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1

Model Theory and Quantum  

E-Print Network (OSTI)

Model Theory and Quantum Groups Sonia L'Innocente Model Theory and Quantum Groups Sonia L'Innocente (University of Mons) Model Theory and Quantum Groups 1 / 40 #12;Model Theory and Quantum Groups Sonia L quantum plane, submitted. This work is inspired by Ivo Herzog's paper: The pseudo-finite dimensional

Mons-Hainaut, Université de

2

Quantum Physics Theory  

Science Conference Proceedings (OSTI)

Quantum Physics Theory. Summary: Theoretical work ... constant. The database is available at http://physics.nist.gov/hdel. Precise ...

2010-10-05T23:59:59.000Z

3

Quantum Field Theory and Representation Theory  

E-Print Network (OSTI)

Quantum Field Theory and Representation Theory Peter Woit woit@math.columbia.edu Department of Mathematics Columbia University Quantum Field Theory and Representation Theory ­ p.1 #12;Outline of the talk · Quantum Mechanics and Representation Theory: Some History Quantum Field Theory and Representation Theory

Woit, Peter

4

MiniDFT  

NLE Websites -- All DOE Office Websites (Extended Search)

MiniDFT MiniDFT MiniDFT Description MiniDFT is a plane-wave denstity functional theory (DFT) mini-app for modeling materials. Given an set of atomic coordinates and pseudopotentials, MiniDFT computes self-consistent solutions of the Kohn-Sham equations using either the LDA or PBE exchange-correlation functionals. For each iteration of the self-consistent field cycle, the Fock matrix is constructed and then diagonalized. To build the Fock matrix, Fast Fourier Transforms are used to tranform orbitals from the plane wave basis ( where the kinetic energy is most readily compted ) to real space (where the potential is evaluated ) and back. Davidson diagonalization is used to compute the orbital energies and update the orbital coefficients. The MiniDFT mini-app was excised from the general-purpose Quantum Espresso

5

Quantum Game Theory  

E-Print Network (OSTI)

Quantum game theory is the study of strategic behavior by agents with access to quantum technology. Broadly speaking, this technology can be employed in either of two ways: As part of a randomization device or as part of a communications protocol. We survey some of the main ideas from both branches of the subject.

Landsburg, Steven E

2011-01-01T23:59:59.000Z

6

Comprehending Quantum Theory from Quantum Fields  

E-Print Network (OSTI)

At the primary level of reality as described by quantum field theory, a fundamental particle like an electron represents a stable, discrete, propagating excited state of its underlying quantum field. QFT also tells us that the lowest vacuum state as well as the excited states of such a field is always very active with spontaneous, unpredictable quantum fluctuations. Also an underlying quantum field is known to be indestructible and immutable possessing the same value in each element of spacetime comprising the universe. These characteristics of the primary quantum fields together with the fact that the quantum fluctuations can be cogently substantiated to be quantum coherent throughout the universe provide a possible ontology of the quantum theory. In this picture, the wave function of a quantum particle represents the reality of the inherent quantum fluctuations at the core of the universe and endows the particle its counter intuitive quantum behavior.

Mani Bhaumik

2013-10-04T23:59:59.000Z

7

Quantum Algorithms for Quantum Field Theories  

E-Print Network (OSTI)

Quantum field theory reconciles quantum mechanics and special relativity, and plays a central role in many areas of physics. We develop a quantum algorithm to compute relativistic scattering probabilities in a massive quantum field theory with quartic self-interactions (phi-fourth theory) in spacetime of four and fewer dimensions. Its run time is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. In the strong-coupling and high-precision regimes, our quantum algorithm achieves exponential speedup over the fastest known classical algorithm.

Stephen P. Jordan; Keith S. M. Lee; John Preskill

2011-11-15T23:59:59.000Z

8

Quantum Algorithms for Quantum Field Theories  

E-Print Network (OSTI)

Quantum field theory reconciles quantum mechanics and special relativity, and plays a central role in many areas of physics. We develop a quantum algorithm to compute relativistic scattering probabilities in a massive quantum field theory with quartic self-interactions (phi-fourth theory) in spacetime of four and fewer dimensions. Its run time is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. In the strong-coupling and high-precision regimes, our quantum algorithm achieves exponential speedup over the fastest known classical algorithm.

Jordan, Stephen P; Preskill, John

2011-01-01T23:59:59.000Z

9

Quantum Field Theory Frank Wilczeky  

E-Print Network (OSTI)

Quantum Field Theory Frank Wilczeky Institute for Advanced Study, School of Natural Science, Olden Lane, Princeton, NJ 08540 I discuss the general principles underlying quantum eld theory, and attempt achieved and prospective. Possible limitations of quantum eld theory are viewed in the light of its history

Wilczek, Frank

10

Quantum Dimensions and Quantum Galois Theory  

E-Print Network (OSTI)

The quantum dimensions of modules for vertex operator algebras are defined and their properties are discussed. The possible values of the quantum dimensions are obtained for rational vertex operator algebras. A criterion for simple currents of a rational vertex operator algebra is given. A full Galois theory for rational vertex operator algebras is established using the quantum dimensions.

Dong, Chongying; Xu, Feng

2012-01-01T23:59:59.000Z

11

Quantum Mechanics and Representation Theory Columbia University  

E-Print Network (OSTI)

Quantum Mechanics and Representation Theory Peter Woit Columbia University Texas Tech, November 21 2013 Peter Woit (Columbia University) Quantum Mechanics and Representation Theory November 2013 1 / 30 #12;Does Anyone Understand Quantum Mechanics? "No One Understands Quantum Mechanics" "I think

Woit, Peter

12

Quantum proof systems and entanglement theory  

E-Print Network (OSTI)

Quantum complexity theory is important from the point of view of not only theory of computation but also quantum information theory. In particular, quantum multi-prover interactive proof systems are defined based on ...

Abolfathe Beikidezfuli, Salman

2009-01-01T23:59:59.000Z

13

Quantum Field Theory in Graphene  

E-Print Network (OSTI)

This is a short non-technical introduction to applications of the Quantum Field Theory methods to graphene. We derive the Dirac model from the tight binding model and describe calculations of the polarization operator (conductivity). Later on, we use this quantity to describe the Quantum Hall Effect, light absorption by graphene, the Faraday effect, and the Casimir interaction.

Fialkovsky, I V

2011-01-01T23:59:59.000Z

14

Quantum Field Theory in Graphene  

E-Print Network (OSTI)

This is a short non-technical introduction to applications of the Quantum Field Theory methods to graphene. We derive the Dirac model from the tight binding model and describe calculations of the polarization operator (conductivity). Later on, we use this quantity to describe the Quantum Hall Effect, light absorption by graphene, the Faraday effect, and the Casimir interaction.

I. V. Fialkovsky; D. V. Vassilevich

2011-11-13T23:59:59.000Z

15

Entanglement in GaAs and CdSe quantum dots: Exact calculations and DFT approximations  

Science Conference Proceedings (OSTI)

We consider two electrons confined in spherical GaAs and CdSe quantum dots and calculate their ground-state spatial entanglement exactly within a parabolic confinement model. We propose a perturbative scheme to approximate the above entanglement within ... Keywords: Density-functional theory, Entanglement, Quantum dots, Quantum information, Semiconductors

J. P. Coe; A. Sudbery; I. D'Amico

2009-03-01T23:59:59.000Z

16

Quantum Dots: Theory  

SciTech Connect

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.

Vukmirovic, Nenad; Wang, Lin-Wang

2009-11-10T23:59:59.000Z

17

Quantum field theory without divergences  

E-Print Network (OSTI)

It is shown that loop divergences emerging in the Green functions in quantum field theory originate from correspondence of the Green functions to {\\em unmeasurable} (and hence unphysical) quantities. This is because no physical quantity can be measured in a point, but in a region, the size of which is constrained by the resolution of measuring equipment. The incorporation of the resolution into the definition of quantum fields $\\phi(x)\\to\\phi^{(A)}(x)$ and appropriate change of Feynman rules results in finite values of the Green functions. The Euclidean $\\phi^4$-field theory is taken as an example.

Altaisky, M V

2010-01-01T23:59:59.000Z

18

Quantum field theory without divergences  

E-Print Network (OSTI)

It is shown that loop divergences emerging in the Green functions in quantum field theory originate from correspondence of the Green functions to {\\em unmeasurable} (and hence unphysical) quantities. This is because no physical quantity can be measured in a point, but in a region, the size of which is constrained by the resolution of measuring equipment. The incorporation of the resolution into the definition of quantum fields $\\phi(x)\\to\\phi^{(A)}(x)$ and appropriate change of Feynman rules results in finite values of the Green functions. The Euclidean $\\phi^4$-field theory is taken as an example.

M. V. Altaisky

2010-02-12T23:59:59.000Z

19

Quantum Theory Event-Probability Interpretation  

Science Conference Proceedings (OSTI)

In this article the propagation of pointlike event probabilities in space is considered. New interpretation of Quantum Theory is formulated.

Quznetsov, Gunn [Chelyabinsk State University, Chelyabinsk, Ural (Russian Federation)

2011-03-28T23:59:59.000Z

20

Beable-Guided Quantum Theories: Generalising Quantum Probability Laws  

E-Print Network (OSTI)

We introduce the idea of a {\\it beable-guided quantum theory}. Beable-guided quantum theories (BGQT) are generalisations of quantum theory, inspired by Bell's concept of beables. They modify the quantum probabilities for some specified set of fundamental events, histories, or other elements of quasiclassical reality by probability laws that depend on the realised configuration of beables. For example, they may define an additional probability weight factor for a beable configuration, independent of the quantum dynamics. BGQT can be fitted to observational data to provide foils against which to compare explanations based on standard quantum theory. For example, a BGQT could, in principle, characterise the effects attributed to dark energy or dark matter, or any other deviation from the predictions of standard quantum dynamics, without introducing extra fields or a cosmological constant. The complexity of the beable-guided theory would then parametrise how far we are from a standard quantum explanation. Less co...

Kent, Adrian

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Foundations of quantum theory and thermodynamics  

Science Conference Proceedings (OSTI)

Physical reasons to support the statement that Quantum theory (Quantum Gravity in particular as well as Classical Gravity) loose applicability due to Thermodynamical effects are presented. The statement is based on several points: 1. N.Bohr requirement that measuring units must have macro size is one of common fundamentals of Quantum theory. 2. The Reference Systemthe base notion of Classical and Quantum theory and of any observation process as well

Victor Olkhov

1998-01-01T23:59:59.000Z

22

Quantum optical experiments and fundamentals of quantum theory  

E-Print Network (OSTI)

Quantum optical experiments and fundamentals of quantum theory Miloslav Dusek Department of Optics, Palacky University 17. listopadu 50, 772 00 Olomouc, Czech Republic ABSTRACT Quantum optics has o ered new possibilities for experimental tests of basic principles of quantum mechanics. It enables us to experimentally

Dusek, Miloslav

23

From Quantum Mechanics to String Theory  

E-Print Network (OSTI)

From Quantum Mechanics to String Theory Relativity (why it makes sense) Quantum mechanics, 2009 #12;Quantum Mechanics: Measurement and Uncertainty Thursday, May 7, 2009 #12;Puzzle: The Stern it. Quantum mechanics understanding: the particle exists in a state without definite position

24

Spaces of Quantum Field Theories  

E-Print Network (OSTI)

The concept of a "space of quantum field theories" or "theory space" was set out in the 1970's in work of Wilson, Friedan and others. This structure should play an important role in organizing and classifying QFTs, and in the study of the string landscape, allowing us to say when two theories are connected by finite variations of the couplings or by RG flows, when a sequence of QFTs converges to another QFT, and bounding the amount of information needed to uniquely specify a QFT, enabling us to estimate their number. As yet we do not have any definition of theory space which can be used to make such arguments. In this talk, we will describe various concepts and tools which should be developed for this purpose, inspired by the analogous mathematical problem of studying the space of Riemannian manifolds. We state two general conjectures about the space of two-dimensional conformal field theories, and we define a distance function on this space, which gives a distance between any pair of theories, whether or not they are connected by varying moduli. Based on talks given at QTS6 (University of Kentucky), Erice, Texas A& M, and Northwestern University. To appear in the proceedings of QTS6.

Michael R. Douglas

2010-05-16T23:59:59.000Z

25

Mathematical Quantum Field Theory and Renormalization Theory  

E-Print Network (OSTI)

This volume of Math-for-Industry Lecture Note Series is dedicated to Professor Izumi Ojima and Professor Kei-ichi Ito on the occasion of their sixtieth birthdays. Professor Izumi Ojima and Professor Kei-ichi Ito have organized a lot of interesting and advanced conferences, e.g., RIMS conference, on quantum field theory and related topics, and they have encouraged not only young but also senior scientists. We would like to express our hearty gratitude to Professor Izumi Ojima and Professor Kei-ichi Ito for their continuous encouragement to us, stimulating our works, innumerable, unbounded helpful comments to our scientific researches. This lecture note is collecting several research papers and survey articles contributed by invited speakers of the international conference

Renormalization

2009-01-01T23:59:59.000Z

26

Spinless Quantum Field Theory and Interpretation  

E-Print Network (OSTI)

Quantum field theory is mostly known as the most advanced and well-developed theory in physics, which combines quantum mechanics and special relativity consistently. In this work, we study the spinless quantum field theory, namely the Klein-Gordon equation, and we find that there exists a Dirac form of this equation which predicts the existence of spinless fermion. For its understanding, we start from the interpretation of quantum field based on the concept of quantum scope, we also extract new meanings of wave-particle duality and quantum statistics. The existence of spinless fermion is consistent with spin-statistics theorem and also supersymmetry, and it leads to several new kinds of interactions among elementary particles. Our work contributes to the study of spinless quantum field theory and could have implications for the case of higher spin.

Dong-Sheng Wang

2013-03-07T23:59:59.000Z

27

Quantum control theory and applications: A survey  

E-Print Network (OSTI)

This paper presents a survey on quantum control theory and applications from a control systems perspective. Some of the basic concepts and main developments (including open-loop control and closed-loop control) in quantum control theory are reviewed. In the area of open-loop quantum control, the paper surveys the notion of controllability for quantum systems and presents several control design strategies including optimal control, Lyapunov-based methodologies, variable structure control and quantum incoherent control. In the area of closed-loop quantum control, the paper reviews closed-loop learning control and several important issues related to quantum feedback control including quantum filtering, feedback stabilization, LQG control and robust quantum control.

Daoyi Dong; Ian R Petersen

2009-10-13T23:59:59.000Z

28

Quantum control theory and applications: A survey  

E-Print Network (OSTI)

This paper presents a survey on quantum control theory and applications from a control systems perspective. Some of the basic concepts and main developments (including open-loop control and closed-loop control) in quantum control theory are reviewed. In the area of open-loop quantum control, the paper surveys the notion of controllability for quantum systems and presents several control design strategies including optimal control, Lyapunov-based methodologies, variable structure control and quantum incoherent control. In the area of closed-loop quantum control, the paper reviews closed-loop learning control and several important issues related to quantum feedback control including quantum filtering, feedback stabilization, LQG control and robust quantum control.

Dong, Daoyi

2009-01-01T23:59:59.000Z

29

From Quantum Mechanics to String Theory  

E-Print Network (OSTI)

From Quantum Mechanics to String Theory Relativity (why it makes sense) Quantum mechanics) New Particles anti-particles (combining special relativity and quantum mechanics pions (mediator mechanics, implies an infinite tower of negative energy states, rather than a ground state suppose

30

From Quantum Mechanics to String Theory  

E-Print Network (OSTI)

From Quantum Mechanics to String Theory Relativity (why it makes sense) Quantum mechanics Extra Dimensions Strings and the Strong Force Thursday, June 4, 2009 #12;The Higgs Mechanism Summary Mechanical Particle Physics General Relativistic Quantum Gravity increasing speed decreasing size increasing

31

Numerical Object Oriented Quantum Field Theory Calculations  

E-Print Network (OSTI)

The qft++ package is a library of C++ classes that facilitate numerical (not algebraic) quantum field theory calculations. Mathematical objects such as matrices, tensors, Dirac spinors, polarization and orbital angular momentum tensors, etc. are represented as C++ objects in qft++. The package permits construction of code which closely resembles quantum field theory expressions, allowing for quick and reliable calculations.

M. Williams

2008-05-19T23:59:59.000Z

32

Quantum field theories on the Lefschetz thimble  

E-Print Network (OSTI)

In these proceedings, we summarize the Lefschetz thimble approach to the sign problem of Quantum Field Theories. In particular, we review its motivations, and we summarize the results of the application of two different algorithms to two test models.

M. Cristoforetti; F. Di Renzo; A. Mukherjee; L. Scorzato

2013-12-04T23:59:59.000Z

33

Neutrix Calculus and Finite Quantum Field Theory  

E-Print Network (OSTI)

In general, quantum field theories (QFT) require regularizations and infinite renormalizations due to ultraviolet divergences in their loop calculations. Furthermore, perturbation series in theories like QED are not convergent series, but are asymptotic series. We apply neutrix calculus, developed in connection with asymptotic series and divergent integrals, to QFT,obtaining finite renormalizations. While none of the physically measurable results in renormalizable QFT is changed, quantum gravity is rendered more manageable in the neutrix framework.

Y. Jack Ng; H. van Dam

2004-10-28T23:59:59.000Z

34

Duality in quantum field theory (and string theory)  

Science Conference Proceedings (OSTI)

These lectures give an introduction to duality in Quantum Field Theory. We discuss the phases of gauge theories and the implications of the electric-magnetic duality transformation to describe the mechanism of confinement. We review the exact results of N=1 supersymmetric QCD and the Seiberg-Witten solution of N=2 super Yang-Mills. Some of its extensions to String Theory are also briefly discussed.

Luis lvarez-Gaum; Frederic Zamora

1998-01-01T23:59:59.000Z

35

A symmetrical theory of nonrelativistic quantum mechanics  

E-Print Network (OSTI)

This paper presents a new Symmetrical Theory (ST) of nonrelativistic quantum mechanics which postulates: quantum mechanics is a theory about complete experiments, not particles; a complete experiment is maximally described by a complex transition amplitude density; and this transition amplitude density never collapses. This new ST is compared to the Conventional Theory (CT) of nonrelativistic quantum mechanics for the analysis of a beam-splitter experiment. The ST makes several experimentally testable predictions that differ from the CT, which can be checked using existing technology. The ST also solves one part of the CT measurement problem, and resolves some of the paradoxes of the CT. This nonrelativistic ST is the low energy limit of a relativistic ST presented in an earlier paper \\cite{Heaney1}.

Michael B. Heaney

2013-10-20T23:59:59.000Z

36

Radiation reaction in nonrelativistic quantum theory. [Review  

SciTech Connect

Some recent work is reviewed on the quantum theory of radiation reaction. The starting point is the Heisenberg operator equation of motion for a nonrelativistic point electron coupled to the quantized electromagnetic field. It is shown that this equation, in contrast to its classical counterpart, leads to a finite value for the electrostatic self-energy of a point electron and, for values of the fine structure constant ..cap alpha.. approximately less than 1, admits neither runaway behavior nor noncausal motion. Furthermore, the correspondence limit of the solution to the quantum mechanical equation of motion agrees with that of the Lorentz--Dirac theory in the classical regime, but without the imposition of additional conditions and with no possibility of observable noncausality. Thus, a consistent picture of a classical point electron emerges in the correspondence limit of the quantum mechanical theory. 17 references.

Sharp, D.H.

1979-01-01T23:59:59.000Z

37

Continuous Wavelet Transform in Quantum Field Theory  

E-Print Network (OSTI)

We describe the application of the continuous wavelet transform to calculation of the Green functions in quantum field theory: scalar $\\phi^4$ theory, quantum electrodynamics, quantum chromodynamics. The method of continuous wavelet transform in quantum field theory presented in M.Altaisky Phys. Rev. D81(2010)125003 for the scalar $\\phi^4$ theory, consists in substitution of the local fields $\\phi(x)$ by those dependent on both the position $x$ and the resolution $a$. The substitution of the action $S[\\phi(x)]$ by the action $S[\\phi_a(x)]$ makes the local theory into nonlocal one, and implies the causality conditions related to the scale $a$, the region causality C. Christensen and L. Crane, J.Math. Phys 46 (2005) 122502. These conditions make the Green functions $G(x_1,a_1,..., x_n,a_n)= $ finite for any given set of regions by means of an effective cutoff scale $A=\\min (a_1,...,a_n)$.

Altaisky, Mikhail V

2013-01-01T23:59:59.000Z

38

Quantum bouncer: theory and experiment  

E-Print Network (OSTI)

The quantum bouncer (QB) concept is a known QM textbook example of confined particle, namely, a solution to the 1D Schroedinger equation for a linear potential (the so-called Airy equation). It would be a great methodological challenge to create such a QM object in laboratory. An attempt of observation of the QB ``running'' in the horizontal direction was recently made by the international team at the Laue-Langevin Institute, Grenoble. The experiment was performed with ultra-cold neutrons. In this paper, the experiment is analyzed in view of the authors' claim that ``neutron quantum states in Earth gravitational field'' are observed. The experimental apparatus is designed for measurements of horizontal flux of neutrons passing through an absorbing wave guide with a variable height of absorber. From our analysis, it follows, however, that in such a layout measured data are not sensitive to quantum probability density in the vertical direction. The overall conclusion is made that the experimental data do not contain sufficient information to justify the claim.

Anatoli Andrei Vankov

2009-06-28T23:59:59.000Z

39

Quantum theory of photonic crystal polaritons  

E-Print Network (OSTI)

We formulate a full quantum mechanical theory of the interaction between electromagnetic modes in photonic crystal slabs and quantum well excitons embedded in the photonic structure. We apply the formalism to a high index dielectric layer with a periodic patterning suspended in air. The strong coupling between electromagnetic modes lying above the cladding light line and exciton center of mass eigenfunctions manifests itself with the typical anticrossing behavior. The resulting band dispersion corresponds to the quasi-particles coming from the mixing of electromagnetic and material excitations, which we call photonic crystal polaritons. We compare the results obtained by using the quantum theory to variable angle reflectance spectra coming from a scattering matrix approach, and we find very good quantitative agreement.

D. Gerace; M. Agio; L. C. Andreani

2004-02-09T23:59:59.000Z

40

NUCLEAR SLAB COLLISION IN A RELATIVISTIC QUANTUM FIELD THEORY  

E-Print Network (OSTI)

Energy under Contract W-7405-ENG-43 LBL-12893 NUCLEAR SLAB COLLISION IN A RELATIVISTIC QUANTUM FIELD THEORY

Muller, K.-H.

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

THE OBJECTIVE INDEFINITENESS INTERPRETATION OF QUANTUM MECHANICS: Partition logic, logical information theory, and quantum mechanics  

E-Print Network (OSTI)

THE OBJECTIVE INDEFINITENESS INTERPRETATION OF QUANTUM MECHANICS: Partition logic, logical information theory, and quantum mechanics David Ellerman University of California at Riverside www ago that quantum mechanics was not compatible with Boolean logic, then the natural thing to do would

Wüthrich, Christian

42

Quantum cryptography: theory and practice  

E-Print Network (OSTI)

A highly attenuated laser pulse which gives a weak coherent state is widely used in quantum key distribution (QKD) experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated eavesdropper. With a small adjustment of the hardware, we prove that the decoy state method can close this loophole and substantially improve the QKD performance. We also propose a few practical decoy state protocols, study statistical fluctuations and perform experimental demonstrations. Moreover, we apply the methods from entanglement distillation protocols based on two-way classical communication to improve the decoy state QKD performance. Furthermore, we study the decoy state methods for other single photon sources, such as triggering parametric down-conversion (PDC) source. We propose a model and post-processing scheme for the entanglement-based QKD with a PDC source. Although the model is proposed to study the entanglement-based QKD, we emphasize that our generic model may also be useful for other non-QKD experiments involving a PDC source. By simulating a real PDC experiment, we show that the entanglement-based QKD can achieve longer maximal secure distance than the single-photon-based QKD schemes. We present a time-shift attack that exploits the efficiency mismatch of two single photon detectors in a QKD system. This eavesdropping strategy can be realized by current technology. We also discuss counter measures against the attack and study the security of a QKD system with efficiency mismatch detectors.

Xiongfeng Ma

2008-08-10T23:59:59.000Z

43

From Entropic Dynamics to Quantum Theory  

SciTech Connect

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.

Caticha, Ariel [Department of Physics, University at Albany-SUNY, Albany, NY 12222 (United States)

2009-12-08T23:59:59.000Z

44

Scalar Quantum Field Theory in Disordered Media  

E-Print Network (OSTI)

A free massive scalar field in inhomogeneous random media is investigated. The coefficients of the Klein-Gordon equation are taken to be random functions of the spatial coordinates. The case of an annealed-like disordered medium, modeled by centered stationary and Gaussian processes, is analyzed. After performing the averages over the random functions, we obtain the two-point causal Green's function of the model up to one-loop. The disordered scalar quantum field theory becomes qualitatively similar to a $\\lambda\\phi^{4}$ self-interacting theory with a frequency-dependent coupling.

Arias, E; Krein, G; Menezes, G; Svaiter, N F

2011-01-01T23:59:59.000Z

45

Quantum Computing and Lie Theory Feynman's suggestion that the only effective way to model quantum phe-  

E-Print Network (OSTI)

Quantum Computing and Lie Theory Feynman's suggestion that the only effective way to model quantum phe- nomena on a computer would be to build a computer that made use of quantum mechanics was one of the cornerstones of the birth of quantum com- puting. In his later years he studied both classical and quantum

D'Agnolo, Andrea

46

Quantum gravity as a group field theory: a sketch  

E-Print Network (OSTI)

We give a very brief introduction to the group field theory approach to quantum gravity, a generalisation of matrix models for 2-dimensional quantum gravity to higher dimension, that has emerged recently from research in spin foam models.

Daniele Oriti

2005-12-07T23:59:59.000Z

47

Quantum mechanics as quantum information (and only a little more), Quantum Theory: Reconsideration of Foundations  

E-Print Network (OSTI)

In this paper, I try once again to cause some good-natured trouble. The issue remains, when will we ever stop burdening the taxpayer with conferences devoted to the quantum foundations? The suspicion is expressed that no end will be in sight until a means is found to reduce quantum theory to two or three statements of crisp physical (rather than abstract, axiomatic) significance. In this regard, no tool appears better calibrated for a direct assault than quantum information theory. Far from a strained application of the latest fad to a time-honored problem, this method holds promise precisely because a large partbut not allof the structure of quantum theory has always concerned information. It is just that the physics community needs reminding. This paper, though takingquant-ph/0106166 as its core, corrects one mistake and offers several observations beyond the previous version. In particular, I identify one element of quantum mechanics that I would not label a subjective term in the theoryit is the integer parameter D traditionally ascribed to a quantum system via its Hilbert-space dimension. 1

Christopher A. Fuchs

2002-01-01T23:59:59.000Z

48

Formulating Quantum Theory as a Causally Neutral Theory of Bayesian Inference  

E-Print Network (OSTI)

Quantum theory can be viewed as a generalization of classical probability theory, but the analogy as it has been developed so far is not complete. Classical probability theory is independent of causal structure, whereas the conventional quantum formalism requires causal structure to be fixed in advance. In this paper, we develop the formalism of quantum conditional states, which unifies the description of experiments involving two systems at a single time with the description of those involving a single system at two times. The analogies between quantum theory and classical probability theory are expressed succinctly within the formalism and it unifies the mathematical description of distinct concepts, such as ensemble preparation procedures, measurements, and quantum dynamics. We introduce a quantum generalization of Bayes' theorem and the associated notion of Bayesian conditioning. Conditioning a quantum state on a classical variable is the correct rule for updating quantum states in light of classical data...

Leifer, M S

2011-01-01T23:59:59.000Z

49

The effective field theory treatment of quantum gravity  

SciTech Connect

This is a pedagogical introduction to the treatment of quantum general relativity as an effective field theory. It starts with an overview of the methods of effective field theory and includes an explicit example. Quantum general relativity matches this framework and I discuss gravitational examples as well as the limits of the effective field theory. I also discuss the insights from effective field theory on the gravitational effects on running couplings in the perturbative regime.

Donoghue, John F. [Department of Physics, University of Massachusetts, Amherst, MA 01003 (United States)

2012-09-24T23:59:59.000Z

50

Thermal Density Functional Theory in Context  

E-Print Network (OSTI)

This chapter introduces thermal density functional theory, starting from the ground-state theory and assuming a background in quantum mechanics and statistical mechanics. We review the foundations of density functional theory (DFT) by illustrating some of its key reformulations. The basics of DFT for thermal ensembles are explained in this context, as are tools useful for analysis and development of approximations. We close by discussing some key ideas relating thermal DFT and the ground state. This review emphasizes thermal DFT's strengths as a consistent and general framework.

Pribram-Jones, Aurora; Gross, E K U; Burke, Kieron

2013-01-01T23:59:59.000Z

51

An application of neutrix calculus to quantum field theory  

E-Print Network (OSTI)

Neutrices are additive groups of negligible functions that do not contain any constants except 0. Their calculus was developed by van der Corput and Hadamard in connection with asymptotic series and divergent integrals. We apply neutrix calculus to quantum field theory, obtaining finite renormalizations in the loop calculations. For renormalizable quantum field theories, we recover all the usual physically observable results. One possible advantage of the neutrix framework is that effective field theories can be accommodated. Quantum gravity theories appear to be more manageable.

Y. Jack Ng; H. van Dam

2005-02-17T23:59:59.000Z

52

Quantum Mind from a Classical Field Theory of the Brain  

E-Print Network (OSTI)

We suggest that, with regard to a theory of quantum mind, brain processes can be described by a classical, dissipative, non-abelian gauge theory. In fact, such a theory has a hidden quantum nature due to its non-abelian character, which is revealed through dissipation, when the theory reduces to a quantum vacuum, where temperatures are of the order of absolute zero, and coherence of quantum states is preserved. We consider in particular the case of pure SU(2) gauge theory with a special anzatz for the gauge field, which breaks Lorentz invariance. In the ansatz, a contraction mapping plays the role of dissipation. In the limit of maximal dissipation, which corresponds to the attractive fixed point of the contraction mapping, the gauge fields reduce, up to constant factors, to the Pauli quantum gates for one-qubit states. Then tubuline-qubits can be processed in the quantum vacuum of the classical field theory of the brain, where decoherence is avoided due to the extremely low temperature. Finally, we interpret the classical SU(2) dissipative gauge theory as the quantum metalanguage (relative to the quantum logic of qubits), which holds the non-algorithmic aspect of the mind.

Paola Zizzi

2011-04-13T23:59:59.000Z

53

Quantum-field theories as representations of a single $^\\ast$-algebra  

E-Print Network (OSTI)

We show that many well-known quantum field theories emerge as representations of a single $^\\ast$-algebra. These include free quantum field theories in flat and curved space-times, lattice quantum field theories, Wightman quantum field theories, and string theories. We prove that such theories can be approximated on lattices, and we give a rigorous definition of the continuum limit of lattice quantum field theories.

Andreas Raab

2013-02-17T23:59:59.000Z

54

EPR Paradox, Locality and Completeness of Quantum Theory  

Science Conference Proceedings (OSTI)

The quantum theory (QT) and new stochastic approaches have no deterministic prediction for a single measurement or for a single time?series of events observed for a trapped ion

M. Kupczynski

2007-01-01T23:59:59.000Z

55

Quantum theory and gravity from a space-time wave  

E-Print Network (OSTI)

The quantum properties and gravitational field of a particle system are derived from a quantum theory of space-time. A field with quantized space-time vibrations has the same properties and equations for a particle field in quantum theory. The statistical nature of quantum mechanics can be explained by assuming the amplitudes of space-time waves serve as additional variables of the theory. The difficulty of associating a physical meaning with the quantum wave due to the unobservable overall phase is resolved. Instead of attempting to derive the properties of space-time from a quantum theory, as is usually the case, the quantum properties of matter can be derived from a theory of space-time. The energy of a space-time wave must correspond to the rest mass of a real particle; the vibrations are thus quantized. It is also demonstrated that the geometrical structure derived from a quantized space-time vibration is equivalent to the gravitational field of a point mass in general relativity. The fundamental questions of why and how a point mass gives rise to its gravitational singularity and curved space-time geometry can thereby be explained.

Hou Yau

2007-06-01T23:59:59.000Z

56

Formulating Quantum Theory as a Causally Neutral Theory of Bayesian Inference  

E-Print Network (OSTI)

Quantum theory can be viewed as a generalization of classical probability theory, but the analogy as it has been developed so far is not complete. Classical probability theory is independent of causal structure, whereas the conventional quantum formalism requires causal structure to be fixed in advance. In this paper, we develop the formalism of quantum conditional states, which unifies the description of experiments involving two systems at a single time with the description of those involving a single system at two times. The analogies between quantum theory and classical probability theory are expressed succinctly within the formalism and it unifies the mathematical description of distinct concepts, such as ensemble preparation procedures, measurements, and quantum dynamics. We introduce a quantum generalization of Bayes' theorem and the associated notion of Bayesian conditioning. Conditioning a quantum state on a classical variable is the correct rule for updating quantum states in light of classical data, regardless of the causal relationship between the classical variable and the quantum degrees of freedom, but it does not include the projection postulate as a special case. We show that previous arguments that projection is the quantum generalization of conditioning are based on misleading analogies. Since our formalism is causally neutral, conditioning provides a unification of the predictive and retrodictive formalisms for prepare-and-measure experiments and leads to an elegant derivation of the set of states that a system can be "steered" to by making measurements on a remote system.

M. S. Leifer; R. W. Spekkens

2011-07-29T23:59:59.000Z

57

Complementarity and Entanglement in Quantum Information Theory  

E-Print Network (OSTI)

The restrictions that nature places on the distribution of correlations in a multipartite quantum system play fundamental roles in the evolution of such systems, and yield vital insights into the design of protocols for the quantum control of ensembles with potential applications in the field of quantum computing. We show how this entanglement sharing behavior may be studied in increasingly complex systems of both theoretical and experimental significance and demonstrate that entanglement sharing, as well as other unique features of entanglement, e.g. the fact that maximal information about a multipartite quantum system does not necessarily entail maximal information about its component subsystems, may be understood as specific consequences of the phenomenon of complementarity extended to composite quantum systems. We also present a local hidden-variable model supplemented by an efficient amount of classical communication that reproduces the quantum-mechanical predictions for the entire class of Gottesman-Kni...

Tessier, T E

2004-01-01T23:59:59.000Z

58

Energy Inequalities in Quantum Field Theory  

E-Print Network (OSTI)

Quantum fields are known to violate all the pointwise energy conditions of classical general relativity. We review the subject of quantum energy inequalities: lower bounds satisfied by weighted averages of the stress-energy tensor, which may be regarded as the vestiges of the classical energy conditions after quantisation. Contact is also made with thermodynamics and related issues in quantum mechanics, where such inequalities find analogues in sharp Gaarding inequalities.

Christopher J. Fewster

2005-01-31T23:59:59.000Z

59

Quantum and semiclassical theories of chemical reaction rates  

DOE Green Energy (OSTI)

A rigorous quantum mechanical theory (and a semiclassical approximation thereto) is described for calculating chemical reaction rates ``directly``, i.e., without having to solve the complete state-to-state reactive scattering problem. The approach has many vestiges of transition state theory, for which it may be thought of as the rigorous generalization.

Miller, W.H. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

1995-09-01T23:59:59.000Z

60

The quantum systems control and the optimal control theory  

E-Print Network (OSTI)

Mathematical theory of the quantum systems control is based on some ideas of the optimal control theory. These ideas are developed here as applied to these systems. The results obtained meet the deficiencies in the basis and algorithms of the control synthesis and expand the application of these methods.

V. F. Krotov

2008-04-21T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

The Quantum Challenge in Concept Theory and Natural Language Processing  

E-Print Network (OSTI)

The mathematical formalism of quantum theory has been successfully used in human cognition to model decision processes and to deliver representations of human knowledge. As such, quantum cognition inspired tools have improved technologies for Natural Language Processing and Information Retrieval. In this paper, we overview the quantum cognition approach developed in our Brussels team during the last two decades, specifically our identification of quantum structures in human concepts and language, and the modeling of data from psychological and corpus-text-based experiments. We discuss our quantum-theoretic framework for concepts and their conjunctions/disjunctions in a Fock-Hilbert space structure, adequately modeling a large amount of data collected on concept combinations. Inspired by this modeling, we put forward elements for a quantum contextual and meaning-based approach to information technologies in which 'entities of meaning' are inversely reconstructed from texts, which are considered as traces of these entities' states.

Diederik Aerts; Jan Broekaert; Sandro Sozzo; Tomas Veloz

2013-06-12T23:59:59.000Z

62

The genesis of the quantum theory of the chemical bond  

E-Print Network (OSTI)

An historical overview is given of the relevant steps that allowed the genesis of the quantum theory of the chemical bond, starting from the appearance of the new quantum mechanics and following later developments till approximately 1931. General ideas and some important details are discussed concerning molecular spectroscopy, as well as quantum computations for simple molecular systems performed within perturbative and variational approaches, for which the Born-Oppenheimer method provided a quantitative theory accounting for rotational, vibrational and electronic states. The novel concepts introduced by the Heitler-London theory, complemented by those underlying the method of the molecular orbitals, are critically analyzed along with some of their relevant applications. Further improvements in the understanding of the nature of the chemical bond are also considered, including the ideas of one-electron and three-electron bonds introduced by Pauling, as well as the generalizations of the Heitler-London theory ...

Esposito, S

2013-01-01T23:59:59.000Z

63

Quantum Field Theory Is Not Merely Quantum Mechanics Applied to Low Energy Effective Degrees of Freedom  

E-Print Network (OSTI)

It is commonly assumed that quantum field theory arises by applying ordinary quantum mechanics to the low energy effective degrees of freedom of a more fundamental theory defined at ultra-high-energy/short-wavelength scales. We shall argue here that, even for free quantum fields, there are holistic aspects of quantum field theory that cannot be properly understood in this manner. Specifically, the ``subtractions'' needed to define nonlinear polynomial functions of a free quantum field in curved spacetime are quite simple and natural from the quantum field theoretic point of view, but are at best extremely ad hoc and unnatural if viewed as independent renormalizations of individual modes of the field. We illustrate this point by contrasting the analysis of the Casimir effect, the renormalization of the stress-energy tensor in time-dependent spacetimes, and anomalies from the point of quantum field theory and from the point of view of quantum mechanics applied to the independent low energy modes of the field. Some implications for the cosmological constant problem are discussed.

Stefan Hollands; Robert M. Wald

2004-05-16T23:59:59.000Z

64

Real-Vector-Space Quantum Theory with a Universal Quantum Bit  

E-Print Network (OSTI)

We explore a model of the world based on real-vector-space quantum theory. In our model the familiar complex phase appearing in quantum states is replaced by a single binary object that we call the ubit, which is not localized and which can interact with any object in the world. Ordinary complex-vector-space quantum theory can be recovered from this model if we simply impose a certain restriction on the sets of allowed measurements and transformations (Stueckelberg's rule), but in this paper we try to obtain the standard theory, or a close approximation to it, without invoking such a restriction. We look particularly at the effective theory that applies to a subsystem when the ubit is interacting with a much larger environment. In a certain limit it turns out that the ubit-environment interaction has the effect of enforcing Stueckelberg's rule automatically, and we obtain a one-parameter family of effective theories--modifications of standard quantum theory--that all satisfy this rule. The one parameter is the ratio s/omega, where s quantifies the strength of the ubit's interaction with the rest of the world and omega is the ubit's rotation rate. We find that when this parameter is small but not zero, the effective theory is similar to standard quantum theory but is characterized by spontaneous decoherence of isolated systems.

Antoniya Aleksandrova; Victoria Borish; William K. Wootters

2012-10-16T23:59:59.000Z

65

Theory Of Alkyl Terminated Silicon Quantum Dots  

DOE Green Energy (OSTI)

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.

Reboredo, F; Galli, G

2004-08-19T23:59:59.000Z

66

Towards a K-theory description of quantum hair  

Science Conference Proceedings (OSTI)

The first steps towards a proposal for a description of the quantum hair in 4D supersymmetric black holes in string Calabi-Yau (CY) compactifications are given. The quantum hair consisting of electric and magnetic fractional charges in black holes are derived from periods of the CY's torsion cycles. In the process a K-theory interpretation of the quantum hair in terms of the Atiyah-Hirzebruch spectral sequence is carried out. Finally, the same procedure is considered for torsion cycles of certain generalized CY's threefolds such as half-flat manifolds.

Garcia-Compean, H.; Loaiza-Brito, O. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del I.P.N., P.O. Box 14-740, 07000, Mexico D.F (Mexico); Departamento de Fisica, Universidad de Guanajuato, C.P. 37150, Leon, Guanajuato (Mexico)

2012-08-24T23:59:59.000Z

67

Almost zero-dimensional PT-symmetric quantum field theories  

E-Print Network (OSTI)

In 1992 Bender, Boettcher, and Lipatov proposed in two papers a new and unusual nonperturbative calculational tool in quantum field theory. The objective was to expand the Green's functions of the quantum field theory as Taylor series in powers of the space-time dimension D. In particular, the vacuum energy for a massless \\phi^{2N} (N=1,2,3,...) quantum field theory was studied. The first two Taylor coefficients in this dimensional expansion were calculated {\\it exactly} and a set of graphical rules were devised that could be used to calculate approximately the higher coefficients in the series. This approach is mathematically valid and gives accurate results, but it has not been actively pursued and investigated. Subsequently, in 1998 Bender and Boettcher discovered that PT-symmetric quantum-mechanical Hamiltonians of the form H=p^2+x^2(ix)^\\epsilon, where \\epsilon\\geq0, have real spectra. These new kinds of complex non-Dirac-Hermitian Hamiltonians define physically acceptable quantum-mechanical theories. Th...

Bender, Carl M

2010-01-01T23:59:59.000Z

68

On Information Theory, Spectral Geometry and Quantum Gravity  

E-Print Network (OSTI)

We show that there exists a deep link between the two disciplines of information theory and spectral geometry. This allows us to obtain new results on a well known quantum gravity motivated natural ultraviolet cutoff which describes an upper bound on the spatial density of information. Concretely, we show that, together with an infrared cutoff, this natural ultraviolet cutoff beautifully reduces the path integral of quantum field theory on curved space to a finite number of ordinary integrations. We then show, in particular, that the subsequent removal of the infrared cutoff is safe.

Achim Kempf; Robert Martin

2007-08-01T23:59:59.000Z

69

Perturbative Aspects of Low-Dimensional Quantum Field Theory  

SciTech Connect

We investigate the low-dimensional applications of Quantum Field Theory (QFT), namely Chern-Simons-Witten Theory (CSWT) and Affine Toda Field Theory (ATFT) in 3- and 2- dimensions. We discuss the perturbative aspects of both theories and compare the results to the exact solutions obtained nonperturbatively. For the three dimensions CSWT case, the perturbative term agree with the nonperturbative polynomial invariants up to third order of the coupling constant 1/k. In the two dimensions ATFT, we investigate the perturbative aspect of S-matrices for A{sub 1}{sup (1)} case in eighth order of the coupling constant {beta}.

Wardaya, Asep Y. [Department of Physics, Diponegoro University, Jl. Prof. Soedarto SH, Semarang (Indonesia); Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, FMIPA, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132 (Indonesia); Zen, Freddy P.; Kosasih, Jusak S.; , Triyanta; Hartanto, Andreas [Indonesia Center for Theoretical and Mathematical Physics (ICTMP) (Indonesia); Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, FMIPA, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132 (Indonesia)

2010-06-22T23:59:59.000Z

70

On quantum field theory with invariant parameter  

Science Conference Proceedings (OSTI)

1/2 particles, except for the so far unobserved Higgs boson, we first have to show that a viable formulation of Dirac theory within PRQT exists; this is especially...

71

Quantum-mechanical theory of optomechanical Brillouin cooling  

SciTech Connect

We analyze how to exploit Brillouin scattering of light from sound for the purpose of cooling optomechanical devices and present a quantum-mechanical theory for Brillouin cooling. Our analysis shows that significant cooling ratios can be obtained with standard experimental parameters. A further improvement of cooling efficiency is possible by increasing the dissipation of the optical anti-Stokes resonance.

Tomes, Matthew; Bahl, Gaurav; Carmon, Tal [Department of Electrical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Marquardt, Florian [Institut fuer Theoretische Physik, Universitaet Erlangen-Nuernberg, Staudtstrasse 7, D-91058 Erlangen (Germany); Max Planck Institute for the Science of Light, Guenther-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany)

2011-12-15T23:59:59.000Z

72

Quantum Theory of Fast Chemical Reactions  

SciTech Connect

The aims of the research under this grant were to develop a theoretical understanding and predictive abiility for a variety of processes occurring in the gas phase. These included bimolecular chemical exchange reactions, photodissociation, predissociation resonances, unimolecular reactions and recombination reactions. In general we assumed a knowledge, from quantum chemistry, of the interactions of the atoms and molecular fragments involved. Our focus was primarily on the accurate (quantum) dynamics of small molecular systems. This has been important for many reactions related to combustion and atmospheric chemistry involving light atom transfer reactions and, for example, resonances in dissociation and recombination reactions. The rates of such reactions, as functions of temperature, internal states, and radiation (light), are fundamental for generating models of overall combustion processes. A number of new approaches to these problems were developed inclluding the use of discrete variable representations (DVR's) for evaluating rate constants with the flux-flux correlation approach, finite range approaches to exact quantum scattering calculations, energy selected basis representations, transition state wave packet approaches and improved semiclassical approaches. These (and others) were applied to a number of reactive systems and molecular systems of interest including (many years ago) the isotopic H + H2 exchange reactions, the H2 + OH (and H + H2O) systems, Ozone resonances, van der Waals molecule reactions, etc. A total of 7 graduate students, and 5 post-doctoral Research Associates were supported, at least in part, under this grant and seven papers were published with a total of 10 external collaborators. The majority of the 36 publications under this grant were supported entirely by DOE.

John C. Light

2007-07-30T23:59:59.000Z

73

N=2 supersymmetric gauge theories and quantum integrable systems  

E-Print Network (OSTI)

We study N=2 supersymmetric gauge theories on the product of a two-sphere and a cylinder. We show that the low-energy dynamics of a BPS sector of such a theory is described by a quantum integrable system, with the Planck constant set by the inverse of the radius of the sphere. If the sphere is replaced with a hemisphere, then our system reduces to an integrable system of the type studied by Nekrasov and Shatashvili. In this case we establish a correspondence between the effective prepotential of the gauge theory and the Yang-Yang function of the integrable system.

Yuan Luo; Meng-Chwan Tan; Junya Yagi

2013-10-02T23:59:59.000Z

74

N=2 supersymmetric gauge theories and quantum integrable systems  

E-Print Network (OSTI)

We study N=2 supersymmetric gauge theories on the product of a two-sphere and a cylinder. We show that the low-energy dynamics of a BPS sector of such a theory is described by a quantum integrable system, with the Planck constant set by the inverse of the radius of the sphere. If the sphere is replaced with a hemisphere, then our system reduces to an integrable system of the type studied by Nekrasov and Shatashvili. In this case we establish a correspondence between the effective prepotential of the gauge theory and the Yang-Yang function of the integrable system.

Luo, Yuan; Yagi, Junya

2013-01-01T23:59:59.000Z

75

Valley splitting theory of SiGe/Si/SiGe quantum wells Mark Friesen,1,  

E-Print Network (OSTI)

Valley splitting theory of SiGe/Si/SiGe quantum wells Mark Friesen,1, * Sucismita Chutia,1 Charles an effective mass theory for SiGe/Si/SiGe quantum wells, with an emphasis on calculating the valley splitting. The theory introduces a valley coupling parameter vv which encapsulates the physics of the quantum well

Sheridan, Jennifer

76

Book Review of Stephen L. Adler's, "Quantum theory as an emergent phenomenon."  

E-Print Network (OSTI)

In Stephen Adler's book, "Quantum theory as an emergent phenomenon," the author starts from a classical mechanics structure and "derives" the formalism of quantum theory, together with wave function collapse dynamics, the latter providing the interpretation of quantum theory. A detailed outline of the author's argument is presented in this book review.

Philip Pearle

2006-02-07T23:59:59.000Z

77

Experimental test of the "special state" theory of quantum measurement  

E-Print Network (OSTI)

An experimental test of the "special state" theory of quantum measurement is proposed. It should be feasible with present-day laboratory equipment and involves a slightly elaborated Stern-Gerlach setup. The "special state" theory is conservative with respect to quantum mechanics, but radical with respect to statistical mechanics, in particular regarding the arrow of time. In this article background material is given on both quantum measurement and statistical mechanics aspects. For example, it is shown that future boundary conditions would not contradict experience, indicating that the fundamental equal-a-priori-probability assumption at the foundations of statistical mechanics is far too strong (since future conditioning reduces the class of allowed states). The test is based on a feature of this theory that was found necessary in order to recover standard (Born) probabilities in quantum measurements. Specifically, certain systems should have "noise" whose amplitude follows the long-tailed Cauchy distribution. This distribution is marked by the occasional occurrence of extremely large signals as well as a non-self-averaging property. The proposed test is a variant of the Stern-Gerlach experiment in which protocols are devised, some of which will require the presence of this noise, some of which will not. The likely observational schemes would involve the distinction between detection and non-detection of that "noise". The signal to be detected (or not) would be either single photons in the visible and UV range or electric fields (and related excitations) in the neighborhood of the ends of the magnets.

L. S. Schulman

2013-10-09T23:59:59.000Z

78

Rigged Hilbert space formalism as an extended mathematical formalism for quantum systems. II. Transformation theory in nonrelativistic quantum mechanics  

Science Conference Proceedings (OSTI)

Results of a previous paper are used to obtain a rigorous mathematical formulation of the transformation theory of nonrelativistic quantum mechanics within the framework of rigged Hilbert spaces.

O. Melsheimer

1974-01-01T23:59:59.000Z

79

Parity violating quantum kinetic theory in (2+1)-dimensions  

E-Print Network (OSTI)

We study the kinetic theory for a (2+1)-dimensional fermionic system with special emphasis on the parity violating properties associated with the fermion mass. The Wigner function approach is used to derive hydrodynamical transport coefficients to the first spatial derivative order. As a first attempt, the collisions between fermions are neglected. The resulting system is dissipationless. The parity violating Hall electric conductivity has the same temperature and chemical potential dependence as the quantum field theory result at one-loop. Vorticity dependent transport properties, which were not considered before, also emerge naturally in this approach.

Jiunn-Wei Chen; Jian-Hua Gao; Juan Liu; Shi Pu; Qun Wang

2013-05-08T23:59:59.000Z

80

Loop Quantum Theory Applied to Biology and Nonlinear Whole Biology  

E-Print Network (OSTI)

The loop quantum theory, which constitutes a very small discontinuous space, as new method is applied to biology. The model of protein folding and lungs is proposed. In the model, some known results are used, and four approximate conclusions are obtained: their structures are quantized, their space regions are finite, various singularities correspond to folding and crossed points, and different types of catastrophe exist. Further, based on the inseparability and correlativity of the biological systems, the nonlinear whole biology is proposed, and four basic hypotheses are formed. It may unify reductionism and holism, structuralism and functionalism. Finally, the medical meaning of the theory is discussed briefly.

Yi-Fang Chang

2008-01-02T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Quantum theory of cold bosonic atoms in optical lattices  

SciTech Connect

Ultracold atoms in optical lattices undergo a quantum phase transition from a superfluid to a Mott insulator as the lattice potential depth is increased. We describe an approximate theory of interacting bosons in optical lattices which provides a qualitative description of both superfluid and insulator states. The theory is based on a change of variables in which the boson coherent state amplitude is replaced by an effective potential which promotes phase coherence between different number states on each lattice site. It is illustrated here by applying it to uniform and fully frustrated lattice cases but is simple enough that it can be applied to spatially inhomogeneous lattice systems.

Tilahun, Dagim [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Department of Physics, Texas State University, San Marcos, Texas 78666 (United States); Duine, R. A. [Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, NL-3584 CE Utrecht (Netherlands); MacDonald, A. H. [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

2011-09-15T23:59:59.000Z

82

Theory of ground state factorization in quantum cooperative systems  

E-Print Network (OSTI)

We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows to determine rigorously existence, location, and exact form of separable ground states in a large variety of, generally non-exactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range.

Giampaolo, S M; Illuminati, F

2008-01-01T23:59:59.000Z

83

Test Functions Space in Noncommutative Quantum Field Theory  

E-Print Network (OSTI)

It is proven that the $\\star$-product of field operators implies that the space of test functions in the Wightman approach to noncommutative quantum field theory is one of the Gel'fand-Shilov spaces $S^{\\beta}$ with $\\beta test functions smears the noncommutative Wightman functions, which are in this case generalized distributions, sometimes called hyperfunctions. The existence and determination of the class of the test function spaces in NC QFT is important for any rigorous treatment in the Wightman approach.

M. Chaichian; M. Mnatsakanova; A. Tureanu; Yu. Vernov

2007-06-12T23:59:59.000Z

84

Time Series, Stochastic Processes and Completeness of Quantum Theory  

Science Conference Proceedings (OSTI)

Most of physical experiments are usually described as repeated measurements of some random variables. Experimental data registered by on?line computers form time series of outcomes. The frequencies of different outcomes are compared with the probabilities provided by the algorithms of quantum theory (QT). In spite of statistical predictions of QT a claim was made that it provided the most complete description of the data and of the underlying physical phenomena. This claim could be easily rejected if some fine structures

2011-01-01T23:59:59.000Z

85

Theory of ground state factorization in quantum cooperative systems  

E-Print Network (OSTI)

We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows to determine rigorously existence, location, and exact form of separable ground states in a large variety of, generally non-exactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range.

S. M. Giampaolo; G. Adesso; F. Illuminati

2008-04-01T23:59:59.000Z

86

Quantum Gauged Neural Network: U(1) Gauge Theory  

E-Print Network (OSTI)

A quantum model of neural network is introduced and its phase structure is examined. The model is an extension of the classical Z(2) gauged neural network of learning and recalling to a quantum model by replacing the Z(2) variables, $S_i = \\pm1$ of neurons and $J_{ij} =\\pm1$ of synaptic connections, to the U(1) phase variables, $S_i = \\exp(i\\phi_i)$ and $J_{ij} = \\exp(i\\theta_{ij}) $. These U(1) variables describe the phase parts of the wave functions (local order parameters) of neurons and synaptic connections. The model takes the form similar to the U(1) Higgs lattice gauge theory, the continuum limit of which is the well known Ginzburg-Landau theory of superconductivity. Its current may describe the flow of electric voltage along axons and chemical materials transfered via synaptic connections. The phase structure of the model at finite temperatures is examined by the mean-field theory, and Coulomb, Higgs and confinement phases are obtained. By comparing with the result of the Z(2) model, the quantum effects is shown to weaken the ability of learning and recalling.

Yukari Fujita; Tetsuo Matsui

2002-06-30T23:59:59.000Z

87

A New Look at the Position Operator in Quantum Theory  

E-Print Network (OSTI)

The postulate that coordinate and momentum representations are related to each other by the Fourier transform has been accepted from the beginning of quantum theory by analogy with classical electrodynamics. As a consequence, an inevitable effect in standard theory is the wave packet spreading (WPS) of the photon coordinate wave function in directions perpendicular to the photon momentum. This leads to the following paradoxes: if the major part of photons emitted by stars are in wave packet states (what is the most probable scenario) then we should see not separate stars but only an almost continuous background from all stars; no anisotropy of the CMB radiation should be observable; data on gamma-ray bursts, signals from directional radio antennas (in particular, in experiments on Shapiro delay) and signals from pulsars show no signs of WPS. In addition, a problem arises why there are no signs of WPS for protons in the LHC ring. We argue that the above postulate is based neither on strong theoretical arguments nor on experimental data and propose a new consistent definition of the position operator. Then WPS in directions perpendicular to the particle momentum is absent and the paradoxes are resolved. Different components of the new position operator do not commute with each other and, as a consequence, there is no wave function in coordinate representation. Implications of the results for entanglement, quantum locality and the problem of time in quantum theory are discussed.

Felix M. Lev

2012-07-04T23:59:59.000Z

88

The Quantum Spin Hall Effect: Theory and Experiment  

SciTech Connect

The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.

Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; /Wurzburg U.; Hughes, Taylor L.; /Stanford U., Phys. Dept.; Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19T23:59:59.000Z

89

Density-gradient theory: a macroscopic approach to quantum confinement and tunneling in semiconductor devices  

Science Conference Proceedings (OSTI)

Density-gradient theory provides a macroscopic approach to modeling quantum transport that is particularly well adapted to semiconductor device analysis and engineering. After some introductory observations, the basis of the theory in macroscopic and ... Keywords: Continuum, Density-gradient, Electron transport, Quantum confinement, Quantum tunneling, Semiconductor device simulation, Thermodynamics

M. G. Ancona

2011-06-01T23:59:59.000Z

90

The Quantum Spin Hall Effect: Theory and Experiment  

Science Conference Proceedings (OSTI)

The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.

Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; /Wurzburg U.; Hughes, Taylor L.; /Stanford U., Phys. Dept.; Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19T23:59:59.000Z

91

Testing axioms for Quantum Mechanics on Probabilistic toy-theories  

E-Print Network (OSTI)

In Ref. [1] one of the authors proposed postulates for axiomatizing Quantum Mechanics as a "fair operational framework", namely regarding the theory as a set of rules that allow the experimenter to predict future events on the basis of suitable tests, having local control and low experimental complexity. In addition to causality, the following postulates have been considered: PFAITH (existence of a pure preparationally faithful state), and FAITHE (existence of a faithful effect). These postulates have exhibited an unexpected theoretical power, excluding all known nonquantum probabilistic theories. Later in Ref. [2] in addition to causality and PFAITH, postulate LDISCR (local discriminability) and PURIFY (purifiability of all states) have been considered, narrowing the probabilistic theory to something very close to Quantum Mechanics. In the present paper we test the above postulates on some nonquantum probabilistic models. The first model, "the two-box world" is an extension of the Popescu-Rohrlich model, which achieves the greatest violation of the CHSH inequality compatible with the no-signaling principle. The second model "the two-clock world" is actually a full class of models, all having a disk as convex set of states for the local system. One of them corresponds to the "the two-rebit world", namely qubits with real Hilbert space. The third model--"the spin-factor"--is a sort of n-dimensional generalization of the clock. Finally the last model is "the classical probabilistic theory". We see how each model violates some of the proposed postulates, when and how teleportation can be achieved, and we analyze other interesting connections between these postulate violations, along with deep relations between the local and the non-local structures of the probabilistic theory.

Giacomo Mauro D'Ariano; Alessandro Tosini

2009-11-29T23:59:59.000Z

92

Molecular quantum mechanical observers, symmetry, and string theory  

E-Print Network (OSTI)

The paper \\cite{Dance0601} tentatively suggested a physical picture that might underlie string theories. The string parameters $\\tau $ and $\\sigma_i $ were interpreted as spacetime dimensions which a simple quantum mechanical observer can observe, while symmetries of the relevant observer states could limit the observability of other dimensions. An atomic observer was the focus of the discussion. The present paper extends the discussion of\\cite{Dance0601} to molecular observers, including the nature of some common molecular bonds and their symmetries.

M. Dance

2010-11-29T23:59:59.000Z

93

Vacuum Energy Problem, Fundamental Length and Deformed Quantum Field Theory  

E-Print Network (OSTI)

The cosmological constant (vacuum energy) problem is analyzed within the scope of quantum theories with UV-cut-off or fundamental length. Various cases associated with the appearance of the latter are considered both using the Generalized Uncertainty Relations and the deformed density matrix,previously introduced in the author's works. The use of the deformed density matrix is examined in detail. It is demonstrated that, provided the Fischler-Susskind cosmic holographic conjecture is valid, the Vacuum Energy Density takes a value close to the experimental one. The arguments supporting the validity of this conjecture are given on the basis of the recently obtained results on Gravitational Holography.

A. E. Shalyt-Margolin

2007-12-19T23:59:59.000Z

94

Book Review: "Quantum Theory as an Emergent Phenomenon", by Stephen L. Adler  

E-Print Network (OSTI)

This is a book review of the book: "Quantum Theory as an Emergent Phenomenon", by Stephen L. Adler (Cambridge University Press - 2004)

A. Bassi

2005-04-28T23:59:59.000Z

95

Understanding High-Temperature Superconductors with Quantum Cluster Theories  

SciTech Connect

Quantum cluster theories are a set of approaches for the theory of correlated and disordered lattice systems, which treat correlations within the cluster explicitly, and correlations at longer length scales either perturbatively or within a mean-field approximation. These methods become exact when the cluster size diverges, and most recover the corresponding (dynamical) mean-field approximation when the cluster size becomes one. Here we will review systematic dynamical cluster simulations of the two-dimensional Hubbard model, that display phenomena remarkably similar to those found in the cuprates, including antiferromagnetism, superconductivity and pseudogap behavior. We will then discuss results for the structure of the pairing mechanism in this model, obtained from a combination of dynamical cluster results and diagrammatic techniques.

Maier, Thomas A [ORNL; Jarrell, Mark [University of Cincinnati; Scalapino, Douglas [University of California, Santa Barbara

2007-01-01T23:59:59.000Z

96

Quantum rotor theory of spinor condensates in tight traps  

Science Conference Proceedings (OSTI)

In this work, we theoretically construct exact mappings of many-particle bosonic systems onto quantum rotor models. In particular, we analyze the rotor representation of spinor Bose-Einstein condensates. In a previous work [R. Barnett et al., Phys. Rev. A 82, 031602(R) (2010)] it was shown that there is an exact mapping of a spin-one condensate of fixed particle number with quadratic Zeeman interaction onto a quantum rotor model. Since the rotor model has an unbounded spectrum from above, it has many more eigenstates than the original bosonic model. Here we show that for each subset of states with fixed spin F{sub z}, the physical rotor eigenstates are always those with the lowest energy. We classify three distinct physical limits of the rotor model: the Rabi, Josephson, and Fock regimes. The last regime corresponds to a fragmented condensate and is thus not captured by the Bogoliubov theory. We next consider the semiclassical limit of the rotor problem and make connections with the quantum wave functions through the use of the Husimi distribution function. Finally, we describe how to extend the analysis to higher-spin systems and derive a rotor model for the spin-two condensate. Theoretical details of the rotor mapping are also provided here.

Barnett, Ryan; Hui, Hoi-Yin; Lin, Chien-Hung; Sau, Jay D.; Das Sarma, S. [Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

2011-02-15T23:59:59.000Z

97

Quantum kinetic theory model of a continuous atom laser  

E-Print Network (OSTI)

We investigate the feasible limits for realising a continuously evaporated atom laser with high-temperature sources. A plausible scheme for realising a truly continuous atom laser is to outcouple atoms from a partially condensed Bose gas, whilst continuously reloading the system with non-condensed thermal atoms and performing evaporative cooling. Here we use quantum kinetic theory to model this system and estimate feasible limits for the operation of such a scheme. For sufficiently high temperatures, the figure of merit for the source is shown to be the phase-space flux. The dominant process limiting the usage of sources with low phase-space flux is the three-body loss of the condensed gas. We conclude that certain double-magneto-optical trap (MOT) sources may produce substantial mean condensate numbers through continuous evaporation, and provide an atom laser source with a narrow linewidth and reasonable flux.

G. R. Dennis; Matthew J. Davis; J. J. Hope

2010-11-24T23:59:59.000Z

98

Generalizing the ADM Computation to Quantum Field Theory  

E-Print Network (OSTI)

The absence of recognizable, low energy quantum gravitational effects requires that some asymptotic series expansion be wonderfully accurate, but the correct expansion might involve logarithms or fractional powers of Newton's constant. That would explain why conventional perturbation theory shows uncontrollable ultraviolet divergences. We explore this possibility in the context of the mass of a charged, gravitating scalar. The classical limit of this system was solved exactly in 1960 by Arnowitt, Deser and Misner, and their solution does exhibit nonanalytic dependence on Newton's constant. We derive an exact functional integral representation for the mass of the quantum field theoretic system, and then develop an alternate expansion for it based on a correct implementation of the method of stationary phase. The new expansion entails adding an infinite class of new diagrams to each order and subtracting them from higher orders. The zeroth order term of the new expansion has the physical interpretation of a first quantized Klein-Gordon scalar which forms a bound state in the gravitational and electromagnetic potentials sourced by its own probability current. We show that such bound states exist and we obtain numerical results for their masses.

P. J. Mora; N. C. Tsamis; R. P. Woodard

2011-08-22T23:59:59.000Z

99

Quantum mechanical analogue of the zeroth law of thermodynamics. (On the problem of incorporating Thermodynamics into Quantum Theory)  

E-Print Network (OSTI)

This approach to the incorporation of stochastic thermodynamics into quantum theory is based on the conception of consistent inclusion of the holistic stochastic environmental influence described by wave functions of the arbitrary vacuum, which was proposed in our paper previously. In this study, we implement the possibility of explicitly incorporating the zeroth law of stochastic thermodynamics in the form of the saturated Schr\\"odinger uncertainty relation into quantum theory. This allows comparatively analyzing the sets of states of arbitrary vacuums, namely, squeezed coherent states (SCSs) and correlated coherent states (CCSs). In addition, we compare the results of the construction of stochastic thermodynamics using SCSs and TCCSs with the versions involving the incorporation of thermodynamics into quantum theory developed previously and based on thermofield dynamics and quantum statistical mechanics.

O. N. Golubjeva; A. D. Sukhanov

2013-03-25T23:59:59.000Z

100

On unentangled Gleason theorems for quantum information theory  

E-Print Network (OSTI)

It is shown here that a strengthening of Wallach's Unentangled Gleason Theorem can be obtained by applying results of the present authors on generalised Gleason theorems for quantum multi-measures arising from investigations of quantum decoherence functionals.

Oliver Rudolph; J. D. M. Wright

2000-04-07T23:59:59.000Z

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101

First-principles quantum transport modeling of thermoelectricity in single-molecule nanojunctions with graphene nanoribbon electrodes  

Science Conference Proceedings (OSTI)

We overview the nonequilibrium Green function combined with density functional theory (NEGF-DFT) approach to modeling of independent electronic and phononic quantum transport in nanoscale thermoelectrics with examples focused on a new class of devices ... Keywords: First-principles quantum transport, Graphene nanoribbons, Molecular electronics, Thermoelectrics

Branislav K. Nikoli?; Kamal K. Saha; Troels Markussen; Kristian S. Thygesen

2012-03-01T23:59:59.000Z

102

Beyond the Quantum Adiabatic Approximation: Adiabatic Perturbation Theory  

E-Print Network (OSTI)

We introduce a perturbative approach to solving the time dependent Schroedinger equation, named adiabatic perturbation theory (APT), whose zeroth order term is the quantum adiabatic approximation. The small parameter in the power series expansion of the time-dependent wave function is the inverse of the time it takes to drive the system's Hamiltonian from the initial to its final form. We review other standard perturbative and non-perturbative ways of going beyond the adiabatic approximation, extending and finding exact relations among them, and also compare the efficiency of those methods against the APT. Most importantly, we determine APT corrections to the Berry phase by use of the Aharonov-Anandan geometric phase. We then solve several time dependent problems allowing us to illustrate that the APT is the only perturbative method that gives the right corrections to the adiabatic approximation. Finally, we propose an experiment to measure the APT corrections to the Berry phase and show, for a particular spin-1/2 problem, that to first order in APT the geometric phase should be two and a half times the (adiabatic) Berry phase.

Gustavo Rigolin; Gerardo Ortiz; Victor Hugo Ponce

2008-07-09T23:59:59.000Z

103

Modern integral equation techniques for quantum reactive scattering theory  

SciTech Connect

Rigorous calculations of cross sections and rate constants for elementary gas phase chemical reactions are performed for comparison with experiment, to ensure that our picture of the chemical reaction is complete. We focus on the H/D+H{sub 2} {yields} H{sub 2}/DH + H reaction, and use the time independent integral equation technique in quantum reactive scattering theory. We examine the sensitivity of H+H{sub 2} state resolved integral cross sections {sigma}{sub v{prime}j{prime},vj}(E) for the transitions (v = 0,j = 0) to (v{prime} = 1,j{prime} = 1,3), to the difference between the Liu-Siegbahn-Truhlar-Horowitz (LSTH) and double many body expansion (DMBE) ab initio potential energy surfaces (PES). This sensitivity analysis is performed to determine the origin of a large discrepancy between experimental cross sections with sharply peaked energy dependence and theoretical ones with smooth energy dependence. We find that the LSTH and DMBE PESs give virtually identical cross sections, which lends credence to the theoretical energy dependence.

Auerbach, S.M.

1993-11-01T23:59:59.000Z

104

Time-to-space conversion in quantum field theory of flavor mixing  

E-Print Network (OSTI)

We consider the problem of time-to-space conversion in quantum field theory of flavor mixing using a generalization of the wave-packet method in quantum mechanics. We work entirely within the canonical formalism of creation and annihilation operators that allows us, unlike the usual wave-packet formulation, to include the nontrivial effect due to flavor condensation in the vacuum.

Chueng-Ryong Ji; Yuriy Mishchenko

2004-03-07T23:59:59.000Z

105

Generalized Galilean Transformations and the Measurement Problem in the Entropic Dynamics Approach to Quantum Theory  

E-Print Network (OSTI)

Quantum mechanics is an extremely successful and accurate physical theory, yet since its inception, it has been afflicted with numerous conceptual difficulties. The primary subject of this thesis is the theory of entropic quantum dynamics (EQD), which seeks to avoid these conceptual problems by interpreting quantum theory from an informational perspective. We begin by reviewing probability theory as a means of rationally quantifying uncertainties. We then discuss how probabilities can be updated with the method of maximum entropy (ME). We then review some motivating difficulties in quantum mechanics before discussing Caticha's work in deriving quantum theory from the approach of entropic dynamics. After entropic dynamics is introduced, we develop the concepts of symmetries and transformations from an informational perspective. The primary result is the formulation of a symmetry condition that any transformation must satisfy in order to qualify as a symmetry in EQD. We then proceed to apply this condition to the extended Galilean transformation. This transformation is of interest as it exhibits features of both special and general relativity. The transformation yields a gravitational potential that arises from an equivalence of information. We conclude the thesis with a discussion of the measurement problem in quantum mechanics. We discuss the difficulties that arise in the standard quantum mechanical approach to measurement before developing our theory of entropic measurement. In entropic dynamics, position is the only observable. We show how a theory built on this one observable can account for the multitude of measurements present in quantum theory. Furthermore, we show that the Born rule need not be postulated, but can be derived in EQD. Finally, we show how the wave function can be updated by the ME method as the phase is constructed purely in terms of probabilities.

David T. Johnson

2011-05-06T23:59:59.000Z

106

Nonlinear relativistic quantum theory of Cherenkov emission of longitudinal Langmuir waves in a plasma  

Science Conference Proceedings (OSTI)

A nonlinear relativistic quantum theory of stimulated Cherenkov emission of longitudinal waves by a relativistic monoenergetic electron beam in a cold isotropic plasma is presented. The theory makes use of a quantum model based on the Klein-Gordon equation. The instability growth rates are obtained in the linear approximation and are shown to go over to the familiar growth rates in the classical limit. The mechanisms for the nonlinear saturation of relativistic Cherenkov beam instabilities are described with allowance for quantum effects, and the corresponding analytic solutions are derived.

Bobylev, Yu. V.; Kuzelev, M. V. [Moscow State University (Russian Federation)

2011-10-15T23:59:59.000Z

107

Questions and Answers - How can I explain the Quantum/Wave theory to my  

NLE Websites -- All DOE Office Websites (Extended Search)

What is a meniscus? What is a meniscus? Previous Question (What is a meniscus?) Questions and Answers Main Index Next Question (What is the sun made from?) What is the sun made from? How can I explain the Quantum/Wave theory to my class? You can't! The folks who have postulated the quantum nature of matter and wave-particle duality, and other quantum theories have trouble explaining it in terms other than mathematical equations. When trying to explain it in conceptual terms, we're asked to accept things that don't make sense, and in some ways, physicists use this as justification that the theory is correct. Anyway, here are a couple ideas for discussing the quantum/wave properties of energy. Until around 1900, when Max Planck developed the idea of quanta, energy had been thought to be a phenomenon of continuous flow - basically waves.

108

Oriented matroid theory and loop quantum gravity in (2+2) and eight dimensions  

E-Print Network (OSTI)

We establish a connection between oriented matroid theory and loop quantum gravity in (2+2) (two time and two space dimensions) and 8-dimensions. We start by observing that supersymmetry implies that the structure constants of the real numbers, complex numbers, quaternions and octonions can be identified with the chirotope concept. This means, among other things, that normed divisions algebras, which are only possible in 1,2, 4 or 8-dimensions, are linked to oriented matroid theory. Therefore, we argue that the possibility for developing loop quantum gravity in 8-dimensions must be taken as important alternative. Moreover, we show that in 4-dimensions, loop quantum gravity theories in the (1+3) or (0+4) signatures are not the only possibilities. In fact, we show that loop quantum gravity associated with the (2+2)-signature may also be an interesting physical structure.

J. A. Nieto

2010-03-24T23:59:59.000Z

109

Quantum simulations of gauge theories with ultracold atoms: local gauge invariance from angular momentum conservation  

E-Print Network (OSTI)

Quantum simulations of High Energy Physics, and especially of gauge theories, is an emerging and exciting direction in quantum simulations. However, simulations of such theories, compared to simulations of condensed matter physics, must satisfy extra restrictions, such as local gauge and Lorentz invariance. In this paper we discuss these special requirements, and present a new method for quantum simulation of lattice gauge theories using ultracold atoms. This method allows to include local gauge invariance as a fundamental symmetry of the atomic Hamiltonian, arising from natural atomic interactions and conservation laws (and not as a property of a low energy sector). This allows us to implement elementary gauge invariant interactions for three lattice gauge theories: compact QED (U(1)), SU(N) and Z_N, which can be used to build quantum simulators in 1+1 dimensions. We also present a new loop method, which uses the elementary interactions as building blocks in the effective construction of quantum simulations for d+1 dimensional lattice gauge theories (d>1), without having to use Gauss's law as a constraint, as in previous proposals. We discuss in detail the quantum simulation of 2+1 dimensional compact QED and provide a numerical proof of principle. The simplicity of the already gauge invariant elementary interactions of this model suggests it may be useful for future experimental realizations.

Erez Zohar; J. Ignacio Cirac; Benni Reznik

2013-03-20T23:59:59.000Z

110

Quantum Computation Quantum Information  

E-Print Network (OSTI)

Quantum Computation and Quantum Information Samuel J. Lomonaco, Jr. and Howard E. Brandt editors Searches with a Quantum Robot .............................................. 12 pages Benioff, Paul Perturbation Theory and Numerical Modeling Quantum Logic Operations with a Large of Qubits

Lomonaco Jr., Samuel J.

111

Theory of classical and quantum frustration in quantum many-body systems  

E-Print Network (OSTI)

We present a general scheme for the study of frustration in quantum systems. After introducing a universal measure of frustration for arbitrary quantum systems, we derive for it an exact inequality in terms of a class of entanglement monotones. We then state sufficient conditions for the ground states of quantum spin systems to saturate the inequality and confirm them with extensive numerical tests. These conditions provide a generalization to the quantum domain of the Toulouse criteria for classical frustration-free systems and establish a unified framework for studying the intertwining of geometric and quantum contributions to frustration.

Giampaolo, S M; Monras, A; Illuminati, F

2011-01-01T23:59:59.000Z

112

Green function identities in Euclidean quantum field theory  

E-Print Network (OSTI)

Given a generic Lagrangian system of even and odd fields, we show that any infinitesimal transformation of its classical Lagrangian yields the identities which Euclidean Green functions of quantum fields satisfy.

G. Sardanashvily

2006-04-01T23:59:59.000Z

113

Pascual Jordan's legacy and the ongoing research in quantum field theory  

E-Print Network (OSTI)

Pascual Jordan's path-breaking role as the protagonist of quantum field theory (QFT) is recalled and his friendly dispute with Dirac's particle-based relativistic quantum theory is presented as the start of the field-particle conundrum which, though in modified form, persists up to this date. Jordan had an intuitive understanding that the existence of a causal propagation with finite propagation speed in a quantum theory led to radically different physical phenomena than those of QM. The conceptional-mathematical understanding for such an approach began to emerge only 30 years later. The strongest link between Jordan's view of QFT and modern "local quantum physics" is the central role of causal locality as the defining principle of QFT as opposed to the Born localization in QM. The issue of causal localization is also the arena where misunderstandings led to a serious derailment of large part of particle theory e.g. the misinterpretation of an infinite component pointlike field resulting from the quantization of the Nambu-Goto Lagrangian as a spacetime quantum string. The new concept of modular localization, which replaces Jordan's causal locality, is especially important to overcome the imperfections of gauge theories for which Jordan was the first to note nonlocal aspects of physical (not Lagrangian) charged fields. Two interesting subjects in which Jordan was far ahead of his contemporaries will be presented in two separate sections.

Bert Schroer

2010-10-21T23:59:59.000Z

114

Communication: Density functional theory overcomes the failure of predicting intermolecular interaction energies  

Science Conference Proceedings (OSTI)

Density-functional theory (DFT) revolutionized the ability of computational quantum mechanics to describe properties of matter and is by far the most often used method. However, all the standard variants of DFT fail to predict intermolecular interaction energies. In recent years, a number of ways to go around this problem has been proposed. We show that some of these approaches can reproduce interaction energies with median errors of only about 5% in the complete range of intermolecular configurations. Such errors are comparable to typical uncertainties of wave-function-based methods in practical applications. Thus, these DFT methods are expected to find broad applications in modelling of condensed phases and of biomolecules.

Podeszwa, Rafal [Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice (Poland); Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Szalewicz, Krzysztof [Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice (Poland)

2012-04-28T23:59:59.000Z

115

Topological gauge theories from supersymmetric quantum mechanics on spaces of connections  

E-Print Network (OSTI)

We rederive the recently introduced $N=2$ topological gauge theories, representing the Euler characteristic of moduli spaces ${\\cal M}$ of connections, from supersymmetric quantum mechanics on the infinite dimensional spaces ${\\cal A}/{\\cal G}$ of gauge orbits. To that end we discuss variants of ordinary supersymmetric quantum mechanics which have meaningful extensions to infinite-dimensional target spaces and introduce supersymmetric quantum mechanics actions modelling the Riemannian geometry of submersions and embeddings, relevant to the projections ${\\cal A}\\rightarrow {\\cal A}/{\\cal G}$ and inclusions ${\\cal M}\\subset{\\cal A}/{\\cal G}$ respectively. We explain the relation between Donaldson theory and the gauge theory of flat connections in $3d$ and illustrate the general construction by other $2d$ and $4d$ examples.

M Blau; G Thompson

1991-12-20T23:59:59.000Z

116

Quantum groups  

Science Conference Proceedings (OSTI)

The theory of Quantum groups, although rather young, since the expression Quantum ... introduction of a suitable form of the quantum group, the algebra A...

117

Quantum Inference and . . . -- Development of a Theory for the Disjunction of Concepts  

E-Print Network (OSTI)

We elaborate a theory for the modeling of concepts using the mathematical structure of quantum mechanics. Items and concepts are represented by vectors in the complex Hilbert space of quantum mechanics and membership weights of items are modeled by quantum weights calculated following the quantum rules. We apply this theory to model the disjunction of concepts and show that the predictions of our theory for the membership weights of items with respect to the disjunction of concepts match with great accuracy the results of an experiment conducted by Hampton (1988b). It is the quantum effects of interference and superposition that are at the origin of the effects of overextension and underextension observed by Hampton as deviations from a classical use of the disjunction. We show that the complex numbers of the Hilbert space are essential to obtaining the experimental predictions, i.e. vector space models over real numbers do not provide predictions matching the experimental data. We put forward an explanation of the effects of overextension and underextension by interpreting the quantum model applied to the modeling of the disjunction of concepts.

Diederik Aerts

2007-01-01T23:59:59.000Z

118

Quantum critical transport, duality, and M-theory  

E-Print Network (OSTI)

We consider charge transport properties of 2+1 dimensional conformal field theories at non-zero temperature. For theories with only Abelian U(1) charges, we describe the action of particle-vortex duality on the hydrodynamic-to-collisionless crossover function: this leads to powerful functional constraints for self-dual theories. For the n=8 supersymmetric, SU(N) Yang-Mills theory at the conformal fixed point, exact hydrodynamic-to-collisionless crossover functions of the SO(8) R-currents can be obtained in the large N limit by applying the AdS/CFT correspondence to M-theory. In the gravity theory, fluctuating currents are mapped to fluctuating gauge fields in the background of a black hole in 3+1 dimensional anti-de Sitter space. The electromagnetic self-duality of the 3+1 dimensional theory implies that the correlators of the R-currents obey a functional constraint similar to that found from particle-vortex duality in 2+1 dimensional Abelian theories. Thus the 2+1 dimensional, superconformal Yang Mills theory obeys a "holographic self duality" in the large N limit, and perhaps more generally.

Christopher P. Herzog; Pavel Kovtun; Subir Sachdev; Dam Thanh Son

2007-01-05T23:59:59.000Z

119

Getting Beyond the State of the Art of Information Retrieval with Quantum Theory  

E-Print Network (OSTI)

According to the probability ranking principle, the document set with the highest values of probability of relevance optimizes information retrieval effectiveness given the probabilities are estimated as accurately as possible. The key point of this principle is the separation of the document set into two subsets with a given level of fallout and with the highest recall. If subsets of set measures are replaced by subspaces and space measures, we obtain an alternative theory stemming from Quantum Theory. That theory is named after vector probability because vectors represent event like sets do in classical probability. The paper shows that the separation into vector subspaces is more effective than the separation into subsets with the same available evidence. The result is proved mathematically and verified experimentally. In general, the paper suggests that quantum theory is not only a source of rhetoric inspiration, but is a sufficient condition to improve retrieval effectiveness in a principled way.

Melucci, Massimo

2011-01-01T23:59:59.000Z

120

Corrections to gauge theories in effective quantum gravity with a cutoff  

E-Print Network (OSTI)

We calculate the lowest order quantum gravity contributions to QED beta function in an effective field theory picture with a momentum cutoff. We use a recently proposed 4 dimensional improved momentum cutoff that preserves gauge and Lorentz symmetries. We find that there is non-vanishing quadratic contribution to the photon 2-point function but that does not lead to the running of the original coupling after renormalization. We argue that gravity cannot turn gauge theories asymptotically free.

G. Cynolter; E. Lendvai

2013-07-17T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Progress in quantum electrodynamics theory of highly charged ions  

E-Print Network (OSTI)

Recent progress in quantum electrodynamics (QED) calculations of highly charged ions is reviewed. The theoretical predictions for the binding energies, the hyperfine splittings, and the g factors are presented and compared with available experimental data. Special attention is paid to tests of bound-state QED at strong field regime. Future prospects for tests of QED at the strongest electric and magnetic fields as well as for determination of the fine structure constant and the nuclear magnetic moments with heavy ions are discussed.

A. V. Volotka; D. A. Glazov; G. Plunien; V. M. Shabaev

2013-09-20T23:59:59.000Z

122

Quantum theory of stimulated Cerenkov radiation of transverse electromagnetic waves by a low-density electron beam in a medium  

Science Conference Proceedings (OSTI)

The quantum theory of stimulated Cerenkov radiation of transverse electromagnetic waves by an electron beam in an anisotropic medium is presented. Relativistic quantum nonlinear equations of the Cerenkov beam instability are obtained. In the linear approximation, the quantum dispersion equation is derived and the instability growth increments are determined. The nonlinear problem of the saturation of the quantum Cerenkov beam instability is solved. (cerenkov radiation)

Kuzelev, Mikhail V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2010-01-31T23:59:59.000Z

123

Bosonic and Baryonic String Theory in Quantum Chromodynamics  

Science Conference Proceedings (OSTI)

Bosonic string formation in gauge theories is reviewed with particular attention to the confining flux in lattice QCD and its effective string theory description. Recent results on the Casimir energy of the ground state and the string excitation spectrum are analyzed in the Dirichlet string limit of large separation between static sources. The closed string-soliton (torelon) with electric flux winding around a compact dimension is discussed and a new bound state tower spectrum at baryon string junctions is presented.

Kuti, Julius [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States)

2007-02-27T23:59:59.000Z

124

An exact RG formulation of quantum gauge theory  

E-Print Network (OSTI)

A gauge invariant Wilsonian effective action is constructed for pure SU(N) Yang-Mills theory by formulating the corresponding flow equation. Manifestly gauge invariant calculations can be performed i.e. without gauge fixing or ghosts. Regularisation is implemented in a novel way which realises a spontaneously broken SU(N|N) supergauge theory. As an example we sketch the computation of the one-loop beta function, performed for the first time without any gauge fixing.

Tim R. Morris

2001-02-19T23:59:59.000Z

125

Double-Scaling Limit of a Broken Symmetry Quantum Field Theory  

E-Print Network (OSTI)

The Ising limit of a conventional Hermitian parity-symmetric scalar quantum field theory is a correlated limit in which two bare Lagrangian parameters, the coupling constant $g$ and the {\\it negative} mass squared $-m^2$, both approach infinity with the ratio $-m^2/g=\\alpha>0$ held fixed. In this limit the renormalized mass of the asymptotic theory is finite. Moreover, the limiting theory exhibits universal properties. For a non-Hermitian $\\cal PT$-symmetric Lagrangian lacking parity symmetry, whose interaction term has the form $-g(i\\phi)^N/N$, the renormalized mass diverges in this correlated limit. Nevertheless, the asymptotic theory still has interesting properties. For example, the one-point Green's function approaches the value $-i\\alpha^{1/(N-2)}$ independently of the space-time dimension $D$ for $D<2$. Moreover, while the Ising limit of a parity-symmetric quantum field theory is dominated by a dilute instanton gas, the corresponding correlated limit of a $\\cal PT$-symmetric quantum field theory wit...

Bender, C M; Jones, H F; Meisinger, P N; Bender, Carl M.; Boettcher, Stefan; Meisinger, Peter N.

2001-01-01T23:59:59.000Z

126

The flux theory of gravitation XVIII: macro and quantum gravity, cosmo waves and applications  

Science Conference Proceedings (OSTI)

This paper explains, for the first time, recent and old astonishing phenomena based on reports from the Hubble in light of the flux theory of gravitation (FTG). Among the astonishing phenomena and their explanation are the following: (1) Accelerated ... Keywords: convertor, cosmic dust, cosmic shock waves, dark matter, energy field, fractal, gamma ray burst, macro and quantum gravity, primum, superstring

E. E. Escultura

2003-07-01T23:59:59.000Z

127

Toward theory of quantum Hall effect in graphene  

E-Print Network (OSTI)

We analyze a gap equation for the propagator of Dirac quasiparticles and conclude that in graphene in a magnetic field, the order parameters connected with the quantum Hall ferromagnetism dynamics and those connected with the magnetic catalysis dynamics necessarily coexist (the latter have the form of Dirac masses and correspond to excitonic condensates). This feature of graphene could lead to important consequences, in particular, for the existence of gapless edge states. Solutions of the gap equation corresponding to recently experimentally discovered novel plateaus in graphene in strong magnetic fields are described.

E. V. Gorbar; V. P. Gusynin; V. A. Miransky

2007-10-18T23:59:59.000Z

128

On triviality of $\\lambda\\phi^4$ quantum field theory in four dimensions  

E-Print Network (OSTI)

Interacting quantum scalar field theories in $dS_D\\times M_d$ spacetime can be reduced to Euclidean field theories in $M_d$ space in the vicinity of $I_+$ infinity of $dS_D$ spacetime. Using this non-perturbative mapping, we analyze the critical behavior of Euclidean $\\lambda\\phi_4^4$ theory in the symmetric phase and find the asymptotic behavior $\\beta(\\lambda)\\sim \\lambda$ of the beta function at strong coupling. Scaling violating contributions to the beta function are also estimated in this regime.

Podolsky, Dmitry I

2010-01-01T23:59:59.000Z

129

Quantum Fluctuations in Holographic Theories with Hyperscaling Violation  

E-Print Network (OSTI)

In this short note we use holographic methods to study the response of quantum critical points with hyperscaling violation to a disturbance caused by a massive charged particle. We give analytical expressions for the two-point functions of the fluctuations of the massive probe as a function of arbitrary (allowed) values of the hyperscaling violation exponent {\\theta} and the dynamical exponent z. We point out the existence of markedly different behaviors of the two-point functions in the parameter space of {\\theta} and z at late times. In particular, as expected, the late-time dynamics of the probe becomes independent of its inertial mass in the range z+2{\\theta}/d>2.

Edalati, Mohammad; Garcia, Walter Tangarife

2012-01-01T23:59:59.000Z

130

Circular dichroism: A general theory based on quantum electrodynamics  

Science Conference Proceedings (OSTI)

A theory of circular dichroism is developed through a direct calculation of the absorption rates for circularly polarized light on molecules. From this a differential rate as between left and right circularly polarized light is calculated. This is immediately related to the experimental data on circular dichroism. When the calculations are restricted to the dipole approximation we reproduce the rotatory strength in the form of a differential Einstein B coefficient. Higher moments are considered in detail and their effects analyzed for both the locked?in situation and the case of randomly oriented molecular absorbers. A general expression is obtained for the differential absorption rate.

E. A. Power; T. Thirunamachandran

1974-01-01T23:59:59.000Z

131

Quantum theory of rotational isomerism and Hill equation  

SciTech Connect

The process of rotational isomerism of linear triatomic molecules is described by the potential with two different-depth minima and one barrier between them. The corresponding quantum-mechanical equation is represented in the form that is a special case of the Hill equation. It is shown that the Hill-Schroedinger equation has a Klein's quadratic group symmetry which, in its turn, contains three invariant subgroups. The presence of these subgroups makes it possible to create a picture of energy spectrum which depends on a parameter and has many merging and branch points. The parameter-dependent energy spectrum of the Hill-Schroedinger equation, like Mathieu-characteristics, contains branch points from the left and from the right of the demarcation line. However, compared to the Mathieu-characteristics, in the Hill-Schroedinger equation spectrum the 'right' points are moved away even further for some distance that is the bigger, the bigger is the less deep well. The asymptotic wave functions of the Hill-Schroedinger equation for the energy values near the potential minimum contain two isolated sharp peaks indicating a possibility of the presence of two stable isomers. At high energy values near the potential maximum, the height of two peaks decreases, and between them there appear chaotic oscillations. This form of the wave functions corresponds to the process of isomerization.

Ugulava, A.; Toklikishvili, Z.; Chkhaidze, S.; Abramishvili, R. [I. Javakhishvili Tbilisi State University, 3, I. Chavchavadze Avenue, 0179 Tbilisi (Georgia); Chotorlishvili, L. [Institut fuer Physik, Martin-Luther Universitat Halle-Wittenberg, Heinrich-Damerow-Str. 4, 06120 Halle (Germany)

2012-06-15T23:59:59.000Z

132

Non-Markovian stochastic Schrdinger equations: Generalization to real-valued noise using quantum measurement theory  

E-Print Network (OSTI)

Do stochastic Schr\\"odinger equations, also known as unravelings, have a physical interpretation? In the Markovian limit, where the system {\\em on average} obeys a master equation, the answer is yes. Markovian stochastic Schr\\"odinger equations generate quantum trajectories for the system state conditioned on continuously monitoring the bath. For a given master equation, there are many different unravelings, corresponding to different sorts of measurement on the bath. In this paper we address the non-Markovian case, and in particular the sort of stochastic \\sch equation introduced by Strunz, Di\\' osi, and Gisin [Phys. Rev. Lett. 82, 1801 (1999)]. Using a quantum measurement theory approach, we rederive their unraveling which involves complex-valued Gaussian noise. We also derive an unraveling involving real-valued Gaussian noise. We show that in the Markovian limit, these two unravelings correspond to heterodyne and homodyne detection respectively. Although we use quantum measurement theory to define these unravelings, we conclude that the stochastic evolution of the system state is not a true quantum trajectory, as the identity of the state through time is a fiction.

Jay Gambetta; H. M. Wiseman

2002-02-20T23:59:59.000Z

133

A relativistically covariant version of Bohm's quantum field theory for the scalar field  

E-Print Network (OSTI)

We give a relativistically covariant, wave-functional formulation of Bohm's quantum field theory for the scalar field based on a general foliation of space-time by space-like hypersurfaces. The wave functional, which guides the evolution of the field, is space-time-foliation independent but the field itself is not. Hence, in order to have a theory in which the field may be considered a beable, some extra rule must be given to determine the foliation. We suggest one such rule based on the eigen vectors of the energy-momentum tensor of the field itself.

George Horton; Chris Dewdney

2004-07-13T23:59:59.000Z

134

Quantum process and the foundation of relational theories of space-time  

E-Print Network (OSTI)

We present current theories about the structure of space and time, where the building blocks are some fundamental entities (yes-no experiment, quantum processes, spin net-work, preparticles) that do not presuppose the existence of space and time. The relations among these objects are the base for a pregeometry of discrete character, the continuous limit of which gives rise to the physical properties of the space and time.

M. Lorente

2003-12-30T23:59:59.000Z

135

The Current C, T Transformation Rules of Quantum Field Theory Must be Redefined  

E-Print Network (OSTI)

In light of the transformation defined in the current quantum field theory, electromagnetic interaction is unchanged under time reversal. However, this kind of time reversal only lets in the Hamiltonian of the coordinate space, without considering that the creation and annihilation processes of particles should also be reversed when the concrete problems are calculated in momentum space. In fact, according to the current transformation of quantum field theory, creation operator of spinor particle is still creation operator and annihilation operator is also still annihilation operator. This result does not represent the real meaning of time reversal. In the interaction process, a particle's creation operator should become the annihilation operator and its annihilation operator should become the creation operator after time reversal. It is proved that when the reversion of creation and annihilation processes is considered in momentum space, under the condition of high energy, a great symmetry violation of time reversal would be caused in some low order processes of electromagnetic interaction just as the Compton scattering in which the propagation lines of fermions are contained. This result contradicts with the experiments of particle physics and is impossible. Meanwhile, it is proved that the normalization processes of the third order vertex angles of electromagnetic interaction also violate time reversal symmetry, no matter in the coordinate space or in the momentum space. But the symmetry violation is small with a magnitude order about 10(-5). The similar problems exist in the current C transformation of quantum field theory. The C transformation of creation and annihilation operator can not be consistent with the C transformation of spinor particle's wave functions in momentum space. We can obtain the correct C transformation of creation and annihilation operator, but can not obtain the correct C transformation of wave functions in momentum space. Therefore, the current rules of C,T transformations in quantum field theory has serious defect and should be redefined.

Mei Xiaochun

2010-03-13T23:59:59.000Z

136

SO(4,1) Yang-Mills theory of quantum gravity  

E-Print Network (OSTI)

The search for a quantum theory of gravity has become one of the most well-known problems in theoretical physics. Problems quantizing general relativity because it is not renormalizable have led to a search for a new theory of gravity that, while still agreeing with measured observations, is renormalizable. In this paper, a spin-1 Yang-Mills force theory with a SO(4,1) or {\\em de Sitter} group symmetry is developed. By deriving the standard geodesic equation and the first post-Newtonian approximation equations, it is shown that this theory, coupled to Dirac fields, predicts all N-body and light observations of gravitational phenomena to within experimental accuracy. Furthermore, because of the separation of gauge covariance from coordinate diffeomorphism, the theory satisfies the strong equivalence principle while maintaining a Minkowski coordinate metric. Cosmology is also briefly addressed: Vacuum energy is the most common explanation for the accelerating expansion of the universe but suffers from the drawback that any reasonable prediction of it is 120 orders of magnitude too large. The de Sitter solution to the Einstein Field Equations is an alternative to vacuum energy as an explanation for the accelerating expansion of the universe but only if the universe is approximately a vacuum. The proposed gauge theory, however, avoids both these problems and, cosmologically, the accelerating expansion of the universe is shown as a consequence of the de Sitter group Lie algebra. In addition, with quantized mass, because it is a generic massless, semi-simple Yang-Mills theory, it is mathematically proved to be a perturbatively renormalizable quantum theory of gravity.

Timothy D. Andersen

2010-05-21T23:59:59.000Z

137

Towards a quantum field theory of primitive string fields  

Science Conference Proceedings (OSTI)

We denote generating functions of massless even higher-spin fields 'primitive string fields' (PSF's). In an introduction we present the necessary definitions and derive propagators and currents of these PDF's on flat space. Their off-shell cubic interaction can be derived after all off-shell cubic interactions of triplets of higher-spin fields have become known. Then we discuss four-point functions of any quartet of PSF's. In subsequent sections we exploit the fact that higher-spin field theories in AdS{sub d+1} are determined by AdS/CFT correspondence from universality classes of critical systems in d-dimensional flat spaces. The O(N) invariant sectors of the O(N) vector models for 1 {=} 4, they are distinguished by their anomalous dimensions (in CFT{sub 3}) or by theirmass (in AdS{sub 4}). We sum over these multiplets and the spins to obtain 'string type fields', one for each such monomial.

Ruehl, W., E-mail: wue_ruehl@t-online.de [Technical University of Kaiserslautern, Department of Physics (Germany)

2012-10-15T23:59:59.000Z

138

Nonlinear eigenvalue problems in Density Functional Theory calculations  

SciTech Connect

Developed in the 1960's by W. Kohn and coauthors, Density Functional Theory (DFT) is a very popular quantum model for First-Principles simulations in chemistry and material sciences. It allows calculations of systems made of hundreds of atoms. Indeed DFT reduces the 3N-dimensional Schroedinger electronic structure problem to the search for a ground state electronic density in 3D. In practice it leads to the search for N electronic wave functions solutions of an energy minimization problem in 3D, or equivalently the solution of an eigenvalue problem with a non-linear operator.

Fattebert, J

2009-08-28T23:59:59.000Z

139

Quantum Exact Non-Abelian Vortices in Non-relativistic Theories  

E-Print Network (OSTI)

Non-Abelian vortices arise when a non-Abelian global symmetry is exact in the ground state but spontaneously broken in the vicinity of their cores. In this case, there appear (non-Abelian) Nambu-Goldstone (NG) modes confined and propagating along the vortex. In relativistic theories, the Coleman-Mermin-Wagner theorem forbids the existence of a spontaneous symmetry breaking, or a long-range order, in 1+1 dimensions: quantum corrections restore the symmetry along the vortex and the NG modes acquire a mass gap. We show that in non-relativistic theories NG modes with quadratic dispersion relation confined on a vortex can remain gapless at quantum level. We provide a concrete and experimentally realizable example of a three-component Bose-Einstein condensate with U(1) x U(2) symmetry. We first show, at the classical level, the existence of S^3 = S^1 |x S^2 (S^1 fibered over S^2) NG modes associated to the breaking U(2) -> U(1) on vortices, where S^1 and S^2 correspond to type I and II NG modes, respectively. We then show, by using a Bethe ansatz technique, that the U(1) symmetry is restored, while the SU(2) symmery remains broken non-pertubatively at quantum level. Accordingly, the U(1) NG mode turns into a c=1 conformal field theory, the Tomonaga-Luttinger liquid, while the S^2 NG mode remains gapless, describing a ferromagnetic liquid. This allows the vortex to be genuinely non-Abelian at quantum level.

Muneto Nitta; Shun Uchino; Walter Vinci

2013-11-21T23:59:59.000Z

140

Renormalization of quantum field theory on curved space-times, a causal approach  

E-Print Network (OSTI)

The subject of the thesis is the construction of a perturbative quantum theory of interacting fields on a curved space-time, following a point of view pioneered by Stueckelberg and Bogoliubov and developed by Epstein-Glaser on the flat Minkowski space-time. In 2000, a breakthrough was done by Brunetti and Fredenhagen who were able to extend the Epstein-Glaser theory by exploiting the point of view developed by Radzikowski to define quantum states on a curved space-time in terms of wave-front sets. These results were further extended by Fredenhagen, Brunetti, Hollands, Wald, Rejzner, etc. to Yang-Mills fields and the gravitation. However, even for theories without gauge invariance, many mathematical details were left unexplored and unquestioned. Our task was precisely to derive fully rigorously this theory in the case there is no gauge invariance. We propose in our work a complete review of the result, solving numerous questions, adding many new results around this program and, eventually, giving more precise details on the counterterms and ambiguities in the renormalization process, and a deeper understanding of the geometry of the wave front set of the n-point functions.

Nguyen Viet Dang

2013-12-19T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Global Solutions of Hartree-Fock Theory and their Consequences for Strongly Correlated Quantum Systems  

E-Print Network (OSTI)

We present a density matrix approach for computing global solutions of Hartree-Fock theory, based on semidefinite programming (SDP), that gives upper and lower bounds on the Hartree-Fock energy of quantum systems. Equality of the upper- and lower-bound energies guarantees that the computed solution is the globally optimal solution of Hartree-Fock theory. For strongly correlated systems the SDP approach requires us to reassess the accuracy of the Hartree-Fock energies and densities from standard software packages for electronic structure theory. Calculations of the H$_{4}$ dimer and N$_{2}$ molecule show that the energies from SDP Hartree-Fock are lower than those from standard Hartree-Fock methods by 100-200 kcal/mol in the dissociation region. The present findings have important consequences for the computation and interpretation of electron correlation, which is typically defined relative to the Hartree-Fock energy and density.

Veeraraghavan, Srikant

2013-01-01T23:59:59.000Z

142

Quantum Tetrahedra  

E-Print Network (OSTI)

We discuss in details the role of Wigner 6j symbol as the basic building block unifying such different fields as state sum models for quantum geometry, topological quantum field theory, statistical lattice models and quantum computing. The apparent twofold nature of the 6j symbol displayed in quantum field theory and quantum computing -a quantum tetrahedron and a computational gate- is shown to merge together in a unified quantum-computational SU(2)-state sum framework.

Mauro Carfora; Annalisa Marzuoli; Mario Rasetti

2010-01-25T23:59:59.000Z

143

U(1) X U(1) XI Z(2) Chern-Simons theory and Z(4) parafermion fractional quantum Hall states  

E-Print Network (OSTI)

We study U(1)U(1)?Z2 Chern-Simons theory with integral coupling constants (k,l) and its relation to certain non-Abelian fractional quantum Hall (FQH) states. For the U(1)U(1)?Z2 Chern-Simons theory, we show how to compute ...

Barkeshli, Maissam

144

A DFT Approach to Non-Covalent Interactions via Monomer Polarization and Pauli Blockade  

E-Print Network (OSTI)

We propose a "DFT+dispersion" treatment which avoids double counting of dispersion terms by deriving the dispersion-free density functional theory (DFT) interaction energy and combining it with DFT-based dispersion. The formalism involves self-consistent polarization of DFT monomers restrained by the exclusion principle via the Pauli blockade technique. Any exchange-correlation potential can be used within monomers, but only the exchange operates between them. The applications to rare-gas dimers, ion-rare gas interactions and hydrogen bonds demonstrate that the interaction energies agree with benchmark values.

Rajchel, Lukasz; Szczesniak, Malgorzata M; Chalasinski, Grzegorz

2009-01-01T23:59:59.000Z

145

PERTURBATION-THEORY RULES FOR COMPUTING THE SELF-ENERGY OPERATOR IN QUANTUM STATISTICAL MECHANICS  

E-Print Network (OSTI)

D. J. Thouless, The Quantum Mechanics of Many-Body Systems (1962). Ba~n, Quantum Statistical Mechanics (Benjamin, I. E.IN QUANTUM STATISTICAL MECHANICS Berkeley, California

Baym, Gordon

2008-01-01T23:59:59.000Z

146

The structure of Green functions in quantum field theory with a general state  

E-Print Network (OSTI)

In quantum field theory, the Green function is usually calculated as the expectation value of the time-ordered product of fields over the vacuum. In some cases, especially in degenerate systems, expectation values over general states are required. The corresponding Green functions are essentially more complex than in the vacuum, because they cannot be written in terms of standard Feynman diagrams. Here, a method is proposed to determine the structure of these Green functions and to derive nonperturbative equations for them. The main idea is to transform the cumulants describing correlations into interaction terms.

Christian Brouder

2007-10-30T23:59:59.000Z

147

A new DFT method for atoms and molecules in Cartesian grid  

E-Print Network (OSTI)

Electronic structure calculation of atoms and molecules, in the past few decades has largely been dominated by density functional methods. This is primarily due to the fact that this can account for electron correlation effects in a rigorous, tractable manner keeping the computational cost at a manageable level. With recent advances in methodological development, algorithmic progress as well as computer technology, larger physical, chemical and biological systems are amenable to quantum mechanical calculations than ever before. Here we report the development of a new method for accurate reliable description of atoms, molecules within the Hohenberg-Kohn-Sham density functional theory (DFT). In a Cartesian grid, atom-centered localized basis set, electron density, molecular orbitals, two-body potentials are directly built on the grid. We employ a Fourier convolution method for classical Coulomb potentials by making an Ewald-type decomposition technique in terms of short- and long-range interactions. One-body ma...

Roy, Amlan K

2013-01-01T23:59:59.000Z

148

Gradient formula for the beta-function of 2d quantum field theory  

E-Print Network (OSTI)

We give a non-perturbative proof of a gradient formula for beta functions of two-dimensional quantum field theories. The gradient formula has the form \\partial_{i}c = - (g_{ij}+\\Delta g_{ij} +b_{ij})\\beta^{j} where \\beta^{j} are the beta functions, c and g_{ij} are the Zamolodchikov c-function and metric, b_{ij} is an antisymmetric tensor introduced by H. Osborn and \\Delta g_{ij} is a certain metric correction. The formula is derived under the assumption of stress-energy conservation and certain conditions on the infrared behaviour the most significant of which is the condition that the large distance limit of the field theory does not exhibit spontaneously broken global conformal symmetry. Being specialized to non-linear sigma models this formula implies a one-to-one correspondence between renormalization group fixed points and critical points of c.

Friedan, Daniel

2009-01-01T23:59:59.000Z

149

Chameleonic dilaton, nonequivalent frames, and the cosmological constant problem in quantum string theory  

Science Conference Proceedings (OSTI)

The chameleonic behavior of the string theory dilaton is suggested. Some of the possible consequences of the chameleonic string dilaton are analyzed in detail. In particular, (1) we suggest a new stringy solution to the cosmological constant problem and (2) we point out the nonequivalence of different conformal frames at the quantum level. In order to obtain these results, we start taking into account the (strong coupling) string loop expansion in the string frame (S-frame), therefore the so-called form factors are present in the effective action. The correct dark energy scale is recovered in the Einstein frame (E-frame) without unnatural fine-tunings and this result is robust against all quantum corrections, granted that we assume a proper structure of the S-frame form factors in the strong coupling regime. At this stage, the possibility still exists that a certain amount of fine-tuning may be required to satisfy some phenomenological constraints. Moreover in the E-frame, in our proposal, all the interactions are switched off on cosmological length scales (i.e., the theory is IR-free), while higher derivative gravitational terms might be present locally (on short distances) and it remains to be seen whether these facts clash with phenomenology. A detailed phenomenological analysis is definitely necessary to clarify these points.

Zanzi, Andrea [Via Pioppa 261, 44123 Pontegradella, Ferrara (Italy)

2010-08-15T23:59:59.000Z

150

Density functional theory (DFT) and ab initio molecular orbital calculations have been employed to determine the structures and energies of the isomers of the OH-toluene adduct, the methyl hydroxycyclohexadienyl radical, and their corresponding transitio  

NLE Websites -- All DOE Office Websites (Extended Search)

Laboratory Investigation of Organic Aerosol Formation from Aromatic Hydrocarbons (DOE Award No. DE-FG02-02ER63098) Prepared by Luisa T. Molina, Renyi Zhang and Mario J. Molina Our work for this DOE funded project includes: (1) measurements of the kinetics and mechanism of the gas-phase oxidation reactions of the aromatic hydrocarbons initiated by OH; (2) measurements of aerosol formation from the aromatic hydrocarbons; and (3) theoretical studies to elucidate the OH-toluene reaction mechanism using quantum-chemical and rate theories. (1) Measurements of Gas-Phase Kinetics and Mechanism Work has been accomplished to develop laboratory instrumentation to conduct kinetic and mechanistic measurements of the aromatic hydrocarbon reactions initiated by OH, using

151

DFT-based molecular dynamics as a new tool for computational biology: first applications and perspective  

Science Conference Proceedings (OSTI)

Static and molecular dynamics (MD) calculations based on density-functional theory (DFT) are emerging as a valuable means for simulations in the field of biology, especially when coupled with classical simulations. In this contribution, we point out ...

W. Andreoni; A. Curioni; T. Mordasini

2001-05-01T23:59:59.000Z

152

Density Functional Theory Approach to Nuclear Fission  

E-Print Network (OSTI)

The Skyrme nuclear energy density functional theory (DFT) is used to model neutron-induced fission in actinides. This paper focuses on the numerical implementation of the theory. In particular, it reports recent advances in DFT code development on leadership class computers, and presents a detailed analysis of the numerical accuracy of DFT solvers for near-scission calculations.

N. Schunck

2012-12-13T23:59:59.000Z

153

Theory of localization and resonance phenomena in the quantum kicked rotor  

E-Print Network (OSTI)

We present an analytic theory of quantum interference and Anderson localization in the quantum kicked rotor (QKR). The behavior of the system is known to depend sensitively on the value of its effective Planck's constant $\\he$. We here show that for rational values of $\\he/(4\\pi)=p/q$, it bears similarity to a disordered metallic ring of circumference $q$ and threaded by an Aharonov-Bohm flux. Building on that correspondence, we obtain quantitative results for the time--dependent behavior of the QKR kinetic energy, $E(\\tilde t)$ (this is an observable which sensitively probes the system's localization properties). For values of $q$ smaller than the localization length $\\xi$, we obtain scaling $E(\\tilde t) \\sim \\Delta \\tilde t^2$, where $\\Delta=2\\pi/q$ is the quasi--energy level spacing on the ring. This scaling is indicative of a long time dynamics that is neither localized nor diffusive. For larger values $q\\gg \\xi$, the functions $E(\\tilde t)\\to \\xi^2$ saturates (up to exponentially small corrections $\\sim\\exp(-q/\\xi)$), thus reflecting essentially localized behavior.

C. Tian; A. Altland

2010-01-25T23:59:59.000Z

154

Theory of quantum metal to superconductor transitions in highly conducting systems  

SciTech Connect

We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.

Spivak, B.

2010-04-06T23:59:59.000Z

155

Contribution from the interaction Hamiltonian to the expectation value of particle number with the non-equilibrium quantum field theory  

SciTech Connect

We develop the method analyzing particle number non-conserving phenomena with non-equilibrium quantum field-theory. In this study, we consider a CP violating model with interaction Hamiltonian that breaks particle number conservation. To derive the quantum Boltzmann equation for the particle number, we solve Schwinger-Dyson equation, which are obtained from two particle irreducible closed-time-path (2PI CTP) effective action. In this calculation, we show the contribution from interaction Hamiltonian to the time evolution of expectation value of particle number.

Hotta, Ryuuichi; Morozumi, Takuya; Takata, Hiroyuki [Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Tomsk state Pedagogical University Tomsk 634041 (Russian Federation)

2012-07-27T23:59:59.000Z

156

Quantum field theory in curved graphene spacetimes, Lobachevsky geometry, Weyl symmetry, Hawking effect, and all that  

E-Print Network (OSTI)

We extensively discuss the theoretical framework to make curved monolayer graphene a realization of quantum field theory in curved spacetime. We rely upon a model of the electron-phonon interaction that reproduces the standard semiclassical Dirac quantum field in a curved spacetime. This model holds for very long wavelengths of the graphene conductivity electrons involved. Provided the full description of the phonon-electron interaction is of a modified gravity-type, the core of the results presented here apply, with due changes, to that case too. Using local Weyl symmetry, we probe into the possibility to reproduce a Hawking effect. For the sake of making the test easier in a laboratory, the whole study is carried out for the case of purely spatial curvatures, and for conformally flat spacetimes. Since we show that for the sphere there is no intrinsic horizon, the focus is on the infinite different surfaces of constant negative Gaussian curvature. Even though, in those cases, deep reasons of Lobachevsky geometry seem to lead to unreachable event horizons, we show under which conditions the horizon is within reach. The Hawking effect, then, takes place on the Beltrami surface. We also explicitly study the spacetimes of the other two pseudospheres, and show their relation to de Sitter, and BTZ black-hole spacetimes. In the same limit that gives a reachable event horizon, these two cases, essentially, reduce to Beltrami. This, together with the fact that all the infinite surfaces in point are applicable to either one of the three pseudospheres, make us conjecture about the possibility for a Hawking effect for a generic surface of the family. The Hawking effect here manifests itself through a finite (Hawking) temperature electronic local density of states, that we exhibit.

Alfredo Iorio; Gaetano Lambiase

2013-08-01T23:59:59.000Z

157

Applied Quantum Information Science  

Science Conference Proceedings (OSTI)

Applied Quantum Information Science. Summary: Theory is being developed and used to devise methods for preserving ...

2012-05-30T23:59:59.000Z

158

Quantum Statistical Mechanics and Quantum Computation  

E-Print Network (OSTI)

Quantum Statistical Mechanics and Quantum Computation 22-23 March 2012 Room 111, Jadwin Hall, focused meeting to explore the intersection between quantum statistical mechanics and quantum computation, specifically quantum complexity theory. Advances in complexity theory have interesting implications for physics

159

Quantum Histories and Quantum Gravity  

E-Print Network (OSTI)

This paper reviews the histories approach to quantum mechanics. This discussion is then applied to theories of quantum gravity. It is argued that some of the quantum histories must approximate (in a suitable sense) to classical histories, if the correct classical regime is to be recovered. This observation has significance for the formulation of new theories (such as quantum gravity theories) as it puts a constraint on the kinematics, if the quantum/classical correspondence principle is to be preserved. Consequences for quantum gravity, particularly for Lorentz symmetry and the idea of "emergent geometry", are discussed.

Joe Henson

2009-01-26T23:59:59.000Z

160

PERTURBATION-THEORY RULES FOR COMPUTING THE SELF-ENERGY OPERATOR IN QUANTUM STATISTICAL MECHANICS  

E-Print Network (OSTI)

J. Thouless) The Quantu~ Mechanics of V ~ny-Body Systems (IN QUANTUM STA TISTICAL MECHANICS Gordon BayrrL and AndrewIN QUANTUM STATISTICAL MECHANICS Gordon Baym and Andrew M.

Baym, Gordon

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Theory and simulation of quantum photovoltaic devices based on the non-equilibrium Green's function formalism  

Science Conference Proceedings (OSTI)

This article reviews the application of the non-equilibrium Green's function formalism to the simulation of novel photovoltaic devices utilizing quantum confinement effects in low dimensional absorber structures. It covers well-known aspects of the fundamental ... Keywords: NEGF, Photovoltaics, Quantum dot, Quantum well

U. Aeberhard

2011-12-01T23:59:59.000Z

162

The Anomalous Nambu-Goldstone Theorem in Relativistic/Nonrelativistic Quantum Field Theory  

E-Print Network (OSTI)

The anomalous Nambu-Goldstone (NG) theorem which is found as a violation of counting law of the number of NG bosons of the normal NG theorem in nonrelativistic and Lorentz-symmetry-violated relativistic theories is studied in detail, with emphasis on its mathematical aspect from Lie algebras, geometry to number theory. The basis of counting law of NG bosons in the anomalous NG theorem is examined by Lie algebras (local) and Lie groups (global). A quasi-Heisenberg algebra is found generically in various symmetry breaking schema of the anomalous NG theorem, and it indicates that it causes a violation/modification of the Heisenberg uncertainty relation in an NG sector which can be experimentally confirmed. The formalism of effective potential is presented for understanding the mechanism of anomalous NG theorem with the aid of our result of Lie algebras. After an investigation on a bosonic kaon condensation model with a finite chemical potential as an explicit Lorentz-symmetry-breaking parameter, a model Lagrangian approach on the anomalous NG theorem is given for our general discussion. Not only the condition of the counting law of true NG bosons, but also the mechanism to generate a mass of massive NG boson is also found by our examination on the kaon condensation model. Furthermore, the generation of a massive mode in the NG sector is understood by the quantum uncertainty relation of the Heisenberg algebra, obtained from a symmetry breaking of a Lie algebra, which realizes in the effective potential of the kaon condensation model. Hence the relation between a symmetry breaking scheme, a Heisenberg algebra, a mode-mode coupling, and the mechanism of mass generation in an NG sector is established. Finally, some relations between the Riemann hypothesis and the anomalous NG theorem are presented.

Tadafumi Ohsaku

2013-12-01T23:59:59.000Z

163

The Thermal Aspects of Relativistic Quantum Field Theory as an Observational Window in a Deeper Layer of Quantum Space-Time or: Dirac's Revenge  

E-Print Network (OSTI)

In this paper we shall derive the thermal properties of the relativistic quantum vacuum from a more primordial underlying structure which shares some properties with the old Dirac-sea picture. We show in particular how the Tomita-KMS structure in RQFT is a consequence of the structure and dynamics of the underlying pattern of vacuum fluctuations. We explain the origin of the doubling phenomenon in thermofield theory and the duality symmetry between a local algebra of fields or observables and its commutant in RQFT and give an interpretation of the notion of thermal time.

Manfred Requardt

2013-09-05T23:59:59.000Z

164

Quantum Thermodynamics  

E-Print Network (OSTI)

Quantum thermodynamics addresses the emergence of thermodynamical laws from quantum mechanics. The link is based on the intimate connection of quantum thermodynamics with the theory of open quantum systems. Quantum mechanics inserts dynamics into thermodynamics giving a sound foundation to finite-time-thermodynamics. The emergence of the 0-law I-law II-law and III-law of thermodynamics from quantum considerations is presented. The emphasis is on consistence between the two theories which address the same subject from different foundations. We claim that inconsistency is the result of faulty analysis pointing to flaws in approximations.

Ronnie Kosloff

2013-05-10T23:59:59.000Z

165

Theory of Electro-optic Modulation via a Quantum Dot Coupled to a Nano-resonator  

E-Print Network (OSTI)

In this paper, we analyze the performance of an electro-optic modulator based on a single quantum dot strongly coupled to a nano-resonator, where electrical control of the quantum dot frequency is achieved via quantum confined Stark effect. Using realistic system parameters, we show that modulation speeds of a few tens of GHz are achievable with this system, while the energy per switching operation can be as small as 0.5 fJ. In addition, we study the non-linear distortion, and the effect of pure quantum dot dephasing on the performance of the modulator.

Arka Majumdar; Nicolas Manquest; Andrei Faraon; Jelena Vuckovic

2009-11-27T23:59:59.000Z

166

Perturbation Theory Based on Darboux Transformation on One-Dimensional Dirac Equation in Quantum Computation  

E-Print Network (OSTI)

We present the recent works \\cite{trisetyarso2011} on the application of Darboux transformation on one-dimensional Dirac equation related to the field of Quantum Information and Computation (QIC). The representation of physical system in one-dimensional equation and its transformation due to the Bagrov, Baldiotti, Gitman, and Shamshutdinova (BBGS)-Darboux transformation showing the possibility admitting the concept of relativity and the trade-off of concurrent condition of quantum and classical physics play into the area of QIC. The applications in cavity quantum electrodynamics and on the proposal of quantum transistor are presented.

Agung Trisetyarso

2010-05-11T23:59:59.000Z

167

A Proposed Alternative Low Energy Quantum Field Theory of Gravity Based on a Bose-Einstein Condensate Effect  

E-Print Network (OSTI)

An alternative quantum field theory for gravity is proposed for low energies based on an attractive effect between contaminants in a Bose-Einstein Condensate rather than on particle exchange. In the ``contaminant in condensate effect," contaminants cause a potential in an otherwise uniform condensate, forcing the condensate between two contaminants to a higher energy state. The energy of the system decreases as the contaminants come closer together, causing an attractive force between contaminants. It is proposed that mass-energy may have a similar effect on Einstein's space-time field, and gravity is quantized by the same method by which the contaminant in condensate effect is quantized. The resulting theory is finite and, if a physical condensate is assumed to underly the system, predictive. However, the proposed theory has several flaws at high energies and is thus limited to low energies. Falsifiable predictions are given for the case that the Higgs condensate is assumed to be the condensate underlying gravity.

Alexander Oshmyansky

2007-03-08T23:59:59.000Z

168

Quantum Structure of Field Theory and Standard Model Based on Infinity-free Loop Regularization/Renormalization  

E-Print Network (OSTI)

To understand better the quantum structure of field theory and standard model in particle physics, it is necessary to investigate carefully the divergence structure in quantum field theories (QFTs) and work out a consistent framework to avoid infinities. The divergence has got us into trouble since developing quantum electrodynamics in 1930s, its treatment via the renormalization scheme is satisfied not by all physicists, like Dirac and Feynman who have made serious criticisms. The renormalization group analysis reveals that QFTs can in general be defined fundamentally with the meaningful energy scale that has some physical significance, which motivates us to develop a new symmetry-preserving and infinity-free regularization scheme called loop regularization (LORE). A simple regularization prescription in LORE is realized based on a manifest postulation that a loop divergence with a power counting dimension larger than and equal to the space-time dimension must vanish. The LORE method is achieved without modifying original theory and leads the divergent Feynman loop integrals well-defined to maintain the divergence structure and meanwhile preserve basic symmetries of original theory. The crucial point in LORE is the presence of two intrinsic energy scales which play the roles of ultraviolet cut-off $M_c$ and infrared cut-off $\\mu_s$ to avoid infinities. The key concept in LORE is the introduction of irreducible loop integrals (ILIs) on which the regularization prescription acts, which leads to a set of gauge invariance consistency conditions between the regularized tensor-type and scalar-type ILIs. The evaluation of ILIs with ultraviolet-divergence-preserving (UVDP) parametrization naturally leads to Bjorken-Drell's analogy between Feynman diagrams and electric circuits. The LORE method has been shown to be applicable to both underlying and effective QFTs.

Yue-Liang Wu

2013-12-05T23:59:59.000Z

169

Senses in which Quantum Theory is an Analogy for Information Retrieval and Science  

E-Print Network (OSTI)

Arafat,S. Proceedings of the Fifth Quantum Interaction Symposium (QI 2011), 27-29 June 2011, Aberdeen, Scotland. Vol 7052. Lecture Notes in Computer Science (LNCS) ed.; 2011. pp 161-71 Springer

Arafat, S.

170

Quantum Chromodynamics  

E-Print Network (OSTI)

Quantum chromodynamics is the quantum gauge field theory that describes the strong interactions. This article reviews the basic structure, successes and challenges of quantum chromodynamics as it manifests itself at short and long distances, including the concepts of asymptotic freedom, confinement and infrared safety.

George Sterman

2005-12-27T23:59:59.000Z

171

New mechanism for nonlocality from string theory: UV-IR quantum entanglement and its imprints on the CMB  

Science Conference Proceedings (OSTI)

Puff field theories (PFT) arise as the decoupling limits of D3 branes in a Melvin universe and exhibit spatially nonlocal dynamics. Unlike other realizations of nonlocality in string theory, PFTs have full SO(3) rotational symmetry. In this work, we analyze the strongly coupled regime of a PFT through gravitational holography. We find a novel mechanism at the heart of the phenomenon of nonlocality: a quantum entanglement of UV and IR dynamics. In the holographic bulk, this translates to an apparent horizon splitting the space into two regions--with the UV completion of the PFT sitting at the horizon. We unravel this intricate UV-IR setting and devise a prescription for computing correlators that extends the original dictionary of holographic renormalization group. We then implement a cosmological scenario where PFT correlators set the initial conditions for primordial fluctuations. We compute the associated power spectrum of the cosmic microwave background and find that the scenario allows for a distinct stringy signature.

Minton, Gregory; Sahakian, Vatche [Harvey Mudd College, Physics Department, 241 Platt Boulevard, Claremont, California 91711 (United States)

2008-01-15T23:59:59.000Z

172

A General Systems Theory for Chaos, Quantum Mechanics and Gravity for Dynamical Systems of all Space-Time Scales  

E-Print Network (OSTI)

Non-local connections, i. e. long-range space-time correlations intrinsic to the observed subatomic dynamics of quantum systems is also exhibited by macro-scale dynamical systems as selfsimilar fractal space-time fluctuations and is identified as self-organized criticality. The author has developed a general systems theory for the observed self-organized criticality applicable to dynamical systems of all space-time scales based on the concept that spatial integration of enclosed small-scale fluctuations results in the formation of large eddy circulation. The eddy energy spectrum therefore represents the statistical normal distribution according to the Central Limit Theorem. The additive amplitudes of eddies, when squared (variance or eddy kinetic energy), represent the statistical normal (probability) distribution, a result observed in the subatomic dynamics of quantum systems. The model predicts Kepler's laws of planetary motion for eddy circulation dynamics. Inverse square law of gravitation therefore applies to the eddy continuum ranging from subatomic to macro-scale dynamical systems, e.g. weather systems. The model is similar to a superstring model for subatomic dynamics which unifies quantum mechanical and classical concepts and manifestation of matter is visualised as vibrational modes in string-like energy flow patterns. The cumulative sum of centripetal forces in a hierarchy of vortex circulations may result in the observed inverse square law form for gravitational attraction between inertial masses of the eddies.

A M Selvam

2005-03-03T23:59:59.000Z

173

Intrinsic atomic orbitals: An unbiased bridge between quantum theory and chemical concepts  

E-Print Network (OSTI)

Modern quantum chemistry can make quantitative predictions on an immense array of chemical systems. However, the interpretation of those predictions is often complicated by the complex wave function expansions used. Here we show that an exceptionally simple algebraic construction allows for defining atomic core and valence orbitals, polarized by the molecular environment, which can exactly represent self-consistent field wave functions. This construction provides an unbiased and direct connection between quantum chemistry and empirical chemical concepts, and can be used, for example, to calculate the nature of bonding in molecules, in chemical terms, from first principles.

Knizia, Gerald

2013-01-01T23:59:59.000Z

174

Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange  

Science Conference Proceedings (OSTI)

One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

2011-01-15T23:59:59.000Z

175

Quantum bundles and quantum interactions  

E-Print Network (OSTI)

A geometric framework for describing quantum particles on a possibly curved background is proposed. Natural constructions on certain distributional bundles (`quantum bundles') over the spacetime manifold yield a quantum ``formalism'' along any 1-dimensional timelike submanifold (a `detector'); in the flat, inertial case this turns out to reproduce the basic results of the usual quantum field theory, while in general it could be seen as a local, ``linearized'' description of the actual physics.

Daniel Canarutto

2005-06-22T23:59:59.000Z

176

Physics as Quantum Information Processing: Quantum Fields as Quantum Automata 1  

E-Print Network (OSTI)

Physics as Quantum Information Processing: Quantum Fields as Quantum Automata 1 Giacomo Mauro D Nazionale di Fisica Nucleare, Gruppo IV, Sezione di Pavia Abstract. Can we reduce Quantum Field Theory (QFT) to a quantum computation? Can physics be simulated by a quantum computer? Do we believe that a quantum field

D'Ariano, Giacomo Mauro

177

Charge transport, configuration interaction and Rydberg states under density functional theory  

E-Print Network (OSTI)

Density functional theory (DFT) is a computationally efficient formalism for studying electronic structure and dynamics. In this work, we develop DFT-based excited-state methods to study electron transport, Rydberg excited ...

Cheng, Chiao-Lun

2008-01-01T23:59:59.000Z

178

The Materials genome : rapid materials screening for renewable energy using high-throughput density functional theory  

E-Print Network (OSTI)

This thesis relates to the emerging field of high-throughput density functional theory (DFT) computation for materials design and optimization. Although highthroughput DFT is a promising new method for materials discovery, ...

Jain, Anubhav, Ph.D. Massachusetts Institute of Technology

2011-01-01T23:59:59.000Z

179

Equivariant spectral triples on the quantum SU(2) group, K-Theory 28  

E-Print Network (OSTI)

We characterize all equivariant odd spectral triples for the quantum SU(2) group acting on its L2-space and having a nontrivial Chern character. It is shown that the dimension of an equivariant spectral triple is at least three, and given any element of the K-homology group of SUq(2), there is an equivariant odd spectral triple of dimension 3 inducing that element. The method employed to get equivariant spectral triples in the quantum case is then used for classical SU(2), and we prove that for p < 4, there does not exist any equivariant spectral triple with nontrivial K-homology class and dimension p acting on the L2-space.

Partha Sarathi Chakraborty; Arupkumar Pal

2003-01-01T23:59:59.000Z

180

Hexakis(4-phormylphenoxy)cyclotriphosphazene: X-ray and DFT-calculated structures  

SciTech Connect

The crystal structure of hexakis(4-phormylphenoxy)cyclotriphosphazene is determined by using X-ray diffraction and then the molecular structure is investigated with density functional theory (DFT). X-Ray study shows that the title compound has C-H-{pi} interaction with phosphazene ring. The molecules in the unit cell are packed with Van der Waals and dipole-dipole interactions and the molecules are packed in zigzag shaped. Optimized molecular geometry is calculated with DFT at B3LYP/6-311G(d,p) level. The results from both experimental and theoretical calculations are compared in this study.

Albayrak, Cigdem, E-mail: calbayrak@sinop.edu.tr; Kosar, Basak [Sinop University, Faculty of Education (Turkey); Odabasoglu, Mustafa [Pamukkale University, Chemical Technology Program (Turkey); Bueyuekguengoer, Orhan [Ondokuz Mayis University, Faculty of Arts and Sciences (Turkey)

2010-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Quantum Theory of Transmission Line Resonator-Assisted Cooling of a Micromechanical Resonator  

E-Print Network (OSTI)

We propose a quantum description of the cooling of a micromechanical flexural oscillator by a one-dimensional transmission line resonator via a force that resembles cavity radiation pressure. The mechanical oscillator is capacitively coupled to the central conductor of the transmission line resonator. At the optimal point, the micromechanical oscillator can be cooled near to the ground state and the cooling can be measured by homodyne detection of the output microwave signal.

Li, Yong; Xue, Fei; Bruder, C

2008-01-01T23:59:59.000Z

182

Quantum Theory of Transmission Line Resonator-Assisted Cooling of a Micromechanical Resonator  

E-Print Network (OSTI)

We propose a quantum description of the cooling of a micromechanical flexural oscillator by a one-dimensional transmission line resonator via a force that resembles cavity radiation pressure. The mechanical oscillator is capacitively coupled to the central conductor of the transmission line resonator. At the optimal point, the micromechanical oscillator can be cooled close to the ground state, and the cooling can be measured by homodyne detection of the output microwave signal.

Yong Li; Ying-Dan Wang; Fei Xue; C. Bruder

2008-04-30T23:59:59.000Z

183

Quantum Gravity An introductory survey  

E-Print Network (OSTI)

Quantum Gravity An introductory survey Hermann Nicolai Max-Planck-Institut f¨ur Gravitationsphysik (Albert­Einstein­Institut, Potsdam) . ­ p.1/25 #12;Why Quantum Gravity? . ­ p.2/25 #12;Why Quantum Gravity theories: . ­ p.2/25 #12;Why Quantum Gravity? General Relativity and Quantum Theory: not only very

Rossak, Wilhelm R.

184

Quantum Cosmology  

E-Print Network (OSTI)

We give an introduction into quantum cosmology with emphasis on its conceptual parts. After a general motivation we review the formalism of canonical quantum gravity on which discussions of quantum cosmology are usually based. We then present the minisuperspace Wheeler--DeWitt equation and elaborate on the problem of time, the imposition of boundary conditions, the semiclassical approximation, the origin of irreversibility, and singularity avoidance. Restriction is made to quantum geometrodynamics; loop quantum gravity and string theory are discussed in other contributions to this volume.

Claus Kiefer; Barbara Sandhoefer

2008-04-04T23:59:59.000Z

185

Topological methods in quantum gravity.  

E-Print Network (OSTI)

??The main technical problem with background independent approaches to quantum gravity is inapplicability of standard quantum field theory methods. New methods are needed which would (more)

Starodubtsev, Artem

2005-01-01T23:59:59.000Z

186

Adaptive DFT-based interferometer fringe tracking  

Science Conference Proceedings (OSTI)

An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three ... Keywords: DFT, IOTA, fringe tracking, interferometry, real time

Edward Wilson; Ettore Pedretti; Jesse Bregman; Robert W. Mah; Wesley A. Traub

2005-01-01T23:59:59.000Z

187

Generalization of the Activated Complex Theory of Reaction Rates. I. Quantum Mechanical Treatment  

DOE R&D Accomplishments (OSTI)

In its usual form activated complex theory assumes a quasi-equilibrium between reactants and activated complex, a separable reaction coordinate, a Cartesian reaction coordinate, and an absence of interaction of rotation with internal motion in the complex. In the present paper a rate expression is derived without introducing the Cartesian assumption. The expression bears a formal resemblance to the usual one and reduces to it when the added assumptions of the latter are introduced.

Marcus, R. A.

1964-00-00T23:59:59.000Z

188

The Particle Adventure | Unsolved Mysteries | String theory  

NLE Websites -- All DOE Office Websites (Extended Search)

String theory String theory Modern physics has good theories for quantum mechanics, relativity, and gravity. But these theories do not quite work with each other. There are...

189

Quantum limit in continuous quantum measurement  

E-Print Network (OSTI)

The quantum noise is calculated based on the description of imprecise measurement theory, which is used to analyse the general detector's quantum limit in continuous quantum measurement. Different from the traditional description of the linear-response theory, we don't introduce the hypotheses on the properties of the susceptibilities of the detector, and first show a rigorous result: The minimum noise added by the detector in quantum measurement is precisely equal to the zero-point noise. We also discuss the statistic characters of the back-action force in quantum measurement and show how to reach the quantum limit.

Shao, ChengGang

2012-01-01T23:59:59.000Z

190

A DFT investigation of methanolysis and hydrolysis of triacetin  

E-Print Network (OSTI)

The thermodynamic and kinetic aspects of the methanolysis and hydrolysis reactions of glycerol triacetate or triacetin, a model triacylglycerol compound, were investigated by using Density Functional Theory (DFT) at the B3LYP/6-31++G(d,p) level of calculation. Twelve elementary steps of triacetin methanolysis were studied under acid-catalyzed and base-catalyzed conditions. The mechanism of acid-catalyzed methanolysis reaction which has not been reported yet for any esters was proposed. The effects of substitution, methanolysis/hydrolysis position, solvent and face of nucleophilic attack on the free energy of reaction and activation energy were examined. The prediction confirmed the facile position at the middle position of glycerol observed by NMR techniques. The calculated activation energy and the trends of those factors agree with existing experimental observations in biodiesel production.

Limpanuparb, Taweetham; Tantirungrotechai, Yuthana; 10.1016/j.theochem.2010.05.022

2012-01-01T23:59:59.000Z

191

Multiparty quantum protocols for assisted entanglement distillation  

Science Conference Proceedings (OSTI)

Quantum information theory is a multidisciplinary field whose objective is to understand what happens when information is stored in the state of a quantum system. Quantum mechanics provides us with a new resource, called quantum entanglement, ...

Nicolas Dutil

2011-01-01T23:59:59.000Z

192

Quantum Theory at Planck Scale, Limiting Values, Deformed Gravity and Dark Energy Problem  

E-Print Network (OSTI)

Within a theory of the existing fundamental length on the order of Planck's a high-energy deformation of the General Relativity for the space with horizon has been constructed. On this basis, Markov's work of the early eighties of the last century has been given a new interpretation to show that the heuristic model considered by him may be placed on a fundamental footing. The obtained results have been applied to solving of the dark energy problem, making it possible to frame the following hypothesis: a dynamic cosmological term is a measure of deviation from a thermodynamic identity (the first law of thermodynamics) of the high-energy (Planck's) deformation of Einstein equations for horizon spaces in their thermodynamic interpretation.

A. E. Shalyt-Margolin

2011-02-24T23:59:59.000Z

193

Sequential Circuit Testing: From DFT to SFT  

Science Conference Proceedings (OSTI)

Sequential circuit testing is an active research area due to its applicability, its practicality, and its complexity. This paper gives an overview of the sequential automatic test pattern generation approaches and the classical and more recent design-for-testability ... Keywords: logic testing, sequential circuit testing, DFT techniques, automatic test pattern generation, design-for-testability methods, synthesis-for-testability, SFT techniques, large sequential circuits, ATPG

R. M. Chou; K. K. Saluja

1997-01-01T23:59:59.000Z

194

Quantum fields as gravitational sources  

E-Print Network (OSTI)

The practice of setting quantum fields as sources for classical general relativity is examined. Several conceptual problems are identified which invalidate apparently innocuous equations. Alternative ways to links classical general relativity with quantum theory using Bohm's theory are proposed.

Mark J Hadley

2008-08-13T23:59:59.000Z

195

Quantum state discrimination with bosonic channels and Gaussian states  

E-Print Network (OSTI)

Discriminating between quantum states is an indispensable part of quantum information theory. This thesis investigates state discrimination of continuous quantum variables, focusing on bosonic communication channels and ...

Tan, Si Hui, Ph. D. Massachusetts Institute of Technology

2010-01-01T23:59:59.000Z

196

Thermalized Non-Equilibrated Matter against Random Matrix Theory, Quantum Chaos and Direct Interaction: Warming up  

E-Print Network (OSTI)

The idea of a thermalized non-equilibrated state of matter offers a conceptually new understanding of the strong angular asymmetry. In this compact review we present some clarifications, corrections and further developments of the approach, and provide a brief account of results previously discussed but not reported in the literature. The cross symmetry compound nucleus $S$-matrix correlations are obtained (i) starting from the unitary $S$-matrix representation, (ii) by explicitly taking into account a process of energy equilibration, and (iii) without taking the thermodynamic limit of an infinite number of particles in the thermalized system. It is conjectured that the long phase memory is due to the exponentially small total spin off-diagonal resonance intensity correlations. This manifestly implies that the strong angular asymmetry intimately relates to extremely small deviations of the eigenfunction distribution from Gaussian law. The spin diagonal resonance intensity correlations determine a new time/energy scale for a validity of random matrix theory. Its definition does not involve overlaps of the many-body interacting configurations with shell model non-interacting states and thus is conceptually different from the physical meaning (inverse energy relaxation time) of the spreading widths introduced by Wigner. Exact Gaussian distribution of the resonance wave functions corresponds to the instantaneous phase relaxation. We invite the nuclear reaction community for the competition to describe, as the first challenge, the strong forward peaking in the typically evaporation part of the proton spectra. This is necessary to initiate revealing long-term misconduct in the heavily cross-disciplinary field, also important for nuclear industry applications.

S. Kun; Y. Li; M. H. Zhao; M. R. Huang

2013-07-17T23:59:59.000Z

197

Accuracy of Density Functional Theory in Prediction of Carbon Dioxide Adsorbent Materials  

E-Print Network (OSTI)

We have performed a thorough computational study to assess the accuracy of density functional theory (DFT) methods in describing the interactions of CO2 with model alkali-earth-metal (AEM, Ca and Li) decorated carbon structures, namely anthracene (C14H10) molecules. We find that gas-adsorption energy and equilibrium structure results obtained with both standard (i.e. LDA and GGA) and hybrid (i.e. PBE0 and B3LYP) exchange-correlation functionals of DFT differ significantly from results obtained with second-order Moller-Plesset perturbation theory (MP2), an accurate computational quantum chemistry method. The major disagreements found can be mostly rationalized in terms of electron correlation errors that lead to inaccurate charge transfers and electrostatic Coulomb interactions between the molecules. Interestingly, we show that when the concentration of AEM atoms in anthracene is tuned to resemble as closely as possible to the electronic structure of AEM-decorated graphene, hybrid exchange-correlation DFT and ...

Cazorla, Claudio

2012-01-01T23:59:59.000Z

198

Tb0.5Bi0.5MnO3: New material. A DFT study  

Science Conference Proceedings (OSTI)

In the present work we have determined the band structure and the densities of states (DOS) of Tb0.5Bi0.5MnO3 in cubic phase using the density functional theory (DFT). The determination of the lattice constant was ... Keywords: 61.50.-f, 62.20.-x, 71.15.Nc, 71.20.-b, 71.55.Ht, 75.20.En, Band structure, DFT, Density of states, Magnetic properties, Mechanical and structural properties, Tb1-xBixMnO3

Miguel Grizalez; M. Jairo Arbey Rodrguez; Jess Heiras; P. Prieto

2008-03-01T23:59:59.000Z

199

Quantum thermal waves in quantum corrals  

E-Print Network (OSTI)

In this paper the possibility of the generation of the thermal waves in 2D electron gas is investigated. In the frame of the quantum heat transport theory the 2D quantum hyperbolic heat transfer equation is formulated and numerically solved. The obtained solutions are the thermal waves in electron 2D gases. As an exapmle the thermal waves in quantum corrals are described. Key words: 2D electron gas, quantum corrals, thermal waves.

J. Marciak-Kozlowska; M. Kozlowski

2004-05-07T23:59:59.000Z

200

Quantum extended crystal PDE's  

E-Print Network (OSTI)

Our recent results on {\\em extended crystal PDE's} are generalized to PDE's in the category $\\mathfrak{Q}_S$ of quantum supermanifolds. Then obstructions to the existence of global quantum smooth solutions for such equations are obtained, by using algebraic topologic techniques. Applications are considered in details to the quantum super Yang-Mills equations. Furthermore, our geometric theory of stability of PDE's and their solutions, is also generalized to quantum extended crystal PDE's. In this way we are able to identify quantum equations where their global solutions are stable at finite times. These results, are also extended to quantum singular (super)PDE's, introducing ({\\em quantum extended crystal singular (super) PDE's}).

Agostino Prstaro

2011-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Quantum Dots: Theory  

E-Print Network (OSTI)

SEPM) has been applied to CdSe [42], InP [43] and Si [42]calculated optical gap on CdSe nanocrystal size is presentedmass approach. In the case of CdSe ? = 1.18. The ? parameter

Vukmirovic, Nenad

2010-01-01T23:59:59.000Z

202

Quantum Fine-Grained Entropy  

E-Print Network (OSTI)

Regarding the strange properties of quantum entropy and entanglement, e.g., the negative quantum conditional entropy, we revisited the foundations of quantum entropy, namely, von Neumann entropy, and raised the new method of quantum fine-grained entropy. With the applications in entanglement theory, quantum information processing, and quantum thermodynamics, we demonstrated the capability of quantum fine-grained entropy to resolve some notable confusions and problems, including the measure of entanglement and quantumness, the additivity conjecture of entanglement of formation etc, and the definition of temperature for single quantum system.

Wang, Dong-Sheng

2012-01-01T23:59:59.000Z

203

Ultraviolet Complete Quantum Gravity  

E-Print Network (OSTI)

An ultraviolet complete (UV) quantum gravity theory is formulated in which vertex functions in Feynman graphs are entire functions and the propagating gravitons are described by local, causal propagators. A scalar-tensor action describes classical gravity theory. The cosmological constant problem is investigated in the context of the UV complete quantum gravity.

Moffat, J W

2010-01-01T23:59:59.000Z

204

A Quantum Bousso Bound  

E-Print Network (OSTI)

The Bousso bound requires that one quarter the area of a closed codimension two spacelike surface exceeds the entropy flux across a certain lightsheet terminating on the surface. The bound can be violated by quantum effects such as Hawking radiation. It is proposed that at the quantum level the bound be modified by adding to the area the quantum entanglement entropy across the surface. The validity of this quantum Bousso bound is proven in a two-dimensional large N dilaton gravity theory.

Andrew Strominger; David Thompson

2003-03-10T23:59:59.000Z

205

Testing quantum mechanics  

E-Print Network (OSTI)

As experiments continue to push the quantum-classical boundary to include increasingly complex dynamical systems, the interpretation of experimental data becomes more and more challenging: when the observations are noisy, indirect, and limited, how can we be sure that we are observing quantum behavior? This tutorial highlights some of the difficulties in such experimental tests of quantum mechanics, using optomechanics as the central example, and discusses how the issues can be resolved using techniques from statistics and insights from quantum information theory.

Mankei Tsang

2013-06-12T23:59:59.000Z

206

Is quantum mechanics exact?  

SciTech Connect

We formulate physically motivated axioms for a physical theory which for systems with a finite number of degrees of freedom uniquely lead to quantum mechanics as the only nontrivial consistent theory. Complex numbers and the existence of the Planck constant common to all systems arise naturally in this approach. The axioms are divided into two groups covering kinematics and basic measurement theory, respectively. We show that even if the second group of axioms is dropped, there are no deformations of quantum mechanics which preserve the kinematic axioms. Thus, any theory going beyond quantum mechanics must represent a radical departure from the usual a priori assumptions about the laws of nature.

Kapustin, Anton [California Institute of Technology, Pasadena, California 91125 (United States)] [California Institute of Technology, Pasadena, California 91125 (United States)

2013-06-15T23:59:59.000Z

207

On Randomness in Quantum Mechanics  

E-Print Network (OSTI)

The quantum mechanical probability densities are compared with the probability densities treated by the theory of random variables. The relevance of their difference for the interpretation of quantum mechanics is commented.

Alberto C. de la Torre

2007-07-19T23:59:59.000Z

208

Quantum Mechanics and Multiply Connected Spaces  

E-Print Network (OSTI)

t is well known that the difference between Quantum Mechanics and Classical Theory appears most crucially in the non Classical spin half of the former theory and the Wilson-Sommerfelt quantization rule. We argue that this is symptomatic of the fact that Quantum Theory is actually a theory in multiply connected space while Classical Theory operates in simply connected space.

B. G. Sidharth

2006-05-16T23:59:59.000Z

209

Session #1: Cutting Edge Methodologies--Beyond Current DFT  

NLE Websites -- All DOE Office Websites (Extended Search)

Session #1: Cutting Edge Methodologies (beyond Current DFT) Moderator: Shengbai Zhang (RPI/ REL) Topics to be addressed: Benchmarking state-of-the-art approaches, accurate energy landscape. Identify problems with the current DFT-LDA and GGA approaches and possible pathways to overcome these problems. PBE PBE How Bad is DFT for vdW Interactions? fcc Ar Benzene dimer PBE LDA Exp CCSD(T) LDA PBE vdW Interaction between H 2 and Carbon � PBE Graphene CCSD(T) LDA Benzene omitted in the LDA and GGA van der Walls (vdW)-DFT: Langreth, Kohn � Fully nonlocal � functional: � � Long-range nonlocal correlation energy functional (omitted in the LDA and GGA) ) ( � Computational cost considerably more than GGA � Added as post-GGA energy correction but force

210

Generalized quantum defect methods in quantum chemistry  

E-Print Network (OSTI)

The reaction matrix of multichannel quantum defect theory, K, gives a complete picture of the electronic structure and the electron - nuclear dynamics for a molecule. The reaction matrix can be used to examine both bound ...

Altunata, Serhan

2006-01-01T23:59:59.000Z

211

Helium under high pressure: A comparative study of all-electron and pseudopotential methods within density functional theory  

E-Print Network (OSTI)

We have calculated the ground state electronic structure of He under pressure from 0 to 1500 GPa using both all-electron full-potential and pseudopotential methods based on the density functional theory (DFT). We find that throughout this pressure range, pseudopotentials yield essentially the same energy-volume curve for all of bcc, fcc, and hcp configurations as does the full-potential method, a strong indication that pseudopotential approximation works well for He both as the common element in some giant planets and as detrimental impurities in fusion reactor materials. The hcp lattice is always the most stable structure and bcc the least stable one. Since the energy preference of hcp over fcc and bcc is within 0.01 eV below 100 GPa and about 0.1 eV at 1500 GPa, on the same order of the error bar in local or semi-local density approximations in DFT, phase transitions can only be discussed with more precise description of electron correlation in Quantum Monte Carlo or DFT-based GW methods.

Xiao, W; Geng, W T

2012-01-01T23:59:59.000Z

212

Hamilton-Jacobi and quantum theory formulations of thermal-wave propagation under the dual-phase lagging model of heat conduction  

SciTech Connect

Dual-phase lagging model is one of the most promising approaches to generalize the Fourier heat conduction equation, and it can be reduced in the appropriate limits to the hyperbolic Cattaneo-Vernotte and to the parabolic equations. In this paper it is shown that the Hamilton-Jacobi and quantum theory formulations that have been developed to study the thermal-wave propagation in the Fourier framework can be extended to include the more general approach based on dual-phase lagging. It is shown that the problem of solving the heat conduction equation can be treated as a thermal harmonic oscillator. In the classical approach a formulation in canonical variables is presented. This formalism is used to introduce a quantum mechanical approach from which the expectation values of observables such as the temperature and heat flux are obtained. These formalisms permit to use a methodology that could provide a deeper insight into the phenomena of heat transport at different time scales in media with inhomogeneous thermophysical properties.

Ordonez-Miranda, J.; Alvarado-Gil, J. J. [Department of Applied Physics, Cinvestav-Unidad Merida, Carretera Antigua a Progreso km. 6, A.P. Postal 73 'Cordemex', Merida, Yucatan 97310 (Mexico); Zambrano-Arjona, Miguel A. [Facultad de Ingenieria, Universidad Autonoma de Yucatan, A.P. 150 Cordemex, Merida, Yucatan 97310 (Mexico)

2010-02-15T23:59:59.000Z

213

Theory of quantum frequency conversion and type-II parametric down-conversion in the high-gain regime  

E-Print Network (OSTI)

Frequency conversion (FC) and type-II parametric down-conversion (PDC) processes serve as basic building blocks for the implementation of quantum optical experiments: type-II PDC enables the efficient creation of quantum states such as photon-number states and Einstein-Podolsky-Rosen-states (EPR-states). FC gives rise to technologies enabling efficient atom-photon coupling, ultrafast pulse gates and enhanced detection schemes. However, despite their widespread deployment, their theoretical treatment remains challenging. Especially the multi-photon components in the high-gain regime as well as the explicit time-dependence of the involved Hamiltonians hamper an efficient theoretical description of these nonlinear optical processes. In this paper, we investigate these effects and put forward two models that enable a full description of FC and type-II PDC in the high-gain regime. We present a rigorous numerical model relying on the solution of coupled integro-differential equations that covers the complete dynamics of the process. As an alternative, we develop a simplified model that, at the expense of neglecting time-ordering effects, enables an analytical solution. While the simplified model approximates the correct solution with high fidelity in a broad parameter range, sufficient for many experimental situations, such as FC with low efficiency, entangled photon-pair generation and the heralding of single photons from type-II PDC, our investigations reveal that the rigorous model predicts a decreased performance for FC processes in quantum pulse gate applications and an enhanced EPR-state generation rate during type-II PDC, when EPR squeezing values above 12 dB are considered.

Andreas Christ; Benjamin Brecht; Wolfgang Mauerer; Christine Silberhorn

2012-10-31T23:59:59.000Z

214

Quantum error control codes  

E-Print Network (OSTI)

It is conjectured that quantum computers are able to solve certain problems more quickly than any deterministic or probabilistic computer. For instance, Shor's algorithm is able to factor large integers in polynomial time on a quantum computer. A quantum computer exploits the rules of quantum mechanics to speed up computations. However, it is a formidable task to build a quantum computer, since the quantum mechanical systems storing the information unavoidably interact with their environment. Therefore, one has to mitigate the resulting noise and decoherence effects to avoid computational errors. In this dissertation, I study various aspects of quantum error control codes - the key component of fault-tolerant quantum information processing. I present the fundamental theory and necessary background of quantum codes and construct many families of quantum block and convolutional codes over finite fields, in addition to families of subsystem codes. This dissertation is organized into three parts: Quantum Block Codes. After introducing the theory of quantum block codes, I establish conditions when BCH codes are self-orthogonal (or dual-containing) with respect to Euclidean and Hermitian inner products. In particular, I derive two families of nonbinary quantum BCH codes using the stabilizer formalism. I study duadic codes and establish the existence of families of degenerate quantum codes, as well as families of quantum codes derived from projective geometries. Subsystem Codes. Subsystem codes form a new class of quantum codes in which the underlying classical codes do not need to be self-orthogonal. I give an introduction to subsystem codes and present several methods for subsystem code constructions. I derive families of subsystem codes from classical BCH and RS codes and establish a family of optimal MDS subsystem codes. I establish propagation rules of subsystem codes and construct tables of upper and lower bounds on subsystem code parameters. Quantum Convolutional Codes. Quantum convolutional codes are particularly well-suited for communication applications. I develop the theory of quantum convolutional codes and give families of quantum convolutional codes based on RS codes. Furthermore, I establish a bound on the code parameters of quantum convolutional codes - the generalized Singleton bound. I develop a general framework for deriving convolutional codes from block codes and use it to derive families of non-catastrophic quantum convolutional codes from BCH codes. The dissertation concludes with a discussion of some open problems.

Abdelhamid Awad Aly Ahmed, Sala

2008-05-01T23:59:59.000Z

215

Quantum Mechanics Without Observers  

E-Print Network (OSTI)

The measurement problem and the role of observers have plagued quantum mechanics since its conception. Attempts to resolve these have introduced anthropomorphic or non-realist notions into physics. A shift of perspective based upon process theory and utilizing methods from combinatorial games, interpolation theory and complex systems theory results in a novel realist version of quantum mechanics incorporating quasi-local, nondeterministic hidden variables that are compatible with the no-hidden variable theorems and relativistic invariance, and reproduce the standard results of quantum mechanics to a high degree of accuracy without invoking observers.

W. H. Sulis

2013-02-18T23:59:59.000Z

216

Quantum Money  

Science Conference Proceedings (OSTI)

Quantum Money. Purpose: ... I will present a concrete quantum money scheme based on quantum superpositions of diagrams that encode knots. ...

2011-10-25T23:59:59.000Z

217

Lattice Quantum Chromodynamics Project and SCience Gateway at...  

NLE Websites -- All DOE Office Websites (Extended Search)

Science at NERSC Nuclear Science Lattice Quantum Chromodynamics Lattice Quantum Chromodynamics Key Challenges: Although the QCD theory has been extensively tested at at...

218

Lattice Quantum Chromodynamics Project and SCience Gateway at...  

NLE Websites -- All DOE Office Websites (Extended Search)

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...

219

STATISTICAL MECHANICS AND FIELD THEORY  

E-Print Network (OSTI)

1. L. 1. Schiff, Quantum Mechanics, third edition (McGraw-two-dimensional quantum mechanics problem vith a potential,Theory Methods to Statistical Mechanics Chapter I The Use of

Samuel, S.A.

2010-01-01T23:59:59.000Z

220

1 String field theory  

E-Print Network (OSTI)

This elementary introduction to string field theory highlights the features and the limitations of this approach to quantum gravity as it is currently understood. String field theory is a formulation of string theory as a field theory in space-time with an infinite number of massive fields. Although existing constructions of string field theory require expanding around a fixed choice of space-time background, the theory is in principle background-independent, in the sense that different backgrounds can be realized as different field configurations in the theory. String field theory is the only string formalism developed so far which, in principle, has the potential to systematically address questions involving multiple asymptotically distinct string backgrounds. Thus, although it is not yet well defined as a quantum theory, string field theory may eventually be helpful for understanding questions related to cosmology in string theory. 1.1

W. Taylor

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

TORSION AND QUANTUM GRAVITY  

E-Print Network (OSTI)

more restrictive context of Einstein's theory of gravity.6782 TORSION AND QUANTUM GRAVITY Andrevr J, Him son Lawrencetorsion in conventional gravity cou~d in fact be dynamicaL A

Hanson, Andrew J.

2011-01-01T23:59:59.000Z

222

(E)-2-[(2-Bromophenylimino)methyl]-5-methoxyphenol: X-ray and DFT-calculated structures  

SciTech Connect

The crystal structure of (E)-2-[(2-Bromophenylimino)methyl]-5-methoxyphenol is determined by using X-ray diffraction and then the molecular structure is investigated with density functional theory (DFT). X-Ray study shows that the title compound has a strong intramolecular O-H-N hydrogen bond and three dimensional crystal structure is primarily determined by C-H-{pi} and weak van der Waals interactions. The strong O-H-N bond is an evidence of the preference for the phenol-imine tautomeric form in the solid state. Optimized molecular geometry is calculated with DFT at the B3LYP/6-31G(d,p) level. The IR spectra of compound were recorded experimentally and calculated to compare with each other. The results from both experiment and theoretical calculations are compared in this study.

Kosar, B., E-mail: bkosar@omu.edu.tr; Albayrak, C. [Sinop University, Faculty of Education (Turkey); Odabasoglu, M. [Pamukkale University, Chemistry Program (Turkey); Bueyuekguengoer, O. [Ondokuz Mayis University, Faculty of Arts and Sciences (Turkey)

2010-12-15T23:59:59.000Z

223

Quantum Physics Einstein's Gravity  

E-Print Network (OSTI)

Quantum Physics confronts Einstein's Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 13 October 2001 #12; Quantum Physics confronts Einstein's Gravity and with Einstein's theory of gravity (the general relativity) is still the single biggest theoretical problem

Visser, Matt

224

Quantum Gravity and Turbulence  

E-Print Network (OSTI)

We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.

Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze

2010-05-18T23:59:59.000Z

225

Quantum discord and other measures of quantum correlation  

E-Print Network (OSTI)

One of the best signatures of nonclassicality in a quantum system is the existence of correlations that have no classical counterpart. Different methods for quantifying the quantum and classical parts of the correlations are amongst the most actively-studied topics of quantum information theory in the past decade. Entanglement is the most prominent of these correlations, but in many cases unentangled states exhibit nonclassical behavior. Thus distinguishing quantum correlation other than entanglement provides a better division between the quantum and classical worlds, especially when considering mixed states. Here we review different notions of classical and quantum correlations quantified by quantum discord and other related measures. In the first half we review the mathematical properties of the measures of quantum correlation, relate them to each other, and discuss the classical-quantum division that is common among them. In the second half, we show that the measures quantum correlation identify and quanti...

Modi, Kavan; Cable, Hugo; Paterek, Tomasz; Vedral, Vlatko

2011-01-01T23:59:59.000Z

226

Quantum and classical vibrational relaxation dynamics of N-methylacetamide on ab initio potential energy surfaces  

E-Print Network (OSTI)

Employing extensive quantum-chemical calculations at the DFT/B3LYP and MP2 level, a quartic force field of isolated N-methylacetamide is constructed. Taking into account 24 vibrational degrees of freedom, the model is employed to perform numerically exact vibrational configuration interaction calculations of the vibrational energy relaxation of the amide I mode. It is found that the energy transfer pathways may sensitively depend on details of the theoretical description. Moreover, the exact reference calculations were used to study the applicability and accuracy of (i) the quasiclassical trajectory method, (ii) time-dependent second-order perturbation theory, and (iii) the instantaneous normal mode description of frequency fluctuations. Based on the results, several strategies to describe vibrational energy relaxation in biomolecular systems are discussed.

Fujisaki, Hiroshi; Hirao, Kimihiko; Straub, John E; Stock, Gerhard

2008-01-01T23:59:59.000Z

227

Lectures on String Theory  

E-Print Network (OSTI)

This is a one semester course on bosonic string theory aimed at beginning graduate students. The lectures assume a working knowledge of quantum field theory and general relativity. Contents: 1. The Classical String 2. The Quantum String 3. Open Strings and D-Branes 4. Introducing Conformal Field Theory 5. The Polyakov Path Integral and Ghosts 6. String Interactions 7. The Low-Energy Effective Action 8. Compactification and T-Duality

Tong, David

2009-01-01T23:59:59.000Z

228

Experimental verification of quantum computations  

E-Print Network (OSTI)

Quantum computers are expected to offer substantial speedups over their classical counterparts and to solve problems that are intractable for classical computers. Beyond such practical significance, the concept of quantum computation opens up new fundamental questions, among them the issue whether or not quantum computations can be certified by entities that are inherently unable to compute the results themselves. Here we present the first experimental verification of quantum computations. We show, in theory and in experiment, how a verifier with minimal quantum resources can test a significantly more powerful quantum computer. The new verification protocol introduced in this work utilizes the framework of blind quantum computing and is independent of the experimental quantum-computation platform used. In our scheme, the verifier is only required to generate single qubits and transmit them to the quantum computer. We experimentally demonstrate this protocol using four photonic qubits and show how the verifier can test the computer's ability to perform measurement-based quantum computations.

Stefanie Barz; Joseph F. Fitzsimons; Elham Kashefi; Philip Walther

2013-08-30T23:59:59.000Z

229

Quantum Geometry in the Lab  

E-Print Network (OSTI)

Standard particle theory is based on quantized matter embedded in a classical geometry. Here, a complementary model is proposed, based on classical matter -- massive bodies, without quantum properties -- embedded in a quantum geometry. It does not describe elementary particles, but may be a better, fully consistent quantum description for position states in laboratory-scale systems. Gravitational theory suggests that the geometrical quantum system has an information density of about one qubit per Planck length squared. If so, the model here predicts that the quantum uncertainty of geometry creates a new form of noise in the position of massive bodies, detectable by interferometers.

Craig Hogan

2013-03-24T23:59:59.000Z

230

Quantum Gravity: Has Spacetime Quantum Properties?  

E-Print Network (OSTI)

The incompatibility between GR and QM is generally seen as a sufficient motivation for the development of a theory of Quantum Gravity. If - so a typical argumentation - QM gives a universally valid basis for the description of all natural systems, then the gravitational field should have quantum properties. Together with the arguments against semi-classical theories of gravity, this leads to a strategy which takes a quantization of GR as the natural avenue to Quantum Gravity. And a quantization of the gravitational field would in some sense correspond to a quantization of geometry. Spacetime would have quantum properties. But, this strategy will only be successful, if gravity is a fundamental interaction. - What, if gravity is instead an intrinsically classical phenomenon? Then, if QM is nevertheless fundamentally valid, gravity can not be a fundamental interaction. An intrinsically classical gravity in a quantum world would have to be an emergent, induced or residual, macroscopic effect, caused by other interactions. The gravitational field (as well as spacetime) would not have any quantum properties. A quantization of GR would lead to artifacts without any relation to nature. The serious problems of all approaches to Quantum Gravity that start from a direct quantization of GR or try to capture the quantum properties of gravity in form of a 'graviton' dynamics - together with the, meanwhile, rich spectrum of approaches to an emergent gravity and/or spacetime - make this latter option more and more interesting for the development of a theory of Quantum Gravity. The most advanced emergent gravity (and spacetime) scenarios are of an information-theoretical, quantum-computational type.

Reiner Hedrich

2009-02-02T23:59:59.000Z

231

A Criterion for Holism in Quantum Mechanics  

E-Print Network (OSTI)

A Criterion for Holism in Quantum Mechanics M.P Seevinck E-mail: M.P.Seevinck@phys.uu.nl Utrecht University, The Netherlands, August 2003. 1 #12; Motivation · The question whether or not quantum mechanics is it that makes quantum mechanics a holistic theory (if so), and other physical theories not (if so). · I propose

Seevinck, Michiel

232

Introduction to Loop Quantum Gravity  

E-Print Network (OSTI)

The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.

Mercuri, Simone

2010-01-01T23:59:59.000Z

233

Introduction to Loop Quantum Gravity  

E-Print Network (OSTI)

The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.

Simone Mercuri

2010-01-08T23:59:59.000Z

234

Quantum Inequalities That Test Locality Dennis Dieks  

E-Print Network (OSTI)

Quantum Inequalities That Test Locality Dennis Dieks Institute for the History and Foundations.g.b.j.dieks@phys.uu.nl 20 June 2002 Abstract Quantum theory violates Bell's inequality, but not to the maxi- mum extent). These are quantum analogues of Bell inequalities, and we show that they can be used to test quantum mechanical lo

Seevinck, Michiel

235

Quantum Structures and their Future Diederik Aerts  

E-Print Network (OSTI)

Quantum Structures and their Future Importance Diederik Aerts FUND and CLEA, Brussels Free physical and mathematical base. The development of quantum mechanics proceeded in a rather haphazard manner, quantum mechanics, com- monly referred to as the `old quantum theory', did not even possess a coherent

Aerts, Diederik

236

Quantum Algorithms for Learning and Testing Juntas  

Science Conference Proceedings (OSTI)

In this article we develop quantum algorithms for learning and testing juntas, i.e. Boolean functions which depend only on an unknown set of k out of n ... Keywords: 03.67.-a, 03.67.Lx, Juntas, computational learning theory, lower bounds, quantum computation, quantum property testing, quantum query algorithms

Alp At?c?; Rocco A. Servedio

2007-10-01T23:59:59.000Z

237

Ru L[subscript 2,3] XANES theoretical simulation with DFT: A test of the core-hole treatment  

SciTech Connect

Density functional theory (DFT)-based relativistic calculations were performed to model the Ru L-edge X-ray absorption near edge structure (XANES) spectra of the hexaammineruthenium complex [Ru(NH{sub 3}){sub 6}]{sup 3+} and 'blue dimer' water oxidation catalyst, cis,cis- [(bpy){sub 2}(H{sub 2}O)Ru{sup III}ORu{sup III}(OH{sub 2})(bpy){sub 2}]{sup 4+} (bpy is 2,2-bipyridine). Two computational approaches were compared: simulations without the core-hole and by modeling of the core-hole within the Z+1 approximation. Good agreement between calculated and experimental XANES spectra is achieved without including the core-hole. Simulations with algorithms beyond the Z+1 approximation were only possible in a framework of the scalar relativistic treatment. Time-dependent DFT (TD-DFT) was used to compute the Ru L-edge spectrum for [Ru(NH{sub 3}){sub 6}]{sup 3+} model compound. Three different core-hole treatments were compared in a real-space full multiple scattering XANES modeling within the Green function formalism (implemented in the FEFF9.5 package) for the [Ru(Mebimpy)(bpm)(H{sub 2}O)]{sup 2+} complex. The latter approaches worked well in cases where spin-orbit treatment of relativistic effects is not required.

Alperovich, Igor; Moonshiram, Dooshaye; Soldatov, Alexander; Pushkar, Yulia (SFU-Russia); (Purdue)

2012-10-09T23:59:59.000Z

238

5.74 Introductory Quantum Mechanics II, Spring 2005  

E-Print Network (OSTI)

Time-dependent quantum mechanics and spectroscopy. Topics covered include perturbation theory, two-level systems, light-matter interactions, relaxation in quantum systems, correlation functions and linear response theory, ...

Tokmakoff, Andrei

239

Quantum Communication With Zero-Capacity Channels  

E-Print Network (OSTI)

Communication over a noisy quantum channel introduces errors in the transmission that must be corrected. A fundamental bound on quantum error correction is the quantum capacity, which quantifies the amount of quantum data that can be protected. We show theoretically that two quantum channels, each with a transmission capacity of zero, can have a nonzero capacity when used together. This unveils a rich structure in the theory of quantum communications, implying that the quantum capacity does not uniquely specify a channel's ability for transmitting quantum information.

Graeme Smith; Jon Yard

2008-07-30T23:59:59.000Z

240

Ligand Discrimination in Myoglobin from Linear-Scaling DFT+U  

E-Print Network (OSTI)

Myoglobin modulates the binding of diatomic molecules to its heme group via hydrogen-bonding and steric interactions with neighboring residues, and is an important benchmark for computational studies of biomolecules. We have performed calculations on the heme binding site and a significant proportion of the protein environment (more than 1000 atoms) using linear-scaling density functional theory and the DFT+U method to correct for self-interaction errors associated with localized 3d states. We confirm both the hydrogen-bonding nature of the discrimination effect (3.6 kcal/mol) and assumptions that the relative strain energy stored in the protein is low (less than 1 kcal/mol). Our calculations significantly widen the scope for tackling problems in drug design and enzymology, especially in cases where electron localization, allostery or long-ranged polarization influence ligand binding and reaction.

Cole, Daniel J; Payne, Mike C

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Quantum stabilizer codes and beyond  

E-Print Network (OSTI)

The importance of quantum error correction in paving the way to build a practical quantum computer is no longer in doubt. Despite the large body of literature in quantum coding theory, many important questions, especially those centering on the issue of "good codes" are unresolved. In this dissertation the dominant underlying theme is that of constructing good quantum codes. It approaches this problem from three rather different but not exclusive strategies. Broadly, its contribution to the theory of quantum error correction is threefold. Firstly, it extends the framework of an important class of quantum codes - nonbinary stabilizer codes. It clarifies the connections of stabilizer codes to classical codes over quadratic extension fields, provides many new constructions of quantum codes, and develops further the theory of optimal quantum codes and punctured quantum codes. In particular it provides many explicit constructions of stabilizer codes, most notably it simplifies the criteria by which quantum BCH codes can be constructed from classical codes. Secondly, it contributes to the theory of operator quantum error correcting codes also called as subsystem codes. These codes are expected to have efficient error recovery schemes than stabilizer codes. Prior to our work however, systematic methods to construct these codes were few and it was not clear how to fairly compare them with other classes of quantum codes. This dissertation develops a framework for study and analysis of subsystem codes using character theoretic methods. In particular, this work established a close link between subsystem codes and classical codes and it became clear that the subsystem codes can be constructed from arbitrary classical codes. Thirdly, it seeks to exploit the knowledge of noise to design efficient quantum codes and considers more realistic channels than the commonly studied depolarizing channel. It gives systematic constructions of asymmetric quantum stabilizer codes that exploit the asymmetry of errors in certain quantum channels. This approach is based on a Calderbank- Shor-Steane construction that combines BCH and finite geometry LDPC codes.

Sarvepalli, Pradeep Kiran

2008-08-01T23:59:59.000Z

242

Quantum physics meets biology  

E-Print Network (OSTI)

Quantum physics and biology have long been regarded as unrelated disciplines, describing nature at the inanimate microlevel on the one hand and living species on the other hand. Over the last decades the life sciences have succeeded in providing ever more and refined explanations of macroscopic phenomena that were based on an improved understanding of molecular structures and mechanisms. Simultaneously, quantum physics, originally rooted in a world view of quantum coherences, entanglement and other non-classical effects, has been heading towards systems of increasing complexity. The present perspective article shall serve as a pedestrian guide to the growing interconnections between the two fields. We recapitulate the generic and sometimes unintuitive characteristics of quantum physics and point to a number of applications in the life sciences. We discuss our criteria for a future quantum biology, its current status, recent experimental progress and also the restrictions that nature imposes on bold extrapolations of quantum theory to macroscopic phenomena.

Markus Arndt; Thomas Juffmann; Vlatko Vedral

2009-11-01T23:59:59.000Z

243

Smartphone data safety with quantum cryptography  

NLE Websites -- All DOE Office Websites (Extended Search)

Smartphone data safety with quantum cryptography Smartphone data safety with quantum cryptography Smartphone data safety with quantum cryptography Laws of quantum physics and information theory ensure that smartphones with QKarD could never be compromised. January 20, 2012 The QKarD encodes security keys on a photon using quantum mechanical principles. The miniature transmitter communicates with a trusted authority to generate random cryptographic keys to encode and decode information. The QKarD encodes security keys on a photon using quantum mechanical principles. The laws of quantum physics and information theory ensure that these keys never can be cracked, regardless of advancements in computer technology. New technology brings quantum cryptography to handhelds Laws of quantum physics and information theory ensure that smartphones with

244

Quantum effect on luminosity-redshift relation  

E-Print Network (OSTI)

There are many different proposals for a theory of quantum gravity. Even leaving aside the fundamental difference among theories such as the string theory and the non-perturbative quantum gravity, we are still left with many ambiguities (and/or parameters to be determined) with regard to the choice of variables, the choice of related groups, etc. Loop quantum gravity is also in such a state. It is interesting to search for experimental observables to distinguish these quantum schemes. This paper investigates the loop quantum gravity effect on luminosity-redshift relation. The quantum bounce behavior of loop quantum cosmology is found to result in multivalued correspondence in luminosity-redshift relation. And the detail multivalued behavior can tell the difference of different quantum parameters. The inverse volume quantum correction does not result in bounce behavior in this model, but affects luminosity-redshift relation also significantly.

Li-Fang Li; Jian-Yang Zhu

2010-06-28T23:59:59.000Z

245

Quantum Locality?  

Science Conference Proceedings (OSTI)

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.

Stapp, Henry

2011-11-10T23:59:59.000Z

246

Quantum Automata and Quantum Grammars Cristopher Moore and James P. Crutchfield  

E-Print Network (OSTI)

Quantum Automata and Quantum Grammars Cristopher Moore and James P. Crutchfield Santa Fe Institute, 1399 Hyde Park Road, Santa Fe NM 87501 USA fmoore,jpcg@santafe.edu Abstract. To study quantum computation, it might be helpful to generalize structures from language and automata theory to the quantum

California at Davis, University of

247

Density functional theory study of the conductivity of the biphenalenyl radical dimer  

E-Print Network (OSTI)

We present ab initio molecular calculations at different levels of density functional theory (DFT) for the spiro-biphenalenyl neurtral radical in its singlet and triplet states. We performed calculations on the dimer to ...

Lu, Aiyan

2007-01-01T23:59:59.000Z

248

Quantum irreversible process in a simple model  

E-Print Network (OSTI)

We present a very simple model of a quantum system in which an irreversible process happens. The model can be used as an example of a quantum dynamical problem in introductory courses of Quantum Mechanics or as the introduction to courses on Quantum Irreversible Processes. In both cases it will help students to build some intuition on dynamical behaviour of quantum systems consisting of many degrees of freedom beyond perturbation theory and classical thermodynamics.

Wjcik, Krzysztof Piotr

2012-01-01T23:59:59.000Z

249

Recent advances in the use of density functional theory to design efficient solar energy-based renewable systems  

Science Conference Proceedings (OSTI)

This article reviews the use of Density Functional Theory (DFT) to study the electronic and optical properties of solar-active materials and dyes used in solar energy conversion applications (dye-sensitized solar cells and water splitting). We first give a brief overview of the DFT its development

Ramy Nashed; Yehea Ismail; Nageh K. Allam

2013-01-01T23:59:59.000Z

250

From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity  

E-Print Network (OSTI)

We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity.

Giesel, Kristina

2012-01-01T23:59:59.000Z

251

Quantum Cryptography and Quantum Computation  

E-Print Network (OSTI)

Quantum Cryptography and Quantum Computation Network Security Course Project Report by Hidayath.2 Bases of the Hilbert space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 Quantum principle . . . . . . . . . . . . . . . . . . . . . . 5 3 Quantum Cryptography 6 3.1 The BB84 protocol

North Carolina at Chapel Hill, University of

252

Transforming quantum operations: quantum supermaps  

E-Print Network (OSTI)

We introduce the concept of quantum supermap, describing the most general transformation that maps an input quantum operation into an output quantum operation. Since quantum operations include as special cases quantum states, effects, and measurements, quantum supermaps describe all possible transformations between elementary quantum objects (quantum systems as well as quantum devices). After giving the axiomatic definition of supermap, we prove a realization theorem, which shows that any supermap can be physically implemented as a simple quantum circuit. Applications to quantum programming, cloning, discrimination, estimation, information-disturbance trade-off, and tomography of channels are outlined.

G. Chiribella; G. M. D'Ariano; P. Perinotti

2008-04-01T23:59:59.000Z

253

On the Structure and Geometry of Biomolecular Binding Motifs (Hydrogen-Bonding, Stacking, X-H ?): WFT and DFT Calculations  

DOE Green Energy (OSTI)

The strengths of noncovalent interactions are generally very sensitive to a number of geometric parameters. Among the most important of these parameters is the separation between the interacting moieties (in the case of an intermolecular interaction, this would be the intermolecular separation). Most works seeking to characterize the properties of intermolecular interactions are mainly concerned with binding energies obtained at the potential energy minimum (as determined at some particular level of theory). In this work, in order to extend our understanding of these types of noncovalent interactions, we investigate the distance dependence of several types of intermolecular interactions, these are hydrogen bonds, stacking interactions, dispersion interactions, and X-H ? interactions. There are several methods that have traditionally been used to treat noncovalent interactions as well as many new methods that have emerged within the past three or four years. Here we obtain reference data using estimated CCSD(T) values at the complete basis set limit (using the CBS(T) method); potential energy curves are also produced using several other methods thought to be accurate for intermolecular interactions, these are MP2/ccpVTZ, MP2/aug-cc-pVDZ,MP2/6-31G*(0.25), SCS(MI)-MP2/cc-pVTZ, estimated MP2.5/CBS, DFT-SAPT/ aug-cc-pVTZ, DFT/M06-2X/6-311+G(2df,2p), and DFT-D/TPSS/6-311++G(3df,3pd). The basis set superposition error is systematically considered throughout the study. It is found that the MP2.5 and DFTSAPT methods, which are both quite computationally intensive, produce potential energy curves that are in very good agreement to those of the reference method. Among the MP2 techniques, which can be said to be of medium computational expense, the best results are obtained with MP2/cc-pVTZ and SCS(MI)-MP2/cc-pVTZ. DFT-D/TPSS/6-311++G(3df,3pd) is the DFT-based method that can be said to give the most well-balanced description of intermolecular interactions.

Riley, Kevin E.; Pitonak, Michal; Cerny, Jiri; Hobza, Pavel

2009-12-09T23:59:59.000Z

254

Quantum Exotic PDE's  

E-Print Network (OSTI)

Following the previous works on the A. Pr\\'astaro's formulation of algebraic topology of quantum (super) PDE's, it is proved that a canonical Heyting algebra ({\\em integral Heyting algebra}) can be associated to any quantum PDE. This is directly related to the structure of its global solutions. This allows us to recognize a new inside in the concept of quantum logic for microworlds. Furthermore, the Prastaro's geometric theory of quantum PDE's is applied to the new category of {\\em quantum hypercomplex manifolds}, related to the well-known Cayley-Dickson construction for algebras. Theorems of existence for local and global solutions are obtained for (singular) PDE's in this new category of noncommutative manifolds. Finally the extension of the concept of exotic PDE's, recently introduced by A.Pr\\'astaro, has been extended to quantum PDE's. Then a smooth quantum version of the quantum (generalized) Poincar\\'e conjecture is given too. These results extend ones for quantum (generalized) Poincar\\'e conjecture, previously given by A. Pr\\'astaro.

Agostino Prstaro

2011-06-04T23:59:59.000Z

255

Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies  

E-Print Network (OSTI)

We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory (QFT). QFT properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in QFT including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects.

Mehdi Ahmadi; David Edward Bruschi; Nicolai Friis; Carlos Sabn; Gerardo Adesso; Ivette Fuentes

2013-07-26T23:59:59.000Z

256

Theory of Interacting Quantum Gases  

Science Conference Proceedings (OSTI)

... superfluid helium film, ii) the surface recombination rate is much larger, and iii) the sample is contaminated with atomic hydro- gen [5 ... 14] CAR S de ...

2010-08-23T23:59:59.000Z

257

Types of quantum information  

E-Print Network (OSTI)

Quantum, in contrast to classical, information theory, allows for different incompatible types (or species) of information which cannot be combined with each other. Distinguishing these incompatible types is useful in understanding the role of the two classical bits in teleportation (or one bit in one-bit teleportation), for discussing decoherence in information-theoretic terms, and for giving a proper definition, in quantum terms, of ``classical information.'' Various examples (some updating earlier work) are given of theorems which relate different incompatible kinds of information, and thus have no counterparts in classical information theory.

Robert B. Griffiths

2007-07-25T23:59:59.000Z

258

Communication: Quantum mechanics without wavefunctions  

SciTech Connect

We present a self-contained formulation of spin-free non-relativistic quantum mechanics that makes no use of wavefunctions or complex amplitudes of any kind. Quantum states are represented as ensembles of real-valued quantum trajectories, obtained by extremizing an action and satisfying energy conservation. The theory applies for arbitrary configuration spaces and system dimensionalities. Various beneficial ramifications--theoretical, computational, and interpretational--are discussed.

Schiff, Jeremy [Department of Mathematics, Bar-Ilan University, Ramat Gan 52900 (Israel); Poirier, Bill [Department of Chemistry and Biochemistry, Texas Tech University, Box 41061, Lubbock, Texas 79409-1061 (United States) and Department of Physics, Texas Tech University, Box 41051, Lubbock, Texas 79409-1051 (United States)

2012-01-21T23:59:59.000Z

259

The Spacetime of Double Field Theory: Review, Remarks, and Outlook  

E-Print Network (OSTI)

We review double field theory (DFT) with emphasis on the doubled spacetime and its generalized coordinate transformations, which unify diffeomorphisms and b-field gauge transformations. We illustrate how the composition of generalized coordinate transformations fails to associate. Moreover, in dimensional reduction, the O(d,d) T-duality transformations of fields can be obtained as generalized diffeomorphisms. Restricted to a half-dimensional subspace, DFT includes `generalized geometry', but is more general in that local patches of the doubled space may be glued together with generalized coordinate transformations. Indeed, we show that for certain T-fold backgrounds with non-geometric fluxes, there are generalized coordinate transformations that induce, as gauge symmetries of DFT, the requisite O(d,d;Z) monodromy transformations. Finally we review recent results on the \\alpha' extension of DFT which, reduced to the half-dimensional subspace, yields intriguing modifications of the basic structures of generalized geometry.

Olaf Hohm; Dieter Lust; Barton Zwiebach

2013-09-11T23:59:59.000Z

260

Quantum fields with topological defects  

E-Print Network (OSTI)

Domain walls, strings and monopoles are extended objects, or defects, of quantum origin with topologically non--trivial properties and macroscopic behavior. They are described in Quantum Field Theory in terms of inhomogeneous condensates. We review the related formalism in the framework of the spontaneous breakdown of symmetry.

M. Blasone; P. Jizba; G. Vitiello

2004-02-13T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Quantum computation and cryptography: an overview  

Science Conference Proceedings (OSTI)

The new Quantum Information Theory augurs powerful machines that obey the "entangled" logic of the subatomic world. Parallelism, entanglement, teleportation, no-cloning and quantum cryptography are typical peculiarities of this novel way of understanding ... Keywords: Algorithms, Cryptography, Entanglement, Logic gates, Parallelism, Quantum computing, Teleportation

Manuel Calixto

2009-12-01T23:59:59.000Z

262

Simulating chemistry using quantum computers  

E-Print Network (OSTI)

The difficulty of simulating quantum systems, well-known to quantum chemists, prompted the idea of quantum computation. One can avoid the steep scaling associated with the exact simulation of increasingly large quantum systems on conventional computers, by mapping the quantum system to another, more controllable one. In this review, we discuss to what extent the ideas in quantum computation, now a well-established field, have been applied to chemical problems. We describe algorithms that achieve significant advantages for the electronic-structure problem, the simulation of chemical dynamics, protein folding, and other tasks. Although theory is still ahead of experiment, we outline recent advances that have led to the first chemical calculations on small quantum information processors.

Ivan Kassal; James D. Whitfield; Alejandro Perdomo-Ortiz; Man-Hong Yung; Aln Aspuru-Guzik

2010-07-15T23:59:59.000Z

263

Quantum polar codes for arbitrary channels  

E-Print Network (OSTI)

We construct a new entanglement-assisted quantum polar coding scheme which achieves the symmetric coherent information rate by synthesizing "amplitude" and "phase" channels from a given, arbitrary quantum channel. We first demonstrate the coding scheme for arbitrary quantum channels with qubit inputs, and we show that quantum data can be reliably decoded by O(N) rounds of coherent quantum successive cancellation, followed by N controlled-NOT gates (where N is the number of channel uses). We also find that the entanglement consumption rate of the code vanishes for degradable quantum channels. Finally, we extend the coding scheme to channels with multiple qubit inputs. This gives a near-explicit method for realizing one of the most striking phenomena in quantum information theory: the superactivation effect, whereby two quantum channels which individually have zero quantum capacity can have a non-zero quantum capacity when used together.

Wilde, Mark M

2012-01-01T23:59:59.000Z

264

Channel simulation with quantum side information  

E-Print Network (OSTI)

We study and solve the problem of classical channel simulation with quantum side information at the receiver. This is a generalization of both the classical reverse Shannon theorem, and the classical-quantum Slepian-Wolf problem. The optimal noiseless communication rate is found to be reduced from the mutual information between the channel input and output by the Holevo information between the channel output and the quantum side information. Our main theorem has two important corollaries. The first is a quantum generalization of the Wyner-Ziv problem: rate-distortion theory with quantum side information. The second is an alternative proof of the trade-off between classical communication and common randomness distilled from a quantum state. The fully quantum generalization of the problem considered is quantum state redistribution. Here the sender and receiver share a mixed quantum state and the sender wants to transfer part of her state to the receiver using entanglement and quantum communication. We present o...

Luo, Z; Devetak, Igor; Luo, Zhicheng

2006-01-01T23:59:59.000Z

265

Materials Theory, Modeling and Simulation | ORNL  

NLE Websites -- All DOE Office Websites (Extended Search)

Functional Materials for Energy Chemistry and Physics at Interfaces Materials Synthesis from Atoms to Systems Materials Characterization Materials Theory and Simulation Quantum...

266

A Criterion for Holism in Quantum Mechanics  

E-Print Network (OSTI)

A Criterion for Holism in Quantum Mechanics M.P Seevinck Utrecht University, The Netherlands, June 2003. 1 #12; Motivation · The question whether or not quantum mechanics (QM) gives rise to some mechanics a holistic theory (if so), and other physical theories not (if so). · I propose an operational

Seevinck, Michiel

267

A Criterion for Holism in Quantum Mechanics  

E-Print Network (OSTI)

A Criterion for Holism in Quantum Mechanics # M.P Seevinck # # Utrecht University, The Netherlands, June 2003. # 1 #12; # Motivation # . The question whether or not quantum mechanics (QM) gives rise mechanics a holistic theory (if so), and other physical theories not (if so). . I propose an operational

Seevinck, Michiel

268

Quantum discord  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum discord Quantum discord 1663 Los Alamos science and technology magazine Latest Issue:November 2013 All Issues » submit Quantum discord A distinguishing aspect of quantum mechanics discovered at Los Alamos that may be critical to building a quantum computer March 25, 2013 Spinning coins turning into binary numbers Quantum computing Quantum computing can be carried out without the delicate entanglement of qubits previously believed to be necessary Quantum computing, in which quantum bits of information (or qubits) juggle a "superposition" of multiple values simultaneously, offers to unleash tremendous computational power if the qubits can be effectively isolated to prevent decoherence: information describing quantum states dispersing into the environment. But recent research has shown that quantum computing can be carried out

269

Quantum Institute  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum Institute 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 cryptography, quantum computing, quantum metrology, and advanced quantum-based sensors, some of which are directly relevant to the Laboratory's national security mission. Mission Foster a vigorous intellectual environment at LANL Define and develop strategic thrusts Target and pursue funding opportunities

270

The Echo of the Quantum Bounce  

E-Print Network (OSTI)

We identify a signature of quantum gravitational effects that survives from the early universe to the current era: Fluctuations of quantum fields as seen by comoving observers are significantly influenced by the history of the early universe. In particular we will show how the existence (or not) of a quantum bounce leaves a trace in the background quantum noise that is not damped and would be non-negligible even nowadays. Furthermore, we will estimate an upper bound to the typical energy and length scales where quantum effects are relevant. We will discuss how this signature might be observed and therefore used to build falsifiability tests of quantum gravity theories.

Luis J. Garay; Mercedes Martin-Benito; Eduardo Martin-Martinez

2013-08-20T23:59:59.000Z

271

Quantum Tachyon Dynamics  

E-Print Network (OSTI)

It is suggested that charged tachyons of extremely large mass M could not only contribute to the dark matter needed to fit astrophysical observations, but could also provide an explanation for gamma ray bursts and ultra high energy cosmic rays. The present paper defines a quantum field theory of tachyons, the latter similar to ordinary leptons, but with momenta larger than energy.

H. M. Fried; Y. Gabellini

2005-05-31T23:59:59.000Z

272

Quantitative Vapor-phase IR Intensities and DFT Computations to Predict Absolute IR Spectra based on Molecular Structure: I. Alkanes  

SciTech Connect

Recently recorded quantitative IR spectra of a variety of gas-phase alkanes are shown to have integrated intensities in both the C-H stretching and C-H bending regions that depend linearly on the molecular size, i.e. the number of C-H bonds. This result is well predicted from CH4 to C15H32 by DFT computations of IR spectra at the B3LYP/6-31+G(d,p) level of DFT theory. A simple model predicting the absolute IR band intensities of alkanes based only on structural formula is proposed: For the C-H stretching band near 2930 cm-1 this is given by (in km/mol): CH_str = (343)*CH (4160) where CH is number of C-H bonds in the alkane. The linearity is explained in terms of coordinated motion of methylene groups rather than the summed intensities of autonomous -CH2- units. The effect of alkyl chain length on the intensity of a C-H bending mode is explored and interpreted in terms of conformer distribution. The relative intensity contribution of a methyl mode compared to the total C-H stretch intensity is shown to be linear in the number of terminal methyl groups in the alkane, and can be used to predict quantitative spectra a priori based on structure alone.

Williams, Stephen D.; Johnson, Timothy J.; Sharpe, Steven W.; Yavelak, Veronica; Oats, R. P.; Brauer, Carolyn S.

2013-11-13T23:59:59.000Z

273

Quantum Criticality and Black Holes  

SciTech Connect

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.

Sachdev, Subir (Harvard)

2007-08-22T23:59:59.000Z

274

EERE PROJECT MANAGEMENT CENTER NFPA DFT1!lUIINATION  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

OFEN:rRGY OFEN:rRGY EERE PROJECT MANAGEMENT CENTER NFPA DFT1!lUIINATION Page 1 of2 RECIPIENT:Middlesex Community College STATE: MA PROJECf TITLE: Middlesex Community College - Geothermal Project Funding Opportunity Announcement Number Procurement Instrument Number NEPA Control Number CID Number N/A DE-EEOOOO323 GF0-0000323-002 EE323 Based on my review ofthe information concerning the proposed action, as NEPA Compliance Officer (authorized under DOE Order 4SI.IA), I have made the following determination: ex, EA, EIS APPENDIX AND NUMBER: Description: A9 Inf ormation gathering, analYSiS, and dissemination 82.1 Workplace enhancements B2.2 Building and equipment instrumentation Information gathering (including, but not limited to, literature surveys, inventories, site visits, and audils),

275

Bohmian Mechanics and Quantum Information  

E-Print Network (OSTI)

Many recent results suggest that quantum theory is about information, and that quantum theory is best understood as arising from principles concerning information and information processing. At the same time, by far the simplest version of quantum mechanics, Bohmian mechanics, is concerned, not with information but with the behavior of an objective microscopic reality given by particles and their positions. What I would like to do here is to examine whether, and to what extent, the importance of information, observation, and the like in quantum theory can be understood from a Bohmian perspective. I would like to explore the hypothesis that the idea that information plays a special role in physics naturally emerges in a Bohmian universe.

Sheldon Goldstein

2009-07-14T23:59:59.000Z

276

Oriented Quantum Algebras and Coalgebras, Invariants of Oriented 1-1 Tangles, Knots and Links  

E-Print Network (OSTI)

In this paper we study oriented quantum coalgebras which are structures closely related to oriented quantum algebras. We study the relationship between oriented quantum coalgebras and oriented quantum algebras and the relationship between oriented quantum coalgebras and quantum coalgebras. We show that there are regular isotopy invariants of oriented 1-1 tangles and of oriented knots and links associated to oriented and twist oriented quantum coalgebras respectively. There are many parallels between the theory of oriented quantum coalgebras and the theory of quantum coalgebras

Kauffman, Louis

2010-01-01T23:59:59.000Z

277

Geometrical Characterization of Adenine And Guanine on Cu(110) By NEXAFS, XPS, And DFT Calculation  

Science Conference Proceedings (OSTI)

Adsorption of purine DNA bases (guanine and adenine) on Cu(1 1 0) was studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine-structure spectroscopy (NEXAFS), and density-functional theory (DFT) calculation. At coverages near 0.2 monolayers, Angular-resolved NEXAFS analysis revealed that adenine adsorbates lie almost flat and that guanine adsorbates are tilted up on the surface with the purine ring parallel to the atom rows of Cu(1 1 0). Referring to the previous studies on pyrimidine DNA bases [M. Furukawa, H. Fujisawa, S. Katano, H. Ogasawara, Y. Kim, T. Komeda, A. Nilsson, M. Kawai, Surf. Sci. 532-535 (2003) 261], the isomerization of DNA bases on Cu(1 1 0) was found to play an important role in the adsorption geometry. Guanine, thymine and cytosine adsorption have an amine-type nitrogen next to a carbonyl group, which is dehydrogenated into imine nitrogen on Cu(1 1 0). These bases are bonded by the inherent portion of - NH-CO - altered by conversion into enolic form and dehydrogenation. Adenine contains no CO group and is bonded to Cu(1 1 0) by participation of the inherent amine parts, resulting in nearly flatly-lying position.

Furukawa, M.; Yamada, T.; /Wako, RIKEN; Katano, S.; /tohoku U.; Kawai, M.; /Wako, RIKEN /Tokyo U.; Ogasawara, H.; /SLAC, SSRL; Nilsson, A.; /SLAC, SSRL /Stockholm U.

2009-04-30T23:59:59.000Z

278

Accuracy of density functional theory in predicting formation energies of ternary oxides from binary oxides and its implication on phase stability  

E-Print Network (OSTI)

The evaluation of reaction energies between solids using density functional theory (DFT) is of practical importance in many technological fields and paramount in the study of the phase stability of known and predicted ...

Hautier, Geoffroy

279

Intervalley splittings of Si quantum wells  

E-Print Network (OSTI)

Multi-valley effective mass theory for silicon quantum well structure is studied taking into account the external fields and the quantum interfaces. It is found that the phenomenological delta function potential, employed to explain the valley splitting caused by the quantum well interface in the previous work [Ref. 10], can be derived self-consistently from the multi-valley effective mass theory. Finite element method is used to solve the multi-valley effective equations. Theoretical predictions are in a reasonably good agreement with the recent experimental observation of valley splitting in a SiO_{2}/Si/SiO_{2} quantum well, which prove the validity of our approach.

S. -H. Park; Y. Y. Lee; Doyeol Ahn

2007-11-05T23:59:59.000Z

280

Quantum capacity under adversarial quantum noise: arbitrarily varying quantum channels  

E-Print Network (OSTI)

We investigate entanglement transmission over an unknown channel in the presence of a third party (called the adversary), which is enabled to choose the channel from a given set of memoryless but non-stationary channels without informing the legitimate sender and receiver about the particular choice that he made. This channel model is called arbitrarily varying quantum channel (AVQC). We derive a quantum version of Ahlswede's dichotomy for classical arbitrarily varying channels. This includes a regularized formula for the common randomness-assisted capacity for entanglement transmission of an AVQC. Quite surprisingly and in contrast to the classical analog of the problem involving the maximal and average error probability, we find that the capacity for entanglement transmission of an AVQC always equals its strong subspace transmission capacity. These results are accompanied by different notions of symmetrizability (zero-capacity conditions) as well as by conditions for an AVQC to have a capacity described by a single-letter formula. In he final part of the paper the capacity of the erasure-AVQC is computed and some light shed on the connection between AVQCs and zero-error capacities. Additionally, we show by entirely elementary and operational arguments motivated by the theory of AVQCs that the quantum, classical, and entanglement-assisted zero-error capacities of quantum channels are generically zero and are discontinuous at every positivity point.

Rudolf Ahlswede; Igor Bjelakovic; Holger Boche; Janis Noetzel

2010-10-03T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Divergences of generalized quantum electrodynamics on the Lorenz gauge  

Science Conference Proceedings (OSTI)

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.

Bufalo, R.; Pimentel, B. M. [Instituto de Fisica Teorica, UNESP - Sao Paulo State University P. O. Box 70532-2, 01156-970, Sao Paulo, SP (Brazil); Zambrano, G. E. [Departamento de Fisica, Universidad de Narino Calle 18 Carrera 50, San Juan de Pasto, Narino (Colombia)

2013-03-25T23:59:59.000Z

282

Quantum Espresso/PWscf at NERSC  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum ESPRESSO/PWscf Quantum ESPRESSO/PWscf Quantum ESPRESSO/PWscf Description Quantum ESPRESSO is an integrated suite of computer codes for electronic structure calculations and materials modeling at the nanoscale. It builds on the electronic structure codes PWscf, PHONON, CP90, FPMD, and Wannier. It is based on density-functional theory, plane waves, and pseudopotentials (both norm-conserving and ultrasoft). How to Access Quantum ESPRESSO NERSC uses modules to manage access to software. To use the default version of Espresso, type: % module load espresso Using Quantum ESPRESSO on a Cray System There are two ways of running Quantum ESPRESSO on a Cray system: submitting a batch job, or running interactively in an interactive batch session. Sample batch script to run Quantum ESPRESSO on Hopper:

283

Simultaneous classical-quantum capacities of quantum multiple access channels  

E-Print Network (OSTI)

The rates at which classical and quantum information can be simultaneously transmitted from two spatially separated senders to a single receiver over an arbitrary quantum channel are characterized. Two main results are proved in detail. The first describes the region of rates at which one sender can send classical information while the other sends quantum information. The second describes those rates at which both senders can send quantum information. For each of these situations, an example of a channel is given for which the associated region admits a single-letter description. This is the author's Ph.D. dissertation, submitted to the Department of Electrical Engineering at Stanford University in March, 2005. It represents an expanded version of the paper quant-ph/0501045, containing a number of tutorial chapters which may be of independent interest for those learning about quantum Shannon theory.

Jon Yard

2005-06-06T23:59:59.000Z

284

Fast plane wave density functional theory molecular dynamics calculations on multi-GPU machines  

Science Conference Proceedings (OSTI)

Plane wave pseudopotential (PWP) density functional theory (DFT) calculation is the most widely used method for material simulations, but its absolute speed stagnated due to the inability to use large scale CPU based computers. By a drastic redesign ... Keywords: Density functional theory, Electronic structure, First-principles, GPU, Molecular dynamics, Plane wave pseudopotential

Weile Jia, Jiyun Fu, Zongyan Cao, Long Wang, Xuebin Chi, Weiguo Gao, Lin-Wang Wang

2013-10-01T23:59:59.000Z

285

Quantum Information Portal  

Science Conference Proceedings (OSTI)

... Quantum Devices; Quantum Information Technology; Quantum Key Distribution; ... Entangled photon generation in a phase-modulated, quasi ...

2013-10-23T23:59:59.000Z

286

Quantum Weak Measurements and Cosmology  

E-Print Network (OSTI)

The indeterminism of quantum mechanics generally permits the independent specification of both an initial and a final condition on the state. Quantum pre-and-post-selection of states opens up a new, experimentally testable, sector of quantum mechanics, when combined with statistical averages of identical weak measurements. In this paper I apply the theory of weak quantum measurements combined with pre-and-post-selection to cosmology. Here, pre-selection means specifying the wave function of the universe or, in a popular semi-classical approximation, the initial quantum state of a subset of quantum fields propagating in a classical back-ground spacetime. The novel feature is post-selection: the additional specification of a condition on the quantum state in the far future. I discuss "natural" final conditions, and show how they may lead to potentially large and observable effects at the present cosmological epoch. I also discuss how pre-and-post-selected quantum contrast to the expectation value of the stress-energy-momentum tensor, resolving a vigorous debate from the 1970's. The paper thus provides a framework for computing large-scale cosmological effects arising from this new sector of quantum mechanics. A simple experimental test is proposed.

Paul Davies

2013-09-03T23:59:59.000Z

287

Joint probabilities and quantum cognition  

E-Print Network (OSTI)

In this paper we discuss the existence of joint probability distributions for quantum-like response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.

J. Acacio de Barros

2012-06-26T23:59:59.000Z

288

The Quantum Zeno Effect -- Watched Pots in the Quantum World  

E-Print Network (OSTI)

In the 5th century B.C.,the philosopher and logician Zeno of Elea posed several paradoxes which remained unresolved for over two thousand five hundred years. The $20^{th}$ century saw some resolutions to Zeno's mind boggling problems. This long journey saw many significant milestones in the form of discoveries like the tools of converging series and theories on infinite sets in mathematics. In recent times, the Zeno effect made an intriguing appearance in a rather unlikely place - a situation involving the time evolution of a quantum system, which is subject to "observations" over a period of time. Leonid Khalfin working in the former USSR in the 1960s and ECG Sudarshan and B. Misra at the University of Texas, Austin, first drew attention to this problem. In 1977, ECG Sudarshan and B. Misra published a paper on the quantum Zeno effect, called "The Zeno's paradox in quantum theory". Their fascinating result revealed the bizarre workings of the quantum world. Misra and Sudarshan's 1977 paper activated over two decades of theoretical and experimental explorations into the subject and still continues to evoke a lot of interest. In the following, the quantum Zeno effect is described and a brief outline of some of the work following Misra and Sudarshan's paper is given. The quantum Zeno effect is yet another example of the myriad unimaginable possibilities that lie waiting in the magical world of the quantum.

Anu Venugopalan

2012-11-15T23:59:59.000Z

289

Entanglement Cost of Quantum Channels  

E-Print Network (OSTI)

The entanglement cost of a quantum channel is the minimal rate at which entanglement (between sender and receiver) is needed in order to simulate many copies of a quantum channel in the presence of free classical communication. In this paper we show how to express this quantity as a regularized optimization of the entanglement formation over states that can be generated between sender and receiver. Our formula is the channel analog of a well-known formula for the entanglement cost of quantum states in terms of the entanglement of formation; and shares a similar relation to the recently shattered hope for additivity. The entanglement cost of a quantum channel can be seen as the analog of the quantum reverse Shannon theorem in the case where free classical communication is allowed. The techniques used in the proof of our result are then also inspired by a recent proof of the quantum reverse Shannon theorem and feature the one-shot formalism for quantum information theory, the post-selection technique for quantum channels as well as von Neumann's minimax theorem. We discuss two applications of our result. First, we are able to link the security in the noisy-storage model to a problem of sending quantum rather than classical information through the adversary's storage device. This not only improves the range of parameters where security can be shown, but also allows us to prove security for storage devices for which no results were known before. Second, our result has consequences for the study of the strong converse quantum capacity. Here, we show that any coding scheme that sends quantum information through a quantum channel at a rate larger than the entanglement cost of the channel has an exponentially small fidelity.

Mario Berta; Fernando Brandao; Matthias Christandl; Stephanie Wehner

2011-08-26T23:59:59.000Z

290

Measurement of Quantum Fluctuations in Geometry  

E-Print Network (OSTI)

A phenomenological calculation is presented of the effect of quantum fluctuations in the spacetime metric, or holographic noise, on interferometeric measurement of the relative positions of freely falling proof masses, in theories where spacetime satisfies covariant entropy bounds and can be represented as a quantum theory on 2+1D null surfaces. The quantum behavior of the 3+1D metric, represented by a commutation relation expressing quantum complementarity between orthogonal position operators, leads to a parameter-free prediction of quantum noise in orthogonal position measurements of freely falling masses. A particular quantum weirdness of this holographic noise is that it only appears in measurements that compare transverse positions, and does not appear at all in purely radial position measurements. The effect on phase signal in an interferometer that continuously measures the difference in the length of orthogonal arms resembles that of a classical random Brownian motion of the beamsplitter with a Planc...

Hogan, Craig J

2007-01-01T23:59:59.000Z

291

Probable Inference and Quantum Mechanics  

SciTech Connect

In its current very successful interpretation the quantum theory is fundamentally statistical in nature. Although commonly viewed as a probability amplitude whose (complex) square is a probability, the wavefunction or state vector continues to defy consensus as to its exact meaning, primarily because it is not a physical observable. Rather than approach this problem directly, it is suggested that it is first necessary to clarify the precise role of probability theory in quantum mechanics, either as applied to, or as an intrinsic part of the quantum theory. When all is said and done the unsurprising conclusion is that quantum mechanics does not constitute a logic and probability unto itself, but adheres to the long-established rules of classical probability theory while providing a means within itself for calculating the relevant probabilities. In addition, the wavefunction is seen to be a description of the quantum state assigned by an observer based on definite information, such that the same state must be assigned by any other observer based on the same information, in much the same way that probabilities are assigned.

Grandy, W. T. Jr. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82070 (United States)

2009-12-08T23:59:59.000Z

292

Application of quantum chemical calculations to two non-trivial cases in the field of molecular spectroscopy  

Science Conference Proceedings (OSTI)

In this paper, we illustrate the contribution of the quantum chemical calculations to the simulation of two types of spectra. In a first part, the calculations of theoretical resonance Raman spectra of transient species are presented. The comparison ... Keywords: Resonance raman intensity, TD-DFT, metal complexation, reaction pathway, transient species

C. Lapouge; J. P. Cornard

2009-04-01T23:59:59.000Z

293

Quantum chaos in elementary quantum mechanics  

E-Print Network (OSTI)

chaos in elementary quantum mechanics so-called integrableIntroduction to Quantum Mechanics (Englewoods Cliff, NJ:Lifshitz E M 1977 Quantum Mechanics (New York: Pergamon) [

Dabaghian, Yuri A; Jensen, R

2005-01-01T23:59:59.000Z

294

From quantum graphs to quantum random walks  

E-Print Network (OSTI)

We give a short overview over recent developments on quantum graphs and outline the connection between general quantum graphs and so-called quantum random walks.

Gregor Tanner

2005-04-29T23:59:59.000Z

295

Thermodynamics of space quanta models quantum gravity  

E-Print Network (OSTI)

Canonically quantized 3+1 general relativity with the global one dimensionality (1D) conjecture defines the model, which dimensionally reduced and secondary quantized yields the 1D quantum field theory wherein generic one-point correlations create physical scales. This simple quantum gravity model, however, can be developed in a wider sense. In this paper we propose to consider ab initio thermodynamics of space quanta as the quantum gravity phenomenology. The thermodynamics is constructed in the entropic formalism.

L. A. Glinka

2009-06-20T23:59:59.000Z

296

Guest column: the quantum PCP conjecture  

Science Conference Proceedings (OSTI)

The classical PCP theorem is arguably the most important achievement of classical complexity theory in the past quarter century. In recent years, researchers in quantum computational complexity have tried to identify approaches and develop tools that ...

Dorit Aharonov; Itai Arad; Thomas Vidick

2013-06-01T23:59:59.000Z

297

Quantum Mechanics and the Generalized Uncertainty Principle  

E-Print Network (OSTI)

The generalized uncertainty principle has been described as a general consequence of incorporating a minimal length from a theory of quantum gravity. We consider a simple quantum mechanical model where the operator corresponding to position has discrete eigenvalues and show how the generalized uncertainty principle results for minimum uncertainty wave packets.

Jang Young Bang; Micheal S. Berger

2006-10-11T23:59:59.000Z

298

Duality Symmetric String and M-Theory  

E-Print Network (OSTI)

We review recent developments in duality symmetric string theory. We begin with the world sheet doubled formalism which describes strings in an extended space time with extra coordinates conjugate to winding modes. This formalism is T-duality symmetric and can accommodate non-geometric T-fold backgrounds which are beyond the scope of Riemannian geometry. Vanishing of the conformal anomaly of this theory can be interpreted as a set of spacetime equations for the background fields. These equations follow from an action principle that has been dubbed Double Field Theory (DFT). We review the aspects of generalised geometry relevant for DFT. We outline recent extensions of DFT and explain how, by relaxing the so-called strong constraint with a Scherk Schwarz ansatz, one can obtain backgrounds that simultaneously depend on both the regular and T-dual coordinates. This provides a purely geometric higher dimensional origin to gauged supergravities that arise from non-geometric compactification. We then turn to M-theory and describe recent progress in formulating an E_{n(n)} U-duality covariant description of the dynamics. We describe how spacetime may be extended to accommodate coordinates conjugate to brane wrapping modes and the construction of generalised metrics in this extend space that unite the bosonic fields of supergravity into a single object. We review the action principles for these theories and their novel gauge symmetries. We also describe how a Scherk Schwarz reduction can be applied in the M-theory context and the resulting relationship to the embedding tensor formulation of maximal gauged supergravities.

David S. Berman; Daniel C. Thompson

2013-06-11T23:59:59.000Z

299

Functional quantum biology in photosynthesis and magnetoreception  

E-Print Network (OSTI)

Is there a functional role for quantum mechanics or coherent quantum effects in biological processes? While this question is as old as quantum theory, only recently have measurements on biological systems on ultra-fast time-scales shed light on a possible answer. In this review we give an overview of the two main candidates for biological systems which may harness such functional quantum effects: photosynthesis and magnetoreception. We discuss some of the latest evidence both for and against room temperature quantum coherence, and consider whether there is truly a functional role for coherence in these biological mechanisms. Finally, we give a brief overview of some more speculative examples of functional quantum biology including the sense of smell, long-range quantum tunneling in proteins, biological photoreceptors, and the flow of ions across a cell membrane.

Lambert, Neill; Cheng, Yuan-Chung; Li, Che-Ming; Chen, Guang-Yin; Nori, Franco

2012-01-01T23:59:59.000Z

300

Functional quantum biology in photosynthesis and magnetoreception  

E-Print Network (OSTI)

Is there a functional role for quantum mechanics or coherent quantum effects in biological processes? While this question is as old as quantum theory, only recently have measurements on biological systems on ultra-fast time-scales shed light on a possible answer. In this review we give an overview of the two main candidates for biological systems which may harness such functional quantum effects: photosynthesis and magnetoreception. We discuss some of the latest evidence both for and against room temperature quantum coherence, and consider whether there is truly a functional role for coherence in these biological mechanisms. Finally, we give a brief overview of some more speculative examples of functional quantum biology including the sense of smell, long-range quantum tunneling in proteins, biological photoreceptors, and the flow of ions across a cell membrane.

Neill Lambert; Yueh-Nan Chen; Yuan-Chung Cheng; Che-Ming Li; Guang-Yin Chen; Franco Nori

2012-05-04T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Theory and fabrication of evanescently-coupled photoluminescent devices  

E-Print Network (OSTI)

This thesis discusses the theory and implementation of evanescently-coupled photoluminescent devices. We demonstrate the feasibility of efficient, spectrally tunable lighting devices through quantum dot photoluminescence. ...

Friend, David Harry

2008-01-01T23:59:59.000Z

302

Quantum Communications  

Science Conference Proceedings (OSTI)

... In summary, we perform research and development (R&D) in quantum communication and related measurement areas with an emphasis on ...

2013-07-24T23:59:59.000Z

303

Quantum Electrical Measurements Portal  

Science Conference Proceedings (OSTI)

NIST Home > Quantum Electrical Measurements Portal. Quantum Electrical Measurements Portal. Subject Areas. Electrical ...

2013-03-21T23:59:59.000Z

304

Background Independent Quantum Mechanics, Classical Geometric Forms and Geometric Quantum Mechanics-I  

E-Print Network (OSTI)

The geometry of the symplectic structures and Fubini-Study metric is discussed. Discussion in the paper addresses geometry of Quantum Mechanics in the classical phase space. Also, geometry of Quantum Mechanics in the projective Hilbert space has been discussed for the chosen Quantum states. Since the theory of classical gravity is basically geometric in nature and Quantum Mechanics is in no way devoid of geometry, the explorations pertaining to more and more geometry in Quantum Mechanics could prove to be valuable for larger objectives such as understanding of gravity.

Aalok Pandya

2008-09-08T23:59:59.000Z

305

A lossy transmission line as a quantum open system in the standard quantum limit  

E-Print Network (OSTI)

We systematically investigate how to quantize a transmission line resonator (TLR) in a mesoscopic electrical circuits in the presence of the resistance and the conductance of the dielectric media. Developed from the quantum bath based effective Hamiltonian method for single mode harmonic oscillator, the approach we presented in this article is a microscopic theory integrating quantum fluctuation-dissipation relation. To qualitatively check the condition under which the TLR can behave as a quantum object we study the classical-quantum boundary characterized by the standard quantum limit.

Y. D. Wang; C. P. Sun

2004-06-30T23:59:59.000Z

306

From ab initio quantum chemistry to molecular dynamics: The delicate case of hydrogen bonding in ammonia  

E-Print Network (OSTI)

The ammonia dimer (NH3)2 has been investigated using high--level ab initio quantum chemistry methods and density functional theory (DFT). The structure and energetics of important isomers is obtained to unprecedented accuracy without resorting to experiment. The global minimum of eclipsed C_s symmetry is characterized by a significantly bent hydrogen bond which deviates from linearity by about 20 degrees. In addition, the so-called cyclic C_{2h} structure is extremely close in energy on an overall flat potential energy surface. It is demonstrated that none of the currently available (GGA, meta--GGA, and hybrid) density functionals satisfactorily describe the structure and relative energies of this nonlinear hydrogen bond. We present a novel density functional, HCTH/407+, designed to describe this sort of hydrogen bond quantitatively on the level of the dimer, contrary to e.g. the widely used BLYP functional. This improved functional is employed in Car-Parrinello ab initio molecular dynamics simulations of liq...

Boese, A D; Martin, J M L; Marx, D; Chandra, Amalendu; Martin, Jan M.L.; Marx, Dominik

2003-01-01T23:59:59.000Z

307

Nuclear quantum effects in the structure and lineshapes of the N2 NEXAFS spectrum  

SciTech Connect

We study the relative ability of several models of the X-ray absorption spectrum to capture the Franck-Condon structure apparent from an experiment on gaseous nitrogen. In doing so, we adopt the Born-Oppenheimer approximation and a constrained density functional theory method for computing the energies of the X-ray-excited molecule. Starting from an otherwise classical model for the spectrum, we systematically introduce more realistic physics, first by substituting the quantum mechanical nuclear radial density in the bond separation R for the classical radial density, then by adding the effect of zero-point energy and other level shifts, and finally by including explicit rovibrational quantization of both the ground and excited states. The quantization is determined exactly, using a discrete variable representation. We show that the NEXAFS spectrum can be predicted semiquantiatively within this framework. We also address the possibility of non-trivial temperature dependence in the spectrum. Finally, we show that it is possible to improve the predicted spectrum by using constrained DFT in combination with more accurate potentials.

Fatehi, Shervin; Schwartz, Craig P.; Saykally, Richard J.; Prendergast, David

2009-12-04T23:59:59.000Z

308

Quantum Networks for Generating Arbitrary Quantum States  

E-Print Network (OSTI)

Quantum protocols often require the generation of specific quantum states. We describe a quantum algorithm for generating any prescribed quantum state. For an important subclass of states, including pure symmetric states, this algorithm is efficient.

Phillip Kaye; Michele Mosca

2004-07-14T23:59:59.000Z

309

Development of the quantum theory of T-odd asymmetries for prescission and evaporated third particles in ternary nuclear fission induced by cold polarized neutrons  

Science Conference Proceedings (OSTI)

A comparative analysis of the results obtained by experimentally and theoretically studying T-odd asymmetries for various third particles in the true and delayed ternary nuclear fission induced by cold polarized neutrons was performed. It was confirmed that the appearance of these asymmetries was associated with the effect of rotation of a polarized system undergoing fission on the angular distributions of prescission and evaporated third particles with respect to the direction along which the emerging fission fragments flew apart, this effect being determined by the Coriolis interaction of the rotational and the internalmotion of the fissioning system. A quantum-mechanical description of particle motion in a rotating coordinate system was generalized to the case where gamma-ray emission was present. It was shown that the separation of the motions of an axially symmetric fissile system into a rotational and an internal motion was valid in the external region as well, where ternary-fission products had already been formed, if it was considered that the motion of fission fragments was tightly connected with the system symmetry axis, which rotated in the laboratory frame. It was found that the dependence of the fissile-system moment of inertia appearing in the Coriolis interaction Hamiltonian on the distance between the fission fragments flying apart generated an additional phase in the amplitude of the radial distribution of fission fragments. It was shown that this phase might change sizably the contribution of the interference between fission amplitudes of neutron resonances excited in a fissile compound nucleus to the absolute values of T -odd asymmetries, especially for third particles such as neutrons and photons, which interacted only slightly with fission fragments.

Kadmensky, S. G., E-mail: kadmensky@phys.vsu.ru [Voronezh State University (Russian Federation); Bunakov, V. E., E-mail: bunakov@vb3190.spbu.ru [Russian Academy of Sciences, Petersburg Nuclear Physics Institute (Russian Federation); Titova, L. V.; Kadmensky, S. S. [Voronezh State University (Russian Federation)

2011-10-15T23:59:59.000Z

310

Relativistic Quantum Communication  

E-Print Network (OSTI)

In this Ph.D. thesis, I investigate the communication abilities of non-inertial observers and the precision to which they can measure parametrized states. I introduce relativistic quantum field theory with field quantisation, and the definition and transformations of mode functions in Minkowski, Schwarzschild and Rindler spaces. I introduce information theory by discussing the nature of information, defining the entropic information measures, and highlighting the differences between classical and quantum information. I review the field of relativistic quantum information. We investigate the communication abilities of an inertial observer to a relativistic observer hovering above a Schwarzschild black hole, using the Rindler approximation. We compare both classical communication and quantum entanglement generation of the state merging protocol, for both the single and dual rail encodings. We find that while classical communication remains finite right up to the horizon, the quantum entanglement generation tends to zero. We investigate the observers' abilities to precisely measure the parameter of a state that is communicated between Alice and Rob. This parameter was encoded to either the amplitudes of a single excitation state or the phase of a NOON state. With NOON states the dual rail encoding provided greater precision, which is different to the results for the other situations. The precision was maximum for a particular number of excitations in the NOON state. We calculated the bipartite communication for Alice-Rob and Alice-AntiRob beyond the single mode approximation. Rob and AntiRob are causally disconnected counter-accelerating observers. We found that Alice must choose in advance with whom, Rob or AntiRob she wants to create entanglement using a particular setup. She could communicate classically to both.

Dominic Hosler

2013-06-20T23:59:59.000Z

311

Quantum Conductance Project/Graphene-Based Quantum ...  

Science Conference Proceedings (OSTI)

Quantum Conductance Project/Graphene-Based Quantum Metrology. Summary: ... Graphene Hall bar developed at NIST by undergraduate students. ...

2011-10-03T23:59:59.000Z

312

Gaussian quantum information  

E-Print Network (OSTI)

The science of quantum information has arisen over the last two decades centered on the manipulation of individual quanta of information, known as quantum bits or qubits. Quantum computers, quantum cryptography, and quantum ...

Weedbrook, Christian

313

Finite groups and quantum physics  

Science Conference Proceedings (OSTI)

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.

Kornyak, V. V., E-mail: kornyak@jinr.ru [Joint Institute for Nuclear Physics, Laboratory of Information Tecnnologies (Russian Federation)

2013-02-15T23:59:59.000Z

314

The dynamics of quantum criticality: Quantum Monte Carlo and holography  

E-Print Network (OSTI)

Understanding the real time dynamics of systems near quantum critical points at non-zero temperatures constitutes an important yet challenging problem, especially in two spatial dimensions where interactions are strong. We present detailed quantum Monte Carlo results for two separate realizations of the superfluid-insulator transition of bosons on a lattice: their low-frequency conductivities are found to have the same universal dependence on imaginary frequency and temperature. We then use the structure of the real time dynamics of conformal field theories described by the holographic gauge/gravity duality to make progress on the difficult problem of analytically continuing the Monte Carlo data to real time. Our method yields quantitative and experimentally testable results on the frequency-dependent conductivity at the quantum critical point, and on the spectrum of quasinormal modes in the vicinity of the superfluid-insulator quantum phase transition. Extensions to other observables and universality classes are discussed.

William Witczak-Krempa; Erik Sorensen; Subir Sachdev

2013-09-11T23:59:59.000Z

315

Experimental and DFT studies of initiation processes for butane isomerization over sulfated-zirconia catalysts  

SciTech Connect

Reaction kinetics studies were conducted of isobutane and n-butane isomerization at 423 K over sulfated-zirconia, with the butane feeds purified of olefins. Dihydrogen evolution was observed during butane isomerization over fresh catalysts, as well as over catalysts selectively poisoned by preadsorbed ammonia. Butane isomerization over sulfated-zirconia can be viewed as a surface chain reaction comprised of initiation, propagation, and termination steps. The primary initiation step in the absence of feed olefins is considered to be the dehydrogenation of butane over sulfated-zirconia, generating butenes which adsorb onto acid sites to form protonated olefinic species associated with the conjugate base form of the acid sites. Quantum-chemical calculations, employing density-functional theory, suggest that the dissociative adsorption of dihydrogen, isobutylene hydrogenation, and dissociative adsorption of isobutane are feasible over the sulfated-zirconia cluster, and these reactions take place over Zr-O sites.

Hong, Z.; Watwe, R.M.; Natal-Santiago, M.A.; Hill, J.M.; Dumesic, J.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical Engineering] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical Engineering; Fogash, K.B. [Air Products and Chemicals, Inc., Allentown, PA (United States)] [Air Products and Chemicals, Inc., Allentown, PA (United States); Kim, B. [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering] [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering; Masqueda-Jimenez, B.I. [Univ. Autonoma de San Luis Potosi (Mexico). Centro de Investigacion y Estudios de Posgrado] [Univ. Autonoma de San Luis Potosi (Mexico). Centro de Investigacion y Estudios de Posgrado

1998-09-10T23:59:59.000Z

316

Fundamental constants in effective theory  

E-Print Network (OSTI)

There is a discussion between L. B. Okun, G. Veneziano and M. J. Duff, concerning the number of fundamental dimensionful constants in physics [1]. They advocated correspondingly 3, 2 and 0 fundamental constants. Here we consider this problem on example of the effective relativistic quantum field theory, which emerges in the low energy corner of quantum liquids and which reproduces many features of our physics including chiral fermions, gauge fields and dynamical gravity. 1 Introduction. The effective relativistic quantum field theory (RQFT) arising as emergent phenomenon in quantum liquids [2], or in other condensed matter systems [3], allows us to look at the problem of fundamental constants from the outside, i.e. from the point of view of an external observer who does not

G. E. Volovik

2008-01-01T23:59:59.000Z

317

8.251 String Theory for Undergraduates, Spring 2003  

E-Print Network (OSTI)

Introduction to the main concepts of string theory to undergraduates. Since string theory is quantum mechanics of a relativistic string, the foundations of the subject can be explained to students exposed to both special ...

Zwiebach, Barton

318

8.251 String Theory for Undergraduates, Spring 2005  

E-Print Network (OSTI)

Introduction to the main concepts of string theory to undergraduates. Since string theory is quantum mechanics of a relativistic string, the foundations of the subject can be explained to students exposed to both special ...

Zwiebach, Barton

319

Quantum Darwinism as a Darwinian process  

E-Print Network (OSTI)

The Darwinian nature of Wojciech Zurek's theory of Quantum Darwinism is evaluated against the criteria of a Darwinian process as understood within Universal Darwinism. The characteristics of a Darwinian process are developed including the consequences of accumulated adaptations resulting in adaptive systems operating in accordance with Friston's free energy principle and employing environmental simulations. Quantum theory, as developed in Zurek's research program and encapsulated by his theory of Quantum Darwinism is discussed from the view that Zurek's derivation of the measurement axioms implies that the evolution of a quantum system entangled with environmental entities is determined solely by the nature of the entangled system. There need be no further logical foundation. Quantum Darwinism is found to conform to the Darwinian paradigm in unexpected detail and is thus may be considered a theory within the framework of Universal Darwinism. With the inclusion of Quantum Darwinism within Universal Darwinism and the explanatory power of Darwinian processes extended beyond biology and the social sciences to include the creation and evolution of scientific subject matter within particle physics, atomic physics and chemistry, it is suggested that Universal Darwinism may be considered a candidate 'Theory of Everything' as anticipated by David Deutsch.

John Campbell

2010-01-05T23:59:59.000Z

320

Quantum Graphical Models and Belief Propagation  

E-Print Network (OSTI)

Belief Propagation algorithms acting on Graphical Models of classical probability distributions, such as Markov Networks, Factor Graphs and Bayesian Networks, are amongst the most powerful known methods for deriving probabilistic inferences amongst large numbers of random variables. This paper presents a generalization of these concepts and methods to the quantum case, based on the idea that quantum theory can be thought of as a noncommutative, operator-valued, generalization of classical probability theory. Some novel characterizations of quantum conditional independence are derived, and definitions of Quantum n-Bifactor Networks, Markov Networks, Factor Graphs and Bayesian Networks are proposed. The structure of Quantum Markov Networks is investigated and some partial characterization results are obtained, along the lines of the Hammersely-Clifford theorem. A Quantum Belief Propagation algorithm is presented and is shown to converge on 1-Bifactor Networks and Markov Networks when the underlying graph is a tree. The use of Quantum Belief Propagation as a heuristic algorithm in cases where it is not known to converge is discussed. Applications to decoding quantum error correcting codes and to the simulation of many-body quantum systems are described.

Matthew Leifer; David Poulin

2007-08-09T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Quantum probabilities of composite events in quantum measurements with multimode states  

E-Print Network (OSTI)

The problem of defining quantum probabilities of composite events is considered. This problem is of high importance for the theory of quantum measurements and for quantum decision theory that is a part of measurement theory. We show that the Luders probability of consecutive measurements is a transition probability between two quantum states and that this probability cannot be treated as a quantum extension of the classical conditional probability. The Wigner distribution is shown to be a weighted transition probability that cannot be accepted as a quantum extension of the classical joint probability. We suggest the definition of quantum joint probabilities by introducing composite events in multichannel measurements. The notion of measurements under uncertainty is defined. We demonstrate that the necessary condition for the mode interference is the entanglement of the composite prospect together with the entanglement of the composite statistical state. As an illustration, we consider an example of a quantum game. A special attention is payed to the application of the approach to systems with multimode states, such as atoms, molecules, quantum dots, or trapped Bose-condensed atoms with several coherent modes.

V. I. Yukalov; D. Sornette

2013-08-26T23:59:59.000Z

322

Covariant Macroscopic Quantum Geometry  

E-Print Network (OSTI)

A covariant noncommutative algebra of position operators is presented, and interpreted as the macroscopic limit of a geometry that describes a collective quantum behavior of the positions of massive bodies in a flat emergent space-time. The commutator defines a quantum-geometrical relationship between world lines that depends on their separation and relative velocity, but on no other property of the bodies, and leads to a transverse uncertainty of the geometrical wave function that increases with separation. The number of geometrical degrees of freedom in a space-time volume scales holographically, as the surface area in Planck units. Ongoing branching of the wave function causes fluctuations in transverse position, shared coherently among bodies with similar trajectories. The theory can be tested using appropriately configured Michelson interferometers.

Hogan, Craig J

2012-01-01T23:59:59.000Z

323

Quantum Computational Complexity  

E-Print Network (OSTI)

This article surveys quantum computational complexity, with a focus on three fundamental notions: polynomial-time quantum computations, the efficient verification of quantum proofs, and quantum interactive proof systems. Properties of quantum complexity classes based on these notions, such as BQP, QMA, and QIP, are presented. Other topics in quantum complexity, including quantum advice, space-bounded quantum computation, and bounded-depth quantum circuits, are also discussed.

John Watrous

2008-04-21T23:59:59.000Z

324

Theory of electron transfer and ionization  

DOE Green Energy (OSTI)

The main effort reported is directed toward charge transfer and ionization in high energy atomic collisions. The research may be divided into classical trajectory calculations, quantum - mechanical collision theory, and phenomenological treatments of quantal interference effects in heavy ion collisions.

Becker, R.L.

1979-01-01T23:59:59.000Z

325

Physicalism versus quantum mechanics  

E-Print Network (OSTI)

Foundations of Quantum Mechanics. (Princeton UniversityMind, Matter, and Quantum Mechanics, (Springer, Berlin & NewMindful Universe: Quantum Mechanics and the Participating

Stapp, Henry P; Theoretical Physics Group; Physics Division

2009-01-01T23:59:59.000Z

326

Prequantum Classical Statistical Field Theory: Fundamentals  

SciTech Connect

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.

Khrennikov, Andrei [International Center for Mathematical Modelling in Physics and Cognitive Sciences, Linnaeus University, Vaexjoe, S-35195 (Sweden)

2011-03-28T23:59:59.000Z

327

Quantum L_p and Orlicz spaces  

E-Print Network (OSTI)

Let $\\A$ ($\\cM$) be a $C^*$-algebra (a von Neumann algebra respectively). By a quantum dynamical system we shall understand the pair $({\\A}, T)$ ($({\\cM}, T)$) where $T : {\\A} \\to {\\A}$ ($T : {\\cM} \\to {\\cM}$) is a linear, positive (normal respectively), and identity preserving map. In our lecture, we discuss how the techniques of quantum Orlicz spaces may be used to study quantum dynamical systems. To this end, we firstly give a brief exposition of the theory of quantum dynamical systems in quantum $L_p$ spaces. Secondly, we describe the Banach space approach to quantization of classical Orlicz spaces. We will discuss the necessity of the generalization of $L_p$-space techniques. Some emphasis will be put on the construction of non-commutative Orlicz spaces. The question of lifting dynamical systems defined on von Neumann algebra to a dynamical system defined in terms of quantum Orlicz space will be discussed.

L. E. Labuschagne; W. A. Majewski

2009-02-25T23:59:59.000Z

328

Quantum Indeterminacy of Emergent Spacetime  

E-Print Network (OSTI)

It is shown that nearly-flat 3+1D spacetime emerging from a dual quantum field theory in 2+1D displays quantum fluctuations from classical Euclidean geometry on macroscopic scales. A covariant holographic mapping is assumed, where plane wave states with wavevector k on a 2D surface map onto classical null trajectories in the emergent third dimension at an angle \\theta=l_P k relative to the surface element normal, where l_P denotes the Planck length. Null trajectories in the 3+1D world then display quantum uncertainty of angular orientation, with standard deviation \\Delta\\theta=\\sqrt{l_P/z} for longitudinal propagation distance z in a given frame. The quantum complementarity of transverse position at macroscopically separated events along null trajectories corresponds to a geometry that is not completely classical, but displays observable holographic quantum noise. A statistical estimator of the fluctuations from Euclidean behavior is given for a simple thought experiment based on measured sides of triangles. The effect can be viewed as sampling noise due to the limited degrees of freedom of such a theory, consistent with covariant bounds on entropy.

Craig J. Hogan

2007-10-22T23:59:59.000Z

329

Structure and energetics of solvated ferrous and ferric ions: Car-Parrinello molecular dynamics in the DFT+U formalism  

E-Print Network (OSTI)

We implemented a rotationally-invariant Hubbard U extension to density-functional theory in the Car-Parrinello molecular dynamics framework, with the goal of bringing the accuracy of the DFT+U approach to finite-temperature simulations, especially for liquids or solids containing transition-metal ions. First, we studied the effects on the Hubbard U on the static equilibrium structure of the hexa-aqua ferrous and ferric ions, and the inner-sphere reorganization energy for the electron-transfer reaction between aqueous ferrous and ferric ions. It is found that the reorganization energy is increased, mostly as a result of the Fe-O distance elongation in the hexa-aqua ferrous ion. Second, we performed a first-principles molecular dynamics study of the solvation structure of the two aqueous ferrous and ferric ions. The Hubbard term is found to change the Fe-O radial distribution function for the ferrous ion, while having a negligible effect on the aqueous ferric ion. Moreover, the frequencies of vibrations between Fe and oxygen atoms in the first-solvation shell are shown to be unaffected by the Hubbard corrections for both ferrous and ferric ions.

P. H. -L. Sit; Matteo Cococcioni; Nicola Marzari

2007-01-12T23:59:59.000Z

330

Dark Energy from Quantum Uncertainty of Simultaneity  

E-Print Network (OSTI)

The observed acceleration expansion of the universe was thought attribute to a mysterious dark energy in the framework of the classical general relativity. The dark energy behaves very similar with a vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a wrong order of the vacuum energy and leads to a severe fine-tuning, known as the cosmological constant problem. We abandon the standard interpretation that time is a global parameter in quantum mechanics, replace it by a quantum dynamical variable playing the role of an operational quantum clock system. In the framework of reinterpretation of time, we find that the synchronization of two quantum clocks distance apart can not be realized in all rigor at quantum level. Thus leading to an intrinsic quantum uncertainty of simultaneity between spatial interval, which implies a visional vacuum energy fluctuation and gives an observed dark energy density $\\rho_{de}=\\frac{6}{\\pi}L_{P}^{-2}L_{H}^{-2}$, where $L_{P}$ and $L_{H}$ are the Planck and Hubble scale cut-off. The expectation value of zero-point energy automatically vanishes under the quantum dynamical time variable. The fraction of the dark energy is precisely given by $\\Omega_{de}=\\frac{2}{\\pi}$, which does not evolve with the quantum dynamical time variable, so it is "always" comparable to the matter energy density or the critical density. This theory is consistent with current cosmic observations.

M. J. Luo

2014-01-11T23:59:59.000Z

331

Channel simulation with quantum side information  

E-Print Network (OSTI)

We study and solve the problem of classical channel simulation with quantum side information at the receiver. This is a generalization of both the classical reverse Shannon theorem, and the classical-quantum Slepian-Wolf problem. The optimal noiseless communication rate is found to be reduced from the mutual information between the channel input and output by the Holevo information between the channel output and the quantum side information. Our main theorem has two important corollaries. The first is a quantum generalization of the Wyner-Ziv problem: rate-distortion theory with quantum side information. The second is an alternative proof of the trade-off between classical communication and common randomness distilled from a quantum state. The fully quantum generalization of the problem considered is quantum state redistribution. Here the sender and receiver share a mixed quantum state and the sender wants to transfer part of her state to the receiver using entanglement and quantum communication. We present outer and inner bounds on the achievable rate pairs.

Zhicheng Luo; Igor Devetak

2006-11-01T23:59:59.000Z

332

Quantum discord in open quantum systems  

E-Print Network (OSTI)

Open quantum systems have attracted great attentions for the inevitable interaction between quantum systems and their environment would largely affect the features of interest in the systems. Quantum discord, as a measure of the total nonclassical correlation in a quantum system, includes but not only the distinct property of quantum entanglement. Quantum discord can exist in separated quantum states and it has been shown to play important roles in many fundamental physical problems and practical quantum information tasks. There have been plentiful investigations on the quantum discord and its counterpart classical correlation in open quantum systems. In this short review, we would focus on the recent development and applications of distinctive properties of quantum discord and classical correlation in open quantum systems. Several related experimental works are included.

Xu, Jin-Shi

2012-01-01T23:59:59.000Z

333

Quantum Electrodynamics for Vector Mesons  

Science Conference Proceedings (OSTI)

Quantum electrodynamics for {rho} mesons is considered. It is shown that, at the tree level, the value of the gyromagnetic ratio of the {rho}{sup +} is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference M{sub {rho}}{sub {sup 0}}-M{sub {rho}}{sub {sup {+-}}}{approx}1 MeV at tree order.

Djukanovic, Dalibor; Schindler, Matthias R.; Scherer, Stefan [Institut fuer Kernphysik, Johannes Gutenberg-Universitaet, 55099 Mainz (Germany); Gegelia, Jambul [Institut fuer Kernphysik, Johannes Gutenberg-Universitaet, 55099 Mainz (Germany); High Energy Physics Institute, Tbilisi State University, Tbilisi (Georgia)

2005-07-01T23:59:59.000Z

334

Quantum Coulomb Gases  

E-Print Network (OSTI)

Lectures on Quantum Coulomb gases delivered at the CIME summer school on Quantum Many Body Systems 2010

Jan Philip Solovej

2010-12-23T23:59:59.000Z

335

Quantum Knots and Riemann Hypothesis  

E-Print Network (OSTI)

In this paper we propose a quantum gauge system from which we construct generalized Wilson loops which will be as quantum knots. From quantum knots we give a classification table of knots where knots are one-to-one assigned with an integer such that prime knots are bijectively assigned with prime numbers and the prime number 2 corresponds to the trefoil knot. Then by considering the quantum knots as periodic orbits of the quantum system and by the identity of knots with integers and an approach which is similar to the quantum chaos approach of Berry and Keating we derive a trace formula which may be called the von Mangoldt-Selberg-Gutzwiller trace formula. From this trace formula we then give a proof of the Riemann Hypothesis. For our proof of the Riemann Hypothesis we show that the Hilbert-Polya conjecture holds that there is a self-adjoint operator for the nontrivial zeros of the Riemann zeta function and this operator is the Virasoro energy operator with central charge $c=\\frac12$. Our approach for proving the Riemann Hypothesis can also be extended to prove the Extended Riemann Hypothesis. We also investigate the relation of our approach for proving the Riemann Hypothesis with the Random Matrix Theory for $L$-functions.

Sze Kui Ng

2006-03-12T23:59:59.000Z

336

Strongly Correlated Quantum Fluids: Ultracold Quantum Gases, Quantum Chromodynamic Plasmas, and Holographic Duality  

E-Print Network (OSTI)

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by more than 20 orders of magnitude in temperature, but they were shown to exhibit very similar hydrodynamic flow. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields, and it also serves as an introduction to the Focus Issue of New Journal of Physics on Strongly Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas. The presentation is made accessible to the general physics reader and includes discussions of the latest research developments in all three areas.

Allan Adams; Lincoln D. Carr; Thomas Schaefer; Peter Steinberg; John E. Thomas

2012-05-23T23:59:59.000Z

337

Theory and Modeling of Weakly Bound/Physisorbed Materials for Hydrogen Storage  

NLE Websites -- All DOE Office Websites (Extended Search)

and Modeling of and Modeling of Weakly Bound/Physisorbed Materials for Hydrogen Storage Andrew Williamson Quantum Simulations Group Lawrence Livermore National Laboratory Tadashi Ogitsu Lawrence Livermore National Laboratory Yong-Hyun Kim, Mike Heben, and Shengbai Zhang National Renewable Energy Laboratory UCRL-209054 This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. Outline * Storage by physisorption: - CNT, fullerenes, carbon aerogels - Doping, Decorating, Charging * Accuracy of Methods: DFT, QMC and Quantum Chemistry - Van der Waals interactions - * Use of DFT to screen for new compounds - 2 binding to doped fullerenes * LDA, GGA and ad-hoc corrections to pseudopotentials

338

Quantum control limited by quantum decoherence  

E-Print Network (OSTI)

We describe quantum controllability under the influences of the quantum decoherence induced by the quantum control itself. It is shown that, when the controller is considered as a quantum system, it will entangle with its controlled system and then cause quantum decoherence in the controlled system. In competition with this induced decoherence, the controllability will be limited by some uncertainty relation in a well-armed quantum control process. In association with the phase uncertainty and the standard quantum limit, a general model is studied to demonstrate the possibility of realizing a decoherence-free quantum control with a finite energy within a finite time. It is also shown that if the operations of quantum control are to be determined by the initial state of the controller, then due to the decoherence which results from the quantum control itself, there exists a low bound for quantum controllability.

Fei Xue; S. X. Yu; C. P. Sun

2005-07-22T23:59:59.000Z

339

Quantum network coding for quantum repeaters  

E-Print Network (OSTI)

This paper considers quantum network coding, which is a recent technique that enables quantum information to be sent on complex networks at higher rates than by using straightforward routing strategies. Kobayashi et al. have recently showed the potential of this technique by demonstrating how any classical network coding protocol gives rise to a quantum network coding protocol. They nevertheless primarily focused on an abstract model, in which quantum resource such as quantum registers can be freely introduced at each node. In this work, we present a protocol for quantum network coding under weaker (and more practical) assumptions: our new protocol works even for quantum networks where adjacent nodes initially share one EPR-pair but cannot add any quantum registers or send any quantum information. A typically example of networks satisfying this assumption is {\\emph{quantum repeater networks}}, which are promising candidates for the implementation of large scale quantum networks. Our results thus show, for the...

Satoh, Takahiko; Imai, Hiroshi

2012-01-01T23:59:59.000Z

340

Is there a Jordan geometry underlying quantum physics?  

E-Print Network (OSTI)

There have been several propositions for a geometric and essentially non-linear formulation of quantum mechanics. From a purely mathematical point of view, the point of view of Jordan algebra theory might give new strength to such approaches: there is a ``Jordan geometry'' belonging to the Jordan part of the algebra of observables, in the same way as Lie groups belong to the Lie part. Both the Lie geometry and the Jordan geometry are well-adapted to describe certain features of quantum theory. We concentrate here on the mathematical description of the Jordan geometry and raise some questions concerning possible relations with foundational issues of quantum theory.

Wolfgang Bertram

2008-01-20T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Feynman Equation in Hamiltonian Quantum Field Theory  

E-Print Network (OSTI)

Functional Schr\\"{o}dinger equations for interacting fields are solved via rigorous non-perturbative Feynman type integrals.

Alexander Dynin

2000-05-26T23:59:59.000Z

342

Theory and application of open quantum systems  

E-Print Network (OSTI)

iii) time-convolutionless (TCL) projection[20, 13], and (iv)P t diagrammatic Born classical NZ TCL additive ME gt Figurebetween the low order TCL and the additive approximation

Chan, Ching-Kit; Chan, Ching-Kit

2012-01-01T23:59:59.000Z

343

Quantum Theory of Dissociative Chemisorption on Metal  

E-Print Network (OSTI)

to the rational design of an improved catalyst was taken for the steam reforming process (which converts methane

344

A Foundation Theory Of Quantum Mechanics  

Science Conference Proceedings (OSTI)

The nRules are empirical regularities that were discovered in macroscopic situations where the outcome is known. When they are projected theoretically into the microscopic domain they predict a novel ontology including the frequent collapse of an atomic wave function

Richard A. Mould

2006-01-01T23:59:59.000Z

345

NIST Quantum Physics Division - 1998  

Science Conference Proceedings (OSTI)

... QUANTUM PHYSICS DIVISION. Fluorescence Trajectory of a Single 30 Angstrom Radius CdSe Quantum Dot. The quantum ...

346

The confining N = 1 supersymmetric gauge theories: A review  

Science Conference Proceedings (OSTI)

The authors give a classification and overview of the confining N = 1 supersymmetric gauge theories. For simplicity they consider only theories based on simple gauge groups and no tree-level superpotential. Classification of these theories can be done according to whether or not there is a superpotential generated for the confined degrees of freedom. The theories with the superpotential include s-confining theories and also theories where the gauge fields participate in the confining spectrum, while theories with no superpotential include theories with a quantum deformed moduli space and theories with an affine moduli space.

Csaki, C. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States). Physics Div.

1998-08-01T23:59:59.000Z

347

Quantum mechanics needs no interpretation  

E-Print Network (OSTI)

Probabilistic description of results of measurements and its consequences for understanding quantum mechanics are discussed. It is shown that the basic mathematical structure of quantum mechanics like the probability amplitude, Born rule, probability density current, commutation relations, momentum operator, uncertainty relations, rules for including the scalar and vector potentials and existence of antiparticles can be derived from the definition of the mean values of the space coordinates and time. Equations of motion of quantum mechanics, the Klein-Gordon equation, Schroedinger equation and Dirac equation are obtained from requirement of the relativistic invariance of the theory. Limit case of localized probability densities leads to the Hamilton-Jacobi equation of classical mechanics. Many particle systems are also discussed.

L. Skala; V. Kapsa

2004-12-22T23:59:59.000Z

348

Directional Entanglement of Quantum Fields with Quantum Geometry  

E-Print Network (OSTI)

A modification of quantum field theory on large scales is conjectured to result from effects of Planck scale limits on directional information. Transversely localized solutions of the relativistic wave equation are used to show that the path of a massless particle with wavelength $\\lambda$ that travels a distance $z$ has a wave function with indeterminacy in direction given by the diffraction scale, $\\langle \\Delta \\theta^2\\rangle > \\sqrt{2}\\lambda /\\pi z$. It is conjectured that the spatial structure of all quantum field states is influenced by a new kind of directional indeterminacy of quantum geometry set by the Planck length, $l_P$, that does not occur in the usual classical background geometry. Entanglement of field and geometry states is described in the small angle approximation. It is shown to have almost no effect on local measurements, microscopic particle interactions, or measurements of propagating states that depend only on longitudinal coordinates, but to significantly alter field states in systems larger than $\\approx \\lambda^2/l_P $ that depend on transverse coordinates or direction. It reduces the information content of fields in large systems, consistent with holographic bounds from gravitation theory, and may lead to quantum-geometrical directional fluctuations of massive bodies detectable with interferometers. Possible connections are discussed with field vacuum energy, black hole information, and inflationary fluctuations.

Craig J. Hogan

2013-12-30T23:59:59.000Z

349

1 Quantum Gravity and Regge Calculus  

E-Print Network (OSTI)

This is an informal review of the formulation of canonical general relativity and of its implications for quantum gravity; the various versions are compared, both in the continuum and in a discretized approximation suggested by Regge calculus. I also show that the weakness of the link with the geometric content of the theory gives rise to what I think is a serious flaw in the claimed derivation of a discrete structure for space at the quantum level. 1.

Giorgio Immirzi A

1997-01-01T23:59:59.000Z

350

Nonequilibrium quantum statistical mechanics and thermodynamics  

E-Print Network (OSTI)

The purpose of this work is to discuss recent progress in deriving the fundamental laws of thermodynamics (0th, 1st and 2nd-law) from nonequilibrium quantum statistical mechanics. Basic thermodynamic notions are clarified and different reversible and irreversible thermodynamic processes are studied from the point of view of quantum statistical mechanics. Special emphasis is put on new adiabatic theorems for steady states close to and far from equilibrium, and on investigating cyclic thermodynamic processes using an extension of Floquet theory.

Walid K. Abou Salem

2006-01-23T23:59:59.000Z

351

Quantum capacity of channel with thermal noise  

E-Print Network (OSTI)

The quantum capacity of thermal noise channel is studied. The extremal input state is obtained at the postulation that the coherent information is convex or concave at its vicinity. When the input energy tends to infinitive, it is verified by perturbation theory that the coherent information reaches its maximum at the product of identical thermal state input. The quantum capacity is obtained for lower noise channel and it is equal the one shot capacity.

Xiao-yu Chen

2006-02-11T23:59:59.000Z

352

Quantum computing  

E-Print Network (OSTI)

This article gives an elementary introduction to quantum computing. It is a draft for a book chapter of the "Handbook of Nature-Inspired and Innovative Computing", Eds. A. Zomaya, G.J. Milburn, J. Dongarra, D. Bader, R. Brent, M. Eshaghian-Wilner, F. Seredynski (Springer, Berlin Heidelberg New York, 2006).

J. Eisert; M. M. Wolf

2004-01-05T23:59:59.000Z

353

CNM Highlight: Quantum Dot-Induced Transparency  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum Dot-Induced Transparency Quantum Dot-Induced Transparency Using rigorous and realistic numerical simulations, staff in the Nanophotonics and Theory and Modeling groups have recently demonstrated that a single semiconductor nanocrystal, or quantum dot, can cancel the scattering and absorption by a much larger metal nanostructure. Placing a quantum dot near a metal is known to strongly modify the rate at which the dot emits light. If the interaction between the dot and the metal is strong enough, scattering and absorption by the metal can be nearly eliminated at the quantum-dot resonance frequency, according to the simulations. This occurs even though the dot by itself simply absorbs light, and even though this absorption is nearly 100,000 times smaller than absorption by the metal nanostructure.

354

A new introductory quantum mechanics curriculum  

E-Print Network (OSTI)

The Institute of Physics New Quantum Curriculum consists of freely available online learning and teaching materials (quantumphysics.iop.org) for a first course in university quantum mechanics starting from two-level systems. This approach immediately immerses students in inherently quantum mechanical aspects by focusing on experiments that have no classical explanation. It allows from the start a discussion of interpretive aspects of quantum mechanics and quantum information theory. This article gives an overview of the resources available at the IOP website. The core text is presented as around 80 articles co-authored by leading experts that are arranged in themes and can be used flexibly to provide a range of alternative approaches. Many of the articles include interactive simulations with accompanying activities and problem sets that can be explored by students to enhance their understanding. Much of the linear algebra needed for this approach is part of the resource. Solutions to activities are available ...

Kohnle, Antje; Browne, Dan; Everitt, Mark; Fomins, Aleksejs; Kok, Pieter; Kulaitis, Gytis; Prokopas, Martynas; Raine, Derek; Swinbank, Elizabeth

2013-01-01T23:59:59.000Z

355

On Quantum Capacity of Compound Channels  

E-Print Network (OSTI)

In this paper we address the issue of universal or robust communication over quantum channels. Specifically, we consider memoryless communication scenario with channel uncertainty which is an analog of compound channel in classical information theory. We determine the quantum capacity of finite compound channels and arbitrary compound channels with informed decoder. Our approach in the finite case is based on the observation that perfect channel knowledge at the decoder does not increase the capacity of finite quantum compound channels. As a consequence we obtain coding theorem for finite quantum averaged channels, the simplest class of channels with long-term memory. The extension of these results to quantum compound channels with uninformed encoder and decoder, and infinitely many constituents remains an open problem.

I. Bjelakovic; H. Boche; J. Noetzel

2008-08-07T23:59:59.000Z

356

Quantum Geometry and Quantum Gravity  

E-Print Network (OSTI)

The purpose of this contribution is to give an introduction to quantum geometry and loop quantum gravity for a wide audience of both physicists and mathematicians. From a physical point of view the emphasis will be on conceptual issues concerning the relationship of the formalism with other more traditional approaches inspired in the treatment of the fundamental interactions in the standard model. Mathematically I will pay special attention to functional analytic issues, the construction of the relevant Hilbert spaces and the definition and properties of geometric operators: areas and volumes.

J. Fernando Barbero G.

2008-04-23T23:59:59.000Z

357

Rethinking Renormalization for Quantum Phase Transitions  

E-Print Network (OSTI)

This is a conceptual paper that re-examines the principles underlying the application of renormalization theory to quantum phase transitions in the light of quantum information theory. We start by describing the intuitive argument known as the Kadanoff ``block-spin'' construction for spins fixed on a lattice and then outline some subsequent ideas by Wilson and White. We then reconstruct these concepts for quantum phase transitions from first principles. This new perspective offers some very natural explanations for some features of renormalization theory that had previously seemed rather mysterious, even contrived. It also offers some suggestions as to how we might modify renormalization methods to make them more successful. We then discuss some possible order parameters and a class of functionals that are analogues of the correlation length in such systems.

Hilary A. Carteret

2004-05-28T23:59:59.000Z

358

Quantum and Post Quantum Cryptography Abderrahmane Nitaj  

E-Print Network (OSTI)

Quantum and Post Quantum Cryptography Abderrahmane Nitaj Laboratoire de Math´ematiques Nicolas based on quantum mechanics for factoring large integers and computing discrete loga- rithms undermined Gamal and ECC. However, some cryptosystems, called post quantum cryptosystems, while not currently

Nitaj, Abderrahmane

359

QUANTUM STOCHASTIC CALCULUS AND QUANTUM NONLINEAR FILTERING  

E-Print Network (OSTI)

QUANTUM STOCHASTIC CALCULUS AND QUANTUM NONLINEAR FILTERING V. P. BELAVKIN Abstract. A ?­algebraic inde...nite structure of quantum stochastic (QS) cal- culus is introduced and a continuity property...nitely dimensional nuclear space. The class of nondemolition output QS processes in quantum open systems

Belavkin, Viacheslav P.

360

Quantum dynamics in dual spaces  

Science Conference Proceedings (OSTI)

Quantum mechanics gives us information about spectra of dynamical variables and transition rates including scattering cross sections. They can be exhibited as spectral information in analytically continued spaces and their duals. Quantum mechanics formulated in these generalized spaces is used to study scattering and time evolution. It is shown that the usual asymptotic condition is inadequate to deal with scattering of composite or unstable particles. Scattering theory needs amendment when the interacting system is not isospectral with the free Hamiltonian, and the amendment is formulated. Perturbation theory in generalized spaces is developed and used to study the deletion and augmentation of the spectrum of the Hamiltonian. A complete set of algebraically independent constants for an interacting system is obtained. The question of the breaking of time symmetry is discussed.

Sudarshan, E.C.G.

1993-12-31T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Warped Conformal Field Theory  

E-Print Network (OSTI)

We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the 2d conformal group, but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near horizon geometry of any extremal black hole are identical to those of a 2d field theory with chiral scaling. We consider two examples: black holes in warped AdS_3 in topologically massive gravity, and in string theory. In both cases, the density of states in the 2d field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

Detournay, Stephane; Hofman, Diego M

2012-01-01T23:59:59.000Z

362

Warped Conformal Field Theory  

E-Print Network (OSTI)

We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the 2d conformal group, but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near horizon geometry of any extremal black hole are identical to those of a 2d field theory with chiral scaling. We consider two examples: black holes in warped AdS_3 in topologically massive gravity, and in string theory. In both cases, the density of states in the 2d field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

Stephane Detournay; Thomas Hartman; Diego M. Hofman

2012-10-01T23:59:59.000Z

363

Information-technology approach to quantum feedback control  

E-Print Network (OSTI)

Quantum control theory is profitably reexamined from the perspective of quantum information, two results on the role of quantum information technology in quantum feedback control are presented and two quantum feedback control schemes, teleportation-based distant quantum feedback control and quantum feedback control with quantum cloning, are proposed. In the first feedback scheme, the output from the quantum system to be controlled is fed back into the distant actuator via teleportation to alter the dynamics of system. The result theoretically shows that it can accomplish some tasks such as distant feedback quantum control that Markovian or Bayesian quantum feedback can't complete. In the second feedback strategy, the design of quantum feedback control algorithms is separated into a state recognition step, which gives "on-off" signal to the actuator through recognizing some copies from the cloning machine, and a feedback (control) step using another copies of cloning machine. A compromise between information acquisition and measurement disturbance is established, and this strategy can perform some quantum control tasks with coherent feedback.

Dao-Yi Dong; Chen-Bin Zhang; Zong-Hai Chen

2005-03-01T23:59:59.000Z

364

Three approaches to classical thermal field theory  

SciTech Connect

Research Highlights: > Classical thermal field theory admits three equivalent path integral formulations. > Classical Feynman rules can be derived for all three formulations. > Quantum Feynman rules reduce to classical ones at high temperatures. > Classical Feynman rules become much simpler when superfields are introduced. - Abstract: In this paper we study three different functional approaches to classical thermal field theory, which turn out to be the classical counterparts of three well-known different formulations of quantum thermal field theory: the closed-time path (CTP) formalism, the thermofield dynamics (TFD) and the Matsubara approach.

Gozzi, E., E-mail: gozzi@ts.infn.it [Department of Physics, University of Trieste, Strada Costiera 11, Miramare - Grignano, 34151 Trieste (Italy); INFN, Sezione di Trieste (Italy); Penco, R., E-mail: rpenco@syr.edu [Department of Physics, Syracuse University, Syracuse, NY 13244-1130 (United States)

2011-04-15T23:59:59.000Z

365

Brain-Computer Interfaces and Quantum Robots  

E-Print Network (OSTI)

The actual (classical) Brain-Computer Interface attempts to use brain signals to drive suitable actuators performing the actions corresponding to subject's intention. However this goal is not fully reached, and when BCI works, it does only in particular situations. The reason of this unsatisfactory result is that intention cannot be conceived simply as a set of classical input-output relationships. It is therefore necessary to resort to quantum theory, allowing the occurrence of stable coherence phenomena, in turn underlying high-level mental processes such as intentions and strategies. More precisely, within the context of a dissipative Quantum Field Theory of brain operation it is possible to introduce generalized coherent states associated, within the framework of logic, to the assertions of a quantum metalanguage. The latter controls the quantum-mechanical computing corresponding to standard mental operation. It thus become possible to conceive a Quantum Cyborg in which a human mind controls, through a quantum metalanguage, the operation of an artificial quantum computer.

Eliano Pessa; Paola zizzi

2009-09-08T23:59:59.000Z

366

Quantum information and general relativity  

E-Print Network (OSTI)

The Einstein-Podolsky-Rosen paradox (1935) is reexamined in the light of Shannon's information theory (1948). The EPR argument did not take into account that the observers' information was localized, like any other physical object. General relativity introduces new problems: there are horizons which act as one-way membranes for the propagation of quantum information, in particular black holes which act like sinks.

Asher Peres

2004-05-21T23:59:59.000Z

367

Joint probabilities and quantum cognition  

SciTech Connect

In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.

Acacio de Barros, J. [Liberal Studies, 1600 Holloway Ave., San Francisco State University, San Francisco, CA 94132 (United States)

2012-12-18T23:59:59.000Z

368

Avoiding Negative Probabilities in Quantum Mechanics  

E-Print Network (OSTI)

As currently understood since its discovery, the bare Klein-Gordon theory consists of negative quantum probabilities which are considered to be physically meaningless if not outright obsolete. Despite this annoying setback, these negative probabilities are what led the great Paul Dirac in 1928 to the esoteric discovery of the Dirac Equation. The Dirac Equation led to one of the greatest advances in our understanding of the physical world. In this reading, we ask the seemingly senseless question, "Do negative probabilities exist in quantum mechanics?" In an effort to answer this question, we arrive at the conclusion that depending on the choice one makes of the quantum probability current, one will obtain negative probabilities. We thus propose a new quantum probability current of the Klein-Gordon theory. This quantum probability current leads directly to positive definite quantum probabilities. Because these negative probabilities are in the bare Klein-Gordon theory, intrinsically a result of negative energies, the fact that we here arrive at a theory with positive probabilities, means that negative energy particles are not to be considered problematic as is the case in the bare Klein-Gordon theory. From an abstract-objective stand-point; in comparison with positive energy particles, the corollary is that negative energy particles should have equal chances to exist. As to why these negative energy particles do not exist, this is analogous to asking why is it that Dirac's antimatter does not exist in equal proportions with matter. This problem of why negative energy particles do not exist in equal proportions with positive energy particles is a problem that needs to be solved by a future theory.

Golden Gadzirayi Nyambuya

2013-08-15T23:59:59.000Z

369

Quantum Indeterminacy of Emergent Spacetime  

E-Print Network (OSTI)

It is shown that nearly-flat 3+1D spacetime emerging from a dual quantum field theory in 2+1D displays quantum fluctuations from classical Euclidean geometry on macroscopic scales. A covariant holographic mapping is assumed, where plane wave states with wavevector k on a 2D surface map onto classical null trajectories in the emergent third dimension at an angle \\theta=l_P k relative to the surface element normal, where l_P denotes the Planck length. Null trajectories in the 3+1D world then display quantum uncertainty of angular orientation, with standard deviation \\Delta\\theta=\\sqrt{l_P/z} for longitudinal propagation distance z in a given frame. The quantum complementarity of transverse position at macroscopically separated events along null trajectories corresponds to a geometry that is not completely classical, but displays observable holographic quantum noise. A statistical estimator of the fluctuations from Euclidean behavior is given for a simple thought experiment based on measured sides of triangles. ...

Hogan, Craig J

2007-01-01T23:59:59.000Z

370

Quantum-Classical Correspondence in Nonrelativistic Electrodynamics  

SciTech Connect

A form of classical electrodynamic field exists which gives exact agreement with the operator field of quantum electrodynamics (QED) for the Lamb shift of a harmonically bound point electron. Here it is pointed out that this form of classical theory with its physically acceptable interpretation is the result of an unconventional resolution of a mathematically ambiguous term in classical field theory. Finally a quantum-classical correspondence principle is shown to exist in the sense that the classical field and expectation value of the QED operator field are identical if retardation is neglected in the latter.

Ritchie, A.B.; Weatherford, C.A.

1999-10-14T23:59:59.000Z

371

Quantum classical correspondence in nonrelativistic electrodynamics  

SciTech Connect

A form of classical electrodynamic field exists which gives exact agreement with the operator field of quantum electrodynamics (QED) for the Lamb shift of a harmonically bound point electron. Here it is pointed out that this form of classical theory, with its physically acceptable interpretation, is the result of an unconventional resolution of a mathematically ambiguous term in classical field theory. Finally, a quantum classical correspondence principle is shown to exist in the sense that the classical field and expectation value of the QED operator field are identical, if retardation is neglected in the latter.

Ritchie, B.; Weatherford, C.A.

1999-12-01T23:59:59.000Z

372

Chaos and Nonlinear Dynamics in a Quantum Artificial Economy  

E-Print Network (OSTI)

Chaos and nonlinear economic dynamics are addressed for a quantum coupled map lattice model of an artificial economy, with quantized supply and demand equilibrium conditions. The measure theoretic properties and the patterns that emerge in both the economic business volume dynamics' diagrams as well as in the quantum mean field averages are addressed and conclusions are drawn in regards to the application of quantum chaos theory to address signatures of chaotic dynamics in relevant discrete economic state variables.

Gonalves, Carlos Pedro

2012-01-01T23:59:59.000Z

373

Chaos and Nonlinear Dynamics in a Quantum Artificial Economy  

E-Print Network (OSTI)

Chaos and nonlinear economic dynamics are addressed for a quantum coupled map lattice model of an artificial economy, with quantized supply and demand equilibrium conditions. The measure theoretic properties and the patterns that emerge in both the economic business volume dynamics' diagrams as well as in the quantum mean field averages are addressed and conclusions are drawn in regards to the application of quantum chaos theory to address signatures of chaotic dynamics in relevant discrete economic state variables.

Carlos Pedro Gonalves

2012-02-29T23:59:59.000Z

374

Quantum Operations and Measurement  

E-Print Network (OSTI)

Quantum Operations and Measurement M.P Seevinck E-mail: M.P.Seevinck@phys.uu.nl Utrecht field in quantum physics ­ or perhaps better, a new way of doing quantum physics ­ . . . Surprisingly of these developments to the conceptual problems of quantum mechanics. In our view, the new work on quantum information

Seevinck, Michiel

375

Quantum Nanomechanics Pritiraj Mohanty  

E-Print Network (OSTI)

Quantum Nanomechanics Pritiraj Mohanty Abstract Quantum Nanomechanics is the emerging field which pertains to the me- chanical behavior of nanoscale systems in the quantum domain. Unlike the conven- tional studies of vibration of molecules and phonons in solids, quantum nanome- chanics is defined as the quantum

376

Quantum Mechanics Measurements, Mutually  

E-Print Network (OSTI)

Quantum Mechanics Measurements, Mutually Unbiased Bases and Finite Geometry Or why six is the first) #12;Quantum Mechanics for Dummies Finite dimensional quantum states are represented by trace one,1 -icS1,1[ ] #12;Quantum systems evolve and are measured. The evolution of a quantum system using

Gruner, Daniel S.

377

Quantum Operations and Measurement  

E-Print Network (OSTI)

Quantum Operations and Measurement # M.P Seevinck # E­mail: M.P.Seevinck@phys.uu.nl Utrecht in quantum physics -- or perhaps better, a new way of doing quantum physics -- . . . Surprisingly, with few to the conceptual problems of quantum mechanics. In our view, the new work on quantum information changes

Seevinck, Michiel

378

Black holes, information, and Hilbert space for quantum gravity  

E-Print Network (OSTI)

A coarse-grained description for the formation and evaporation of a black hole is given within the framework of a unitary theory of quantum gravity preserving locality, without dropping the information that manifests as ...

Nomura, Yasunori

379

Markovs maximon and quantum black holes  

Science Conference Proceedings (OSTI)

It is shown that the modern theory predicts the existence of a minimum mass of quantum black holes. Such minimal black holes are a natural candidate for the maximon

V. A. Berezin

1998-01-01T23:59:59.000Z

380

Quantum Buckling  

E-Print Network (OSTI)

We study the mechanical buckling of a two dimensional membrane coated with a thin layer of superfluid. It is seen that a singularity (vortex or anti-vortex defect) in the phase of the quantum order parameter, distorts the membrane metric into a negative conical singularity surface, irrespective of the defect sign. The defect-curvature coupling and the observed instability is in striking contrast with classical elasticity where, the in-plane strain induced by positive (negative) disclinations is screened by a corresponding positive (negative) conical singularity surface. Defining a dimensionless ratio between superfluid stiffness and membrane bending modulus, we derive conditions under which the quantum buckling instability occurs. An ansatz for the resulting shape of the buckled membrane is analytically and numerically confirmed.

N. Upadhyaya; V. Vitelli

2011-06-23T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Multi-Determinant Wave-functions in Quantum Monte Carlo  

Science Conference Proceedings (OSTI)

Quantum Monte Carlo methods have received considerable attention over the last decades due to the great promise they have for the direct solution to the many-body Schrodinger equation for electronic systems. Thanks to a low scaling with number of particles, they present one of the best alternatives in the accurate study of large systems and solid state calculations. In spite of such promise, the method has not become popular in the quantum chemistry community, mainly due to the lack of control over the fixed-node error which can be large in many cases. In this article we present the application of large multi-determinant expansions in quantum Monte Carlo, studying its performance with first row dimers and the 55 molecules of the G1 test set. We demonstrate the potential of the wave-function to systematically reduce the fixed-node error in the calculations, achieving chemical accuracy in almost all cases studied. When compared to traditional methods in quantum chemistry, the results show a marked improvement over most methods including MP2, CCSD(T) and DFT with various functionals; in fact the only method able to produce better results is the explicitly-correlated CCSD(T) method with a large basis set. With recent developments in trial wave functions and algorithmic improvements in Quantum Monte Carlo, we are quickly approaching a time where the method can become the standard in the study of large molecular systems and solids.

Morales, Miguel A [Lawrence Livermore National Laboratory (LLNL); Mcminis, Jeremy [University of Illinois, Urbana-Champaign; Clark, Bryan K. [Princeton University; Kim, Jeongnim [ORNL; Scuseria, Gustavo E [Rice University

2012-01-01T23:59:59.000Z

382

$a-c$ test of holography vs quantum renormalization group  

E-Print Network (OSTI)

We show that a "constructive derivation" of the AdS/CFT correspondence based on the quantum local renormalization group in large N quantum field theories consistently provides the a-c holographic Weyl anomaly in d=4 at the curvature squared order in the bulk action. The consistency of the construction further predicts the form of the metric beta function.

Yu Nakayama

2014-01-21T23:59:59.000Z

383

Macroscopic quantum tunnelling in a current biased Josephson junction  

SciTech Connect

We discuss in this work an attempt to answer experimentally the question: do macroscopic variables obey quantum mechanics. More precisely, this experiment deals with the question of quantum-mechanical tunnelling of a macroscopic variable, a subject related to the famous Schrodinger's cat problem in the theory of measurement.

Martinis, J.M.; Devoret, M.H.; Clarke, J.; Urbina, C.

1984-11-01T23:59:59.000Z

384

Entanglement, Holography, and the Quantum Phases of Matter  

SciTech Connect

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 states, by relating them to theories of gravitation in curved spacetimes with an extra dimension. I will discuss the impact of such ideas on studies of quantum phase transitions, and of novel metals.

Sachdev, Subir [Harvard University

2012-11-07T23:59:59.000Z

385

Quantum Signatures of Spacetime Graininess Quantum Signatures of Spacetime  

E-Print Network (OSTI)

Quantum Signatures of Spacetime Graininess Quantum Signatures of Spacetime "Graininess" Sachindeo September 2009 #12;Quantum Signatures of Spacetime Graininess Introduction 1 Length scales in physics 2 Spacetime noncommutativity from quantum uncertainties 3 Quantum Mechanics on Noncommutative Spacetime 4

386

Quantum logic as superbraids of entangled qubit world lines  

E-Print Network (OSTI)

Presented is a topological representation of quantum logic that views entangled qubit spacetime histories (or qubit world lines) as a generalized braid, referred to as a superbraid. The crossing of world lines is purely quantum in nature, most conveniently expressed analytically with ladder-operator-based quantum gates. At a crossing, independent world lines can become entangled. Complicated superbraids are systematically reduced by recursively applying novel quantum skein relations. If the superbraid is closed (e.g. representing quantum circuits with closed-loop feedback, quantum lattice gas algorithms, loop or vacuum diagrams in quantum field theory), then one can decompose the resulting superlink into an entangled superposition of classical links. In turn, for each member link, one can compute a link invariant, e.g. the Jones polynomial. Thus, a superlink possesses a unique link invariant expressed as an entangled superposition of classical link invariants.

Jeffrey Yepez

2009-07-30T23:59:59.000Z

387

Causal signal transmission by quantum fields. II. Quantum-statistical response of interacting bosons  

E-Print Network (OSTI)

We analyse nonperturbatively signal transmission patterns in Green's functions of interacting quantum fields. Quantum field theory is re-formulated in terms of the nonlinear quantum-statistical response of the field. This formulation applies equally to interacting relativistic fields and nonrelativistic models. Of crucial importance is that all causality properties to be expected of a response formulation indeed hold. Being by construction equivalent to Schwinger's closed-time-loop formalism, this formulation is also shown to be related naturally to both Kubo's linear response and Glauber's macroscopic photodetection theories, being a unification of the two with generalisation to the nonlinear quantum-statistical response problem. In this paper we introduce response formulation of bosons; response reformulation of fermions will be subject of a separate paper.

L. I. Plimak; S. Stenholm

2008-04-25T23:59:59.000Z

388

Probabilistic bisimulations for quantum processes  

Science Conference Proceedings (OSTI)

Modeling and reasoning about concurrent quantum systems is very important for both distributed quantum computing and quantum protocol verification. As a consequence, a general framework formally describing communication and concurrency in complex quantum ... Keywords: Congruence, Probabilistic bisimulation, Quantum process

Yuan Feng; Runyao Duan; Zhengfeng Ji; Mingsheng Ying

2007-11-01T23:59:59.000Z

389

Quantum Espresso Quick Start Introduction  

E-Print Network (OSTI)

Quantum Espresso Quick Start Introduction Quantum Espresso (http://www.quantum properties eg., phonon dispersion, NMR shifts and band structure to name a few. Quantum Espresso is available. Matter 21, 395502 (2009). Online Guide for QE : http://www.quantum

Bjørnstad, Ottar Nordal

390

Indeterminacy of Quantum Geometry  

E-Print Network (OSTI)

An effective theory of quantum spacetime geometry based on wave optics is used to describe fundamental limits on propagation and measurement of information in holographic spacetimes. Wavefunctions describing spacetime event positions are modeled as complex disturbances of quasi-monochromatic Planck wavelength radiation. The transverse position on a two-dimensional geometrical wavefront, represented by the optical complex degree of coherence, is related to a prepared state represented by a transverse distribution of intensity on an initial wavefront. The transverse position distributions describing two macroscopically null-separated events are shown to approximate Fourier transforms of each other. This relationship is interpreted as an uncertainty inherent to spacetime: the product of standard deviations of transverse position of two events is equal to the product of their separation and the Planck length. For macroscopically separated events the uncertainty is much larger than the Planck length, and is predic...

Hogan, Craig J

2008-01-01T23:59:59.000Z

391

Consistent probabilities in loop quantum cosmology  

E-Print Network (OSTI)

A fundamental issue for any quantum cosmological theory is to specify how probabilities can be assigned to various quantum events or sequences of events such as the occurrence of singularities or bounces. In previous work, we have demonstrated how this issue can be successfully addressed within the consistent histories approach to quantum theory for Wheeler-DeWitt-quantized cosmological models. In this work, we generalize that analysis to the exactly solvable loop quantization of a spatially flat, homogeneous and isotropic cosmology sourced with a massless, minimally coupled scalar field known as sLQC. We provide an explicit, rigorous and complete decoherent histories formulation for this model and compute the probabilities for the occurrence of a quantum bounce vs. a singularity. Using the scalar field as an emergent internal time, we show for generic states that the probability for a singularity to occur in this model is zero, and that of a bounce is unity, complementing earlier studies of the expectation values of the volume and matter density in this theory. We also show from the consistent histories point of view that all states in this model, whether quantum or classical, achieve arbitrarily large volume in the limit of infinite `past' or `future' scalar `time', in the sense that the wave function evaluated at any arbitrary fixed value of the volume vanishes in that limit. Finally, we briefly discuss certain misconceptions concerning the utility of the consistent histories approach in these models.

David A. Craig; Parampreet Singh

2013-06-26T23:59:59.000Z

392

From Quantum Cheating to Quantum Security  

E-Print Network (OSTI)

For thousands of years, code-makers and code-breakers have been competing for supremacy. Their arsenals may soon include a powerful new weapon: quantum mechanics. We give an overview of quantum cryptology as of November 2000.

Daniel Gottesman; Hoi-Kwong Lo

2001-11-19T23:59:59.000Z

393

General quantum modeling of combining concepts: A quantum field model in Fock space  

E-Print Network (OSTI)

We extend a quantum model in Hilbert space developed in Aerts (2007a) into a quantum field theoric model in Fock space for the modeling of the combination of concepts. Items and concepts are represented by vectors in Fock space and membership weights of items are modeled by quantum probabilities. We apply this theory to model the disjunction of concepts and show that the predictions of our theory for the membership weights of items regarding the disjunction of concepts match with great accuracy the complete set of results of an experiment conducted by Hampton (1988b). It are the quantum effects of interference and superposition of that are at the origin of the effects of overextension and underextension observed by Hampton as deviations from a classical use of the disjunction. It is essential for the perfect matches we obtain between the predictions of the quantum field model and Hamptons experimental data that items can be in superpositions of different numbers states which proves that the genuine structure of quantum field theory is needed to match predictions with experimental data.

Diederik Aerts

2007-01-01T23:59:59.000Z

394

Electroweak Theory  

Science Conference Proceedings (OSTI)

The electroweak theory unifies two basic forces of nature: the weak force and electromagnetism. This 2007 book is a concise introduction to the structure of the electroweak theory and its applications. It describes the structure and properties of field ...

E. A. Paschos

2010-06-01T23:59:59.000Z

395

Quantum Process Tomography via L1-norm Minimization  

E-Print Network (OSTI)

For an initially well designed but imperfect quantum information system, the process matrix is almost sparse in an appropriate basis. Existing theory and associated computational methods (L1-norm minimization) for reconstructing sparse signals establish conditions under which the sparse signal can be perfectly reconstructed from a very limited number of measurements (resources). Although a direct extension to quantum process tomography of the L1-norm minimization theory has not yet emerged, the numerical examples presented here, which apply L1-norm minimization to quantum process tomography, show a significant reduction in resources to achieve a desired estimation accuracy over existing methods.

Robert L. Kosut

2008-12-23T23:59:59.000Z

396

Factor groups, semidirect product and quantum chemistry  

E-Print Network (OSTI)

In this paper we prove some general theorems about representations of finite groups arising from the semidirect product of groups and we show how these results can be used for standard applications of group theory in quantum chemistry. This approach is illustrated by the dihedral group.

Marco A. S. Trindade

2013-09-20T23:59:59.000Z

397

A Quantum Genetic Algorithm for Operon Prediction  

Science Conference Proceedings (OSTI)

Operon is a fundamental unit of transcription which is usually used to understand gene regulations and functions in entire genomes. Detecting operon experimentally is difficult and time-consuming, thus many bioinformatics algorithms have been proposed ... Keywords: quantum theory, intergenic distance, metabolic pathway, COG

Li-Yeh Chuang; Yi-Cheng Chiang; Cheng-Hong Yang

2012-03-01T23:59:59.000Z

398

Shape Dynamics and Effective Field Theory  

E-Print Network (OSTI)

Shape Dynamics is a gauge theory based on spatial diffeomorphism- and Weyl-invariance which is locally indistinguishable form classical General Relativity. If taken seriously, it suggests that the spacetime--geometry picture that underlies General Relativity can be replaced by a picture based on spatial conformal geometry. This classically well understood trading of gauge symmetries opens new conceptual avenues in many approaches to quantum gravity. I focus on the general implications for quantum gravity and effective field theory and consider the application of the Shape Dynamics picture in the exact renormalization group approaches to gravity, loop- and polymer- quantization approaches to gravity and low energy effective field theories. I also discuss the interpretation of known results through in the Shape Dynamics picture, in particular holographic renormalization and the problem of time in canonical quantum gravity.

Tim Koslowski

2013-05-07T23:59:59.000Z

399

Unconditional conversion between quantum particles and waves  

E-Print Network (OSTI)

Wave-particle duality is a basic notion of quantum mechanics, which has largely contributed to many debates on the foundations of quantum theory. Besides this fundamental aspect of the wave-particle nature of quantum systems, recently, it turned out that, in order to construct more advanced and efficient protocols in quantum communication and information processing, it is also beneficial to combine continuous-wave and discrete-particle features in a so-called hybrid fashion. However, in traditional, quantum optical complementarity tests, monitoring the light waves would still happen in an effectively particle-like fashion, detecting the fields click by click. Similarly, close-to-classical, wave-like coherent states, as readily available from standard laser sources, or other Gaussian states generated through nonlinear optical interactions, have been so far experimentally converted into non-classical quantum superpositions of distinct waves only in a conditional fashion. Here we experimentally demonstrate the deterministic conversion of a single-photon state into a quantum superposition of two weak coherent states with opposite phases - a Schrodinger kitten state - and back. Conceptually different from all previous experiments, as being fully reversible, this can be interpreted as a quantum gate, connecting the complementary regimes of particle-like and wave-like light fields in a unitary fashion, like in a quantum computation. Such an unconditional conversion is achieved by means of a squeezing operation, demonstrating a fundamental feature of any quantum system: particle-like and wave-like properties can be reversibly altered, with no need for filtering out either through detection.

Yoshichika Miwa; Jun-ichi Yoshikawa; Noriaki Iwata; Mamoru Endo; Petr Marek; Radim Filip; Peter van Loock; Akira Furusawa

2012-09-13T23:59:59.000Z

400

Quantum Geometry of the Dynamical Space-time  

E-Print Network (OSTI)

Quantum theory of field (extended) objects without a priori space-time geometry has been represented. Intrinsic coordinates in the tangent fibre bundle over complex projective Hilbert state space $CP(N-1)$ are used instead of space-time coordinates. The fate of quantum system modeled by the generalized coherent states is rooted in this manifold. Dynamical (state-dependent) space-time arises only at the stage of the quantum "yes/no" measurement. The quantum measurement of the gauge ``field shell'' of the generalized coherent state is described in terms of the affine parallel transport of the local dynamical variables in $CP(N-1)$.

Peter Leifer

2006-11-20T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

A new approach to quantum gravity  

E-Print Network (OSTI)

A new idea of quantum gravity is developed based on Gravitational Complementary Principle. This principle states that gravity has dual complement features: The quantum and classical aspects of gravity are complement and absolutely separated by the planck length into planckian and over-planckian domains, respectively. The classical Einstein equations are correct at the fundamental level at over-planckian domain and general relativity is not a low energy limit of a more fundamental theory. The quantum gravity is totally confined to the planckian domain with a new kind of ultra-short range interaction, mediated by massive (Planck mass) particles, through the virtual microscopic wormholes of the Planck scale with action h. There is no room for gravitons or extra dimensions in ?e-mail:f.darabi@azaruniv.edu 1this scenario. It is shown that the hierarchy problem can solve the cosmological constant problem via this new quantum gravity. 2 1

F. Darabi

2008-01-01T23:59:59.000Z

402

Sliding mode control of quantum systems  

E-Print Network (OSTI)

This paper proposes a new robust control method for quantum systems with uncertainties involving sliding mode control (SMC). Sliding mode control is a widely used approach in classical control theory and industrial applications. We show that SMC is also a useful method for robust control of quantum systems. In this paper, we define two specific classes of sliding modes (i.e., eigenstates and state subspaces) and propose two novel methods combining unitary control and periodic projective measurements for the design of quantum sliding mode control systems. Two examples including a two-level system and a three-level system are presented to demonstrate the proposed SMC method. One of main features of the proposed method is that the designed control laws can guarantee desired control performance in the presence of uncertainties in the system Hamiltonian. This sliding mode control approach provides a useful control theoretic tool for robust quantum information processing with uncertainties.

Daoyi Dong; Ian R. Petersen

2009-10-31T23:59:59.000Z

403

Magnetothermoelectric Response near Quantum Critical Points  

E-Print Network (OSTI)

Following on from our previous work [Phys. Rev. Lett. 98, 166801 (2007)] we examine the finite temperature magnetothermoelectric response in the vicinity of a quantum critical point (QCP). We begin with general scaling considerations relevant to an arbitrary QCP, either with or without Lorentz invariance, and in arbitrary dimension. In view of the broad connections to high temperature superconductivity, and cold atomic gases, we focus on the quantum critical fluctuations of the relativistic Landau--Ginzburg theory. This paradigmatic model arises in many contexts, and describes the (particle-hole symmetric) superfluid--Mott insulator quantum phase transition in the Bose--Hubbard model. The application of a magnetic field opens up a wide range of physical observables, and we present a detailed overview of the charge and thermal transport and thermodynamic response. We combine several different approaches including the epsilon expansion and associated Quantum Boltzmann Equation (QBE), entropy drift, and argument...

Bhaseen, M J; Sondhi, S L

2009-01-01T23:59:59.000Z

404

Quantum information in a nutshell () Quantum mechanics + information science  

E-Print Network (OSTI)

Quantum information in a nutshell (?²¤¶) Quantum mechanics + information science = quantum information science = quantum information transfer + quantum algorithm (software) + quantum computer (hardware) + quantum simulation +... = a field rapidly growing in the last 10 years ®v½d¤j¾?ª«²z¨t ±i©ú-õ #12;Brief

Chang, Ming-Che

405

FREE-SPACE QUANTUM CRYPTOGRAPHY IN DAYLIGHT  

Science Conference Proceedings (OSTI)

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.

Hughes, R.J.; Buttler, W.T. [and others

2000-01-01T23:59:59.000Z

406

Quantum Dating Market  

E-Print Network (OSTI)

We consider the dating market decision problem under the quantum mechanics point of view. Quantum states whose associated amplitudes are modified by men strategies are used to represent women. Grover quantum search algorithm is used as a playing strategy. Success is more frequently obtained by playing quantum than playing classic.

O. G. Zabaleta; C. M. Arizmendi

2010-03-04T23:59:59.000Z

407

Quantum Dots Executive Overview  

E-Print Network (OSTI)

Quantum Dot Sol-Gel Nanocomposites (patent pending) n Nanocrystal Quantum Dot Light Emitting Diode (patent (CRADA) Business Opportunities LANL's quantum dot portfolio includes a high-efficiency light emitting diode (LED) design based on non-radiative energy transfer from a quantum well into a layer of colloidal

408

Ergodic Quantum Computing  

Science Conference Proceedings (OSTI)

We propose a (theoretical) model for quantum computation where the result can be read out from the time average of the Hamiltonian dynamics of a 2-dimensional crystal on a cylinder.The Hamiltonian is a spatially local interaction among Wigner--Seitz ... Keywords: Hamiltonian of a quantum computer, Quantum cellular automata, solid state quantum computing, thermodynamics of computation

Dominik Janzing; Pawel Wocjan

2005-06-01T23:59:59.000Z

409

Quantum chaology Michael Berry  

E-Print Network (OSTI)

1 Quantum chaology Michael Berry Physics Department, University of Bristol Physics pp104-5 of Quantum: a guide for the perplexed by Jim Al-Khalili (Weidenfeld and Nicolson 2003) The quantum world appears very different from the world of classical physics that it superseded. Quantum energy levels

Berry, Michael Victor

410

QUANTUM GROUPS JOHAN KUSTERMANS  

E-Print Network (OSTI)

QUANTUM GROUPS JOHAN KUSTERMANS Syllabus: #15; The de#12;nition of a locally compact quantum group: motivational ex- amples and special cases. The classical case, compact and discrete quantum groups. #15 for weights. #15; The general de#12;nition of a locally compact quantum group and its basic consequences

Schürmann, Michael

411

Quantum Statistics Madalin Guta  

E-Print Network (OSTI)

Quantum Statistics Madalin Gut¸a School of Mathematics University of Nottingham 1 #12;The old paradigm Quantum Mechanics up to the 80's Quantum measurements have random results Only probability particles, any more than we can raise Ichtyosauria in the zoo 2 #12;The new paradigm Individual quantum

Guta, Madalin

412

Quantum Walks Norio Konno  

E-Print Network (OSTI)

Quantum Walks Norio Konno Yokohama National University Two types of quantum (random) walks, discrete-time (coined) or continuous- time, were introduced as the quantum mechanical extension of the corresponding classical random walks in connection with quantum computing and have been extensively studied over

Schürmann, Michael

413

Quantum discord and Markovianity of quantum dynamics  

E-Print Network (OSTI)

The problem of recognizing (non-)Markovianity of a quantum dynamics is revisited through analyzing quan- tum correlations. We argue that instantaneously-vanishing quantum discord provides a necessary and sufficient condition for Markovianity of a quantum map. This is used to introduce a measure of non-Markovianity. This measure, however, requires demanding knowledge about the system and the environment. By using a quantum correlation monogamy property and an ancillary system, we propose a simplified measure with less require- ments. Non-Markovianity is thereby decided by quantum state tomography of the system and the ancilla.

Alipour, S

2012-01-01T23:59:59.000Z

414

The fundamental obscurity in quantum mechanics. Could the problem be considered universal?  

E-Print Network (OSTI)

The contemporary controversy about the fundamental obscurity in quantum mechanics keeps on the old one about the aim of science, which was between the founders of the quantum theory. The orthodox quantum mechanics could be created only at the cost of renunciation of reality as the aim of natural science. The description only of phenomena, i.e. results of observation, should not be universal if no one believes that these phenomena are manifestation of a unique reality. Such belief concerning quantum mechanics is quite unacceptable because of irremediably conflict with special relativity. Nevertheless the quantum mechanics was developed and apprehended by most physicists as a universal theory of a quantum world. This fundamental discrepancy between the essence of the orthodox quantum mechanics and its history of development and studying has resulted both to an illusion about the aim of its description among most physicists and to the consideration of its fundamental obscurity as a universal problem among experts in quantum foundation. The aim of this paper is to show that quantum phenomena can not be described universally. It is indicated that rather the Schrodinger's than Born's interpretation of the wave function is valid for description of many quantum phenomena. The fundamental obscurity with which we are faced at the description, for example, macroscopic quantum phenomena differs fundamentally from the one with which the founders of the quantum theory were faced on atomic level.

A. V. Nikulov

2010-12-20T23:59:59.000Z

415

Diffeomorphisms in group field theories  

SciTech Connect

We study the issue of diffeomorphism symmetry in group field theories (GFT), using the noncommutative metric representation introduced by A. Baratin and D. Oriti [Phys. Rev. Lett. 105, 221302 (2010).]. In the colored Boulatov model for 3d gravity, we identify a field (quantum) symmetry which ties together the vertex translation invariance of discrete gravity, the flatness constraint of canonical quantum gravity, and the topological (coarse-graining) identities for the 6j symbols. We also show how, for the GFT graphs dual to manifolds, the invariance of the Feynman amplitudes encodes the discrete residual action of diffeomorphisms in simplicial gravity path integrals. We extend the results to GFT models for higher-dimensional BF theories and discuss various insights that they provide on the GFT formalism itself.

Baratin, Aristide [Triangle de la Physique, CPHT Ecole Polytechnique, IPhT Saclay, LPT Orsay and Laboratoire de Physique Theorique, CNRS UMR 8627, Universite Paris XI, F-91405 Orsay Cedex (France); Girelli, Florian [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia); Oriti, Daniele [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Am Muehlenberg 1, 14467 Golm (Germany)

2011-05-15T23:59:59.000Z

416

LANL | Physics | Quantum Information  

NLE Websites -- All DOE Office Websites (Extended Search)

Breakthrough quantum information Breakthrough quantum information science and technology Physics Division's quantum information science and technology capability supports present and future Laboratory missions in cyber-security, sensing, nonproliferation, information science, and materials. Collaborating with researchers throughout Los Alamos and leading institutions in the nation, Physics Division scientists are involved in projects in quantum communications, including quantum key distribution and quantum-enabled security and networking, and in quantum cold-atom physics. Recent fundamental science results include the ability to "paint" potentials that can trap Bose-Einstein condensates into geometric forms, such as the toroidal ring of clusters, the density of which is measured in

417

Quantum Computational Complexity John Watrous  

E-Print Network (OSTI)

Quantum Computational Complexity John Watrous Institute for Quantum Computing and School of the subject and its importance II. Introduction III. The quantum circuit model IV. Polynomial-time quantum computations V. Quantum proofs VI. Quantum interactive proof systems VII. Other selected notions in quantum

Watrous, John

418

Quantum optical waveform conversion  

E-Print Network (OSTI)

Currently proposed architectures for long-distance quantum communication rely on networks of quantum processors connected by optical communications channels [1,2]. The key resource for such networks is the entanglement of matter-based quantum systems with quantum optical fields for information transmission. The optical interaction bandwidth of these material systems is a tiny fraction of that available for optical communication, and the temporal shape of the quantum optical output pulse is often poorly suited for long-distance transmission. Here we demonstrate that nonlinear mixing of a quantum light pulse with a spectrally tailored classical field can compress the quantum pulse by more than a factor of 100 and flexibly reshape its temporal waveform, while preserving all quantum properties, including entanglement. Waveform conversion can be used with heralded arrays of quantum light emitters to enable quantum communication at the full data rate of optical telecommunications.

Kielpinski, D; Wiseman, HM

2010-01-01T23:59:59.000Z

419

Quantum Ice : a quantum Monte Carlo study  

E-Print Network (OSTI)

Ice states, in which frustrated interactions lead to a macroscopic ground-state degeneracy, occur in water ice, in problems of frustrated charge order on the pyrochlore lattice, and in the family of rare-earth magnets collectively known as spin ice. Of particular interest at the moment are "quantum spin ice" materials, where large quantum fluctuations may permit tunnelling between a macroscopic number of different classical ground states. Here we use zero-temperature quantum Monte Carlo simulations to show how such tunnelling can lift the degeneracy of a spin or charge ice, stabilising a unique "quantum ice" ground state --- a quantum liquid with excitations described by the Maxwell action of 3+1-dimensional quantum electrodynamics. We further identify a competing ordered "squiggle" state, and show how both squiggle and quantum ice states might be distinguished in neutron scattering experiments on a spin ice material.

Nic Shannon; Olga Sikora; Frank Pollmann; Karlo Penc; Peter Fulde

2011-05-20T23:59:59.000Z

420

Quantum Tachyon Dynamics  

E-Print Network (OSTI)

It is suggested that charged tachyons of extremely large mass M could not only contribute to the dark matter needed to fit astrophysical observations, but could also provide an explanation for gamma ray bursts and ulta high energy cosmic rays. The present paper defines a quantum field theory of tachyons, particles similar to ordinary leptons, but with momenta larger than energy. The theory is invariant under the full CPT transformation, but separately violates P and T invariance. Micro causality is broken for space-time intervals smaller than 1/M, but is effectively preserved for larger separations. Charged fermionic, rather than charged scalar tachyons are considered in order to minimize the probability of Cerenkov-like radiation by the tachyon, thereby permitting a high energy tachyon to retain its energy over galactic distances. Topics treated include the choice and Schwinger Action Principle variations of an appropriate Lagrangian, spinorial wave functions, relevant Green's functions, a functional description of an S-Matrix and generating functional, and a variety of interesting kinematical processes, including photon emission and reabsorption, and relevant annihilation and scattering effects. A version of Ehrenfest's theorem is developed, in order to provide a foundation for a classical description of charged tachyons in an external electromagnetic field. Applications are then made to three outstanding astrophysical puzzles : dark matter, gamma ray bursts and ultra high energy cosmic rays.

H. M. Fried; Y. Gabellini

2007-09-04T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Quantum solitons at strong coupling  

E-Print Network (OSTI)

We examine the effect of one loop quantum corrections on the formation of nontopological solitons in a strongly coupled scalar-fermionic Yukawa theory. The exact one fermion loop contribution is incorporated by using a nonlocal method to correct the local derivative expansion approximation (DE) of the effective action. As the Yukawa coupling is increased we find that the nonlocal corrections play an increasingly important role. The corrections cause the scalar field to increase in depth while maintaining its size. This increases the energy of the bag configuration, but this is compensated for by more tightly bound fermionic states with lower energy. In contrast to the semi-classical picture without quantum corrections, the binding energy is small, and the total energy scales directly with the Yukawa coupling. This confirms the qualitative behavior found in earlier work using the second order DE, although the quantitative solutions differ.

Stewart, I W; Stewart, Iain W.; Blunden, Peter G.

1997-01-01T23:59:59.000Z

422

Emergence of Quantum Mechanics from a Sub-Quantum Statistical Mechanics  

E-Print Network (OSTI)

A research program within the scope of theories on "Emergent Quantum Mechanics" is presented, which has gained some momentum in recent years. Via the modeling of a quantum system as a non-equilibrium steady-state maintained by a permanent throughput of energy from the zero-point vacuum, the quantum is considered as an emergent system. We implement a specific "bouncer-walker" model in the context of an assumed sub-quantum statistical physics, in analogy to the results of experiments by Couder's group on a classical wave-particle duality. We can thus give an explanation of various quantum mechanical features and results on the basis of a "21st century classical physics", such as the appearance of Planck's constant, the Schr\\"odinger equation, etc. An essential result is given by the proof that averaged particle trajectories' behaviors correspond to a specific type of anomalous diffusion termed "ballistic" diffusion on a sub-quantum level. It is further demonstrated both analytically and with the aid of computer simulations that our model provides explanations for various quantum effects such as double-slit or n-slit interference. We show the averaged trajectories emerging from our model to be identical to Bohmian trajectories, albeit without the need to invoke complex wave functions or any other quantum mechanical tool. Finally, the model provides new insights into the origins of entanglement, and, in particular, into the phenomenon of a "systemic" nonlocality.

Gerhard Groessing

2013-04-12T23:59:59.000Z

423

Gravity as BF theory plus potential  

E-Print Network (OSTI)

Spin foam models of quantum gravity are based on Plebanski's formulation of general relativity as a constrained BF theory. We give an alternative formulation of gravity as BF theory plus a certain potential term for the B-field. When the potential is taken to be infinitely steep one recovers general relativity. For a generic potential the theory still describes gravity in that it propagates just two graviton polarizations. The arising class of theories is of the type amenable to spin foam quantization methods, and, we argue, may allow one to come to terms with renormalization in the spin foam context.

Kirill Krasnov

2009-07-23T23:59:59.000Z

424

Quantum chromodynamics and nuclear physics at extreme energy density. Progress report, May 15, 1993--May 14, 1994  

SciTech Connect

This report briefly discusses the following topics: quark-gluon plasma and high-energy collisions; hadron structure and chiral dynamics; nonperturbative studies and nonabelian gauge theories; and studies in quantum field theory.

Mueller, B.; Springer, R.P.

1994-05-15T23:59:59.000Z

425

Parabolic Whittaker Functions and Topological Field Theories I  

E-Print Network (OSTI)

First, we define a generalization of the standard quantum Toda chain inspired by a construction of quantum cohomology of partial flags spaces GL(\\ell+1)/P, P a parabolic subgroup. Common eigenfunctions of the parabolic quantum Toda chains are generalized Whittaker functions given by matrix elements of infinite-dimensional representations of gl(\\ell+1). For maximal parabolic subgroups (i.e. for P such that GL(\\ell+1)/P=\\mathbb{P}^{\\ell}) we construct two different representations of the corresponding parabolic Whittaker functions as correlation functions in topological quantum field theories on a two-dimensional disk. In one case the parabolic Whittaker function is given by a correlation function in a type A equivariant topological sigma model with the target space \\mathbb{P}^{\\ell}. In the other case the same Whittaker function appears as a correlation function in a type B equivariant topological Landau-Ginzburg model related with the type A model by mirror symmetry. This note is a continuation of our project of establishing a relation between two-dimensional topological field theories (and more generally topological string theories) and Archimedean (\\infty-adic) geometry. From this perspective the existence of two, mirror dual, topological field theory representations of the parabolic Whittaker functions provide a quantum field theory realization of the local Archimedean Langlands duality for Whittaker functions. The established relation between the Archimedean Langlands duality and mirror symmetry in two-dimensional topological quantum field theories should be considered as a main result of this note.

Anton Gerasimov; Dimitri Lebedev; Sergey Oblezin

2010-02-12T23:59:59.000Z

426

Continuous Emission of A Radiation Quantum  

E-Print Network (OSTI)

It is in accordance with such experiments as single photon self-interference that a photon, conveying one radiation energy quantum "$ h \\times$ frequency", is spatially extensive and stretches an electromagnetic wave train. A wave train, hence an energy quantum, can only be emitted by its source gradually. In both the two processes the wave and "particle" attributes of the radiation field are simultaneously prominent, where an overall satisfactory theory has been lacking. This paper presents a first principles treatment, in a unified framework of the classical and quantum mechanics, of the latter process, the emission of a single radiation quantum based on the dynamics of the radiation-emitting source, a charged oscillator which is itself extensive across its confining potential well. During the emission of one single radiation quantum, the extensive charged oscillator undergoes a continuous radiation damping and is non-stationary. This process is in this work treated using a quasi stationary approach, whereby the classical equation of motion, which directly facilitates the correspondence principle for a particle oscillator, and the quantum wave equation are established for each sufficiently brief time interval. As an inevitable consequence of the division of the total time for emitting one single quantum, a fractional Planck constant $h$ is introduced. The solutions to the two simultaneous equations yield for the charged oscillator a continuously exponentially decaying Hamiltonian that is at the same time quantised with respect to the fractional-$h$ at any instant of time; and the radiation wave field emitted over time stretches a wave train of finite length. The total system of the source and radiation field maintains at any time (integer $n$ times) one whole energy quantum, $h \\times$ frequency, in complete accordance with the notion of quantum mechanics and experiment.

J. X. Zheng-Johansson

2013-11-29T23:59:59.000Z

427

Geometrical perspective on quantum states and quantum computation  

E-Print Network (OSTI)

We interpret quantum computing as a geometric evolution process by reformulating finite quantum systems via Connes' noncommutative geometry. In this formulation, quantum states are represented as noncommutative connections, while gauge transformations on the connections play a role of unitary quantum operations. Thereby, a geometrical model for quantum computation is presented, which is equivalent to the quantum circuit model. This result shows a geometric way of realizing quantum computing and as such, provides an alternative proposal of building a quantum computer.

Zeqian Chen

2013-11-20T23:59:59.000Z

428

Entanglement Theory and the Second Law of Thermodynamics  

E-Print Network (OSTI)

Entanglement is central both to the foundations of quantum theory and, as a novel resource, to quantum information science. The theory of entanglement establishes basic laws, such as the non-increase of entanglement under local operations, that govern its manipulation and aims to draw from them formal analogies to the second law of thermodynamics. However, while in the second law the entropy uniquely determines whether a state is adiabatically accessible from another, the manipulation of entanglement under local operations exhibits a fundamental irreversibility which prevents the existence of such an order. Here we show that a reversible theory of entanglement and a rigorous relationship with thermodynamics may be established when one considers all non-entangling transformations. The role of the entropy in the second law is taken by the asymptotic relative entropy of entanglement in the basic law of entanglement. We show the usefulness of this new approach to general resource theories and to quantum information theory.

Fernando G. S. L. Brandao; Martin B. Plenio

2008-10-14T23:59:59.000Z

429

A Graphic Representation of States for Quantum Copying Machines  

E-Print Network (OSTI)

The aim of this paper is to introduce a new graphic representation of quantum states by means of a specific application: the analysis of two models of quantum copying machines. The graphic representation by diagrams of states offers a clear and detailed visualization of quantum information's flow during the unitary evolution of not too complex systems. The diagrams of states are exponentially more complex in respect to the standard representation and this clearly illustrates the discrepancy of computational power between quantum and classical systems. After a brief introductive exposure of the general theory, we present a constructive procedure to illustrate the new representation by means of concrete examples. Elementary diagrams of states for single-qubit and two-qubit systems and a simple scheme to represent entangled states are presented. Quantum copying machines as imperfect cloners of quantum states are introduced and the quantum copying machines of Griffiths and Niu and of Buzek and Hillery are analyzed, determining quantum circuits of easier interpretation. The method has indeed shown itself to be extremely successful for the representation of the involved quantum operations and it has allowed to point out the characteristic aspects of the quantum computations examined.

Sara Felloni; Giuliano Strini

2006-09-29T23:59:59.000Z

430

The 2 1 reconstruction of the rutile TiO2(011) surface: A combined density functional theory, X-ray diffraction, and scanning  

E-Print Network (OSTI)

t An extensive search for possible structural models of the (2 ? 1)-reconstructed rutile TiO2(011) surface was carried out by means of density functional theory (DFT) calculations. A number of models were iden- tified that have much lower surface energies than the previously-proposed `titanyl' and `microfaceting' models

Diebold, Ulrike

431

The information-theoretic costs of simulating quantum measurements  

E-Print Network (OSTI)

Winter's measurement compression theorem stands as one of the most penetrating insights of quantum information theory (QIT). In addition to making an original and profound statement about measurement in quantum theory, it also underlies several other general protocols in QIT. In this paper, we provide a full review of Winter's measurement compression theorem, detailing the information processing task, giving examples for understanding it, reviewing Winter's achievability proof, and detailing a new approach to its single-letter converse theorem. We prove an extension of the theorem to the case in which the sender is not required to receive the outcomes of the simulated measurement. The total cost of common randomness and classical communication can be lower for such a "non-feedback" simulation, and we prove a single-letter converse theorem demonstrating optimality. We then review the Devetak-Winter theorem on classical data compression with quantum side information, providing new proofs of its achievability and converse parts. From there, we outline a new protocol that we call "measurement compression with quantum side information," announced previously by two of us in our work on triple trade-offs in quantum Shannon theory. This protocol has several applications, including its part in the "classically-assisted state redistribution" protocol, which is the most general protocol on the static side of the quantum information theory tree, and its role in reducing the classical communication cost in a task known as local purity distillation. We also outline a connection between measurement compression with quantum side information and recent work on entropic uncertainty relations in the presence of quantum memory. Finally, we prove a single-letter theorem characterizing measurement compression with quantum side information when the sender is not required to obtain the measurement outcome.

Mark M. Wilde; Patrick Hayden; Francesco Buscemi; Min-Hsiu Hsieh

2012-06-19T23:59:59.000Z

432

Macroscopic quantum behaviour of periodic quantum systems  

E-Print Network (OSTI)

In this paper we introduce a simple procedure for computing the macroscopic quantum behaviour of periodic quantum systems in the high energy regime. The macroscopic quantum coherence is ascribed to a one-particle state, not to a condensate of a many-particle system; and we are referring to a system of high energy but with few degrees of freedom. We show that, in the first order of approximation, the quantum probability distributions converge to its classical counterparts in a clear fashion, and that the interference effects are strongly suppressed. The harmonic oscillator provides a testing ground for these ideas and yields excellent results.

A. Martn-Ruiz; J. Bernal; Adrin Carbajal-Domnguez

2013-09-02T23:59:59.000Z

433

Stripe Dynamics, Global Phase Ordering and Quantum  

E-Print Network (OSTI)

By modeling the stripe phase in cuprates as spin gapped stripes coupled to the RVB liquid of preformed electron pairs, I derive the low energy effective theory of the RVB phase variable. It is found that the effect of stripe dynamics (including both longitudinal and transverse modes) leads to incipient temporal phase stiffness in the RVB liquid, which tunes a quantum phase transition toward a superconducting ground state with global phase order. Physical consequences of this quantum criticality are discussed. Typeset using REVTEX 1 I.

Criticality High; Tc Superconductors; Wenjun Zheng

2000-01-01T23:59:59.000Z

434

The pre-history of quantum computation  

E-Print Network (OSTI)

The main ideas behind developments in the theory and technology of quantum computation were formulated in the late 1970s and early 1980s by two physicists in the West and a mathematician in the former Soviet Union. It is not generally known in the West that the subject has roots in the Russian technical literature. The author hopes to present as impartial a synthesis as possible of the early history of thought on this subject. The role of reversible and irreversible computational processes is examined briefly as it relates to the origins of quantum computing and the so-called Information Paradox in physics.

P. H. Potgieter

2004-02-17T23:59:59.000Z

435

Robustness and Errors in Quantum Optimal Control  

E-Print Network (OSTI)

We introduce a new approach to quantify the robustness of optimal control of closed quantum systems. Our theory allows to assess the degree of distortion that can be applied to a set of known optimal control parameters, which are solutions of an optimal control problem. The formalism is applied to an exactly solvable model and to the Landau-Zener model, whose optimal control problem is solvable only numerically. The presented method is of importance for any application where a high degree of controllability of the quantum system dynamics is required.

Calarco, Antonio Negretti; Rosario Fazio; Tommaso

2010-01-01T23:59:59.000Z

436

NONEQUILIBRIUM QUANTUM STATISTICAL MECHANICS AND THERMODYNAMICS ?  

E-Print Network (OSTI)

The purpose of this work is to discuss recent progress in deriving the fundamental laws of thermodynamics (0 th, 1 st and 2 nd-law) from nonequilibrium quantum statistical mechanics. Basic thermodynamic notions are clarified and different reversible and irreversible thermodynamic processes are studied from the point of view of quantum statistical mechanics. Special emphasis is put on new adiabatic theorems for steady states close to and far from equilibrium, and on investigating cyclic thermodynamic processes using an extension of Floquet theory. This work is based on the authors doctoral thesis, ETH-Diss 16187.

Walid K. Abou Salem

2006-01-01T23:59:59.000Z

437

Modeling Quantum Information Systems abstract  

Science Conference Proceedings (OSTI)

Paul E. Black and Andrew W. Lane, Modeling Quantum Information Systems, Proc. SPIE, Vol. 5436, Quantum Information ...

2013-05-07T23:59:59.000Z

438

Quantum logic and coherent control  

Science Conference Proceedings (OSTI)

... CS Wood, "Quantum Computation, Spectroscopy of ... K. Fujikawa (Elsevier Science, Amsterdam, 1999 ... of trapped atomic ions," Advances in Quantum ...

2013-06-15T23:59:59.000Z

439

NIST Quantum Physics Division Staff  

Science Conference Proceedings (OSTI)

Quantum Physics Division. Staff. Name, Position, Phone. ... Physics Laboratory. Quantum Physics Division. Thomas O'Brian, Acting Chief. ...

2013-09-10T23:59:59.000Z

440

Quantum logarithmic Sobolev inequalities and rapid mixing  

Science Conference Proceedings (OSTI)

A family of logarithmic Sobolev inequalities on finite dimensional quantum state spaces is introduced. The framework of non-commutative L{sub p}-spaces is reviewed and the relationship between quantum logarithmic Sobolev inequalities and the hypercontractivity of quantum semigroups is discussed. This relationship is central for the derivation of lower bounds for the logarithmic Sobolev (LS) constants. Essential results for the family of inequalities are proved, and we show an upper bound to the generalized LS constant in terms of the spectral gap of the generator of the semigroup. These inequalities provide a framework for the derivation of improved bounds on the convergence time of quantum dynamical semigroups, when the LS constant and the spectral gap are of the same order. Convergence bounds on finite dimensional state spaces are particularly relevant for the field of quantum information theory. We provide a number of examples, where improved bounds on the mixing time of several semigroups are obtained, including the depolarizing semigroup and quantum expanders.

Kastoryano, Michael J. [Dahlem Center for Complex Quantum Systems, Freie Universitaet Berlin, 14195 Berlin (Germany)] [Dahlem Center for Complex Quantum Systems, Freie Universitaet Berlin, 14195 Berlin (Germany); Temme, Kristan [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2013-05-15T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Density-functional theory study of gramicidin A ion channel geometry and electronic properties  

E-Print Network (OSTI)

Understanding the mechanisms underlying ion channel function from the atomic-scale requires accurate ab initio modelling as well as careful experiments. Here, we present a density functional theory (DFT) study of the ion channel gramicidin A, whose inner pore conducts only monovalent cations and whose conductance has been shown to depend on the side chains of the amino acids in the channel. We investigate the ground-state geometry and electronic properties of the channel in vacuum, focusing on their dependence on the side chains of the amino acids. We find that the side chains affect the ground state geometry, while the electrostatic potential of the pore is independent of the side chains. This study is also in preparation for a full, linear scaling DFT study of gramicidin A in a lipid bilayer with surrounding water. We demonstrate that linear scaling DFT methods can accurately model the system with reasonable computational cost. Linear scaling DFT allows ab initio calculations with 10,000 to 100,000 atoms an...

Todorovi?, Milica; Gillan, M J; Miyazaki, Tsuyoshi

2013-01-01T23:59:59.000Z

442

Radiation reaction in nonrelativistic quantum electrodynamics  

SciTech Connect

We derive the Heisenberg operator equation of motion for a nonrelativistic point electron coupled to the quantized electromagnetic field, including radiation reaction. The derivation proceeds in close analogy with the classical theory of extended charges (with the Compton wavelength formally playing the role of a size parameter), and we give a systematic treatment of the classical problem, showing explicitly from the equation of motion that the classical theory shows no runaway solutions or preacceleration when the electron size exceeds the classical electron radius. In the quantum-mechanical case, we show that the electrostatic self-energy of a point electron is zero and that, for values of the fine-structure constant ..cap alpha.. approximately-less-than 1, the equation of motion admits neither runaway solutions nor noncausal motion. Furthermore, the correspondence limit of the solutions to the quantum-mechanical equation of motion agrees with that of the Lorentz-Dirac theory in the classical regime, but without the imposition of additional conditions and with no possibility of observable noncausality. Thus, a consistent picture of a classical point electron emerges in the correspondence limit of the quantum-mechanical theory.

Moniz, E.J.; Sharp, D.H.

1977-05-15T23:59:59.000Z

443

QUANTUM CONVERSION IN PHOTOSYNTHESIS  

E-Print Network (OSTI)

W _7405-eng- 4B QUANTUM CONVERSION IN PHOTOSYNTHESIS Melvint r UCRL-9 533 QUANrUM CONVERSION IN PHWOSYNTHESIS * Melvinitself. The primary quantum conversion act is an ionization

Calvin, Melvin

2008-01-01T23:59:59.000Z

444

Instrumentation for quantum computers  

E-Print Network (OSTI)

Quantum computation poses challenging engineering and basic physics issues for the control of nanoscale systems. In particular, experimental realizations of up to seven-qubit NMR quantum computers have acutely illustrated ...

Huang, Wei-Han, 1979-

2004-01-01T23:59:59.000Z

445

Quantum Chevalley groups  

E-Print Network (OSTI)

The goal of this paper is to construct quantum analogues of Chevalley groups inside completions of quantum groups or, more precisely, inside completions of Hall algebras of finitary categories.

Berenstein, Arkady

2012-01-01T23:59:59.000Z

446

Searching with Quantum Computers  

E-Print Network (OSTI)

This article introduces quantum computation by analogy with probabilistic computation. A basic description of the quantum search algorithm is given by representing the algorithm as a C program in a novel way.

Lov K. Grover

2000-11-30T23:59:59.000Z

447

Quantum walks: a comprehensive review  

E-Print Network (OSTI)

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important resul...

Venegas-Andraca, Salvador E

2012-01-01T23:59:59.000Z

448

Quantum discord as a resource in quantum protocols  

E-Print Network (OSTI)

We show quantum discord to be a resource in quantum information processing. This is accomplished by proving a relation between quantum discord and the yield of the quantum protocols. Our results are derived by studying the fully quantum Slepian-Wolf protocol -- a unification of all bipartite, unidirectional and memoryless quantum communication protocols -- in the presence of noise. As examples, we elucidate the significance of quantum discord in quantum teleportation, superdense coding, and entanglement distillation. Finally, we provide the first quantitative relation between quantum discord and the query complexity of quantum computations.

Madhok, Vaibhav

2012-01-01T23:59:59.000Z

449

Quantum money from knots  

E-Print Network (OSTI)

Quantum money is a cryptographic protocol in which a mint can produce a quantum state, no one else can copy the state, and anyone (with a quantum computer) can verify that the state came from the mint. We present a concrete quantum money scheme based on superpositions of diagrams that encode oriented links with the same Alexander polynomial. We expect our scheme to be secure against computationally bounded adversaries.

Farhi, Edward; Hassidim, Avinatan; Lutomirski, Andrew; Shor, Peter

2010-01-01T23:59:59.000Z

450

Quantum money from knots  

E-Print Network (OSTI)

Quantum money is a cryptographic protocol in which a mint can produce a quantum state, no one else can copy the state, and anyone (with a quantum computer) can verify that the state came from the mint. We present a concrete quantum money scheme based on superpositions of diagrams that encode oriented links with the same Alexander polynomial. We expect our scheme to be secure against computationally bounded adversaries.

Edward Farhi; David Gosset; Avinatan Hassidim; Andrew Lutomirski; Peter Shor

2010-04-28T23:59:59.000Z

451

Quantum Algorithm Zoo  

Science Conference Proceedings (OSTI)

... 27 Andrew M. Childs, Richard Cleve, Stephen P. Jordan, and David Yeung Discrete-query quantum algorithm for NAND trees. ...

2013-11-11T23:59:59.000Z

452

Quantum Physics Portal  

Science Conference Proceedings (OSTI)

... for Science and Technology (CODATA) issues recommended values of the fundamental physical constants ... see all Quantum Physics programs and ...

2013-03-07T23:59:59.000Z

453

Quantum Physics Division Homepage  

Science Conference Proceedings (OSTI)

... Contact. Physical Measurement Laboratory Quantum Physics Division General Information: 303-735-1985 Telephone 303-492-5235 Facsimile. ...

2013-06-28T23:59:59.000Z

454

Free Energy of ABJM Theory  

E-Print Network (OSTI)

The free energy of ABJM theory has previously been computed in the strong and weak coupling limits. In this note, we report on results for the computation of the first non-vanishing quantum correction to the free energy, from the field theory side. The correction can be expressed in terms of a thermal mass for the scalar fields. This mass vanishes to 1-loop order, but there is a non-vanishing result to 2-loop order. Hence, the leading correction to the free energy is non-analytic in the 't Hooft coupling constant lambda. The reason is that the infrared divergences necessitate a resummation of ring diagrams and a related reorganization of perturbation theory, in which already the leading correction receives contributions from all orders in lambda. These results suggest that the free energy interpolates smoothly between weak and strong coupling.

Mikael Smedbck

2011-03-24T23:59:59.000Z

455

Curvature and Frontier Orbital Energies in Density Functional Theory  

SciTech Connect

Perdew et al. [Phys. Rev. Lett 49, 1691 (1982)] discovered and proved two different properties that exact Kohn-Sham density functional theory (DFT) must obey: (i) The exact total energy versus particle number must be a series of linear segments between integer electron points; (ii) Across an integer number of electrons, the exchange-correlation potential may ``jump by a constant, known as the derivative discontinuity (DD). Here, we show analytically that in both the original and the generalized Kohn-Sham formulation of DFT, the two are in fact two sides of the same coin. Absence of a derivative discontinuity necessitates deviation from piecewise linearity, and the latter can be used to correct for the former, thereby restoring the physical meaning of the orbital energies. Using selected small molecules, we show that this results in a simple correction scheme for any underlying functional, including semi-local and hybrid functionals as well as Hartree-Fock theory, suggesting a practical correction for the infamous gap problem of density functional theory. Moreover, we show that optimally-tuned range-separated hybrid functionals can inherently minimize both DD and curvature, thus requiring no correction, and show that this can be used as a sound theoretical basis for novel tuning strategies.

Stein, Tamar; Autschbach, Jochen; Govind, Niranjan; Kronik, Leeor; Baer, Roi

2012-12-20T23:59:59.000Z

456

NREL: Energy Sciences - Solid-State Theory  

NLE Websites -- All DOE Office Websites (Extended Search)

Solid-State Theory Solid-State Theory Image showing a roughly spherical red shape that looks like an apple that is floating within a yellow hemispherical shell. The shell is floating over a square below that shows an orange ring pattern bordered by yellow, then light blue, then darker blue. Square of the wave function (red) of a hole state in a spherical CdSe colloidal quantum dot (shape in yellow). The main research activities of the Solid-State Theory team within NREL's Theoretical Materials Science Group include the following: Theory of photovoltaic semiconductors Statistical and electronic theory of metal and semiconductor alloys Semiconductor nanostructures Inverse design of materials Computational methods in first-principles theories. This team provides the main theoretical thrust in the Center for Inverse

457

Vacuum energy: quantum hydrodynamics vs quantum gravity  

E-Print Network (OSTI)

We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.

G. E. Volovik

2005-05-20T23:59:59.000Z

458

Multiphoton Quantum Optics and Quantum State Engineering  

E-Print Network (OSTI)

We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all aspects of such an enormously vast subject. Here we choose to concentrate our attention on parametric processes in nonlinear media, with special emphasis on the engineering of nonclassical states of photons and atoms. We present a detailed analysis of the methods and techniques for the production of genuinely quantum multiphoton processes in nonlinear media, and the corresponding models of multiphoton effective interactions. We review existing proposals for the classification, engineering, and manipulation of nonclassical states, including Fock states, macroscopic superposition states, and multiphoton generalized coherent states. We introduce and discuss the structure of canonical multiphoton quantum optics and the associated one- and two-mode canonical multiphoton squeezed states. This framework provides a consistent multiphoton generalization of two-photon quantum optics and a consistent Hamiltonian description of multiphoton processes associated to higher-order nonlinearities. Finally, we discuss very recent advances that by combining linear and nonlinear optical devices allow to realize multiphoton entangled states of the electromnagnetic field, that are relevant for applications to efficient quantum computation, quantum teleportation, and related problems in quantum communication and information.

F. Dell'Anno; S. De Siena; F. Illuminati

2007-01-09T23:59:59.000Z

459

Stephen Hawking Quantum Gravity  

E-Print Network (OSTI)

Stephen Hawking and Quantum Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 4 Nov 2000 #12; Stephen Hawking and Quantum Gravity Abstract: Through research, Stephen Hawking has captured a place in the popular imagina- tion. Quantum gravity in its various

Visser, Matt

460

Quantum money from knots  

E-Print Network (OSTI)

Quantum money is a cryptographic protocol in which a mint can produce a quantum state, no one else can copy the state, and anyone (with a quantum computer) can verify that the state came from the mint. We present a concrete ...

Farhi, Edward

Note: This page contains sample records for the topic "theory dft quantum" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Quantum Computing Computer Scientists  

E-Print Network (OSTI)

Quantum Computing for Computer Scientists Noson S. Yanofsky and Mirco A. Mannucci #12;© May 2007 Noson S. Yanofsky Mirco A. Mannucci #12;Quantum Computing for Computer Scientists Noson S. Yanofsky of Vector Spaces 3 The Leap From Classical to Quantum 3.1 Classical Deterministic Systems 3.2 Classical

Yanofsky, Noson S.

462

Topological Quantum Distillation  

E-Print Network (OSTI)

We construct a class of topological quantum codes to perform quantum entanglement distillation. These codes implement the whole Clifford group of unitary operations in a fully topological manner and without selective addressing of qubits. This allows us to extend their application also to quantum teleportation, dense coding and computation with magic states.

H. Bombin; M. A. Martin-Delgado

2006-05-16T23:59:59.000Z

463

A metageometric enquiry concerning time, space, and quantum physics  

E-Print Network (OSTI)

An enquiry into the physical nature of time and space and into the ontology of quantum mechanics from a metageometric perspective, resulting from the belief that geometric thought and language are powerless to farther understanding of these issues, restricting instead physical progress. The nature and assumptions of quantum gravity are analysed critically, including misgivings about the relevance of the Planck scale to it and its lack of observational referent in the natural world. The anthropic foundations of geometry are investigated. The exclusive use of geometric thought from antiquity to present-day physics is found to permeate all new attempts towards better theories, including quantum gravity and, within it, even pregeometry. The problem of the ether is found to have perpetuated itself up to the present by transmuting its form from mechanical, through metric, to geometric. A clarification is made of the physical, mathematical, and psychological foundations of relativity and quantum theories. The former...

Meschini, Diego

2008-01-01T23:59:59.000Z

464

Quantum radiative corrections to slow-roll inflation  

E-Print Network (OSTI)

We consider the nonminimally coupled lambda phi^4 scalar field theory in de Sitter space and construct the renormalization group improved renormalized effective theory at the one-loop level. Based on the corresponding quantum Friedmann equation and the scalar field equation of motion, we calculate the quantum radiative corrections to the scalar spectral index n_s, gravitational wave spectral index n_g and the ratio r of tensor to scalar perturbations. When compared with the standard (tree-level) values, we find that the quantum contributions are suppressed by lambda N^2 where N denotes the number of e-foldings. Hence there is an N^2 enhancement with respect to the naive expectation, which is due to the infrared enhancement of scalar vacuum fluctuations characterising de Sitter space. Since observations constrain lambda to be very small lambda ~ 10^(-12) and N ~ 50-60, the quantum corrections in this inflationary model are unobservably small.

Ante Bilandzic; Tomislav Prokopec

2007-04-15T23:59:59.000Z

465

Quantum Information Science | ornl.gov  

NLE Websites -- All DOE Office Websites (Extended Search)

Engineering Analysis Behavioral Sciences Geographic Information Science and Technology Quantum Information Science Quantum Communication and Security Quantum-Enhanced Sensing...

466

The Nonperturbative Quantum de Sitter Universe  

E-Print Network (OSTI)

The dynamical generation of a four-dimensional classical universe from nothing but fundamental quantum excitations at the Planck scale is a long-standing challenge to theoretical physicists. A candidate theory of quantum gravity which achieves this goal without invoking exotic ingredients or excessive fine-tuning is based on the nonperturbative and background-independent technique of Causal Dynamical Triangulations. We demonstrate in detail how in this approach a macroscopic de Sitter universe, accompanied by small quantum fluctuations, emerges from the full gravitational path integral, and how the effective action determining its dynamics can be reconstructed uniquely from Monte Carlo data. We also provide evidence that it may be possible to penetrate to the sub-Planckian regime, where the Planck length is large compared to the lattice spacing of the underlying regularization of geometry.

J. Ambjorn; A. Goerlich; J. Jurkiewicz; R. Loll

2008-07-28T23:59:59.000Z

467

Notes on entropic characteristics of quantum channels  

E-Print Network (OSTI)

One of most important issues in quantum information theory concerns transmission of information through noisy quantum channels. We discuss few channel characteristics expressed by means of generalized entropies. Such characteristics can often be dealt in line with more usual treatment based on the von Neumann entropies. For any channel, we show that the $q$-average output entropy of degree $q\\geq1$ is bounded from above by the $q$-entropy of the input density matrix. Concavity properties of the $(q,s)$-entropy exchange are considered. Fano type quantum bounds on the $(q,s)$-entropy exchange are derived. We also give upper bounds on the map $(q,s)$-entropies in terms of the output entropy, corresponding to the completely mixed input.

Alexey E. Rastegin

2012-06-14T23:59:59.000Z

468

Projective Structures in Loop Quantum Cosmology  

E-Print Network (OSTI)

Projective structures have successfully been used for the construction of measures in the framework of loop quantum gravity. In the present paper we establish such a structure for the space $R \\sqcup R_Bohr$ recently constructed in the context of homogeneous isotropic loop quantum cosmology. This space has the advantage to be canonically embedded into the quantum configuration space of the full theory, but, in contrast to the traditional space $R_Bohr$, there exists no Haar measure on $R \\sqcup R_Bohr$. The introduced projective structure, however, allows to construct a family of canonical measures on $R \\sqcup R_Bohr$ whose corresponding Hilbert spaces of square integrable functions we finally investigate.

Maximilian Hanusch

2013-09-03T23:59:59.000Z

469

Quantum Energy Inequality for the Massive Ising Model  

E-Print Network (OSTI)

A Quantum Energy Inequality (QEI) is derived for the massive Ising model, giving a state-independent lower bound on suitable averages of the energy density; the first QEI to be established for an interacting quantum field theory with nontrivial S-matrix. It is shown that the Ising model has one-particle states with locally negative energy densities, and that the energy density operator is not additive with respect to combination of one-particle states into multi-particle configurations.

Bostelmann, Henning; Fewster, Christopher J

2013-01-01T23:59:59.000Z

470

Biased nonlocal quantum games  

E-Print Network (OSTI)

We address the question of when quantum entanglement is a useful resource for information processing tasks by presenting a new class of nonlocal games that are simple, direct, generalizations of the Clauser Horne Shimony Holt game. For some ranges of the parameters that specify the games, quantum mechanics offers an advantage, while, surprisingly, for others quantum mechanics is no more powerful than classical mechanics in performing the nonlocal task. This sheds new light on the difference between classical, quantum and super-quantum correlations.

Thomas Lawson; Noah Linden; Sandu Popescu

2010-11-29T23:59:59.000Z

471

Quantum Multiobservable Control  

E-Print Network (OSTI)

We present deterministic algorithms for the simultaneous control of an arbitrary number of quantum observables. Unlike optimal control approaches based on cost function optimization, quantum multiobservable tracking control (MOTC) is capable of tracking predetermined homotopic trajectories to target expectation values in the space of multiobservables. The convergence of these algorithms is facilitated by the favorable critical topology of quantum control landscapes. Fundamental properties of quantum multiobservable control landscapes that underlie the efficiency of MOTC, including the multiobservable controllability Gramian, are introduced. The effects of multiple control objectives on the structure and complexity of optimal fields are examined. With minor modifications, the techniques described herein can be applied to general quantum multiobjective control problems.

Raj Chakrabarti; Rebing Wu; Herschel Rabitz

2008-05-12T23:59:59.000Z

472