-oxide superconductors are paving the way to a new theory of superconductivity," said...
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Weinberg, Alvin M.; Noderer, L. C.
1951-05-15
The large scale release of nuclear energy in a uranium fission chain reaction involves two essentially distinct physical phenomena. On the one hand there are the individual nuclear processes such as fission, neutron capture, and neutron scattering. These are essentially quantum mechanical in character, and their theory is non-classical. On the other hand, there is the process of diffusion -- in particular, diffusion of neutrons, which is of fundamental importance in a nuclear chain reaction. This process is classical; insofar as the theory of the nuclear chain reaction depends on the theory of neutron diffusion, the mathematical study of chain reactions is an application of classical, not quantum mechanical, techniques.
Magnetoelectroluminescence of organic heterostructures: Analytical theory
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and spectrally resolved measurements (Journal Article) | SciTech Connect Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements Citation Details In-Document Search Title: Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the
Significant Quantum Effects in Hydrogen Activation
Kyriakou, Georgios; Davidson, Erlend R.; Peng, Guowen; Roling, Luke T.; Singh, Suyash; Boucher, Matthew B.; Marcinkowski, Matthew D.; Mavrikakis, Manos; Michaelides, Angelos; Sykes, E. Charles H.
2014-05-27
Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to 190 K and for D2 up to 140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.
Analysis of Nuclear Quantum Phase Transitions
Li, Z. P.; Meng, J.; Niksic, T.; Vretenar, D.; Lalazissis, G. A.; Ring, P.
2009-08-26
A microscopic analysis, based on nuclear energy density functionals, is presented for shape phase transitions in Nd isotopes. Low-lying excitation spectra and transition probabilities are calculated starting from a five-dimensional Hamiltonian, with parameters determined by constrained relativistic mean-field calculations for triaxial shapes. The results reproduce available data, and show that there is an abrupt change of structure at N = 90, that corresponds to a first-order quantum phase transition between spherical and axially deformed shapes.
Competing interactions in semiconductor quantum dots
van den Berg, R.; Brandino, G. P.; El Araby, O.; Konik, R. M.; Gritsev, V.; Caux, J. -S.
2014-10-01
We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions at longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.
Competing interactions in semiconductor quantum dots
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
van den Berg, R.; Brandino, G. P.; El Araby, O.; Konik, R. M.; Gritsev, V.; Caux, J. -S.
2014-10-14
In this study, we introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions atmore » longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less
New Field Laboratories and Related Research To Help Promote Environmen...
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... aimed at addressing specific areas of interest; these feature both initial laboratory ... field potential, development of upscaling theory, and field testing of the cyclic gas ...
Optimal quantum control in nanostructures: Theory and application...
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A; Journal Volume: 66; Journal Issue: 5; Other Information: DOI: 10.1103PhysRevA.66.053811; (c) 2002 The American Physical Society; Country of input: International Atomic Energy ...
Quantum Electronic Stress: Density-Functional-Theory Formulation...
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Additional Journal Information: Journal Volume: 109; Journal Issue: 5; Journal ID: ISSN 0031-9007 Publisher: American Physical Society Sponsoring Org: USDOE Country of...
Microscopic theory of quantum anomalous Hall effect in graphene...
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American Physical Society Sponsoring Org: USDOE Country of Publication: United States Language: English Word Cloud More Like This Free Publicly Accessible Full Text Accepted...
Quantum Optics, Diffraction Theory, and Elementary Particle Physics
None
2011-10-06
Physical optics has expanded greatly in recent years. Though it remains part of the ancestry of elementary particle physics, there are once again lessons to be learned from it. I shall discuss several of these, including some that have emerged at CERN and Brookhaven.
Quantum signatures of the self-trapping transition in attractive lattice bosons
Buonsante, P.; Penna, V.; Vezzani, A.
2010-10-15
We consider the Bose-Hubbard model describing attractive bosonic particles hopping across the sites of a translation-invariant lattice and compare the relevant ground-state properties with those of the corresponding symmetry-breaking semiclassical nonlinear theory. The introduction of a suitable measure allows us to highlight many correspondences between the nonlinear theory and the inherently linear quantum theory, characterized by the well-known self-trapping phenomenon. In particular we demonstrate that the localization properties and bifurcation pattern of the semiclassical ground state can be clearly recognized at the quantum level. Our analysis highlights a finite-number effect.
Maunz, Peter Lukas Wilhelm; Sterk, Jonathan David; Lobser, Daniel; Parekh, Ojas D.; Ryan-Anderson, Ciaran
2016-01-01
In recent years, advanced network analytics have become increasingly important to na- tional security with applications ranging from cyber security to detection and disruption of ter- rorist networks. While classical computing solutions have received considerable investment, the development of quantum algorithms to address problems, such as data mining of attributed relational graphs, is a largely unexplored space. Recent theoretical work has shown that quan- tum algorithms for graph analysis can be more efficient than their classical counterparts. Here, we have implemented a trapped-ion-based two-qubit quantum information proces- sor to address these goals. Building on Sandia's microfabricated silicon surface ion traps, we have designed, realized and characterized a quantum information processor using the hyperfine qubits encoded in two 171 Yb + ions. We have implemented single qubit gates using resonant microwave radiation and have employed Gate set tomography (GST) to characterize the quan- tum process. For the first time, we were able to prove that the quantum process surpasses the fault tolerance thresholds of some quantum codes by demonstrating a diamond norm distance of less than 1 . 9 x 10 [?] 4 . We used Raman transitions in order to manipulate the trapped ions' motion and realize two-qubit gates. We characterized the implemented motion sensitive and insensitive single qubit processes and achieved a maximal process infidelity of 6 . 5 x 10 [?] 5 . We implemented the two-qubit gate proposed by Molmer and Sorensen and achieved a fidelity of more than 97 . 7%.
Molecular Quantum Mechanics 2010: From Methylene to DNA and Beyond Conference Support
2013-05-15
This grant was $12500 for partial support of an international conference, Molecular Quantum Mechanics 2010, which was held on the campus of the University of California, Berkeley, from 24 to 29 May 2010. The conference involved more than 250 participants. The conference schedule ran from as early as 8:00 AM to as late as 10:30 PM at night, in order to accommodate six historical lectures, 16 plenary lectures, 42 invited talks and two very strong poster sessions containing 143 contributed posters. Since 1989, the Molecular Quantum Mechanics (MQM) series of international conferences has show- cased the frontiers of research in quantum chemistry with a strong focus on basic theory and algorithms, as well as highlights of topical applications. Both were strongly in evidence at MQM 2010. At the same time as embracing the future, the MQM conferences also honour the lifetime contributions of some of the most prominent scientists in the field of theoretical and computational quantum chemistry. MQM 2010 recognised the work of Prof. Henry F. ‘Fritz’ Schaefer of the Center for Computational Chemistry at the University of Georgia, who was previously on the faculty at Berkeley The travel of invited speakers was partially covered by sponsorships from Dell Computer, Hewlett-Packard, Journal of Chemical Theory and Computation, Virginia Tech College of Science, Molecular Physics, Q-Chem Inc and the American Institute of Physics. By contrast, the conference grant from the Department of Energy was used to provide fellowships and scholarships to enable graduate students and postdoctoral fellows to attend the meeting, and thereby broaden the participation of young scientists at a meeting where in the past most of the attendees have been more senior faculty researchers. We believe that we were very successful in this regard: 118 students and postdocs attended out of the total of 256 participants. In detail, the DOE sponsorship money was partially used for dormitory scholarships that covered the cost of shared accommodation for students and postdocs at Berkeley dormitories. This covered the $200-$305 cost of a shared room for the 5-day duration of the conference. The only condition of these scholarships was that the awardee must present a poster at the meeting. Approximately $7565 was spent for these dormitory scholarships. The remaining expenditures of $4800 was used for 12 merit scholarships which were awarded to students whose poster presentations were judged the best at the conference. This amount covered a significant part of their travel and registration fees.
RKKY interaction in a chirally coupled double quantum dot system (Journal
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Article) | SciTech Connect RKKY interaction in a chirally coupled double quantum dot system Citation Details In-Document Search Title: RKKY interaction in a chirally coupled double quantum dot system The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the
Fattebert, J; Law, R J; Bennion, B; Lau, E Y; Schwegler, E; Lightstone, F C
2009-04-24
We evaluate the accuracy of density functional theory quantum calculations of biomolecular subsystems using a simple electrostatic embedding scheme. Our scheme is based on dividing the system of interest into a primary and secondary subsystem. A finite difference discretization of the Kohn-Sham equations is used for the primary subsystem, while its electrostatic environment is modeled with a simple one-electron potential. Force-field atomic partial charges are used to generate smeared Gaussian charge densities and to model the secondary subsystem. We illustrate the utility of this approach with calculations of truncated dipeptide chains. We analyze quantitatively the accuracy of this approach by calculating atomic forces and comparing results with fullQMcalculations. The impact of the choice made in terminating dangling bonds at the frontier of the QM region is also investigated.
Quantum Solar | Open Energy Information
Solar Jump to: navigation, search Name: Quantum Solar Place: Santa Fe, New Mexico Zip: 87507 Product: New Mexico-based PV cell technology company. References: Quantum Solar1 This...
Twisted injectivity in projected entangled pair states and the classification of quantum phases
Buerschaper, Oliver
2014-12-15
We introduce a class of projected entangled pair states (PEPS) which is based on a group symmetry twisted by a 3-cocycle of the group. This twisted symmetry is expressed as a matrix product operator (MPO) with bond dimension greater than1 and acts on the virtual boundary of a PEPS tensor. We show that it gives rise to a new standard form for PEPS from which we construct a family of local Hamiltonians which are gapped, frustration-free and include fixed points of the renormalization group flow. Based on this insight, we advance the classification of 2D gapped quantum spin systems by showing how this new standard form for PEPS determines the emergent topological order of these local Hamiltonians. Specifically, we identify their universality class as DIJKGRAAFWITTEN topological quantum field theory (TQFT). - Highlights: We introduce a new standard form for projected entangled pair states via a twisted group symmetry which is given by nontrivial matrix product operators. We construct a large family of gapped, frustration-free Hamiltonians in two dimensions from this new standard form. We rigorously show how this new standard form for low energy states determines the emergent topological order.
Quasiperiodically kicked quantum systems
Milonni, P.W.; Ackerhalt, J.R.; Goggin, M.E.
1987-02-15
We consider a two-state system kicked quasiperiodically by an external force. When the two kicking frequencies assumed for the force are incommensurate, there can be quantum chaos in the sense that (a) the autocorrelation function of the state vector decays, (b) the power spectrum of the state vector is broadband, and (c) the motion on the Bloch sphere is ergodic. The time evolution of the state vector is nevertheless dynamically stable in the sense that memory of the initial state is retained. We also consider briefly the kicked quantum rotator and find, in agreement with Shepelyansky (Physica 8D, 208 (1983)), that the quantum localization effect is greatly weakened by the presence of two incommensurate driving frequencies.
Authentication of quantum messages.
Barnum, Howard; Crépeau, Jean-Claude; Gottesman, D.; Smith, A.; Tapp, Alan
2001-01-01
Authentication is a well-studied area of classical cryptography: a sender A and a receiver B sharing a classical private key want to exchange a classical message with the guarantee that the message has not been modified or replaced by a dishonest party with control of the communication line. In this paper we study the authentication of messages composed of quantum states. We give a formal definition of authentication in the quantum setting. Assuming A and B have access to an insecure quantum channel and share a private, classical random key, we provide a non-interactive scheme that both enables A to encrypt and authenticate (with unconditional security) an m qubit message by encoding it into m + s qubits, where the probability decreases exponentially in the security parameter s. The scheme requires a private key of size 2m + O(s). To achieve this, we give a highly efficient protocol for testing the purity of shared EPR pairs. It has long been known that learning information about a general quantum state will necessarily disturb it. We refine this result to show that such a disturbance can be done with few side effects, allowing it to circumvent cryptographic protections. Consequently, any scheme to authenticate quantum messages must also encrypt them. In contrast, no such constraint exists classically: authentication and encryption are independent tasks, and one can authenticate a message while leaving it publicly readable. This reasoning has two important consequences: On one hand, it allows us to give a lower bound of 2m key bits for authenticating m qubits, which makes our protocol asymptotically optimal. On the other hand, we use it to show that digitally signing quantum states is impossible, even with only computational security.
Efetov, K.B. [Max-Planck Institut fuer Physik komplexer Systeme, Heisenbergstrasse 1, 70569 Stuttgart (Germany)] [Max-Planck Institut fuer Physik komplexer Systeme, Heisenbergstrasse 1, 70569 Stuttgart (Germany); [L.D. Landau Institute for Theoretical Physics, Moscow (Russia)
1997-07-01
Quantum disordered problems with a direction (imaginary vector potential) are discussed and mapped onto a supermatrix {sigma} model. It is argued that the 0D version of the {sigma} model may describe a broad class of phenomena that can be called directed quantum chaos. It is demonstrated by explicit calculations that these problems are equivalent to those of random asymmetric or non-Hermitian matrices. A joint probability of complex eigenvalues is obtained. The fraction of states with real eigenvalues proves to be always finite for time reversal invariant systems. {copyright} {ital 1997} {ital The American Physical Society}
Quantum Statistical Testing of a Quantum Random Number Generator
Humble, Travis S
2014-01-01
The unobservable elements in a quantum technology, e.g., the quantum state, complicate system verification against promised behavior. Using model-based system engineering, we present methods for verifying the opera- tion of a prototypical quantum random number generator. We begin with the algorithmic design of the QRNG followed by the synthesis of its physical design requirements. We next discuss how quantum statistical testing can be used to verify device behavior as well as detect device bias. We conclude by highlighting how system design and verification methods must influence effort to certify future quantum technologies.
Quantum dynamics of fast chemical reactions
Light, J.C.
1993-12-01
The aims of this research are to explore, develop, and apply theoretical methods for the evaluation of the dynamics of gas phase collision processes, primarily chemical reactions. The primary theoretical tools developed for this work have been quantum scattering theory, both in time dependent and time independent forms. Over the past several years, the authors have developed and applied methods for the direct quantum evaluation of thermal rate constants, applying these to the evaluation of the hydrogen isotopic exchange reactions, applied wave packet propagation techniques to the dissociation of Rydberg H{sub 3}, incorporated optical potentials into the evaluation of thermal rate constants, evaluated the use of optical potentials for state-to-state reaction probability evaluations, and, most recently, have developed quantum approaches for electronically non-adiabatic reactions which may be applied to simplify calculations of reactive, but electronically adiabatic systems. Evaluation of the thermal rate constants and the dissociation of H{sub 3} were reported last year, and have now been published.
A tamper-indicating quantum seal
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Williams, Brian P.; Britt, Keith A.; Humble, Travis S.
2016-01-04
Technical means for identifying when tampering occurs is a critical part of many containment and surveillance technologies. Conventional fiber optic seals provide methods for monitoring enclosed inventories, but they are vulnerable to spoofing attacks based on classical physics. We address these vulnerabilities with the development of a quantum seal that offers the ability to detect the intercept-resend attack using quantum integrity verification. Our approach represents an application of entanglement to provide guarantees in the authenticity of the seal state by verifying it was transmitted coherently. We implement these ideas using polarization-entangled photon pairs that are verified after passing through amore » fiber-optic channel testbed. Using binary detection theory, we find the probability of detecting inauthentic signals is greater than 0.9999 with a false alarm chance of 10–9 for a 10 second sampling interval. In addition, we show how the Hong-Ou-Mandel effect concurrently provides a tight bound on redirection attack, in which tampering modifies the shape of the seal. Our measurements limit the tolerable path length change to sub-millimeter disturbances. As a result, these tamper-indicating features of the quantum seal offer unprecedented security for unattended monitoring systems.« less
Zeno-logic applications of semiconductor quantum dots
Schneebeli, L.; Peyghambarian, N.; Feldtmann, T.; Kira, M.; Koch, S. W.
2010-05-15
Microscopic calculations show that CdSe-based semiconductor quantum dots with confined exciton and biexciton states are suitable candidates for Zeno-logic applications. The frequencies of the control and signal fields are chosen to guarantee very high transmission of the individual beams. If both fields are present simultaneously, they are strongly absorbed due to efficient ground-state-to-biexciton transitions. The optical Bloch equations for a three-level quantum-dot model with self-consistent light-matter coupling are solved numerically. The influence of dephasing and/or inhomogeneous dot distributions is analyzed and the conditions for satisfactory device operation are identified.
Comparison of the attempts of quantum discord and quantum entanglement to
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capture quantum correlations (Journal Article) | SciTech Connect Comparison of the attempts of quantum discord and quantum entanglement to capture quantum correlations Citation Details In-Document Search Title: Comparison of the attempts of quantum discord and quantum entanglement to capture quantum correlations Measurements of quantum systems disturb their states. To quantify this nonclassical characteristic, Zurek and Ollivier [Phys. Rev. Lett. 88, 017901 (2001)] introduced the quantum
Comparison of quantum confinement effects between quantum wires and dots
Li, Jingbo; Wang, Lin-Wang
2004-03-30
Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratio of band-gap-increases between quantum wires and dots is material-dependent, and slightly deviates from 0.586 predicted by effective-mass approximation. Highly linear polarization of photoluminescence in quantum wires is found. The degree of polarization decreases with the increasing temperature and size.
Shifman, M.
2015-03-15
We discuss similarities and differences between the resurgence program in quantum mechanics and the operator product expansion in strongly coupled Yang-Mills theories. In N = 1 super-Yang-Mills theories, renormalons are peculiar and are not quite similar to renormalons in QCD.
Nanowire terahertz quantum cascade lasers
Grange, Thomas
2014-10-06
Quantum cascade lasers made of nanowire axial heterostructures are proposed. The dissipative quantum dynamics of their carriers is theoretically investigated using non-equilibrium Green functions. Their transport and gain properties are calculated for varying nanowire thickness, from the classical-wire regime to the quantum-wire regime. Our calculation shows that the lateral quantum confinement provided by the nanowires allows an increase of the maximum operation temperature and a strong reduction of the current density threshold compared to conventional terahertz quantum cascade lasers.
Large N phase transitions in massive N = 2 gauge theories
Russo, J. G.
2014-07-23
Using exact results obtained from localization on S{sup 4}, we explore the large N limit of N = 2 super Yang-Mills theories with massive matter multiplets. In this talk we discuss two cases: N = 2* theory, describing a massive hypermultiplet in the adjoint representation, and super QCD with massive quarks. When the radius of the four-sphere is sent to infinity these theories are described by solvable matrix models, which exhibit a number of interesting phenomena including quantum phase transitions at finite 't Hooft coupling.
Modeling and Field Results from Seismic Stimulation
Majer, E.; Pride, S.; Lo, W.; Daley, T.; Nakagawa, Seiji; Sposito, Garrison; Roberts, P.
2006-05-30
Modeling the effect of seismic stimulation employing Maxwell-Boltzmann theory shows that the important component of stimulation is mechanical rather than fluid pressure effects. Modeling using Biot theory (two phases) shows that the pressure effects diffuse too quickly to be of practical significance. Field data from actual stimulation will be shown to compare to theory.
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Science Drivers: Theory Stefan H¨ oche SLAC National Accelerator Laboratory DOE Exascale Requirements Review (HEP) June 10, 2015 P5 recommendations [http://www.usparticlephysics.org/p5] From the summary: Specific investments in particle accelerator, instrumentation, and computing research and development are required to support the program and to ensure the long-term productivity of the field. From the report: Computing cuts across all activities in particle physics, and these activities spur
ALS Evidence Confirms Combustion Theory
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ALS Evidence Confirms Combustion Theory Print Researchers recently uncovered the first step in the process that transforms gas-phase molecules into solid particles like soot and other carbon-based compounds. It's a discovery that could help combustion chemists make more efficient, less polluting fuels and help materials scientists fine-tune their carbon nanotubes and graphene sheets for faster, smaller electronics. In addition, the results could have implications for the burgeoning field of
ALS Evidence Confirms Combustion Theory
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
ALS Evidence Confirms Combustion Theory Print Researchers recently uncovered the first step in the process that transforms gas-phase molecules into solid particles like soot and other carbon-based compounds. It's a discovery that could help combustion chemists make more efficient, less polluting fuels and help materials scientists fine-tune their carbon nanotubes and graphene sheets for faster, smaller electronics. In addition, the results could have implications for the burgeoning field of
ALS Evidence Confirms Combustion Theory
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
ALS Evidence Confirms Combustion Theory Print Researchers recently uncovered the first step in the process that transforms gas-phase molecules into solid particles like soot and other carbon-based compounds. It's a discovery that could help combustion chemists make more efficient, less polluting fuels and help materials scientists fine-tune their carbon nanotubes and graphene sheets for faster, smaller electronics. In addition, the results could have implications for the burgeoning field of
ALS Evidence Confirms Combustion Theory
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
ALS Evidence Confirms Combustion Theory Print Researchers recently uncovered the first step in the process that transforms gas-phase molecules into solid particles like soot and other carbon-based compounds. It's a discovery that could help combustion chemists make more efficient, less polluting fuels and help materials scientists fine-tune their carbon nanotubes and graphene sheets for faster, smaller electronics. In addition, the results could have implications for the burgeoning field of
Metric redefinitions in Einstein-Aether theory
Foster, Brendan Z.
2005-08-15
'Einstein-Aether' theory, in which gravity couples to a dynamical, timelike, unit-norm vector field, provides a means for studying Lorentz violation in a generally covariant setting. Demonstrated here is the effect of a redefinition of the metric and 'aether' fields in terms of the original fields and two free parameters. The net effect is a change of the coupling constants appearing in the action. Using such a redefinition, one of the coupling constants can be set to zero, simplifying studies of solutions of the theory.
Nexus: a modular workflow management system for quantum simulation codes
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Krogel, Jaron T.
2015-08-24
The management of simulation workflows is a significant task for the individual computational researcher. Automation of the required tasks involved in simulation work can decrease the overall time to solution and reduce sources of human error. A new simulation workflow management system, Nexus, is presented to address these issues. Nexus is capable of automated job management on workstations and resources at several major supercomputing centers. Its modular design allows many quantum simulation codes to be supported within the same framework. Current support includes quantum Monte Carlo calculations with QMCPACK, density functional theory calculations with Quantum Espresso or VASP, and quantummore » chemical calculations with GAMESS. Users can compose workflows through a transparent, text-based interface, resembling the input file of a typical simulation code. A usage example is provided to illustrate the process.« less
Deformation Quantization: Quantum Mechanic Lives and Works in...
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of the density matrix. It has been useful in describing quantum flows in: quantum optics; nuclear physics; decoherence (eg, quantum computing); quantum chaos; 'Welcher Weg'...
Quantum chaos of an ion trapped in a linear ion trap (Journal Article) |
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SciTech Connect Quantum chaos of an ion trapped in a linear ion trap Citation Details In-Document Search Title: Quantum chaos of an ion trapped in a linear ion trap We describe the transition to quantum chaos of an ion trapped in a linear ion trap and interacting with two laser fields. Under the conditions of adiabatic illumination of the upper level of the ion, and when the frequencies of the two laser beams are slightly different, the system is reduced to a quantum linear oscillator
Spatially indirect excitons in coupled quantum wells
Lai, Chih-Wei Eddy
2004-03-01
Microscopic quantum phenomena such as interference or phase coherence between different quantum states are rarely manifest in macroscopic systems due to a lack of significant correlation between different states. An exciton system is one candidate for observation of possible quantum collective effects. In the dilute limit, excitons in semiconductors behave as bosons and are expected to undergo Bose-Einstein condensation (BEC) at a temperature several orders of magnitude higher than for atomic BEC because of their light mass. Furthermore, well-developed modern semiconductor technologies offer flexible manipulations of an exciton system. Realization of BEC in solid-state systems can thus provide new opportunities for macroscopic quantum coherence research. In semiconductor coupled quantum wells (CQW) under across-well static electric field, excitons exist as separately confined electron-hole pairs. These spatially indirect excitons exhibit a radiative recombination time much longer than their thermal relaxation time a unique feature in direct band gap semiconductor based structures. Their mutual repulsive dipole interaction further stabilizes the exciton system at low temperature and screens in-plane disorder more effectively. All these features make indirect excitons in CQW a promising system to search for quantum collective effects. Properties of indirect excitons in CQW have been analyzed and investigated extensively. The experimental results based on time-integrated or time-resolved spatially-resolved photoluminescence (PL) spectroscopy and imaging are reported in two categories. (i) Generic indirect exciton systems: general properties of indirect excitons such as the dependence of exciton energy and lifetime on electric fields and densities were examined. (ii) Quasi-two-dimensional confined exciton systems: highly statistically degenerate exciton systems containing more than tens of thousands of excitons within areas as small as (10 micrometer){sup 2} were observed. The spatial and energy distributions of optically active excitons were used as thermodynamic quantities to construct a phase diagram of the exciton system, demonstrating the existence of distinct phases. Optical and electrical properties of the CQW sample were examined thoroughly to provide deeper understanding of the formation mechanisms of these cold exciton systems. These insights offer new strategies for producing cold exciton systems, which may lead to opportunities for the realization of BEC in solid-state systems.
In the OSTI Collections: Quantum Chaos | OSTI, US Dept of Energy, Office of
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Scientific and Technical Information Quantum Chaos View Past "In the OSTI Collections" Articles. Article Acknowledgement: Dr. William N. Watson, Physicist DOE Office of Scientific and Technical Information The correspondence principle Billiards Chaos in specific quantum-physical systems Explorations of general theoretical concepts References Research Organizations Reports available through E-print Network Additional References The correspondence principle Any theory whose logical
Entropic dynamics: From entropy and information geometry to Hamiltonians and quantum mechanics
Caticha, Ariel; Bartolomeo, Daniel; Reginatto, Marcel
2015-01-13
Entropic Dynamics is a framework in which quantum theory is derived as an application of entropic methods of inference. There is no underlying action principle. Instead, the dynamics is driven by entropy subject to the appropriate constraints. In this paper we show how a Hamiltonian dynamics arises as a type of non-dissipative entropic dynamics. We also show that the particular form of the 'quantum potential' that leads to the Schrdinger equation follows naturally from information geometry.
Transport signatures of quantum critically in Cr at high pressure.
Jaramillo, R.; Feng, Y.; Wang, J.; Rosenbaum, T. F.
2010-08-03
The elemental antiferromagnet Cr at high pressure presents a new type of naked quantum critical point that is free of disorder and symmetry-breaking fields. Here we measure magnetotransport in fine detail around the critical pressure, P{sub c} {approx} 10 GPa, in a diamond anvil cell and reveal the role of quantum critical fluctuations at the phase transition. As the magnetism disappears and T {yields} 0, the magntotransport scaling converges to a non-mean-field form that illustrates the reconstruction of the magnetic Fermi surface, and is distinct from the critical scaling measured in chemically disordered Cr:V under pressure. The breakdown of itinerant antiferromagnetism only comes clearly into view in the clean limit, establishing disorder as a relevant variable at a quantum phase transition.
Intrinsic decoherence dynamics in smooth Hamiltonian systems: Quantum-classical correspondence
Gong, Jiangbin; Brumer, Paul [Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Canada M5S 3H6 (Canada)
2003-08-01
A direct classical analog of the quantum dynamics of intrinsic decoherence in Hamiltonian systems, characterized by the time dependence of the linear entropy of the reduced density operator, is introduced. The similarities and differences between the classical and quantum decoherence dynamics of an initial quantum state are exposed using both analytical and computational results. In particular, the classicality of early-time intrinsic decoherence dynamics is explored analytically using a second-order perturbative treatment, and an interesting connection between decoherence rates and the stability nature of classical trajectories is revealed in a simple approximate classical theory of intrinsic decoherence dynamics. The results offer deeper insights into decoherence, dynamics of quantum entanglement, and quantum chaos.
All-optical quantum computing with a hybrid solid-state processing unit
Pei Pei; Zhang Fengyang; Li Chong; Song Heshan [School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China)
2011-10-15
We develop an architecture of a hybrid quantum solid-state processing unit for universal quantum computing. The architecture allows distant and nonidentical solid-state qubits in distinct physical systems to interact and work collaboratively. All the quantum computing procedures are controlled by optical methods using classical fields and cavity QED. Our methods have a prominent advantage of the insensitivity to dissipation process benefiting from the virtual excitation of subsystems. Moreover, the quantum nondemolition measurements and state transfer for the solid-state qubits are proposed. The architecture opens promising perspectives for implementing scalable quantum computation in a broader sense that different solid-state systems can merge and be integrated into one quantum processor afterward.
Analytic Properties of Expectation Values of Products of Field Operators. Lectures
DOE R&D Accomplishments [OSTI]
Salam, A , Okubo, S
1958-12-15
A review is presented of the latest work on the axiomatic approach of field theory. An account is given of recent work in dispersion theory. (A.C.)
Soft Collinear Effective Theory (Journal Article) | SciTech Connect
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Soft Collinear Effective Theory Citation Details In-Document Search Title: Soft Collinear Effective Theory In this talk I review soft collinear effective theory. After a discussion of the formalism and properties of the effective field theory, I turn to phenomenology. I present results on color-suppressed B {yields} D decays, and on the {upsilon} radiative decay spectrum. Authors: Fleming, Sean [1] + Show Author Affiliations Physics Department, University of Arizona, Tucson, AZ 85719 (United
Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; Bowers, C. R.
2014-10-29
A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al_{0.1}Ga_{0.9}As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximations made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; et al
2014-10-29
A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al0.1Ga0.9As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximationsmore » made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals« less
Gabrielse, Gerald [Harvard University, Cambridge, Massachusetts, United States
2009-09-01
Remarkably, the famous UW measurement of the electron magnetic moment has stood since 1987. With QED theory, this measurement has determined the accepted value of the fine structure constant. This colloquium is about a new Harvard measurement of these fundamental constants. The new measurement has an uncertainty that is about six times smaller, and it shifts the values by 1.7 standard deviations. One electron suspended in a Penning trap is used for the new measurement, like in the old measurement. What is different is that the lowest quantum levels of the spin and cyclotron motion are resolved, and the cyclotron as well as spin frequencies are determined using quantum jump spectroscopy. In addition, a 0.1 mK Penning trap that is also a cylindrical microwave cavity is used to control the radiation field, to suppress spontaneous emission by more than a factor of 100, to control cavity shifts, and to eliminate the blackbody photons that otherwise stimulate excitations from the cyclotron ground state. Finally, great signal-to-noise for one-quantum transitions is obtained using electronic feedback to realize the first one-particle self-excited oscillator. The new methods may also allow a million times improved measurement of the 500 times small antiproton magnetic moment.
Resonances in Coupled ?K??K Scattering from Quantum Chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; Wilson, David J.
2014-10-01
Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled ?K, ?K scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.
Lifetime statistics of quantum chaos studied by a multiscale analysis
Di Falco, A.; Krauss, T. F. [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Fratalocchi, A. [PRIMALIGHT, Faculty of Electrical Engineering, Applied Mathematics and Computational Science, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)
2012-04-30
In a series of pump and probe experiments, we study the lifetime statistics of a quantum chaotic resonator when the number of open channels is greater than one. Our design embeds a stadium billiard into a two dimensional photonic crystal realized on a silicon-on-insulator substrate. We calculate resonances through a multiscale procedure that combines energy landscape analysis and wavelet transforms. Experimental data is found to follow the universal predictions arising from random matrix theory with an excellent level of agreement.
The quantum chaos conjecture and generalized continued fractions
Pustyl'nikov, L D [M.V. Keldysh Institute for Applied Mathematics, Russian Academy of Sciences, Moscow (Russian Federation)
2003-04-30
The proof of the quantum chaos conjecture is given for a class of systems including as a special case the model of a rotating particle under the action of periodic impulse perturbations. (The distribution of the distances between adjacent energy levels is close to the Poisson distribution and differs from it by terms of the third order of smallness.) The proof reduces to a result in number theory on the distribution of the distances between adjacent fractional parts of values of a polynomial, while the estimate of the remainder term is based on the new theory of generalized continued fractions for vectors.
Color transparency and the structure of the proton in quantum chromodynamics
Brodsky, S.J.
1989-06-01
Many anomalies suggest that the proton itself is a much more complex object than suggested by simple non-relativistic quark models. Recent analyses of the proton distribution amplitude using QCD sum rules points to highly-nontrivial proton structure. Solutions to QCD in one-space and one-time dimension suggest that the momentum distributions of non-valence quarks in the hadrons have a non-trivial oscillatory structure. The data seems also to be suggesting that the intrinsic'' bound state structure of the proton has a non-negligible strange and charm quark content, in addition to the extrinsic'' sources of heavy quarks created in the collision itself. As we shall see in this lecture, the apparent discrepancies with experiment are not so much a failure of QCD, but rather symptoms of the complexity and richness of the theory. An important tool for analyzing this complexity is the light-cone Fock state representation of hadron wavefunctions, which provides a consistent but convenient framework for encoding the features of relativistic many-body systems in quantum field theory. 121 refs., 44 figs., 1 tab.
Interband magneto-spectroscopy in InSb square and parabolic quantum wells
Kasturiarachchi, T.; Edirisooriya, M.; Mishima, T. D.; Doezema, R. E.; Santos, M. B.; Saha, D.; Pan, X.; Sanders, G. D.; Stanton, C. J.
2015-06-07
We measure the magneto-optical absorption due to intersubband optical transitions between conduction and valence subband Landau levels in InSb square and parabolic quantum wells. InSb has the narrowest band gap (0.24 eV at low temperature) of the III–V semiconductors leading to a small effective mass (0.014 m{sub 0}) and a large g–factor (−51). As a result, the Landau level spacing is large at relatively small magnetic fields (<8 T), and one can observe spin-splitting of the Landau levels. We examine two structures: (i) a multiple-square-well structure and (ii) a structure containing multiple parabolic wells. The energies and intensities of the strongest features are well explained by a modified Pidgeon-Brown model based on an 8-band k•p model that explicitly incorporates pseudomorphic strain. The strain is essential for obtaining agreement between theory and experiment. While modeling the square well is relatively straight-forward, the parabolic well consists of 43 different layers of various thickness to approximate a parabolic potential. Agreement between theory and experiment for the parabolic well validates the applicability of the model to complicated structures, which demonstrates the robustness of our model and confirms its relevance for developing electronic and spintronic devices that seek to exploit the properties of the InSb band structure.
On the Condensed Matter Analog of Baryon Chiral Perturbation Theory
Bruegger, C.; Moser, M.; Wiese, U.-J.; Hofmann, C. P.; Kaempfer, F.; Pepe, M.
2009-04-20
It is shown that baryon chiral perturbation theory, i.e., the low-energy effective theory for pions and nucleons in quantum chromodynamics, has its condensed matter analog: A low-energy effective theory describing magnons as well as holes (or electrons) doped into antiferromagnets. We briefly present a symmetry analysis of the Hubbard and t-J-type models, and review the construction of the leading terms in the effective Lagrangian. As a nontrivial application we study different phases of hole- and electron-doped antiferromagnets--in particular, we investigate whether a so-called spiral phase with an inhomogeneous staggered magnetization (order parameter) may be stable. We would like to emphasize that the effective theory is universal and makes model-independent predictions for a large class of systems, whereas the material-specific properties enter the effective theory only through the numerical values of a few low-energy parameters.
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Quantum Monte Carlo for the Electronic Structure of Atoms and Molecules Brian Austin Lester Group, U.C. Berkeley BES Requirements Workshop Rockville, MD February 9, 2010 Outline Applying QMC to diverse chemical systems Select systems with high interest and impact Phenol: bond dissociation energy Retinal: excitation energy Algorithmic details Parallel Strategy Wave function evaluation O-H Bond Dissociation Energy of Phenol Ph-OH Ph-O * + H * (36 valence electrons)
'Giant' Nanocrystal Quantum Dots
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'Giant' Nanocrystal Quantum Dots - Sandia Energy Energy Search Icon Sandia Home Locations Contact Us Employee Locator Energy & Climate Secure & Sustainable Energy Future Stationary Power Energy Conversion Efficiency Solar Energy Wind Energy Water Power Supercritical CO2 Geothermal Natural Gas Safety, Security & Resilience of the Energy Infrastructure Energy Storage Nuclear Power & Engineering Grid Modernization Battery Testing Nuclear Fuel Cycle Defense Waste Management Programs
Comparison of the attempts of quantum discord and quantum entanglement...
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bipartite systems and give general results on the relationship between discord, entanglement, and linear entropy. ... Information and Quantum Control, University of Toronto, ...
Four-level entangled quantum heat engines
Zhang Ting; Liu, W.-T.; Chen, P.-X.; Li, C.-Z.
2007-06-15
Based on a two-qubit one-dimensional isotropic spin-1/2 Heisenberg spin chain in a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE) and investigate the influence of entanglement between two qubits on basic thermodynamic quantities, i.e., the heat transferred and the work done in a cycle, and the efficiency of the QHE. The validity of the second law of thermodynamics is confirmed in the entangled system. We also find several interesting features of the variation of the efficiency with the entanglement of two different thermal equilibrium states in a work cycle in zero and finite magnetic field. An abrupt transition of efficiency is found in zero field.
Quantum Hall effect in HgTe quantum wells at nitrogen temperatures
Kozlov, D. A. Kvon, Z. D.; Mikhailov, N. N.; Dvoretskii, S. A.; Weishupl, S.; Krupko, Y.; Portal, J.-C.
2014-09-29
We report on the observation of quantized Hall plateaus in a system of two-dimensional Dirac fermions, implemented in a 6.6?nm HgTe quantum well at magnetic fields up to 34?T at nitrogen temperatures. The activation energies determined from the temperature dependence of the longitudinal resistivity are found to be almost equal for the filling factors ? of 1 and 2. This indicates that the large values of the g-factor (about 3040) remain unchanged at very strong magnetic fields.
ON THE MAGNETIC FIELD OF PULSARS WITH REALISTIC NEUTRON STAR CONFIGURATIONS
Belvedere, R.; Rueda, Jorge A.; Ruffini, R. E-mail: jorge.rueda@icra.it
2015-01-20
We have recently developed a neutron star model fulfilling global and not local charge neutrality, both in the static and in the uniformly rotating cases. The model is described by the coupled Einstein-Maxwell-Thomas-Fermi equations, in which all fundamental interactions are accounted for in the framework of general relativity and relativistic mean field theory. Uniform rotation is introduced following Hartle's formalism. We show that the use of realistic parameters of rotating neutron stars, obtained from numerical integration of the self-consistent axisymmetric general relativistic equations of equilibrium, leads to values of the magnetic field and radiation efficiency of pulsars that are very different from estimates based on fiducial parameters that assume a neutron star mass M = 1.4 M {sub ☉}, radius R = 10 km, and moment of inertia I = 10{sup 45} g cm{sup 2}. In addition, we compare and contrast the magnetic field inferred from the traditional Newtonian rotating magnetic dipole model with respect to the one obtained from its general relativistic analog, which takes into account the effect of the finite size of the source. We apply these considerations to the specific high-magnetic field pulsar class and show that, indeed, all of these sources can be described as canonical pulsars driven by the rotational energy of the neutron star, and have magnetic fields lower than the quantum critical field for any value of the neutron star mass.
Jiang, F.-J.; Wiese, U.-J.
2011-04-15
The two-dimensional (2D) spin-(1/2) Heisenberg antiferromagnet with exchange coupling J is investigated on a periodic square lattice of spacing a at very small temperatures using the loop-cluster algorithm. Monte Carlo data for the staggered and uniform susceptibilities are compared with analytic results obtained in the systematic low-energy effective field theory for the staggered magnetization order parameter. The low-energy parameters of the effective theory, i.e., the staggered magnetization density M{sub s}=0.307 43(1)/a{sup 2}, the spin stiffness {rho}{sub s}=0.180 81(11)J, and the spin wave velocity c=1.6586(3)Ja, are determined with very high precision. Our study may serve as a test case for the comparison of lattice quantum chromodynamics Monte Carlo data with analytic predictions of the chiral effective theory for pions and nucleons, which is vital for the quantitative understanding of the strong interaction at low energies.
Vector-tensor nature of Bekenstein's relativistic theory of modified gravity
Zlosnik, T. G.; Ferreira, P. G.; Starkman, Glenn D.
2006-08-15
Bekenstein's theory of relativistic gravity is conventionally written as a bimetric theory. The two metrics are related by a disformal transformation defined by a dynamical vector field and a scalar field. In this paper we show that the theory can be rewritten as vector-tensor theory akin to Einstein-Aether theories with noncanonical kinetic terms. We discuss some of the implications of this equivalence.
Quantum Computing: Solving Complex Problems
DiVincenzo, David [IBM Watson Research Center
2009-09-01
One of the motivating ideas of quantum computation was that there could be a new kind of machine that would solve hard problems in quantum mechanics. There has been significant progress towards the experimental realization of these machines (which I will review), but there are still many questions about how such a machine could solve computational problems of interest in quantum physics. New categorizations of the complexity of computational problems have now been invented to describe quantum simulation. The bad news is that some of these problems are believed to be intractable even on a quantum computer, falling into a quantum analog of the NP class. The good news is that there are many other new classifications of tractability that may apply to several situations of physical interest.
Electron density magnification of the collective spin-orbit field in
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quantum wells (Journal Article) | SciTech Connect Electron density magnification of the collective spin-orbit field in quantum wells Citation Details In-Document Search This content will become publicly available on September 27, 2016 Title: Electron density magnification of the collective spin-orbit field in quantum wells Authors: Baboux, F. ; Perez, F. ; Ullrich, C. A. ; Karczewski, G. ; Wojtowicz, T. Publication Date: 2015-09-28 OSTI Identifier: 1222050 Grant/Contract Number:
Brida, G.; Fornaro, G. A.; Genovese, M.; Berchera, I. Ruo; Chekhova, M. V.; Lopaeva, E. D.
2011-06-15
We present a complete and exhaustive theory of signal-to-noiseratio in bipartite ghost imaging with classical (thermal) and quantum (twin beams) light. The theory is compared with experiment for both twin beams and thermal light in a certain regime of interest.
An analog model for quantum lightcone fluctuations in nonlinear optics
Ford, L.H.; De Lorenci, V.A.; Menezes, G.; Svaiter, N.F.
2013-02-15
We propose an analog model for quantum gravity effects using nonlinear dielectrics. Fluctuations of the spacetime lightcone are expected in quantum gravity, leading to variations in the flight times of pulses. This effect can also arise in a nonlinear material. We propose a model in which fluctuations of a background electric field, such as that produced by a squeezed photon state, can cause fluctuations in the effective lightcone for probe pulses. This leads to a variation in flight times analogous to that in quantum gravity. We make some numerical estimates which suggest that the effect might be large enough to be observable. - Highlights: Black-Right-Pointing-Pointer Lightcone fluctuations, quantum fluctuations of the effective speed of light, are a feature of quantum gravity. Black-Right-Pointing-Pointer Nonlinear dielectrics have a variable speed of light, analogous to the effects of gravity. Black-Right-Pointing-Pointer Fluctuating electric fields create the effect of lightcone fluctuations in a nonlinear material. Black-Right-Pointing-Pointer We propose to use squeezed light in a nonlinear material as an analog model of lightcone fluctuations. Black-Right-Pointing-Pointer Variation in the speed of propagation of pulses is the observational signature of lightcone fluctuations.
Decay of transverse correlations in quantum Heisenberg models
Björnberg, Jakob E. E-mail: daniel@ueltschi.org; Ueltschi, Daniel E-mail: daniel@ueltschi.org
2015-04-15
We study a class of quantum spin systems that include the S=1/2 Heisenberg and XY-models and prove that two-point correlations exhibit exponential decay in the presence of a transverse magnetic field. The field is not necessarily constant, it may be random, and it points in the same direction. Our proof is entirely probabilistic and it relies on a random loop representations of the correlation functions, on stochastic domination and on first-passage percolation.
Quantum fluctuations and saturable absorption in mesoscale lasers
Roy-Choudhury, Kaushik [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484 (United States); Levi, A. F. J. [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484 (United States); Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089-2533 (United States)
2011-04-15
We present a quantum-mechanical treatment of fluctuations and saturable absorption in mesoscale lasers. The time evolution of the density matrix is obtained from numerical integration and field-field and intensity-intensity correlations are calculated to obtain steady-state linewidth and photon statistics. Inclusion of a saturable absorber in the otherwise homogeneous medium is shown to suppress lasing, increase fluctuations, and enhance spontaneous emission near threshold.
Duplex quantum communication through a spin chain
Wang Zhaoming; Gu Yongjian [Department of Physics, Ocean University of China, Qingdao 266100 (China); Bishop, C. Allen [Department of Physics, Southern Illinois University, Carbondale, Illinois 62901-4401 (United States); Shao Bin [Department of Physics, Beijing Institute of Technology, Beijing 100081 (China)
2011-08-15
Data multiplexing within a quantum computer can allow for the simultaneous transfer of multiple streams of information over a shared medium thereby minimizing the number of channels needed for requisite data transmission. Here, we investigate a two-way quantum communication protocol using a spin chain placed in an external magnetic field. In our scheme, Alice and Bob each play the role of a sender and a receiver as two states, cos(({theta}{sub 1}/2))0+sin(({theta}{sub 1}/2))e{sup i{phi}{sub 1}}1 and cos(({theta}{sub 2}/2))0+sin(({theta}{sub 2}/2))e{sup i{phi}{sub 2}}1, are transferred through one channel simultaneously. We find that the transmission fidelity at each end of a spin chain can usually be enhanced by the presence of a second party. This is an important result for establishing the viability of duplex quantum communication through spin chain networks.
Imperfect relativistic mirrors in the quantum regime
Mendonça, J. T.; Serbeto, A.; Galvão, R. M. O.
2014-05-15
The collective backscattering of intense laser radiation by energetic electron beams is considered in the relativistic quantum regime. Exact solutions for the radiation field are obtained, for arbitrary electron pulse shapes and laser intensities. The electron beams act as imperfect nonlinear mirrors on the incident laser radiation. This collective backscattering process can lead to the development of new sources of ultra-short pulse radiation in the gamma-ray domain. Numerical examples show that, for plausible experimental conditions, intense pulses of gamma-rays, due to the double Doppler shift of the harmonics of the incident laser radiation, can be produced using the available technology, with durations less than 1 as.
Quantum error-correcting codes and devices
Gottesman, Daniel
2000-10-03
A method of forming quantum error-correcting codes by first forming a stabilizer for a Hilbert space. A quantum information processing device can be formed to implement such quantum codes.
Space-time contours to treat intense field-dressed molecular states
Paul, Amit K.; Adhikari, Satrajit; Baer, Michael
2010-01-21
In this article we consider a molecular system exposed to an intense short-pulsed external field. It is a continuation of a previous publication [A. K. Paul, S. Adhikari, D. Mukhopadhyay et al., J. Phys. Chem. A 113, 7331 (2009)] in which a theory is presented that treats quantum effects due to nonclassical photon states (known also as Fock states). Since these states became recently a subject of intense experimental efforts we thought that they can be treated properly within the existing quantum formulation of dynamical processes. This was achieved by incorporating them in the Born-Oppenheimer (BO) treatment with time-dependent coefficients. The extension of the BO treatment to include the Fock states results in a formidable enhancement in numerical efforts expressed, in particular, in a significant increase in CPU time. In the present article we discuss an approach that yields an efficient and reliable approximation with only negligible losses in accuracy. The approximation is tested in detail for the dissociation process of H{sub 2}{sup +} as caused by a laser field.
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Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.
1984-04-19
In a field-effect transistor comprising a semiconductor having therein a source, a drain, a channel and a gate in operational relationship, there is provided an improvement wherein said semiconductor is a superlattice comprising alternating quantum well and barrier layers, the quantum well layers comprising a first direct gap semiconductor material which in bulk form has a certain bandgap and a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, the barrier layers comprising a second semiconductor material having a bandgap wider than that of said first semiconductor material, wherein the layer thicknesses of said quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice having a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, and wherein the thicknesses of said quantum well layers are selected to provide a superlattice curve of electron velocity versus applied electric field whereby, at applied electric fields higher than that at which the maximum electron velocity occurs in said first material when in bulk form, the electron velocities are higher in said superlattice than they are in said first semiconductor material in bulk form.
Quantum interference within the complex quantum Hamilton-Jacobi formalism
Chou, Chia-Chun; Sanz, Angel S.; Miret-Artes, Salvador; Wyatt, Robert E.
2010-10-15
Quantum interference is investigated within the complex quantum Hamilton-Jacobi formalism. As shown in a previous work [Phys. Rev. Lett. 102 (2009) 250401], complex quantum trajectories display helical wrapping around stagnation tubes and hyperbolic deflection near vortical tubes, these structures being prominent features of quantum caves in space-time Argand plots. Here, we further analyze the divergence and vorticity of the quantum momentum function along streamlines near poles, showing the intricacy of the complex dynamics. Nevertheless, despite this behavior, we show that the appearance of the well-known interference features (on the real axis) can be easily understood in terms of the rotation of the nodal line in the complex plane. This offers a unified description of interference as well as an elegant and practical method to compute the lifetime for interference features, defined in terms of the average wrapping time, i.e., considering such features as a resonant process.
Quantum Darwinism, Decoherence, and the Randomness of Quantum Jumps
Zurek, Wojciech H.
2014-06-05
Tracing flows of information in our quantum Universe explains why we see the world as classical. Quantum principle of superposition decrees every combination of quantum states a legal quantum state. This is at odds with our experience. Decoherence selects preferred pointer states that survive interaction with the environment. They are localized and effectively classical. They persist while their superpositions decohere. Here we consider emergence of `the classical' starting at a more fundamental pre-decoherence level, tracing the origin of preferred pointer states and deducing their probabilities from the core quantum postulates. We also explore role of the environment as medium through which observers acquire information. This mode of information transfer leads to perception of objective classical reality.
QuantumSphere Inc | Open Energy Information
QuantumSphere Inc Jump to: navigation, search Name: QuantumSphere Inc Place: Santa Ana, California Zip: Santa Ana, CA 92705 Product: Manufacturer of metallic nanopowders for...
Hybrid Rotaxanes: Interlocked Structures for Quantum Computing...
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Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Print Wednesday, 26 August 2009 00:00 Rotaxanes are...
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Quantum Technology AQT Jump to: navigation, search Name: Applied Quantum Technology (AQT) Place: Santa Clara, California Zip: 95054 Product: California-based manufacturer of CIGS...
Nuclear Scission and Quantum Localization (Journal Article) ...
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Journal Article: Nuclear Scission and Quantum Localization Citation Details In-Document Search Title: Nuclear Scission and Quantum Localization Authors: Younes, W ; Gogny, D ...
Nuclear Scission and Quantum Localization (Journal Article) ...
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Nuclear Scission and Quantum Localization Citation Details In-Document Search Title: Nuclear Scission and Quantum Localization Authors: Younes, W. ; Gogny, D. Publication Date: ...
Quantum Enabled Security (QES) for Optical Communications
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Laboratory has developed Quantum Enabled Security (QES), a revolutionary new cybersecurity capability using quantum (single-photon) communications integrated with optical...
Methods of quantum mechanics applied to partially coherent light beams
Gase, R.
1994-07-01
Whenever the natural modes of the modal expansion of the cross-spectral density have a common waist, the wave equation in the waist plane has the form of a two-dimensional Schroedinger equation. Thus the results of quantum mechanics and quantum statistics, including the quantized Schroedinger field, can be transferred to partially coherent light. Such conceptions as temperature, entropy, and energy are used advantageously. A subclass of radiation, radiation in thermal equilibrium, is introduced, and, as examples, the Gaussian Schell-model beam and the quasi-rectangle model beam are investigated. The M{sup 2} factor is strongly related to the mean value of energy. 29 refs., 3 figs.
Accelerator-mode-based technique for studying quantum chaos
D'Arcy, M.B.; Godun, R.M.; Cassettari, D. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Summy, G.S. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078-3072 (United States)
2003-02-01
We experimentally demonstrate a method for selecting small regions of phase space for kicked rotor quantum chaos experiments with cold atoms. Our technique uses quantum accelerator modes to selectively accelerate atomic wave packets with localized spatial and momentum distributions. The potential used to create the accelerator mode and subsequently realize the kicked rotor system is formed by a set of off-resonant standing-wave light pulses. We also propose a method for testing whether a selected region of phase space exhibits chaotic or regular behavior using a Ramsey type separated field experiment.
A quantum mechanical description of particle spin rotation in channeling
Silenko, A.Ya.
1995-04-01
Spin rotation of spin-1/2 particles involved in planar channeling in straight and bent crystals is described in a consistent quantum mechanical manner. This is done by solving the Dirac equation in the Foldy-Wouthuysen representation, constructing an operator equation of motion for the spin, and calculating the average value of the spin precession frequency. For the case of channeling in bent crystals agreement is observed between the classical and quantum mechanical expressions, provided that the field of the planes is approximated by a harmonic potential. The effect of spin rotation in straight crystals is also examined. 17 refs.
Topos models for physics and topos theory
Wolters, Sander
2014-08-15
What is the role of topos theory in the topos models for quantum theory as used by Isham, Butterfield, Dring, Heunen, Landsman, Spitters, and others? In other words, what is the interplay between physical motivation for the models and the mathematical framework used in these models? Concretely, we show that the presheaf topos model of Butterfield, Isham, and Dring resembles classical physics when viewed from the internal language of the presheaf topos, similar to the copresheaf topos model of Heunen, Landsman, and Spitters. Both the presheaf and copresheaf models provide a quantum logic in the form of a complete Heyting algebra. Although these algebras are natural from a topos theoretic stance, we seek a physical interpretation for the logical operations. Finally, we investigate dynamics. In particular, we describe how an automorphism on the operator algebra induces a homeomorphism (or isomorphism of locales) on the associated state spaces of the topos models, and how elementary propositions and truth values transform under the action of this homeomorphism. Also with dynamics the focus is on the internal perspective of the topos.
Quantum gravity slows inflation
Tsamis, N.C. |; Woodard, R.P.
1996-02-01
We consider the quantum gravitational back-reaction on an initially inflating, homogeneous and isotropic universe whose topology is T{sup 3} {times} {Re}. Although there is no secular effect at one loop, an explicit calculation shows that two-loop processes act to slow the rate of expansion by an amount which becomes non-pertubatively large at late times. By exploiting Feynman`s tree theorem we show that all higher loops act in the same sense. 18 refs., 1 fig.
PERTURBATION APPROACH FOR QUANTUM COMPUTATION
G. P. BERMAN; D. I. KAMENEV; V. I. TSIFRINOVICH
2001-04-01
We discuss how to simulate errors in the implementation of simple quantum logic operations in a nuclear spin quantum computer with many qubits, using radio-frequency pulses. We verify our perturbation approach using the exact solutions for relatively small (L = 10) number of qubits.
Novel nuclear phenomena in quantum chromodynamics
Brodsky, S.J.
1987-08-01
Many of the key issues in understanding quantum chromodynamics involve processes in nuclear targets at intermediate energies. A range of hadronic and nuclear phenomena-exclusive processes, color transparency, hidden color degrees of freedom in nuclei, reduced nuclear amplitudes, jet coalescence, formation zone effects, hadron helicity selection rules, spin correlations, higher twist effects, and nuclear diffraction were discussed as tools for probing hadron structure and the propagation of quark and gluon jets in nuclei. Several areas were also reviewed where there has been significant theoretical progress determining the form of hadron and nuclear wave functions, including QCD sum rules, lattice gauge theory, and discretized light-cone quantization. A possible interpretation was also discussed of the large spin correlation A/sub NN/ in proton-proton scattering, and how relate this effect to an energy and angular dependence of color transparency in nuclei. 76 refs., 24 figs.
Interface effect in coupled quantum wells
Hao, Ya-Fei
2014-06-28
This paper intends to theoretically investigate the effect of the interfaces on the Rashba spin splitting of two coupled quantum wells. The results show that the interface related Rashba spin splitting of the two coupled quantum wells is both smaller than that of a step quantum well which has the same structure with the step quantum well in the coupled quantum wells. And the influence of the cubic Dresselhaus spin-orbit interaction of the coupled quantum wells is larger than that of a step quantum well. It demonstrates that the spin relaxation time of the two coupled quantum wells will be shorter than that of a step quantum well. As for the application in the spintronic devices, a step quantum well may be better than the coupled quantum wells, which is mentioned in this paper.
Quantum interference in polyenes
Tsuji, Yuta; Hoffmann, Roald; Movassagh, Ramis; Datta, Supriyo
2014-12-14
The explicit form of the zeroth Green's function in the Hckel model, approximated by the negative of the inverse of the Hckel matrix, has direct quantum interference consequences for molecular conductance. We derive a set of rules for transmission between two electrodes attached to a polyene, when the molecule is extended by an even number of carbons at either end (transmission unchanged) or by an odd number of carbons at both ends (transmission turned on or annihilated). These prescriptions for the occurrence of quantum interference lead to an unexpected consequence for switches which realize such extension through electrocyclic reactions: for some specific attachment modes the chemically closed ring will be the ON position of the switch. Normally the signs of the entries of the Green's function matrix are assumed to have no physical significance; however, we show that the signs may have observable consequences. In particular, in the case of multiple probe attachments if coherence in probe connections can be arranged in some cases new destructive interference results, while in others one may have constructive interference. One such case may already exist in the literature.
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... fields (14) quantum chromodynamics (6) color model (5) lattice field theory (5) quantum ... Erratum: Two-color quark matter: U(1)sub A restoration, superfluidity, and quarkyonic ...
Universal quantum computation in a semiconductor quantum wire network
Sau, Jay D.; Das Sarma, S.; Tewari, Sumanta
2010-11-15
Universal quantum computation (UQC) using Majorana fermions on a two-dimensional topological superconducting (TS) medium remains an outstanding open problem. This is because the quantum gate set that can be generated by braiding of the Majorana fermions does not include any two-qubit gate and also no single-qubit {pi}/8 phase gate. In principle, it is possible to create these crucial extra gates using quantum interference of Majorana fermion currents. However, it is not clear if the motion of the various order parameter defects (vortices, domain walls, etc.), to which the Majorana fermions are bound in a TS medium, can be quantum coherent. We show that these obstacles can be overcome using a semiconductor quantum wire network in the vicinity of an s-wave superconductor, by constructing topologically protected two-qubit gates and any arbitrary single-qubit phase gate in a topologically unprotected manner, which can be error corrected using magic-state distillation. Thus our strategy, using a judicious combination of topologically protected and unprotected gate operations, realizes UQC on a quantum wire network with a remarkably high error threshold of 0.14 as compared to 10{sup -3} to 10{sup -4} in ordinary unprotected quantum computation.
Theory Modeling and Simulation
Shlachter, Jack
2012-08-23
Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.
Chiral anomaly of antisymmetric tensor fields
Reuter, M.
1988-03-15
For antisymmetric tensor gauge fields of rank 2n-1 coupled to gravity in 4n dimensions it is shown that the symmetry under duality rotations is broken by quantum effects. The anomaly is related to a local version of the signature index theorem. The zeta-function technique, Fujikawa's method, and the stochastic regularization scheme are discussed.
Lincoln, Don
2014-09-30
The Big Bang is the name of the most respected theory of the creation of the universe. Basically, the theory says that the universe was once smaller and denser and has been expending for eons. One common misconception is that the Big Bang theory says something about the instant that set the expansion into motion, however this isn’t true. In this video, Fermilab’s Dr. Don Lincoln tells about the Big Bang theory and sketches some speculative ideas about what caused the universe to come into existence.
Krokhin, Arkadii
2014-04-18
New applications of the theory of homogenization for heterogeneous metamaterials, in particular for acoustic cloaking and for design and engineering of tunable phononic crystal.
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the phase-space integral ...III-1 I. S. Towner and J. C. Hardy The evaluation of V ud , experiment and theory ......
Filtration theory using computer simulations
Bergman, W.; Corey, I.
1997-01-01
We have used commercially available fluid dynamics codes based on Navier-Stokes theory and the Langevin particle equation of motion to compute the particle capture efficiency and pressure drop through selected two- and three- dimensional fiber arrays. The approach we used was to first compute the air velocity vector field throughout a defined region containing the fiber matrix. The particle capture in the fiber matrix is then computed by superimposing the Langevin particle equation of motion over the flow velocity field. Using the Langevin equation combines the particle Brownian motion, inertia and interception mechanisms in a single equation. In contrast, most previous investigations treat the different capture mechanisms separately. We have computed the particle capture efficiency and the pressure drop through one, 2-D and two, 3-D fiber matrix elements.