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1

Novel Materials Become Multifunctional at the Ultimate Quantum Limit |  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Outsmarting Flu Viruses Outsmarting Flu Viruses How Lead-Free Solder (Mis)Behaves under Stress Dynamics of Polymer Chains Atop Different Materials Priming the Pump in the Fight against Drug-Resistant Tuberculosis The Ties that Bind Metals to Proteins Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Novel Materials Become Multifunctional at the Ultimate Quantum Limit NOVEMBER 9, 2012 Bookmark and Share Illustration of a 4-unit-cell film of NdNiO3 (white) confined by LaAlO3 (blue) at the boundaries to make a quantum well structure. Our computers carry out their functions on several semiconducting devices layered together in the very smallest of spaces, known as quantum wells,

2

Outsmarting Flu Viruses | Advanced Photon Source  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

How Lead-Free Solder (Mis)Behaves under Stress How Lead-Free Solder (Mis)Behaves under Stress Dynamics of Polymer Chains Atop Different Materials Priming the Pump in the Fight against Drug-Resistant Tuberculosis The Ties that Bind Metals to Proteins A Novel Nanobio Catalyst for Biofuels Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Outsmarting Flu Viruses OCTOBER 9, 2012 Bookmark and Share Surface representation of influenza hemagglutinin (white) with the newly identified sites of vulnerability colored red. Each site is unique and targeted by a different antibody. CR8033 (blue) binds to the head of HA, CR8071 (green) just below the head, while CR9114 (yellow) binds the stem. The stem binding CR9114, with its cross-neutralizing ability for influenza

3

Quantum limits to estimation of photon deformation  

E-Print Network [OSTI]

We address potential deviations of radiation field from the bosonic behaviour and employ local quantum estimation theory to evaluate the ultimate bounds to precision in the estimation of these deviations using quantum-limited measurements on optical signals. We consider different classes of boson deformation and found that intensity measurement on coherent or thermal states would be suitable for their detection making, at least in principle, tests of boson deformation feasible with current quantum optical technology. On the other hand, we found that the quantum signal-to-noise ratio (QSNR) is vanishing with the deformation itself for all the considered classes of deformations and probe signals, thus making any estimation procedure of photon deformation inherently inefficient. A partial way out is provided by the polynomial dependence of the QSNR on the average number of photon, which suggests that, in principle, it would be possible to detect deformation by intensity measurements on high-energy thermal states.

Giovanni De Cillis; Matteo G. A. Paris

2014-07-08T23:59:59.000Z

4

Quantum dynamics in the thermodynamic limit  

SciTech Connect (OSTI)

The description of spontaneous symmetry breaking that underlies the connection between classically ordered objects in the thermodynamic limit and their individual quantum-mechanical building blocks is one of the cornerstones of modern condensed-matter theory and has found applications in many different areas of physics. The theory of spontaneous symmetry breaking, however, is inherently an equilibrium theory, which does not address the dynamics of quantum systems in the thermodynamic limit. Here, we will use the example of a particular antiferromagnetic model system to show that the presence of a so-called thin spectrum of collective excitations with vanishing energy - one of the well-known characteristic properties shared by all symmetry-breaking objects - can allow these objects to also spontaneously break time-translation symmetry in the thermodynamic limit. As a result, that limit is found to be able, not only to reduce quantum-mechanical equilibrium averages to their classical counterparts, but also to turn individual-state quantum dynamics into classical physics. In the process, we find that the dynamical description of spontaneous symmetry breaking can also be used to shed some light on the possible origins of Born's rule. We conclude by describing an experiment on a condensate of exciton polaritons which could potentially be used to experimentally test the proposed mechanism.

Wezel, Jasper van [Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom)

2008-08-01T23:59:59.000Z

5

Thermodynamic Limits, Non-commutative Probability, and Quantum Entanglement  

E-Print Network [OSTI]

We construct a rigourous model of quantum measurement. A two-state model of a negative temperature amplifier, such as a laser, is taken to a classical thermodynamic limit. In the limit, it becomes a classical measurement apparatus obeying the stochastic axioms of quantum mechanics. Thus we derive the probabilities from a deterministic Schroedinger's equation by procedures analogous to those of classical statistical mechanics. This requires making precise the notion of `macroscopic.'

Joseph F. Johnson

2005-07-02T23:59:59.000Z

6

Quantum Apices: Identifying Limits of Entanglement, Nonlocality, & Contextuality  

E-Print Network [OSTI]

This work develops analytic methods to quantitatively demarcate quantum reality from its subset of classical phenomenon, as well as from the superset of general probabilistic theories. Regarding quantum nonlocality, we discuss how to determine the quantum limit of Bell-type linear inequalities. In contrast to semidefinite programming approaches, our method allows for the consideration of inequalities with abstract weights, by means of leveraging the Hermiticity of quantum states. Recognizing that classical correlations correspond to measurements made on separable states, we also introduce a practical method for obtaining sufficient separability criteria. We specifically vet the candidacy of driven and undriven superradiance as schema for entanglement generation. We conclude by reviewing current approaches to quantum contextuality, emphasizing the operational distinction between nonlocal and contextual quantum statistics. We utilize our abstractly-weighted linear quantum bounds to explicitly demonstrate a set of conditional probability distributions which are simultaneously compatible with quantum contextuality while being incompatible with quantum nonlocality. It is noted that this novel statistical regime implies an experimentally-testable target for the Consistent Histories theory of quantum gravity.

Elie Wolfe

2014-09-08T23:59:59.000Z

7

ETHTH/9926 ON A CLASSICAL LIMIT OF QUANTUM THEORY  

E-Print Network [OSTI]

--8093 Z¨urich, Switzerland 2 Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10471, USA #12; On a Classical Limit of Quantum Theory . . . , 1 1 GeneralB and ~, and from the speed of light, c, and Newton's law of gravitational attraction he could then infer

8

The optimal bound of quantum erasure with limited means  

E-Print Network [OSTI]

In practical applications of quantum information science, quantum systems can have non-negligible interactions with the environment, and this generally degrades the power of quantum protocols as it introduces noise. Counteracting this by appropriately measuring the environment (and therefore projecting its state) would require access all the necessary degrees of freedom, which in practice can be far too hard to achieve. To better understand one's limitations, we calculate the upper bound of optimal quantum erasure (i.e. the highest recoverable visibility, or "coherence"), when erasure is realistically limited to an accessible subspace of the whole environment. In the particular case of a two-dimensional accessible environment, the bound is given by the sub-fidelity of two particular states of the \\emph{inaccessible} environment, which opens a new window into understanding the connection between correlated systems. We also provide an analytical solution for a three-dimensional accessible environment. This result provides also an interesting operational interpretation of sub-fidelity. We end with a statistical analysis of the expected visibility of an optimally erased random state and we find that 1) if one picks a random pure state of 2 qubits, there is an optimal measurement that allows one to distill a 1-qubit state with almost 90\\% visibility and 2) if one picks a random pure state of 2 qubits in an inaccessible environment, there is an optimal measurement that allows one to distill a 1-qubit state with almost twice its initial visibility.

Filippo M. Miatto; Kevin Piché; Thomas Brougham; Robert W. Boyd

2014-10-08T23:59:59.000Z

9

The Limiting Distribution of Decoherent Quantum Random Walks  

E-Print Network [OSTI]

The behaviors of one-dimensional quantum random walks are strikingly different from those of classical ones. However, when decoherence is involved, the limiting distributions take on many classical features over time. In this paper, we study the decoherence on both position and ``coin'' spaces of the particle. We propose a new analytical approach to investigate these phenomena and obtain the generating functions which encode all the features of these walks. Specifically, from these generating functions, we find exact analytic expressions of several moments for the time and noise dependence of position. Moreover, the limiting position distributions of decoherent quantum random walks are shown to be Gaussian in an analytical manner. These results explicitly describe the relationship between the system and the level of decoherence.

Kai Zhang

2008-04-28T23:59:59.000Z

10

An optically trapped mirror for reaching the standard quantum limit  

E-Print Network [OSTI]

The preparation of a mechanical oscillator driven by quantum back-action is a fundamental requirement to reach the standard quantum limit (SQL) for force measurement, in optomechanical systems. However, thermal fluctuating force generally dominates a disturbance on the oscillator. In the macroscopic scale, an optical linear cavity including a suspended mirror has been used for the weak force measurement, such as gravitational-wave detectors. This configuration has the advantages of reducing the dissipation of the pendulum (i.e., suspension thermal noise) due to a gravitational dilution by using a thin wire, and of increasing the circulating laser power. However, the use of the thin wire is weak for an optical torsional anti-spring effect in the cavity, due to the low mechanical restoring force of the wire. Thus, there is the trade-off between the stability of the system and the sensitivity. Here, we describe using a triangular optical cavity to overcome this limitation for reaching the SQL. The triangular cavity can provide a sensitive and stable system, because it can optically trap the mirror's motion of the yaw, through an optical positive torsional spring effect. To show this, we demonstrate a measurement of the torsional spring effect caused by radiation pressure forces.

Nobuyuki Matsumoto; Yuta Michimura; Yoichi Aso; Kimio Tsubono

2014-05-19T23:59:59.000Z

11

Nonrelativistic Limit of a Dirac Polaron in Relativistic Quantum Electrodynamics  

E-Print Network [OSTI]

# Department of Mathematics, Hokkaido University Sapporo 060­0810, Japan E­mail: arai@math.sci.hokudai.ac.jp February 22, 2006 Abstract A quantum system of a Dirac particle interacting with the quantum radiation particle with spin 1/2--- in an external potential V and interacting with the quantum radiation field

12

Experimental demonstration of information to energy conversion in a quantum system at the Landauer Limit  

E-Print Network [OSTI]

Landauer's principle sets fundamental thermodynamic constraints for classical and quantum information processing. Here we measure, for the first time, the heat dissipated in elementary quantum logic gates, at the Landauer limit, implemented in a Nuclear Magnetic Resonance system. This allows for the detailed study of irreversible entropy production in quantum information processors.

John P. P. Silva; Roberto S. Sarthour; Alexandre M. Souza; Ivan S. Oliveira; John Goold; Kavan Modi; Diogo O. Soares-Pinto; Lucas C. Céleri

2014-12-23T23:59:59.000Z

13

Limits on classical communication from quantum entropy power inequalities  

E-Print Network [OSTI]

Almost all modern communication systems rely on electromagnetic fields as a means of information transmission, and finding the capacities of these systems is a problem of significant practical importance. The Additive White Gaussian Noise (AWGN) channel is often a good approximate description of such systems, and its capacity is given by a simple formula. However, when quantum effects are important, estimating the capacity becomes difficult: a lower bound is known, but a similar upper bound is missing. We present strong new upper bounds for the classical capacity of quantum additive noise channels, including quantum analogues of the AWGN channel. Our main technical tool is a quantum entropy power inequality that controls the entropy production as two quantum signals combine at a beam splitter. Its proof involves a new connection between entropy production rates and a quantum Fisher information, and uses a quantum diffusion that smooths arbitrary states towards gaussians.

Robert Koenig; Graeme Smith

2012-05-15T23:59:59.000Z

14

AN EXPERIMENT ON THE LIMITS OF QUANTUM ELECTRODYNAMICS HEPL-170  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

tt^ tt^ \ # AN EXPERIMENT ON THE LIMITS OF QUANTUM ELECTRODYNAMICS HEPL-170 l6K/Gen-2 *'%.. W. C, Barber, Burton Rlchter, and W. Ko H. Panofsky, Stanford University, Facsimile Price $_ M i c r o f i l m Price $ A v a i l a b l e from the O f f i c e o f Technical Services Department of Commerce Washington 25, D. C. and G. K. O'Neill and B. Gittelman, Princeton University Internal Report Not to be Published June 1959 Supported by the joint program of the Office of Naval Research and the U. S. Atomic Energy Commission under Contract N6onr-25ll6 (NR 022 026). High-Energy Physics Laboratory W. W. Hansen Laboratories of Physics Stanford University Stanford, California f>)iiafra9KMaiegTAwn>. fictmefo S MKie u AfVMivEQ. mxam* M l U m T H E RCtOVING SECMIk DISCLAIMER This report was prepared as an account of work sponsored by an

15

Title of Ph.D. Dissertation: NEAR QUANTUM LIMITED MEASUREMENT IN NANOELECTROMECHANICAL SYSTEMS  

E-Print Network [OSTI]

Abstract Title of Ph.D. Dissertation: NEAR QUANTUM LIMITED MEASUREMENT IN NANOELECTROMECHANICAL quality factors. Since these systems can be cooled close to their ground states with existing cryogenic detection scheme, quantum mechanics places a lower limit on the product of position shot noise, Sx

16

White noise approach to the low density limit of a quantum particle in a gas  

E-Print Network [OSTI]

The white noise approach to the investigation of the dynamics of a quantum particle interacting with a dilute and in general non-equilibrium gaseous environment in the low density limit is outlined. The low density limit is the kinetic Markovian regime when only pair collisions (i.e., collisions of the test particle with one particle of the gas at one time moment) contribute to the dynamics. In the white noise approach one first proves that the appropriate operators describing the gas converge in the sense of appropriate matrix elements to certain operators of quantum white noise. Then these white noise operators are used to derive quantum white noise and quantum stochastic equations describing the approximate dynamics of the total system consisting of the particle and the gas. The derivation is given ab initio, starting from the exact microscopic quantum dynamics. The limiting dynamics is described by a quantum stochastic equation driven by a quantum Poisson process. This equation then applied to the derivation of quantum Langevin equation and linear Boltzmann equation for the reduced density matrix of the test particle. The first part of the paper describes the approach which was developed by L. Accardi, I.V. Volovich and the author and uses the Fock-antiFock (or GNS) representation for the CCR algebra of the gas. The second part presents the approach to the derivation of the limiting equations directly in terms of the correlation functions, without use of the Fock-antiFock representation. This approach simplifies the derivation and allows to express the strength of the quantum number process directly in terms of the one-particle $S$-matrix.

Alexander Pechen

2006-07-19T23:59:59.000Z

17

Implementations of quantum logic: fundamental and experimental limits  

Science Journals Connector (OSTI)

...these to come closer to the fundamental limits, such that at least...of computation reveals the fundamental connections between the laws...at the output of the OR gate does not provide enough information...motional state, but this operator does not change the dressed-state...

1998-01-01T23:59:59.000Z

18

16-QAM Quantum Receiver with Hybrid Structure Outperforming the Standard Quantum Limit  

E-Print Network [OSTI]

We present a quantum receiver for 16-QAM signals discrimination with hybrid structure containing a homodyne receiver and a displacement receiver, which can outperform the SQL, and the performance can be improved by an optimized displacement.

Yuan Zuo; Ke Li; Bing Zhu

2014-12-15T23:59:59.000Z

19

Einstein gravity as the thermodynamic limit of an underlying quantum statistics  

E-Print Network [OSTI]

The black hole area theorem suggests that classical general relativity is the thermodynamic limit of a quantum statistics. The degrees of freedom of the statistical theory cannot be the spacetime metric. We argue that the statistical theory should be constructed from a noncommutative gravity, whose classical, and thermodynamic, approximation is Einstein gravity. The noncommutative gravity theory exhibits a duality between quantum fields and macroscopic black holes, which is used to show that the black hole possesses an entropy of the order of its area. The principle on which this work is based also provides a possible explanation for the smallness of the cosmological constant, and for the quantum measurement problem, indicating that this is a promising avenue towards the merger of quantum mechanics and gravity.

T. P. Singh

2009-05-15T23:59:59.000Z

20

Quantum Behavior of Graphene Transistors near the Scaling Limit Yanqing Wu,,  

E-Print Network [OSTI]

Quantum Behavior of Graphene Transistors near the Scaling Limit Yanqing Wu,, * Vasili Perebeinos properties of graphene have been a key research focus for the past few years. However, external components interference effects were demonstrated in graphene heterojunctions formed by a top gate. Here phase coherent

Perebeinos, Vasili

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Limiter  

DOE Patents [OSTI]

A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

1984-10-19T23:59:59.000Z

22

Squeezed-light-enhanced atom interferometry below the standard quantum limit  

E-Print Network [OSTI]

We investigate the prospect of enhancing the phase sensitivity of atom interferometers in the Mach-Zehnder configuration with squeezed light. Ultimately, this enhancement is achieved by transferring the quantum state of squeezed light to one or more of the atomic input beams, thereby allowing operation below the standard quantum limit. We analyze in detail three specific schemes that utilize (1) single-mode squeezed optical vacuum (i.e. low frequency squeezing), (2) two-mode squeezed optical vacuum (i.e. high frequency squeezing) transferred to both atomic inputs, and (3) two-mode squeezed optical vacuum transferred to a single atomic input. Crucially, our analysis considers incomplete quantum state transfer (QST) between the optical and atomic modes, and the effects of depleting the initially-prepared atomic source. Unsurprisingly, incomplete QST degrades the sensitivity in all three schemes. We show that by measuring the transmitted photons and using information recycling [Phys. Rev. Lett. 110, 053002 (2013)], the degrading effects of incomplete QST on the sensitivity can be substantially reduced. In particular, information recycling allows scheme (2) to operate at the Heisenberg limit irrespective of the QST efficiency, even when depletion is significant. Although we concentrate on Bose-condensed atomic systems, our scheme is equally applicable to ultracold thermal vapors.

Stuart S. Szigeti; Behnam Tonekaboni; Wing Yung S. Lau; Samantha N. Hood; Simon A. Haine

2014-12-22T23:59:59.000Z

23

Optical properties of quantum wires: Fermi-edge singularity exponents and the low-density limit  

Science Journals Connector (OSTI)

A simple many-body treatment of the Fermi-edge singularities in absorption and photoemission in quasi-one-dimensional quantum wires is presented. The problem of calculating the transition probabilities is reduced to numerically evaluating a sufficient number of determinants describing the overlap of the appropriate many-body wave functions. It is found that the edge singularity exponents can be determined from the size dependence of these determinants. The well-known connection between these exponents and the phase shifts at the Fermi surface are explicitly checked for one-dimensional quantum wires. The singular edge behavior is interpreted in terms of Friedel’s replacement transitions and is found to be due to a replacement transition to the bound state, a result confirmed by considering the evolution of the spectra in the low-density limit. © 1996 The American Physical Society.

H. H. von Grünberg; K. P. Jain; R. J. Elliott

1996-07-15T23:59:59.000Z

24

Limiter  

DOE Patents [OSTI]

A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

Cohen, Samuel A. (Hopewell, NJ); Hosea, Joel C. (Princeton, NJ); Timberlake, John R. (Allentown, NJ)

1986-01-01T23:59:59.000Z

25

Quantum-limited phase-matching effect in a {Lambda}-type laser system  

SciTech Connect (OSTI)

The theory of a quantum-limited phase-matching effect in a {Lambda}-type lasing system is studied in detail based on the quantum Langevin approach. Two quasimonochromatic fields are directly generated based on two lasing transitions. We find that the coherence between two lasers can well exceed the linewidth of either laser field. This result denotes that two field phases match each other although either laser field has a high phase fluctuation. Unlike the phase-matching effect based on atomic absorption, the final coherence between two laser fields here is not limited by saturation broadening, and the higher laser intensities lead to a higher coherence. Additionally, based on a linear stability analysis, we find that the instability of the field steady state can substantially restrict the occurrence of this phase-matching effect in the bad-cavity limit for a high pump rate. We also discuss the spectrum of amplitude fluctuations of output fields, and the result shows that the squeezing of amplitude fluctuations at low frequencies for a single field oscillating inside the cavity is damaged in the case of two fields oscillating.

Yu Deshui [Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Chen Jingbiao [Institute of Quantum Electronics, and State Key Laboratory of Advanced Optical Communication System and Network, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

2011-06-15T23:59:59.000Z

26

Limit Theorems for the Discrete-Time Quantum Walk on a Graph with Joined Half Lines  

E-Print Network [OSTI]

We consider a discrete-time quantum walk $W_{t,\\kappa}$ at time $t$ on a graph with joined half lines $\\mathbb{J}_\\kappa$, which is composed of $\\kappa$ half lines with the same origin. Our analysis is based on a reduction of the walk on a half line. The idea plays an important role to analyze the walks on some class of graphs with \\textit{symmetric} initial states. In this paper, we introduce a quantum walk with an enlarged basis and show that $W_{t,\\kappa}$ can be reduced to the walk on a half line even if the initial state is \\textit{asymmetric}. For $W_{t,\\kappa}$, we obtain two types of limit theorems. The first one is an asymptotic behavior of $W_{t,\\kappa}$ which corresponds to localization. For some conditions, we find that the asymptotic behavior oscillates. The second one is the weak convergence theorem for $W_{t,\\kappa}$. On each half line, $W_{t,\\kappa}$ converges to a density function like the case of the one-dimensional lattice with a scaling order of $t$. The results contain the cases of quantum walks starting from the general initial state on a half line with the general coin and homogeneous trees with the Grover coin.

Kota Chisaki; Norio Konno; Etsuo Segawa

2010-09-07T23:59:59.000Z

27

Limits to Quantum Gravity Effects from Observations of TeV Flares in Active Galaxies  

E-Print Network [OSTI]

We have used data from the TeV gamma-ray flare associated with the active galaxy Markarian 421 observed on 15 May 1996 to place bounds on the possible energy-dependence of the speed of light in the context of an effective quantum gravitational energy scale. The possibility of an observable time dispersion in high energy radiation has recently received attention in the literature, with some suggestions that the relevant energy scale could be less than the Planck mass and perhaps as low as 10^16 GeV. The limits derived here indicate this energy scale to be in excess of 4x10^16 GeV at the 95% confidence level. To the best of our knowledge, this constitutes the first convincing limit on such phenomena in this energy regime.

S. D. Biller; A. C. Breslin; J. Buckley; M. Catanese; M. Carson; D. A. Carter-Lewis; M. F. Cawley; D. J. Fegan; J. Finley; J. A. Gaidos; A. M. Hillas; F. Krennrich; R. C. Lamb; R. Lessard; C. Masterson; J. E. McEnery; B. McKernan; P. Moriarty; J. Quinn; H. J. Rose; F. Samuelson; G. Sembroski; P. Skelton; T. C. Weekes

1998-10-13T23:59:59.000Z

28

The fundamental limit on the rate of quantum dynamics: the unified bound is tight  

E-Print Network [OSTI]

The question of how fast a quantum state can evolve has attracted a considerable attention in connection with quantum measurement, metrology, and information processing. Since only orthogonal states can be unambiguously distinguished, a transition from a state to an orthogonal one can be taken as the elementary step of a computational process. Therefore, such a transition can be interpreted as the operation of "flipping a qubit", and the number of orthogonal states visited by the system per unit time can be viewed as the maximum rate of operation. A lower bound on the orthogonalization time, based on the energy spread DeltaE, was found by Mandelstam and Tamm. Another bound, based on the average energy E, was established by Margolus and Levitin. The bounds coincide, and can be exactly attained by certain initial states if DeltaE=E; however, the problem remained open of what the situation is otherwise. Here we consider the unified bound that takes into account both DeltaE and E. We prove that there exist no initial states that saturate the bound if DeltaE is not equal to E. However, the bound remains tight: for any given values of DeltaE and E, there exists a one-parameter family of initial states that can approach the bound arbitrarily close when the parameter approaches its limit value. The relation between the largest energy level, the average energy, and the orthogonalization time is also discussed. These results establish the fundamental quantum limit on the rate of operation of any information-processing system.

Lev B. Levitin; Tommaso Toffoli

2009-05-20T23:59:59.000Z

29

Bohmian mechanics, the quantum-classical correspondence and the classical limit: the case of the square billiard  

E-Print Network [OSTI]

Square billiards are quantum systems complying with the dynamical quantum-classical correspondence. Hence an initially localized wavefunction launched along a classical periodic orbit evolves along that orbit, the spreading of the quantum amplitude being controlled by the spread of the corresponding classical statistical distribution. We investigate wavepacket dynamics and compute the corresponding de Broglie-Bohm trajectories in the quantum square billiard. We also determine the trajectories and statistical distribution dynamics for the equivalent classical billiard. Individual Bohmian trajectories follow the streamlines of the probability flow and are generically non-classical. This can also hold even for short times, when the wavepacket is still localized along a classical trajectory. This generic feature of Bohmian trajectories is expected to hold in the classical limit. We further argue that in this context decoherence cannot constitute a viable solution in order to recover classicality.

A. Matzkin

2008-06-19T23:59:59.000Z

30

Non-relativistic Limit of a Dirac-Maxwell Operator in Relativistic Quantum  

E-Print Network [OSTI]

Arai #3; Department of Mathematics, Hokkaido University Sapporo 060-0810, Japan E-mail: arai | a relativistic charged particle with spin 1=2 | interacting with the quantum radiation #12;eld. For convenience the Dirac particle system only, H rad is the free Hamiltonian of the quantum radiation #12;eld (a quantum

31

Limiting Factors for High Temperature Operation of THz Quantum Cascade Lasers  

Science Journals Connector (OSTI)

We theoretically investigate the temperature dependence of the carrier transport in GaAs-based THz quantum cascade lasers and identify the factors restricting high-temperature...

Jirauschek, Christian; Lugli, Paolo

32

Cyclotron resonance to 100 mK of a GaAs heterojunction in the ultra-quantum limit  

Science Journals Connector (OSTI)

A helium dilution refrigerator has been modified to enable cyclotron resonance measurements to 100 mK on low-density, 2D electron systems in the ultra-quantum limit. Previous cyclotron resonance work to 300 mK indicates the presence of a phase boundary at a filling factor of vc?110, separating gas-like behavior at vmK, the system is spin polarized only at low values of v.

J.G. Michels; S. Hill; R.J. Warburton; G.M. Summers; P. Gee; J. Singleton; R.J. Nicholas; C.T. Foxon; J.J. Harris

1994-01-01T23:59:59.000Z

33

Theoretical Limits of Photovoltaics Efficiency and Possible Improvements by Intuitive Approaches Learned from Photosynthesis and Quantum Coherence  

E-Print Network [OSTI]

In this review, we present and discussed the main trends in photovoltaics with emphasize on the conversion efficiency limits. The theoretical limits of various photovoltaics device concepts are presented and analyzed using a flexible detailed balance model where more discussion emphasize is toward the losses. Also, few lessons from nature and other fields to improve the conversion efficiency in photovoltaics are presented and discussed as well. From photosynthesis, the perfect exciton transport in photosynthetic complexes can be utilized for PVs. Also, we present some lessons learned from other fields like recombination suppression by quantum coherence. For example, the coupling in photosynthetic reaction centers is used to suppress recombination in photocells.

Fahhad H Alharbi; Sabre Kais

2014-02-09T23:59:59.000Z

34

FIRST EXPERIMENTAL RESULTS FROM DEGAS, THE QUANTUM LIMITED BRIGHTNESS ELECTRON SOURCE  

E-Print Network [OSTI]

LIMITED BRIGHTNESS ELECTRON SOURCE* M. S. Zolotorev 1 , E.limited brightness electron source, has been completed atand by a thermionic electron source placed at the DEGAS IR

Zolotorev, Max S.

2008-01-01T23:59:59.000Z

35

Engineering quantum pure states of a trapped cold ion beyond the Lamb-Dicke limit  

Science Journals Connector (OSTI)

Based on the conditional quantum dynamics of laser-ion interactions, we propose an efficient theoretical scheme to deterministically generate quantum pure states of a single trapped cold ion without performing the Lamb-Dicke approximation. An arbitrary quantum state can be created by sequentially using a series of classical laser pulses with selected frequencies, initial phases and durations. As special examples, we further show how to create or approximate several typical macroscopic quantum states, such as the phase state and the even/odd coherent states. Unlike previous schemes operating in the Lamb-Dicke regime, the present one does well for an arbitrary-strength coupling between the internal and external degrees of freedom of the ion. The experimental realizability of this approach is also discussed.

L. F. Wei; Yu-xi Liu; Franco Nori

2004-12-01T23:59:59.000Z

36

Engineering quantum pure states of a trapped cold ion beyond the Lamb-Dicke limit  

E-Print Network [OSTI]

Based on the conditional quantum dynamics of laser-ion interaction, we propose an efficient theoretical scheme to deterministically generate quantum pure states of a single trapped cold ion without performing the Lamb-Dicke approximation. An arbitrary quantum state can be created by using a series of classical laser beams with selected frequencies, initial phases and durations. As special examples, we further show how to create or approximate several typical macroscopic quantum states, such as the phase state and (even/odd) coherent states. Unlike previous schemes operated in the Lamb-Dicke regime, the present one does well for arbitrary strength coupling between the internal and external degrees of freedom of the ion. The experimental realizability of this approach is also discussed.

L. F. Wei; Yu-xi Liu; Franco Nori

2003-08-14T23:59:59.000Z

37

Relativeness in Quantum Gravity: Limitations and Frame Dependence of Semiclassical Descriptions  

E-Print Network [OSTI]

Consistency between quantum mechanical and general relativistic views of the world is a longstanding problem, which becomes particularly prominent in black hole physics. We develop a coherent picture addressing this issue by studying the quantum mechanics of an evolving black hole. After interpreting the Bekenstein-Hawking entropy as the entropy representing the degrees of freedom that are coarse-grained to obtain a semiclassical description from the microscopic theory of quantum gravity, we discuss the properties these degrees of freedom exhibit when viewed from the semiclassical standpoint. We are led to the conclusion that they show features which we call extreme relativeness and spacetime-matter duality---a nontrivial reference frame dependence of their spacetime distribution and the dual roles they play as the "constituents" of spacetime and as thermal radiation. We describe black hole formation and evaporation processes in distant and infalling reference frames, showing that these two properties allow u...

Nomura, Yasunori; Weinberg, Sean J

2014-01-01T23:59:59.000Z

38

The Retrocausal Nature of Quantum Measurement Revealed by Partial and Weak Measurements  

SciTech Connect (OSTI)

Quantum measurement is sometimes more effective when its result is not definite. Partial measurement turns the initial superposition not into a certain state but to a greater probability for it, enabling probing the quantum state in cases where complete measurement makes the noncommuting variables inaccessible. It also enables full quantum erasure that, unlike prevailing method, can be carried out even on recorded results. Aharonov's weak measurement is another method of imprecisely measuring quantum variables, outsmarting the uncertainty principle in even subtler ways. Happily, the two methods complement and corroborate one another in several interesting ways. We gedankenly apply these measurements to the EPR case. A pair of entangled particles undergoes more than one pair of partial and weak measurements, which, unlike complete measurements, leave them partially correlated. Their erasure is then shown to be as nonlocal as measurement itself. Surprisingly, the temporal relations between such measurements in the EPR setting do not follow the temporal sequence perceived by an external observer. For each particle, the measurements performed on the other operate as if they occurred (with signs reversed) in its own past, and in reversed order. This fully accords with Cramer's transactional interpretation and Aharonov's two state-vector formalism.

Elitzur, Avshalom C. [Iyar, Israeli Institute for Advanced Research, Rehovot (Israel); Cohen, Eliahu [School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel)

2011-11-29T23:59:59.000Z

39

Two-loop fermion self-energy in reduced quantum electrodynamics and application to the ultra-relativistic limit of graphene  

E-Print Network [OSTI]

We compute the two-loop fermion self-energy in massless reduced quantum electrodynamics for an arbitrary gauge using the method of integration by parts. Focusing on the limit where the photon field is four-dimensional, our formula involves only recursively one-loop integrals and can therefore be evaluated exactly. From this formula, we deduce the anomalous scaling dimension of the fermion field as well as the renormalized fermion propagator up to two loops. The results are then applied to the ultra-relativistic limit of graphene and compared with similar results obtained for four-dimensional and three-dimensional quantum electrodynamics.

A. V. Kotikov; S. Teber

2014-02-07T23:59:59.000Z

40

Unitary limit and quantum interference effect in disordered two-dimensional crystals with nearly half-filled bands  

Science Journals Connector (OSTI)

Based on the self-consistent T-matrix approximation, the quantum interference (QI) effects are studied with the diagrammatic technique in weakly disordered two-dimensional crystals with nearly half-filled bands. In addition to the usual 0-mode cooperon and diffuson, there exists ?-mode cooperon and diffuson in the unitary limit due to the particle-hole symmetry. The diffusive ? modes are gapped by the deviation from the exactly nested Fermi surface. The conductivity diagrams with the gapped ?-mode cooperon or diffuson are found to give rise to unconventional features of the QI effects. Besides inelastic scattering, thermal fluctuation is also shown to be an important dephasing mechanism in the QI processes related to the diffusive ? modes. In the proximity of the nesting case, a power-law antilocalization effect appears due to the ?-mode diffuson. For large deviation from the nested Fermi surface, this antilocalization effect is suppressed, and the conductivity remains to have the usual logarithmic weak-localization correction contributed by the 0-mode cooperon. As a result, the dc conductivity in the unitary limit becomes a nonmonotonic function of the temperature or the sample size, which is quite different from the prediction of the usual weak-localization theory.

Y. H. Yang; Y. G. Wang; M. Liu; D. Y. Xing

2003-07-29T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Equation of state of dense plasmas: Orbital-free molecular dynamics as the limit of quantum molecular dynamics for high-Z elements  

SciTech Connect (OSTI)

The applicability of quantum molecular dynamics to the calculation of the equation of state of a dense plasma is limited at high temperature by computational cost. Orbital-free molecular dynamics, based on a semiclassical approximation and possibly on a gradient correction, is a simulation method available at high temperature. For a high-Z element such as lutetium, we examine how orbital-free molecular dynamics applied to the equation of state of a dense plasma can be regarded as the limit of quantum molecular dynamics at high temperature. For the normal mass density and twice the normal mass density, we show that the pressures calculated with the quantum approach converge monotonically towards those calculated with the orbital-free approach; we observe a faster convergence when the orbital-free approach includes the gradient correction. We propose a method to obtain an equation of state reproducing quantum molecular dynamics results up to high temperatures where this approach cannot be directly implemented. With the results already obtained for low-Z plasmas, the present study opens the way for reproducing the quantum molecular dynamics pressure for all elements up to high temperatures.

Danel, J.-F.; Blottiau, P.; Kazandjian, L.; Piron, R.; Torrent, M. [CEA, DAM, DIF, 91297 Arpajon (France)

2014-10-15T23:59:59.000Z

42

Quantum theory of optical temporal phase and instantaneous frequency. II. Continuous-time limit and state-variable approach to phase-locked loop design  

SciTech Connect (OSTI)

We consider the continuous-time version of our recently proposed quantum theory of optical temporal phase and instantaneous frequency [M. Tsang et al., Phys. Rev. A 78, 053820 (2008)]. Using a state-variable approach to estimation, we design homodyne phase-locked loops that can measure the temporal phase with quantum-limited accuracy. We show that postprocessing can further improve the estimation performance if delay is allowed in the estimation. We also investigate the fundamental uncertainties in the simultaneous estimation of harmonic-oscillator position and momentum via continuous optical phase measurements from the classical estimation theory perspective. In the case of delayed estimation, we find that the inferred uncertainty product can drop below that allowed by the Heisenberg uncertainty relation. Although this result seems counterintuitive, we argue that it does not violate any basic principle of quantum mechanics.

Tsang, Mankei; Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Lloyd, Seth [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2009-05-15T23:59:59.000Z

43

Investigation of photoexcited parallel conduction in GaAs/AlGaAs heterostructures in the quantum limit  

E-Print Network [OSTI]

', giving rise to the persistent photoconductivity (PPC). As the density of 2-DEG carriers in- creased the systematic shift of the quantum Hall plateaus and corresponding 40 12. 10. T = 75mK Iso= 500 nA 0 b cd c hl 6. Q. 0. 0. 0 1. 0 2. 0 3. 0 4... resistance between 0. 0 and 0. 3 T. 16, 2-DEG carrier density determined from SdH oscillations versus natural logarithm of photon dose at 75 mK. 17, (a) Deviation of the Hall resistance from quantized value at i = 4 plateau versus photon dose; (b...

Kobiela, Pawel Stanislaw

1986-01-01T23:59:59.000Z

44

Electronic topological transition in an n-BiSb semiconductor alloy in the quantum limit range of magnetic fields for H-parallel C{sub 2}  

SciTech Connect (OSTI)

The galvanomagnetic properties of single-crystal samples of the Bi{sub 0.93}Sb{sub 0.07} semiconductor alloy with the electron density n = 1.6 x 10{sup 17} cm{sup -3} in magnetic fields up to 14 T at T = 1.6 K have been investigated. The resistivity {rho} and Hall coefficient R have been measured as functions of the magnetic field directed along the binary axis of a crystal for a current flowing through a sample along the bisector axis; i.e., the components {rho}{sub 22} and R{sub 32,1} have been measured. The strong anisotropy of the electron spectrum of the samples makes it possible to separately observe quantum oscillations of the magnetoresistance {rho}{sub 22}(H) for H -parallel C{sub 2} in low magnetic fields for two equivalent ellipsoids with small extremal cross sections (secondary ellipsoids) and in high magnetic fields for electrons of the ellipsoid with a large extremal cross section (main ellipsoid). An increase in the energy of the electrons of secondary ellipsoids in the quantum limit magnetic fields is accompanied by the flow of electrons to the main ellipsoid; i.e., an electronic topological transition occurs from the three-valley electron spectrum to the single-valley one. After the flow stops, the Fermi energy E{sub F} increases from 18 meV to 27.8 meV. With an increase in the quantizing magnetic field, the Fermi energy of the electrons decreases both in the region of quantum oscillations of the resistance that are attributed to the electrons of the secondary ellipsoids and in the region of oscillations associated with the electrons of the main ellipsoid. The Hall coefficient R{sub 32,1} decreases in high magnetic fields; this behavior indicates the absence of the electron magnetic freezing effect.

Red'ko, N. A., E-mail: nikolaj.a.redko@mail.ioffe.ru; Kagan, V. D.; Volkov, M. P. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2010-08-15T23:59:59.000Z

45

Limited Lawn & Limited Commercial  

E-Print Network [OSTI]

Limited Lawn & Ornamental Limited Commercial Landscape Maintenance Review and Exams Limited for Commercial Landscape Maintenance Application: http://www.flaes.org/ pdf/lndspckt.pdf Limited Certification.floridatermitehelp.org or request by phone at 850-921-4177. Limited Lawn & Ornamental/Limited Commercial Landscape Maintenance

Watson, Craig A.

46

Limited Lawn & Limited Commercial  

E-Print Network [OSTI]

Limited Lawn & Ornamental Limited Commercial Landscape Maintenance Review and Exams Limited-921-4177. Limited Lawn & Ornamental/Limited Commercial Landscape Maintenance: Ornamental and Turf Pest Control (SM 7&O/Structural only). See web locations below for applications. Limited Certification for Commercial Landscape

Jawitz, James W.

47

Quantum melting of charge ice and non-Fermi-liquid behavior: An exact solution for the extended Falicov-Kimball model in the ice-rule limit  

E-Print Network [OSTI]

An exact solution is obtained for a model of itinerant electrons coupled to ice-rule variables on the tetrahedron Husimi cactus, an analogue of the Bethe lattice of corner-sharing tetrahedra. It reveals a quantum critical point with the emergence of non-Fermi-liquid behavior in melting of the "charge ice" insulator. The electronic structure is compared with the numerical results for the pyrochlore-lattice model to elucidate the physics of electron systems interacting with the tetrahedron ice rule.

Masafumi Udagawa; Hiroaki Ishizuka; Yukitoshi Motome

2010-06-04T23:59:59.000Z

48

Quantum melting of charge ice and non-Fermi-liquid behavior: An exact solution for the extended Falicov-Kimball model in the ice-rule limit  

E-Print Network [OSTI]

An exact solution is obtained for a model of itinerant electrons coupled to ice-rule variables on the tetrahedron Husimi cactus, an analogue of the Bethe lattice of corner-sharing tetrahedra. It reveals a quantum critical point with the emergence of non-Fermi-liquid behavior in melting of the "charge ice" insulator. The electronic structure is compared with the numerical results for the pyrochlore-lattice model to elucidate the physics of electron systems interacting with the tetrahedron ice rule.

Udagawa, Masafumi; Motome, Yukitoshi

2010-01-01T23:59:59.000Z

49

Quantum Bootstrapping via Compressed Quantum Hamiltonian Learning  

E-Print Network [OSTI]

Recent work has shown that quantum simulation is a valuable tool for learning empirical models for quantum systems. We build upon these results by showing that a small quantum simulators can be used to characterize and learn control models for larger devices for wide classes of physically realistic Hamiltonians. This leads to a new application for small quantum computers: characterizing and controlling larger quantum computers. Our protocol achieves this by using Bayesian inference in concert with Lieb-Robinson bounds and interactive quantum learning methods to achieve compressed simulations for characterization. Whereas Fisher information analysis shows that current methods which employ short-time evolution are suboptimal, interactive quantum learning allows us to overcome this limitation. We illustrate the efficiency of our bootstrapping protocol by showing numerically that an 8-qubit Ising model simulator can be used to calibrate and control a 50 qubit Ising simulator while using only about 750 kilobits of experimental data.

Nathan Wiebe; Christopher Granade; David G. Cory

2014-09-04T23:59:59.000Z

50

Limitations on entropic Bell inequalities  

E-Print Network [OSTI]

The derivation of Bell inequalities in terms of quantum statistical (thermodynamic) entropies is considered. Inequalities of the Wigner form are derived but shown to be extremely limiting in their applicability due to the nature of the density matrices involved. This also helps to identify a limitation in the Cerf-Adami inequalities.

Ian T. Durham

2006-08-01T23:59:59.000Z

51

Engineering Thin-Film Oxide Interfaces | Advanced Photon Source  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Novel Materials Become Multifunctional at the Ultimate Quantum Limit Novel Materials Become Multifunctional at the Ultimate Quantum Limit Outsmarting Flu Viruses How Lead-Free Solder (Mis)Behaves under Stress Dynamics of Polymer Chains Atop Different Materials Priming the Pump in the Fight against Drug-Resistant Tuberculosis Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Engineering Thin-Film Oxide Interfaces NOVEMBER 12, 2012 Bookmark and Share LAO thin films on STO substrates are depicted in the top schematics (LAO indicated by blue spheres, STO by green spheres). The top left-hand panel demonstrates a chemically broad interface resulting from conventional growth in a low pressure oxygen environment. In contrast, the top

52

Plasmonic Quantum Cascade Laser Antenna  

Science Journals Connector (OSTI)

We demonstrate the plasmonic quantum cascade laser antenna, that can confine mid-infrared radiation beyond the diffraction limit, by integrating gold optical antennas on the laser...

Yu, Nanfang; Cubukcu, Ertugrul; Diehl, Laurent; Crozier, Kenneth; Capasso, Federico

53

Quantum Thermometry  

E-Print Network [OSTI]

In this review article we revisit and spell out the details of previous work on how Berry phase can be used to construct a precision quantum thermometer. An important advantage of such a scheme is that there is no need for the thermometer to acquire thermal equilibrium with the sample. This reduces measurement times and avoids precision limitations. We also review how such methods can be used to detect the Unruh effect.

Robert B. Mann; Eduardo Martin-Martinez

2014-05-22T23:59:59.000Z

54

Nested Quantum Error Correction Codes  

E-Print Network [OSTI]

The theory of quantum error correction was established more than a decade ago as the primary tool for fighting decoherence in quantum information processing. Although great progress has already been made in this field, limited methods are available in constructing new quantum error correction codes from old codes. Here we exhibit a simple and general method to construct new quantum error correction codes by nesting certain quantum codes together. The problem of finding long quantum error correction codes is reduced to that of searching several short length quantum codes with certain properties. Our method works for all length and all distance codes, and is quite efficient to construct optimal or near optimal codes. Two main known methods in constructing new codes from old codes in quantum error-correction theory, the concatenating and pasting, can be understood in the framework of nested quantum error correction codes.

Zhuo Wang; Kai Sun; Hen Fan; Vlatko Vedral

2009-09-28T23:59:59.000Z

55

Quantum Privacy and Quantum Coherence  

Science Journals Connector (OSTI)

We derive a simple relation between a quantum channel's capacity to convey coherent (quantum) information and its usefulness for quantum cryptography.

Benjamin Schumacher and Michael D. Westmoreland

1998-06-22T23:59:59.000Z

56

Hybrid Quantum Computation in Quantum Optics  

E-Print Network [OSTI]

We propose a hybrid quantum computing scheme where qubit degrees of freedom for computation are combined with quantum continuous variables for communication. In particular, universal two-qubit gates can be implemented deterministically through qubit-qubit communication, mediated by a continuous-variable bus mode ("qubus"), without direct interaction between the qubits and without any measurement of the qubus. The key ingredients are controlled rotations of the qubus and unconditional qubus displacements. The controlled rotations are realizable through typical atom-light interactions in quantum optics. For such interactions, our scheme is universal and works in any regime, including the limits of weak and strong nonlinearities.

P. van Loock; W. J. Munro; Kae Nemoto; T. P. Spiller; T. D. Ladd; Samuel L. Braunstein; G. J. Milburn

2007-01-11T23:59:59.000Z

57

Classical limits of unconstrained QFT  

E-Print Network [OSTI]

In nonrelativistic limits for states labeled by minimum packets with constrained spatial spreads and over a short term, states of unconstrained quantum field theories evolve on trajectories described by Newton's equations for the $1/r^2$ force. These states include bound solutions in the attractive force case.

Glenn Eric Johnson

2014-12-21T23:59:59.000Z

58

Dose Limits  

Broader source: Energy.gov [DOE]

Dose Limits ERAD (Question Posted to ERAD in May 2012) Who do you define as a member of the public for the onsite MEI? This question implies that there may be more than one maximally exposed individual (MEI), one on-site and one off-site, when demonstrating compliance with the Public Dose Limit of DOE Order 458.1. Although all potential MEIs should be considered and documented, as well as the calculated doses and pathways considered, the intent of DOE Order 458.1 is in fact to ultimately identify only one MEI, a theoretical individual who could be either on-site or off-site.

59

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

60

RNA Folding: A Little Cooperation Goes a Long Way | Advanced Photon Source  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

A New Phase in Cellular Communication A New Phase in Cellular Communication Engineering Thin-Film Oxide Interfaces Novel Materials Become Multifunctional at the Ultimate Quantum Limit Outsmarting Flu Viruses How Lead-Free Solder (Mis)Behaves under Stress Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed RNA Folding: A Little Cooperation Goes a Long Way NOVEMBER 19, 2012 Bookmark and Share Shown here is the energy landscape for folding of a ribozyme, and how cooperation between tertiary interactions at different parts of the structure (red dots) help the RNA reach its unique native structure and avoid non-native intermediates. The nucleic acid RNA is an essential part of the critical process by which

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

A New Phase in Cellular Communication | Advanced Photon Source  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Engineering Thin-Film Oxide Interfaces Engineering Thin-Film Oxide Interfaces Novel Materials Become Multifunctional at the Ultimate Quantum Limit Outsmarting Flu Viruses How Lead-Free Solder (Mis)Behaves under Stress Dynamics of Polymer Chains Atop Different Materials Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed A New Phase in Cellular Communication NOVEMBER 15, 2012 Bookmark and Share Interactions between N-WASP, phospho-Nephrin and Nck produce large polymers (top panel) that phase separate to produce liquid droplets suspended in aqueous solution (bottom panel). In many physical processes, substances undergo phase transitions, where they are transformed from one state (solid, liquid, or gas) to another.

62

Quantum correlation via quantum coherence  

E-Print Network [OSTI]

Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition--------quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits it is directly connected with quantum nonlocality.

Chang-shui Yu; Yang Zhang; Haiqing Zhao

2014-02-19T23:59:59.000Z

63

Smartphone data safety with quantum cryptography  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

QKarD could fit into smartphones Current quantum key distribution systems are bulky, rack-mounted systems requiring dedicated fiber optic lines to connect users within limited...

64

Hybrid quantum-classical models as constrained quantum systems  

E-Print Network [OSTI]

Constrained Hamiltonian description of the classical limit is utilized in order to derive consistent dynamical equations for hybrid quantum-classical systems. Starting with a compound quantum system in the Hamiltonian formulation conditions for classical behavior are imposed on one of its subsystems and the corresponding hybrid dynamical equations are derived. The presented formalism suggests that the hybrid systems have properties that are not exhausted by those of quantum and classical systems.

M. Radonjic; S. Prvanovic; N. Buric

2012-06-07T23:59:59.000Z

65

Comment on "A limit on the variation of the speed of light arising from quantum gravity effects" aka "Testing Einstein's special relativity with Fermi's short hard gamma-ray burst GRB090510"  

E-Print Network [OSTI]

Recently the Fermi GBM and LAT Collaborations reported their new observational data disfavoring quite a number of the quantum gravity theories, including the one suggesting the nonlinear (logarithmic) modification of a quantum wave equation. We show that the latter is still far from being ruled out: it is not only able to explain the new data but also its phenomenological implications turn out to be more vast (and more interesting) than one expected before.

Konstantin G. Zloshchastiev

2009-11-30T23:59:59.000Z

66

Quantum-enhanced absorption refrigerators  

E-Print Network [OSTI]

Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators.

Luis A. Correa; José P. Palao; Daniel Alonso; Gerardo Adesso

2013-08-19T23:59:59.000Z

67

Quantum Institute  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

68

Quantum discord  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

69

Quantum Simulation  

E-Print Network [OSTI]

Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

I. M. Georgescu; S. Ashhab; Franco Nori

2014-03-13T23:59:59.000Z

70

Quantum Machines  

E-Print Network [OSTI]

We discuss quantum information processing machines. We start with single purpose machines that either redistribute quantum information or identify quantum states. We then move on to machines that can perform a number of functions, with the function they perform being determined by a program, which is itself a quantum state. Examples of both deterministic and probabilistic programmable machines are given, and we conclude with a discussion of the utility of quantum programs.

Mark Hillery; Vladimir Buzek

2009-03-24T23:59:59.000Z

71

Quantum discord between relatively accelerated observers  

E-Print Network [OSTI]

We calculate the quantum discord between two free modes of a scalar field which start in a maximally entangled state and then undergo a relative, constant acceleration. In a regime where there is no distillable entanglement due to the Unruh effect, we show that there is a finite amount of quantum discord, which is a measure of purely quantum correlations in a state, over and above quantum entanglement. Even in the limit of infinite acceleration of the observer detecting one of the modes, we provide evidence for a non-zero amount of purely quantum correlations, which might be exploited to gain non-trivial quantum advantages.

Animesh Datta

2009-05-20T23:59:59.000Z

72

Optical Hybrid Quantum Information Processing  

E-Print Network [OSTI]

Historically, two complementary approaches to optical quantum information processing have been pursued: qubits and continuous-variables, each exploiting either particle or wave nature of light. However, both approaches have pros and cons. In recent years, there has been a significant progress in combining both approaches with a view to realizing hybrid protocols that overcome the current limitations. In this chapter, we first review the development of the two approaches with a special focus on quantum teleportation and its applications. We then introduce our recent research progress in realizing quantum teleportation by a hybrid scheme, and mention its future applications to universal and fault-tolerant quantum information processing.

Shuntaro Takeda; Akira Furusawa

2014-04-09T23:59:59.000Z

73

Quantum-noise quenching in quantum tweezers  

E-Print Network [OSTI]

The efficiency of extracting single atoms or molecules from an ultracold bosonic reservoir is theoretically investigated for a protocol based on lasers, coupling the hyperfine state in which the atoms form a condensate to another stable state, in which the atom experiences a tight potential in the regime of collisional blockade, the quantum tweezers. The transfer efficiency into the single-atom ground state of the tight trap is fundamentally limited by the collective modes of the condensate, which are thermally and dynamically excited and constitute the ultimate noise sources. This quantum noise can be quenched for sufficiently long laser pulses, thereby achieving high efficiencies, and showing that this protocol can be applied for quantum information processing based on tweezer traps for neutral atoms.

Zippilli, Stefano; Lutz, Eric; Morigi, Giovanna; Schleich, Wolfgang

2010-01-01T23:59:59.000Z

74

Coherent Quantum-Noise Cancellation for Optomechanical Sensors  

E-Print Network [OSTI]

Using a flowchart representation of quantum optomechanical dynamics, we design coherent quantum-noise-cancellation schemes that can eliminate the back-action noise induced by radiation pressure at all frequencies and thus overcome the standard quantum limit of force sensing. The proposed schemes can be regarded as novel examples of coherent feedforward quantum control.

Mankei Tsang; Carlton M. Caves

2010-08-17T23:59:59.000Z

75

Berry Phase Quantum Thermometer  

E-Print Network [OSTI]

We show how Berry phase can be used to construct an ultra-high precision quantum thermometer. An important advantage of our scheme is that there is no need for the thermometer to acquire thermal equilibrium with the sample. This reduces measurement times and avoids precision limitations.

Martin-Martinez, E; Mann, R B; Fuentes, I

2011-01-01T23:59:59.000Z

76

Berry Phase Quantum Thermometer  

E-Print Network [OSTI]

We show how Berry phase can be used to construct an ultra-high precision quantum thermometer. An important advantage of our scheme is that there is no need for the thermometer to acquire thermal equilibrium with the sample. This reduces measurement times and avoids precision limitations.

E. Martin-Martinez; A. Dragan; R. B. Mann; I. Fuentes

2013-05-28T23:59:59.000Z

77

The Quantum Computing Challenge Paul Vit'anyi ?  

E-Print Network [OSTI]

The Quantum Computing Challenge Paul Vit'anyi ? CWI Abstract. The laws of physics imposes limits limits to energy dissipation in conventional irreversible technology. Quantum computing is a new, the earliest mention of quantum computing is by Paul Benioff [14] who demonstrated how to implement a classical

Vitanyi, Paul M.B.

78

Quantum Data Compression of a Qubit Ensemble  

E-Print Network [OSTI]

Data compression is a ubiquitous aspect of modern information technology, and the advent of quantum information raises the question of what types of compression are feasible for quantum data, where it is especially relevant given the extreme difficulty involved in creating reliable quantum memories. We present a protocol in which an ensemble of quantum bits (qubits) can in principle be perfectly compressed into exponentially fewer qubits. We then experimentally implement our algorithm, compressing three photonic qubits into two. This protocol sheds light on the subtle differences between quantum and classical information. Furthermore, since data compression stores all of the available information about the quantum state in fewer physical qubits, it could provide a vast reduction in the amount of quantum memory required to store a quantum ensemble, making even today's limited quantum memories far more powerful than previously recognized.

Lee A. Rozema; Dylan H. Mahler; Alex Hayat; Peter S. Turner; Aephraim M. Steinberg

2014-10-15T23:59:59.000Z

79

A Parallel Quantum Computer Simulator  

E-Print Network [OSTI]

A Quantum Computer is a new type of computer which can efficiently solve complex problems such as prime factorization. A quantum computer threatens the security of public key encryption systems because these systems rely on the fact that prime factorization is computationally difficult. Errors limit the effectiveness of quantum computers. Because of the exponential nature of quantum com puters, simulating the effect of errors on them requires a vast amount of processing and memory resources. In this paper we describe a parallel simulator which accesses the feasibility of quantum computers. We also derive and validate an analytical model of execution time for the simulator, which shows that parallel quantum computer simulation is very scalable.

Kevin M. Obenland; Alvin M. Despain

1998-04-16T23:59:59.000Z

80

Quantum metrology and its application in biology  

E-Print Network [OSTI]

Quantum metrology provides a route to overcome practical limits in sensing devices. It holds particular relevance in biology, where sensitivity and resolution constraints restrict applications both in fundamental biophysics and in medicine. Here, we review quantum metrology from this biological context. The understanding of quantum mechanics developed over the past century has already enabled important applications in biology, including positron emission tomography (PET) with entangled photons, magnetic resonance imaging (MRI) using nuclear magnetic resonance, and bio-magnetic imaging with superconducting quantum interference devices (SQUIDs). With the birth of quantum information science came the realization that an even greater range of applications arise from the ability to not just understand, but to engineer coherence and correlations in systems at the quantum level. In quantum metrology, quantum coherence and quantum correlations are engineered to enable new approaches to sensing. This review focusses specifically on optical quantum metrology, where states of light that exhibit non-classical photon correlations are used to overcome practical and fundamental constraints, such as the shot-noise and diffraction limits. Recent experiments have demonstrated quantum enhanced sensing of biological systems, and established the potential for quantum metrology in biophysical research. These experiments have achieved capabilities that may be of significant practical benefit, including enhanced sensitivity and resolution, immunity to imaging artifacts, and characterisation of the biological response to light at the single-photon level. New quantum measurement techniques offer even greater promise, raising the prospect for improved multi-photon microscopy and magnetic imaging, among many other possible applications.

Michael A. Taylor; Warwick P. Bowen

2014-09-03T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Information and noise in quantum measurement  

Science Journals Connector (OSTI)

Even though measurement results obtained in the real world are generally both noisy and continuous, quantum measurement theory tends to emphasize the ideal limit of perfect precision and quantized measurement results. In this article, a more general concept of noisy measurements is applied to investigate the role of quantum noise in the measurement process. In particular, it is shown that the effects of quantum noise can be separated from the effects of information obtained in the measurement. However, quantum noise is required to “cover up” negative probabilities arising as the quantum limit is approached. These negative probabilities represent fundamental quantum-mechanical correlations between the measured variable and the variables affected by quantum noise.

Holger F. Hofmann

2000-07-06T23:59:59.000Z

82

I, Quantum Robot: Quantum Mind control on a Quantum Computer  

E-Print Network [OSTI]

The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.

Paola Zizzi

2008-12-25T23:59:59.000Z

83

Quantum optical technologies for metrology, sensing and imaging  

E-Print Network [OSTI]

Over the past 20 years, bright sources of entangled photons have led to a renaissance in quantum optical interferometry. Optical interferometry has been used to test the foundations of quantum mechanics and implement some of the novel ideas associated with quantum entanglement such as quantum teleportation, quantum cryptography, quantum lithography, quantum computing logic gates, and quantum metrology. In this paper, we focus on the new ways that have been developed to exploit quantum optical entanglement in quantum metrology to beat the shot-noise limit, which can be used, e.g., in fiber optical gyroscopes and in sensors for biological or chemical targets. We also discuss how this entanglement can be used to beat the Rayleigh diffraction limit in imaging systems such as in LIDAR and optical lithography.

Jonathan P. Dowling; Kaushik P. Seshadreesan

2014-12-24T23:59:59.000Z

84

A multiplexed quantum memory  

Science Journals Connector (OSTI)

A quantum repeater is a system for long-distance quantum communication that employs quantum memory elements to mitigate optical fiber transmission losses. The multiplexed quantum...

Lan, S -Y; Radnaev, A G; Collins, O A; Matsukevich, D N; Kennedy, T A; Kuzmich, A

2009-01-01T23:59:59.000Z

85

Mediated Semi-Quantum Key Distribution  

E-Print Network [OSTI]

In this paper, we design a new quantum key distribution protocol, allowing two limited semi-quantum or "classical" users to establish a shared secret key with the help of a fully quantum server. A semi-quantum user can only prepare and measure qubits in the computational basis and so must rely on this quantum server to produce qubits in alternative bases and also to perform alternative measurements. However, we assume that the sever is untrusted and we prove the unconditional security of our protocol even in the worst case: when this quantum server is an all-powerful adversary. We also compute a lower bound of the key rate of our protocol, in the asymptotic scenario, as a function of the observed error rate in the channel allowing us to compute the maximally tolerated error of our protocol. Our results show that a semi-quantum protocol may hold similar security to a fully quantum one.

Walter O. Krawec

2014-11-21T23:59:59.000Z

86

Quantum Bidding in Bridge  

Science Journals Connector (OSTI)

Quantum methods allow us to reduce communication complexity of some computational tasks, with several separated partners, beyond classical constraints. Nevertheless, experimental demonstrations of this have thus far been limited to some abstract problems, far away from real-life tasks. We show here, and demonstrate experimentally, that the power of reduction of communication complexity can be harnessed to gain an advantage in a famous, immensely popular, card game—bridge. The essence of a winning strategy in bridge is efficient communication between the partners. The rules of the game allow only a specific form of communication, of very low complexity (effectively, one has strong limitations on the number of exchanged bits). Surprisingly, our quantum technique does not violate the existing rules of the game (as there is no increase in information flow). We show that our quantum bridge auction corresponds to a biased nonlocal Clauser-Horne-Shimony-Holt game, which is equivalent to a 2?1 quantum random access code. Thus, our experiment is also a realization of such protocols. However, this correspondence is not complete, which enables the bridge players to have efficient strategies regardless of the quality of their detectors.

Sadiq Muhammad; Armin Tavakoli; Maciej Kurant; Marcin Paw?owski; Marek ?ukowski; Mohamed Bourennane

2014-06-12T23:59:59.000Z

87

Quantum Interferometric Sensors  

E-Print Network [OSTI]

Quantum entanglement has the potential to revolutionize the entire field of interferometric sensing by providing many orders of magnitude improvement in interferometer sensitivity. The quantum-entangled particle interferometer approach is very general and applies to many types of interferometers. In particular, without nonlocal entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales like $1/\\sqrt{N}$, where $N$ is the number of particles passing through the interferometer per unit time. However, if carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity improves by a factor of $\\sqrt{N}$ to scale like 1/N, which is the limit imposed by the Heisenberg Uncertainty Principle. For optical interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds to an eight-order-of-magnitude improvement of signal to noise. This effect can translate into a tremendous science pay-off for space missions. For example, one application of this new effect is to fiber optical gyroscopes for deep-space inertial guidance and tests of General Relativity (Gravity Probe B). Another application is to ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity Observatory (LIGO) and the European Laser Interferometer Space Antenna (LISA), respectively. Other applications are to Satellite-to-Satellite laser Interferometry (SSI) proposed for the next generation Gravity Recovery And Climate Experiment (GRACE II).

Kishore T. Kapale; Leo D. Didomenico; Hwang Lee; Pieter Kok; Jonathan P. Dowling

2005-07-15T23:59:59.000Z

88

Scalar Field Quantum Inequalities in Static Spacetimes  

E-Print Network [OSTI]

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spacetime. This supports the use of flat space quantum inequalities to constrain negative energy effects in curved spacetime. Using the exact Euclidean two-point function method, we develop the quantum inequalities for perfectly reflecting planar mirrors in flat spacetime. We then look at the quantum inequalities in static de~Sitter spacetime, Rindler spacetime and two- and four-dimensional black holes. In the case of a four-dimensional Schwarzschild black hole, explicit forms of the inequality are found for static observers nea...

Pfenning, M J; Pfenning, Michael J.

1998-01-01T23:59:59.000Z

89

Quantum friction  

E-Print Network [OSTI]

The Brownian motion of a light quantum particle in a heavy classical gas is theoretically described and a new expression for the friction coefficient is obtained for arbitrary temperature. At zero temperature it equals to the de Broglie momentum of the mean free path divided by the mean free path. Alternatively, the corresponding mobility of the quantum particle in the classical gas is equal to the square of the mean free path divided by the Planck constant. The Brownian motion of a quantum particle in a quantum environment is also discussed.

R. Tsekov

2012-03-12T23:59:59.000Z

90

Quantum technology and its applications  

SciTech Connect (OSTI)

Quantum states of matter can be exploited as high performance sensors for measuring time, gravity, rotation, and electromagnetic fields, and quantum states of light provide powerful new tools for imaging and communication. Much attention is being paid to the ultimate limits of this quantum technology. For example, it has already been shown that exotic quantum states can be used to measure or image with higher precision or higher resolution or lower radiated power than any conventional technologies, and proof-of-principle experiments demonstrating measurement precision below the standard quantum limit (shot noise) are just starting to appear. However, quantum technologies have another powerful advantage beyond pure sensing performance that may turn out to be more important in practical applications: the potential for building devices with lower size/weight/power (SWaP) and cost requirements than existing instruments. The organizers of Quantum Technology Applications Workshop (QTAW) have several goals: (1) Bring together sponsors, researchers, engineers and end users to help build a stronger quantum technology community; (2) Identify how quantum systems might improve the performance of practical devices in the near- to mid-term; and (3) Identify applications for which more long term investment is necessary to realize improved performance for realistic applications. To realize these goals, the QTAW II workshop included fifty scientists, engineers, managers and sponsors from academia, national laboratories, government and the private-sector. The agenda included twelve presentations, a panel discussion, several breaks for informal exchanges, and a written survey of participants. Topics included photon sources, optics and detectors, squeezed light, matter waves, atomic clocks and atom magnetometry. Corresponding applications included communication, imaging, optical interferometry, navigation, gravimetry, geodesy, biomagnetism, and explosives detection. Participants considered the physics and engineering of quantum and conventional technologies, and how quantum techniques could (or could not) overcome limitations of conventional systems. They identified several auxiliary technologies that needed to be further developed in order to make quantum technology more accessible. Much of the discussion also focused on specific applications of quantum technology and how to push the technology into broader communities, which would in turn identify new uses of the technology. Since our main interest is practical improvement of devices and techniques, we take a liberal definition of 'quantum technology': a system that utilizes preparation and measurement of a well-defined coherent quantum state. This nomenclature encompasses features broader than entanglement, squeezing or quantum correlations, which are often more difficult to utilize outside of a laboratory environment. Still, some applications discussed in the workshop do take advantage of these 'quantum-enhanced' features. They build on the more established quantum technologies that are amenable to manipulation at the quantum level, such as atom magnetometers and atomic clocks. Understanding and developing those technologies through traditional engineering will clarify where quantum-enhanced features can be used most effectively, in addition to providing end users with improved devices in the near-term.

Boshier, Malcolm [Los Alamos National Laboratory; Berkeland, Dana [USG; Govindan, Tr [ARO; Abo - Shaeer, Jamil [DARPA

2010-12-10T23:59:59.000Z

91

Frequency tuning of THz quantum cascade lasers  

Science Journals Connector (OSTI)

Tunable single-mode THz quantum cascade lasers are crucial for spectroscopy applications. Current and temperature tuning are limited to a few GHz and other solutions have to be...

Tredicucci, Alessandro

92

Rovelli' s relational quantum mechanics, monism and quantum becoming  

E-Print Network [OSTI]

In this paper I present and defend Rovelli's relation quantum mechanics from some foreseeable objections, so as to clarify its philosophical implications vis a vis rival interpretations. In particular I ask whether RQM presupposes a hidden recourse to both a duality of evolutions and of ontology (the relationality of quantum world and the intrinsicness of the classical world, which in the limit must be recovered from the former). I then concentrate on the pluralistic, antimonistic metaphysical consequences of the theory, due to the impossibility of assigning a state to the quantum universe. Finally, in the last section I note interesting consequences of RQM with respect to the possibility of defining a local, quantum relativistic becoming (in flat spacetimes).Given the difficulties of having the cosmic form of becoming that would be appropriate for priority monism, RQM seems to present an important advantage with respect to monistic views, at least as far as the possibility of explaining our experience of time is concerned.

Mauro Dorato

2013-08-31T23:59:59.000Z

93

Engineering the Quantum Foam  

E-Print Network [OSTI]

In 1990 Alcubierre, within the General Relativity model for space-time, proposed a scenario for `warp drive' faster than light travel, in which objects would achieve such speeds by actually being stationary within a bubble of space which itself was moving through space, the idea being that the speed of the bubble was not itself limited by the speed of light. However that scenario required exotic matter to stabilise the boundary of the bubble. Here that proposal is re-examined within the context of the new modelling of space in which space is a quantum system, viz a quantum foam, with on-going classicalisation. This model has lead to the resolution of a number of longstanding problems, including a dynamical explanation for the so-called `dark matter' effect. It has also given the first evidence of quantum gravity effects, as experimental data has shown that a new dimensionless constant characterising the self-interaction of space is the fine structure constant. The studies here begin the task of examining to what extent the new spatial self-interaction dynamics can play a role in stabilising the boundary without exotic matter, and whether the boundary stabilisation dynamics can be engineered; this would amount to quantum gravity engineering.

Reginald T. Cahill

2005-06-06T23:59:59.000Z

94

Quantum states prepared by realistic entanglement swapping  

E-Print Network [OSTI]

Entanglement swapping between photon pairs is a fundamental building block in schemes using quantum relays or quantum repeaters to overcome the range limits of long distance quantum key distribution. We develop a closed-form solution for the actual quantum states prepared by realistic entanglement swapping, which takes into account experimental deficiencies due to inefficient detectors, detector dark counts and multi-photon-pair contributions of parametric down conversion sources. We investigate how the entanglement present in the final state of the remaining modes is affected by the real-world imperfections. To test the predictions of our theory, comparison with experimental entanglement swapping is provided.

Scherer, Artur; Sanders, Barry C; Tittel, Wolfgang

2009-01-01T23:59:59.000Z

95

Quantum states prepared by realistic entanglement swapping  

E-Print Network [OSTI]

Entanglement swapping between photon pairs is a fundamental building block in schemes using quantum relays or quantum repeaters to overcome the range limits of long-distance quantum key distribution. We develop a closed-form solution for the actual quantum states prepared by realistic entanglement swapping, which takes into account experimental deficiencies due to inefficient detectors, detector dark counts, and multiphoton-pair contributions of parametric down-conversion sources. We investigate how the entanglement present in the final state of the remaining modes is affected by the real-world imperfections. To test the predictions of our theory, comparison with previously published experimental entanglement swapping is provided.

Artur Scherer; Regina B. Howard; Barry C. Sanders; Wolfgang Tittel

2009-04-07T23:59:59.000Z

96

How energy conservation limits our measurements  

E-Print Network [OSTI]

Observations in Quantum Mechanics are subject to complex restrictions arising from the principle of energy conservation. Determining such restrictions, however, has been so far an elusive task, and only partial results are known. In this paper we discuss how constraints on the energy spectrum of a measurement device translate into limitations on the measurements which we can effect on a target system with non-trivial energy operator. We provide efficient algorithms to characterize such limitations and we quantify them exactly when the target is a two-level quantum system. Our work thus identifies the boundaries between what is possible or impossible to measure, i.e., between what we can see or not, when energy conservation is at stake.

Miguel Navascues; Sandu Popescu

2012-11-09T23:59:59.000Z

97

Quantum Chromodynamics  

Science Journals Connector (OSTI)

The theory of the strong interaction of elementary particles, Quantum Chromodynamics (QCD), is a non-abelian gauge theory with SU(3) as gauge group. The degrees of freedom corresponding to this SU(3) are called c...

Prof. Dr. rer. nat. Manfred Böhm…

2001-01-01T23:59:59.000Z

98

The Quantum Absorption Refrigerator  

E-Print Network [OSTI]

A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified, the cooling power J_c vanishes as J_c proportional to T_c^{alpha}, when T_c approach 0, where alpha =d+1 for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where d is the dimension of the bath.

Amikam Levy; Ronnie Kosloff

2011-09-04T23:59:59.000Z

99

Classical versus quantum coherence  

Science Journals Connector (OSTI)

...M. Stoneham Classical versus quantum coherence P. T. Greenland Department of Physics...nanostructures| Classical versus quantum coherence. | Quantum dots are structures engineered...2002.1134 Classical versus quantum coherence By P. T. Greenland Department of Physics...

2003-01-01T23:59:59.000Z

100

Graph isomorphism and adiabatic quantum computing  

Science Journals Connector (OSTI)

In the graph isomorphism (GI) problem two N-vertex graphs G and G? are given and the task is to determine whether there exists a permutation of the vertices of G that preserves adjacency and transforms G?G?. If yes, then G and G? are said to be isomorphic; otherwise they are nonisomorphic. The GI problem is an important problem in computer science and is thought to be of comparable difficulty to integer factorization. In this paper we present a quantum algorithm that solves arbitrary instances of GI and which also provides an approach to determining all automorphisms of a given graph. We show how the GI problem can be converted to a combinatorial optimization problem that can be solved using adiabatic quantum evolution. We numerically simulate the algorithm's quantum dynamics and show that it correctly (i) distinguishes nonisomorphic graphs; (ii) recognizes isomorphic graphs and determines the permutation(s) that connect them; and (iii) finds the automorphism group of a given graph G. We then discuss the GI quantum algorithm's experimental implementation, and close by showing how it can be leveraged to give a quantum algorithm that solves arbitrary instances of the NP-complete subgraph isomorphism problem. The computational complexity of an adiabatic quantum algorithm is largely determined by the minimum energy gap ?(N) separating the ground and first-excited states in the limit of large problem size N?1. Calculating ?(N) in this limit is a fundamental open problem in adiabatic quantum computing, and so it is not possible to determine the computational complexity of adiabatic quantum algorithms in general, nor consequently, of the specific adiabatic quantum algorithms presented here. Adiabatic quantum computing has been shown to be equivalent to the circuit model of quantum computing, and so development of adiabatic quantum algorithms continues to be of great interest.

Frank Gaitan and Lane Clark

2014-02-28T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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.


101

LANSCE beam current limiter  

SciTech Connect (OSTI)

The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the Beam Current Limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beam line below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described.

Gallegos, F.R.

1996-06-01T23:59:59.000Z

102

Toward quantum opto-mechanics in a gram-scale suspended mirror interferometer  

E-Print Network [OSTI]

A new generation of interferometric gravitational wave detectors, currently under construction, will closely approach the fundamental quantum limits of measurement, serving as a prominent example of quantum mechanics at ...

Wipf, Christopher (Christopher Conrad)

2013-01-01T23:59:59.000Z

103

Quantum Catalysis of Magnetic Phase Transitions in a Quantum Simulator  

E-Print Network [OSTI]

We control quantum fluctuations to create the ground state magnetic phases of a classical Ising model with a tunable longitudinal magnetic field using a system of 6 to 10 atomic ion spins. Due to the long-range Ising interactions, the various ground state spin configurations are separated by multiple first-order phase transitions, which in our zero temperature system cannot be driven by thermal fluctuations. We instead use a transverse magnetic field as a quantum catalyst to observe the first steps of the complete fractal devil's staircase, which emerges in the thermodynamic limit and can be mapped to a large number of many-body and energy-optimization problems.

Philip Richerme; Crystal Senko; Simcha Korenblit; Jacob Smith; Aaron Lee; Rajibul Islam; Wesley C. Campbell; Christopher Monroe

2013-03-27T23:59:59.000Z

104

Limited Test Ban Treaty  

National Nuclear Security Administration (NNSA)

Detection System (USNDS), which monitors compliance with the international Limited Test Ban Treaty (LTBT). The LTBT, signed by 108 countries, prohibits nuclear testing in the...

105

A Review of Procedure to Evolve Quantum Procedures  

E-Print Network [OSTI]

There exist quantum algorithms that are more efficient than their classical counterparts; such algorithms were invented by Shor in 1994 and then Grover in 1996. A lack of invention since Grover's algorithm has been commonly attributed to the non-intuitive nature of quantum algorithms to the classically trained person. Thus, the idea of using computers to automatically generate quantum algorithms based on an evolutionary model emerged. A limitation of this approach is that quantum computers do not yet exist and quantum simulation on a classical machine has an exponential order overhead. Nevertheless, early research into evolving quantum algorithms has shown promise. This paper provides an introduction into quantum and evolutionary algorithms for the computer scientist not familiar with these fields. The exciting field of using evolutionary algorithms to evolve quantum algorithms is then reviewed.

Adrian Gepp; Phil Stocks

2007-08-24T23:59:59.000Z

106

Quantum++ - A C++11 quantum computing library  

E-Print Network [OSTI]

Quantum++ is a general-purpose multi-threaded quantum computing library written in C++11 and composed solely of header files. The library is not restricted to qubit systems or specific quantum information processing tasks, being capable of simulating arbitrary quantum processes. The main design factors taken in consideration were ease of use, portability, and performance.

Vlad Gheorghiu

2014-12-15T23:59:59.000Z

107

Quantum arithmetic with the Quantum Fourier Transform  

E-Print Network [OSTI]

The Quantum Fourier Transform offers an interesting way to perform arithmetic operations on a quantum computer. We review existing Quantum Fourier Transform adders and multipliers and propose some modifications that extend their capabilities. Among the new circuits, we propose a quantum method to compute the weighted average of a series of inputs in the transform domain.

Lidia Ruiz-Perez; Juan Carlos Garcia-Escartin

2014-11-21T23:59:59.000Z

108

Quantum measurement of hyperfine interaction in nitrogen-vacancy center  

E-Print Network [OSTI]

We propose an efficient quantum measurement protocol for the hyperfine interaction between the electron spin and the $^{15}$N nuclear spin of a diamond nitrogen-vacancy center. In this protocol, a sequence of quantum operations of successively increasing duration is utilized to estimate the hyperfine interaction with successively higher precision approaching the quantum metrology limit. This protocol does not need the preparation of the nuclear spin state. In the presence of realistic operation errors and electron spin decoherence, the overall precision of our protocol still surpasses the standard quantum limit.

Kilhyun Bang; Wen Yang; L. J. Sham

2012-05-23T23:59:59.000Z

109

Physics as Quantum Information Processing: Quantum Fields as Quantum Automata  

E-Print Network [OSTI]

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 is ultimately made of a numerable set of quantum systems that are unitarily interacting? A positive answer to these questions corresponds to substituting QFT with a theory of quantum cellular automata (QCA), and the present work is examining this hypothesis. These investigations are part of a large research program on a "quantum-digitalization" of physics, with Quantum Theory as a special theory of information, and Physics as emergent from the same quantum-information processing. A QCA-based QFT has tremendous potential advantages compared to QFT, being quantum "ab-initio" and free from the problems plaguing QFT due to the continuum hypothesis. Here I will show how dynamics emerges from the quantum processing, how the QCA can reproduce the Dirac-field phenomenology at large scales, and the kind of departures from QFT that that should be expected at a Planck-scale discreteness. I will introduce the notions of linear field quantum automaton and local-matrix quantum automaton, in terms of which I will provide the solution to the Feynman's problem about the possibility of simulating a Fermi field with a quantum computer.

Giacomo Mauro D'Ariano

2011-10-31T23:59:59.000Z

110

Quantum coherence and correlations in quantum system  

E-Print Network [OSTI]

Criteria of measure quantifying quantum coherence, a unique property of quantum system, are proposed recently. In this paper, we investigate the relative entropic measure of coherence. Based on its analytical expression, we give an operational interpretation of it with respect to the concept of quantum channel. On this basis, we derive the relation about the coherence and the coherent information in any quantum state. From the point of view of quantum measurement, we furthermore give three trade-offs among the coherence, discord-like and deficit-like quantum correlation quantities for any bipartite quantum state. As an application, we discuss the coherent property of the amplitude damping channel.

Zhengjun Xi; Yongming Li; Heng Fan

2014-08-14T23:59:59.000Z

111

Pulsed homodyne Gaussian quantum tomography with low detection efficiency  

E-Print Network [OSTI]

Pulsed homodyne quantum tomography usually requires a high detection efficiency limiting its applicability in quantum optics. Here, it is shown that the presence of low detection efficiency ($<50\\%$) does not prevent the tomographic reconstruction of quantum states of light, specifically, of Gaussian type. This result is obtained by applying the so-called "minimax" adaptive reconstruction of the Wigner function to pulsed homodyne detection. In particular, we prove, by both numerical and real experiments, that an effective discrimination of different Gaussian quantum states can be achieved. Our finding paves the way to a more extensive use of quantum tomographic methods, even in physical situations in which high detection efficiency is unattainable.

Martina Esposito; Fabio Benatti; Roberto Floreanini; Stefano Olivares; Francesco Randi; Kelvin Titimbo; Marco Pividori; Fabio Novelli; Federico Cilento; Fulvio Parmigiani; Daniele Fausti

2014-02-19T23:59:59.000Z

112

Quantum computing in a piece of glass  

E-Print Network [OSTI]

Quantum gates and simple quantum algorithms can be designed utilizing the diffraction phenomena of a photon within a multiplexed holographic element. The quantum eigenstates we use are the photon's linear momentum (LM) as measured by the number of waves of tilt across the aperture. Two properties of quantum computing within the circuit model make this approach attractive. First, any conditional measurement can be commuted in time with any unitary quantum gate - the timeless nature of quantum computing. Second, photon entanglement can be encoded as a superposition state of a single photon in a higher-dimensional state space afforded by LM. Our theoretical and numerical results indicate that OptiGrate's photo-thermal refractive (PTR) glass is an enabling technology. We will review our previous design of a quantum projection operator and give credence to this approach on a representative quantum gate grounded on coupled-mode theory and numerical simulations, all with parameters consistent with PTR glass. We discuss the strengths (high efficiencies, robustness to environment) and limitations (scalability, crosstalk) of this technology. While not scalable, the utility and robustness of such optical elements for broader quantum information processing applications can be substantial.

Warner A. Miller; Grigoriy Kreymerman; Christopher Tison; Paul M. Alsing; Jonathan R. McDonald

2011-12-15T23:59:59.000Z

113

Modeling of the quantum dot filling and the dark current of quantum dot infrared photodetectors  

SciTech Connect (OSTI)

A generalized drift-diffusion model for the calculation of both the quantum dot filling profile and the dark current of quantum dot infrared photodetectors is proposed. The confined electrons inside the quantum dots produce a space-charge potential barrier between the two contacts, which controls the quantum dot filling and limits the dark current in the device. The results of the model reasonably agree with a published experimental work. It is found that increasing either the doping level or the temperature results in an exponential increase of the dark current. The quantum dot filling turns out to be nonuniform, with a dot near the contacts containing more electrons than one in the middle of the device where the dot occupation approximately equals the number of doping atoms per dot, which means that quantum dots away from contacts will be nearly unoccupied if the active region is undoped.

Ameen, Tarek A.; El-Batawy, Yasser M.; Abouelsaood, A. A. [Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza (Egypt)

2014-02-14T23:59:59.000Z

114

Preserving photon qubits in an unknown quantum state with Knill Dynamical Decoupling - Towards an all optical quantum memory  

E-Print Network [OSTI]

The implementation of polarization-based quantum communication is limited by signal loss and decoherence caused by the birefringence of a single-mode fiber. We investigate the Knill dynamical decoupling scheme, implemented using half-wave plates, to minimize decoherence and show that a fidelity greater than $99\\%$ can be achieved in absence of rotation error and fidelity greater than $96\\%$ can be achieved in presence of rotation error. Such a scheme can be used to preserve any quantum state with high fidelity and has potential application for constructing all optical quantum delay line, quantum memory, and quantum repeater.

Manish K. Gupta; Erik J. Navarro; Todd A. Moulder; Jason D. Mueller; Ashkan Balouchi; Katherine L. Brown; Hwang Lee; Jonathan P. Dowling

2014-12-19T23:59:59.000Z

115

Quantum enhanced estimation of optical detector efficiencies  

E-Print Network [OSTI]

Quantum mechanics establishes the ultimate limit to the scaling of the precision on any parameter, by iden- tifying optimal probe states and measurements. While this paradigm is, at least in principle, adequate for the metrology of quantum channels involving the estimation of phase and loss parameters, we show that estimat- ing the loss parameters associated with a quantum channel and a realistic quantum detector are fundamentally different. While Fock states are provably optimal for the former, we identify a crossover in the nature of the optimal probe state for estimating detector imperfections as a function of the loss parameter. We provide explicit results for on-off and homodyne detectors, the most widely used detectors in quantum photonics technologies.

Barbieri, Marco; Bartley, Tim J; Jin, Xian-Min; Kolthammer, W Steven; Walmsley, Ian A

2015-01-01T23:59:59.000Z

116

Time-optimal navigation through quantum wind  

E-Print Network [OSTI]

The quantum navigation problem of finding the time-optimal control Hamiltonian that transports a given initial state to a target state through quantum wind, that is, under the influence of external fields, is analysed. By lifting the problem from the state space to the space of unitary gates realising the required task, we are able to deduce the form of the solution to the problem by deriving a universal quantum speed limit. The expression thus obtained indicates that further simplifications of this apparently difficult problem are possible if we switch to the interaction picture of quantum mechanics. A complete solution to the navigation problem for an arbitrary quantum system is then obtained, and the behaviour of the solution is illustrated in the case of a two-level system.

Dorje C. Brody; Gary W. Gibbons; David M. Meier

2014-11-17T23:59:59.000Z

117

Time-optimal navigation through quantum wind  

E-Print Network [OSTI]

The quantum navigation problem of finding the time-optimal control Hamiltonian that transports a given initial state to a target state through quantum wind, that is, under the influence of external fields or potentials, is analysed. By lifting the problem from the state space to the space of unitary gates realising the required task, we are able to deduce the form of the solution to the problem by deriving a universal quantum speed limit. The expression thus obtained indicates that further simplifications of this apparently difficult problem are possible if we switch to the interaction picture of quantum mechanics. A complete solution to the navigation problem for an arbitrary quantum system is then obtained, and the behaviour of the solution is illustrated in the case of a two-level system.

Dorje C. Brody; Gary W. Gibbons; David M. Meier

2015-02-19T23:59:59.000Z

118

Time-Energy Measure for Quantum Processes  

E-Print Network [OSTI]

Quantum mechanics sets limits on how fast quantum processes can run given some system energy through time-energy uncertainty relations, and they imply that time and energy are tradeoff against each other. Thus, we propose to measure the time-energy as a single unit for quantum channels. We consider a time-energy measure for quantum channels and compute lower and upper bounds of it using the channel Kraus operators. For a special class of channels (which includes the depolarizing channel), we can obtain the exact value of the time-energy measure. One consequence of our result is that erasing quantum information requires $\\sqrt{(n+1)/n}$ times more time-energy resource than erasing classical information, where $n$ is the system dimension.

Chi-Hang Fred Fung; H. F. Chau

2013-05-24T23:59:59.000Z

119

Quantum Energy Regression using Scattering Transforms  

E-Print Network [OSTI]

We present a novel approach to the regression of quantum mechanical energies based on a scattering transform of an intermediate electron density representation. A scattering transform is a deep convolution network computed with a cascade of multiscale wavelet transforms. It possesses appropriate invariant and stability properties for quantum energy regression. This new framework removes fundamental limitations of Coulomb matrix based energy regressions, and numerical experiments give state-of-the-art accuracy over planar molecules.

Hirn, Matthew; Mallat, Stephane

2015-01-01T23:59:59.000Z

120

Optical limiting materials  

DOE Patents [OSTI]

Optical limiting materials. Methanofullerenes, fulleroids and/or other fullerenes chemically altered for enhanced solubility, in liquid solution, and in solid blends with transparent glass (SiO.sub.2) gels or polymers, or semiconducting (conjugated) polymers, are shown to be useful as optical limiters (optical surge protectors). The nonlinear absorption is tunable such that the energy transmitted through such blends saturates at high input energy per pulse over a wide range of wavelengths from 400-1100 nm by selecting the host material for its absorption wavelength and ability to transfer the absorbed energy into the optical limiting composition dissolved therein. This phenomenon should be generalizable to other compositions than substituted fullerenes.

McBranch, Duncan W. (Santa Fe, NM); Mattes, Benjamin R. (Santa Fe, NM); Koskelo, Aaron C. (Los Alamos, NM); Heeger, Alan J. (Santa Barbara, CA); Robinson, Jeanne M. (Los Alamos, NM); Smilowitz, Laura B. (Los Alamos, NM); Klimov, Victor I. (Los Alamos, NM); Cha, Myoungsik (Goleta, CA); Sariciftci, N. Serdar (Santa Barbara, CA); Hummelen, Jan C. (Groningen, NL)

1998-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Quantum nonlocality  

SciTech Connect (OSTI)

It is argued that the validity of the predictions of quantum theory in certain spin-correlation experiments entails a violation of Einstein's locality idea that no causal influence can act outside the forward light cone. First, two preliminary arguments suggesting such a violation are reviewed. They both depend, in intermediate stages, on the idea that the results of certain unperformed experiments are physically determinate. The second argument is entangled also with the problem of the meaning of physical reality. A new argument having neither of these characteristics is constructed. It is based strictly on the orthodox ideas of Bohr and Heisenberg, and has no realistic elements, or other ingredients, that are alien to orthodox quantum thinking.

Stapp, H.P.

1988-04-01T23:59:59.000Z

122

How red is a quantum black hole?  

E-Print Network [OSTI]

Radiating black holes pose a number of puzzles for semiclassical and quantum gravity. These include the transplanckian problem -- the nearly infinite energies of Hawking particles created near the horizon, and the final state of evaporation. A definitive resolution of these questions likely requires robust inputs from quantum gravity. We argue that one such input is a quantum bound on curvature. We show how this leads to an upper limit on the redshift of a Hawking emitted particle, to a maximum temperature for a black hole, and to the prediction of a Planck scale remnant.

Viqar Husain; Oliver Winkler

2005-05-30T23:59:59.000Z

123

Quantum thermal machines with single nonequilibrium environments  

E-Print Network [OSTI]

We propose a scheme for a quantum thermal machine made by atoms interacting with a single non-equilibrium electromagnetic field. The field is produced by a simple configuration of macroscopic objects held at thermal equilibrium at different temperatures. We show that these machines can deliver all thermodynamic tasks (cooling, heating and population inversion), and this by establishing quantum coherence with the body on which they act. Remarkably, this system allows to reach efficiencies at maximum power very close to the Carnot limit, much more than in existing models. Our findings offer a new paradigm for efficient quantum energy flux management, and can be relevant for both experimental and technological purposes.

Bruno Leggio; Bruno Bellomo; Mauro Antezza

2015-01-08T23:59:59.000Z

124

Next steps in understanding the asymptotics of $3d$ quantum gravity  

E-Print Network [OSTI]

Based on a combinatorial approach and random matrix theory, we show a central limit theorem that gives important insight into causally triangulated $3d$ quantum gravity.

Maria Simonetta Bernabei; Horst Thaler

2014-12-10T23:59:59.000Z

125

Scalar Field Quantum Inequalities in Static Spacetimes  

E-Print Network [OSTI]

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spacetime. This supports the use of flat space quantum inequalities to constrain negative energy effects in curved spacetime. Using the exact Euclidean two-point function method, we develop the quantum inequalities for perfectly reflecting planar mirrors in flat spacetime. We then look at the quantum inequalities in static de~Sitter spacetime, Rindler spacetime and two- and four-dimensional black holes. In the case of a four-dimensional Schwarzschild black hole, explicit forms of the inequality are found for static observers near the horizon and at large distances. It is show that there is a quantum averaged weak energy condition (QAWEC), which states that the energy density averaged over the entire worldline of a static observer is bounded below by the vacuum energy of the spacetime. In particular, for an observer at a fixed radial distance away from a black hole, the QAWEC says that the averaged energy density can never be less than the Boulware vacuum energy density.

Michael J. Pfenning; L. H. Ford

1997-10-09T23:59:59.000Z

126

The Noncommutative Anandan's Quantum Phase  

E-Print Network [OSTI]

In this work we study the noncommutative nonrelativistic quantum dynamics of a neutral particle, that possesses permanent magnetic and electric dipole momenta, in the presence of an electric and magnetic fields. We use the Foldy-Wouthuysen transformation of the Dirac spinor with a non-minimal coupling to obtain the nonrelativistic limit. In this limit, we will study the noncommutative quantum dynamics and obtain the noncommutative Anandan's geometric phase. We analyze the situation where magnetic dipole moment of the particle is zero and we obtain the noncommutative version of the He-McKellar-Wilkens effect. We demonstrate that this phase in the noncommutative case is a geometric dispersive phase. We also investigate this geometric phase considering the noncommutativity in the phase space and the Anandan's phase is obtained.

E. Passos; L. R. Ribeiro; C. Furtado; J. R. Nascimento

2007-06-18T23:59:59.000Z

127

The Noncommutative Anandan's Quantum Phase  

E-Print Network [OSTI]

In this work we study the noncommutative nonrelativistic quantum dynamics of a neutral particle, that possesses permanent magnetic and electric dipole momenta, in the presence of an electric and magnetic fields. We use the Foldy-Wouthuysen transformation of the Dirac spinor with a non-minimal coupling to obtain the nonrelativistic limit. In this limit, we will study the noncommutative quantum dynamics and obtain the noncommutative Anandan's geometric phase. We analyze the situation where magnetic dipole moment of the particle is zero and we obtain the noncommutative version of the He-McKellar-Wilkens effect. We demonstrate that this phase in the noncommutative case is a geometric dispersive phase. We also investigate this geometric phase considering the noncommutativity in the phase space and the Anandan's phase is obtained.

Passos, E; Nascimento, J R; Ribeiro, L R

2006-01-01T23:59:59.000Z

128

Terahertz quantum cascade lasers  

Science Journals Connector (OSTI)

...Michael Pepper Terahertz quantum cascade lasers Jerome Faist 1 Lassaad Ajili...developments in terahertz quantum cascade lasers are reviewed. Structures...magnetic confinement| Terahertz quantum cascade lasers. | Recent developments in...

2004-01-01T23:59:59.000Z

129

Optical quantum memory  

E-Print Network [OSTI]

Quantum memory is important to quantum information processing in many ways: a synchronization device to match various processes within a quantum computer, an identity quantum gate that leaves any state unchanged, and a tool to convert heralded photons to photons-on-demand. In addition to quantum computing, quantum memory would be instrumental for the implementation of long-distance quantum communication using quantum repeaters. The importance of this basic quantum gate is exemplified by the multitude of optical quantum memory mechanisms being studied: optical delay lines, cavities, electromagnetically-induced transparency, photon-echo, and off-resonant Faraday interaction. Here we report on the state-of-the-art in the field of optical quantum memory, including criteria for successful quantum memory and current performance levels.

A. I. Lvovsky; B. C. Sanders; W. Tittel

2010-02-24T23:59:59.000Z

130

Limited Commercial Maintenance (LCLM) Limited Lawn & Ornamental (LLO)  

E-Print Network [OSTI]

, Limited Commercial Landscape Maintenance, Ornamental & Turf, Private Ag, or General Standards CORE for Limited Commercial Landscape Maintenance (LCLM), you must attend all day to earn the 6 CEUs required. Limited Commercial Maintenance (LCLM) Limited Lawn & Ornamental (LLO) Training & Exams Date

Florida, University of

131

The Thermal Mass limit of Neutron Cores  

E-Print Network [OSTI]

Static thermal equilibrium of a quantum self-gravitating ideal gas in General Relativity is studied at any temperature, taking into account the Tolman-Ehrenfest effect. Thermal contribution to the gravitational stability of static neutron cores is quantified. The curve of maximum mass with respect to temperature is reported. At low temperatures is recovered the Oppenheimer-Volkoff calculation, while at high temperatures is recovered the, recently reported, classical gas calculation. An ultimate upper mass limit $M = 2.43M_\\odot$ of all maximum values is found to occur at Tolman temperature $ T = 1.27mc^2$ with radius $R = 15.2km$.

Roupas, Zacharias

2014-01-01T23:59:59.000Z

132

Quantum Locality?  

SciTech Connect (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

133

Quantum Learning Machine  

E-Print Network [OSTI]

We propose a novel notion of a quantum learning machine for automatically controlling quantum coherence and for developing quantum algorithms. A quantum learning machine can be trained to learn a certain task with no a priori knowledge on its algorithm. As an example, it is demonstrated that the quantum learning machine learns Deutsch's task and finds itself a quantum algorithm, that is different from but equivalent to the original one.

Jeongho Bang; James Lim; M. S. Kim; Jinhyoung Lee

2008-03-20T23:59:59.000Z

134

Optimized multiparty quantum clock synchronization  

SciTech Connect (OSTI)

A multiparty protocol for distributed quantum clock synchronization has been claimed to provide universal limits on the clock accuracy, viz., that accuracy monotonically decreases with the number n of party members. But this is only true for synchronization when one limits oneself to W states. This work shows that the usage of Z (Symmetric Dicke) states, a generalization of W states, results in improved accuracy, having a maximum when Left-Floor n/2 Right-Floor of its members have their qubits with a |1> eigenstate.

Ben-Av, Radel; Exman, Iaakov [Software Engineering Department, Jerusalem College of Engineering, POB 3566, Jerusalem, 91035 (Israel)

2011-07-15T23:59:59.000Z

135

Extractable work from ensembles of quantum batteries. Entanglement helps  

E-Print Network [OSTI]

Motivated by the recent interest in thermodynamics of micro- and mesoscopic quantum systems we study the maximal amount of work that can be reversibly extracted from a quantum system used to store temporarily energy. Guided by the notion of passivity of a quantum state we show that entangling unitary controls extract in general more work than independent ones. In the limit of large number of copies one can reach the thermodynamical bound given by the variational principle for free energy.

Robert Alicki; Mark Fannes

2012-11-19T23:59:59.000Z

136

Speed Meter As a Quantum Nondemolition Measuring Device for Force  

E-Print Network [OSTI]

Quantum noise is an important issue for advanced LIGO. Although it is in principle possible to beat the Standard Quantum Limit (SQL), no practical recipe has been found yet. This paper dicusses quantum noise in the context of speedmeter-a devise monitoring the speed of the testmass. The scheme proposed to overcome SQL in this case might be more practical than the methods based on monitoring position of the testmass.

F. Ya. Khalili; Yu. Levin

1996-03-26T23:59:59.000Z

137

Elementary quantum cloning machines  

E-Print Network [OSTI]

The task of reception of a copy of an arbitrary quantum state with use of a minimum quantity of quantum operations is considered.

V. N. Dumachev

2006-02-03T23:59:59.000Z

138

Automated searching for quantum subsystem codes  

E-Print Network [OSTI]

Quantum error correction allows for faulty quantum systems to behave in an effectively error free manner. One important class of techniques for quantum error correction is the class of quantum subsystem codes, which are relevant both to active quantum error correcting schemes as well as to the design of self-correcting quantum memories. Previous approaches for investigating these codes have focused on applying theoretical analysis to look for interesting codes and to investigate their properties. In this paper we present an alternative approach that uses computational analysis to accomplish the same goals. Specifically, we present an algorithm that computes the optimal quantum subsystem code that can be implemented given an arbitrary set of measurement operators that are tensor products of Pauli operators. We then demonstrate the utility of this algorithm by performing a systematic investigation of the quantum subsystem codes that exist in the setting where the interactions are limited to 2-body interactions between neighbors on lattices derived from the convex uniform tilings of the plane.

Gregory M. Crosswhite; Dave Bacon

2010-09-11T23:59:59.000Z

139

Security Proof of a Semi-Quantum Key Distribution Protocol  

E-Print Network [OSTI]

Semi-quantum key distribution protocols are designed to allow two users to establish a secure secret key when one of the two users is limited to performing certain "classical" operations. There have been several such protocols developed recently, however, due to their reliance on a two-way quantum communication channel (and thus, the attacker's opportunity to interact with the qubit twice), their security analysis is difficult and little is known concerning how secure they are compared to their fully quantum counterparts. In this paper we prove the unconditional security of a particular semi-quantum protocol. We derive an expression for the key rate of this protocol, in the asymptotic scenario, as a function of the quantum channel's noise. Finally, we will show that this semi-quantum protocol can tolerate a maximal noise level comparable to certain fully quantum protocols.

Walter O. Krawec

2014-11-30T23:59:59.000Z

140

Simulating quantum systems on a quantum computer  

Science Journals Connector (OSTI)

...A-eigenstates in the original system state. Also after each observation...1998) Simulating quantum systems on a quantum computer 321 system will be in an eigenstate of...the energy eigenstates. An analysis shows that the relative accuracy...

1998-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Security Clearances; Limitations  

Broader source: Energy.gov (indexed) [DOE]

SEC. 1072. SECURITY CLEARANCES; LIMITATIONS. SEC. 1072. SECURITY CLEARANCES; LIMITATIONS. (a) In General.-Title III of the Intelligence Reform and Terrorism Prevention Act of 2004 (50 U.S.C. 435b) is amended by adding at the end the following new section: "SEC. 3002. SECURITY CLEARANCES; LIMITATIONS. "(a) Definitions.-In this section: "(1) Controlled substance.-The term `controlled substance' has the meaning given that term in section 102 of the Controlled Substances Act (21 U.S.C. 802). "(2) Covered person.-The term `covered person' means- "(A) an officer or employee of a Federal agency; "(B) a member of the Army, Navy, Air Force, or Marine Corps who is on active duty or is in an active status; and "(C) an officer or employee of a contractor of a Federal agency.

142

Born--Oppenheimer decomposition for quantum fields on quantum spacetimes  

E-Print Network [OSTI]

Quantum Field Theory on Curved Spacetime (QFT on CS) is a well established theoretical framework which intuitively should be a an extremely effective description of the quantum nature of matter when propagating on a given background spacetime. If one wants to take care of backreaction effects, then a theory of quantum gravity is needed. It is now widely believed that such a theory should be formulated in a non-perturbative and therefore background independent fashion. Hence, it is a priori a puzzle how a background dependent QFT on CS should emerge as a semiclassical limit out of a background independent quantum gravity theory. In this article we point out that the Born-Oppenheimer decomposition (BOD) of the Hilbert space is ideally suited in order to establish such a link, provided that the Hilbert space representation of the gravitational field algebra satisfies an important condition. If the condition is satisfied, then the framework of QFT on CS can be, in a certain sense, embedded into a theory of quantum gravity. The unique representation of the holonomy-flux algebra underlying Loop Quantum Gravity (LQG) violates that condition. While it is conceivable that the condition on the representation can be relaxed, for convenience in this article we consider a new classical gravitational field algebra and a Hilbert space representation of its restriction to an algebraic graph for which the condition is satisfied. An important question that remains and for which we have only partial answers is how to construct eigenstates of the full gravity-matter Hamiltonian whose BOD is confined to a small neighbourhood of a physically interesting vacuum spacetime.

Kristina Giesel; Johannes Tambornino; Thomas Thiemann

2009-11-27T23:59:59.000Z

143

Quantum Solar Energy Conversion and Application to Organic Solar Cells  

Science Journals Connector (OSTI)

When studying the limits of solar energy conversion, either by thermal or quantum processes, the sun has traditionally been treated as a blackbody (thermal equilibrium) radiator with surface temperature 5 800 ...

Gottfried H. Bauer; Peter Würfel

2003-01-01T23:59:59.000Z

144

Generation and quantum control of giant plasmon pulses by transient quantum coherence  

E-Print Network [OSTI]

Amplified ultrashort laser pulses are useful in many fields of science and engineering. Pushing the frontiers of ultrashort pulse generation will lead to new applications in biomedical imaging, communications and sensing. We propose a new, quantum approach to ultrashort pulse generation using transient quantum coherence which predicts order of magnitude stronger pulses generated with lower input energy than in the steady-state regime, reducing the practical heating limitations. This femtosecond quantum-coherent analog of nanosecond Q-switching is not limited by the pulse duration constraints of the latter, and, in principle, may be used for a variety of lasers including x-ray and plasmon nanolasers. We apply this approach to generation of giant plasmon pulses and achieve quantum control of plasmon relaxation dynamics by varying the drive pulse delay, amplitude and duration. We provide insights into the control mechanisms, and discuss future implementations and applications of this new source of ultrashort nan...

Huo, Weiguang; Scully, Marlan

2014-01-01T23:59:59.000Z

145

Quantum Cybernetics and Complex Quantum Systems Science - A Quantum Connectionist Exploration  

E-Print Network [OSTI]

Quantum cybernetics and its connections to complex quantum systems science is addressed from the perspective of complex quantum computing systems. In this way, the notion of an autonomous quantum computing system is introduced in regards to quantum artificial intelligence, and applied to quantum artificial neural networks, considered as autonomous quantum computing systems, which leads to a quantum connectionist framework within quantum cybernetics for complex quantum computing systems. Several examples of quantum feedforward neural networks are addressed in regards to Boolean functions' computation, multilayer quantum computation dynamics, entanglement and quantum complementarity. The examples provide a framework for a reflection on the role of quantum artificial neural networks as a general framework for addressing complex quantum systems that perform network-based quantum computation, possible consequences are drawn regarding quantum technologies, as well as fundamental research in complex quantum systems science and quantum biology.

Carlos Pedro Gonçalves

2014-02-05T23:59:59.000Z

146

Quantum implicit computational complexity  

Science Journals Connector (OSTI)

We introduce a quantum lambda calculus inspired by Lafont's Soft Linear Logic and capturing the polynomial quantum complexity classes EQP, BQP and ZQP. The calculus is based on the ''classical control and quantum data'' paradigm. This is the first example ... Keywords: Implicit computational complexity, Lambda calculus, Quantum computation

Ugo Dal Lago; Andrea Masini; Margherita Zorzi

2010-01-01T23:59:59.000Z

147

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

148

Hybrid quantum devices and quantum engineering  

E-Print Network [OSTI]

We discuss prospects of building hybrid quantum devices involving elements of atomic and molecular physics, quantum optics and solid state elements with the attempt to combine advantages of the respective systems in compatible experimental setups. In particular, we summarize our recent work on quantum hybrid devices and briefly discuss recent ideas for quantum networks. These include interfacing of molecular quantum memory with circuit QED, and using nanomechanical elements strongly coupled to qubits represented by electronic spins, as well as single atoms or atomic ensembles.

Margareta Wallquist; Klemens Hammerer; Peter Rabl; Mikhail Lukin; Peter Zoller

2009-11-19T23:59:59.000Z

149

LANL | Physics | Quantum Information  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

150

Hybrid Quantum Cloning Machine  

E-Print Network [OSTI]

In this work, we introduce a special kind of quantum cloning machine called Hybrid quantum cloning machine. The introduced Hybrid quantum cloning machine or transformation is nothing but a combination of pre-existing quantum cloning transformations. In this sense it creates its own identity in the field of quantum cloners. Hybrid quantum cloning machine can be of two types: (i) State dependent and (ii) State independent or Universal. We study here the above two types of Hybrid quantum cloning machines. Later we will show that the state dependent hybrid quantum-cloning machine can be applied on only four input states. We will also find in this paper another asymmetric universal quantum cloning machine constructed from the combination of optimal universal B-H quantum cloning machine and universal anti-cloning machine. The fidelities of the two outputs are different and their values lie in the neighborhood of ${5/6} $

Satyabrata Adhikari; A. K. Pati; Indranil Chakrabarty; B. S. Choudhury

2007-05-04T23:59:59.000Z

151

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.

D Kielpinski; JF Corney; HM Wiseman

2010-10-11T23:59:59.000Z

152

Integrable Quantum Computation  

E-Print Network [OSTI]

Integrable quantum computation is defined as quantum computing via the integrable condition, in which two-qubit gates are either nontrivial unitary solutions of the Yang--Baxter equation or the Swap gate (permutation). To make the definition clear, in this article, we explore the physics underlying the quantum circuit model, and then present a unified description on both quantum computing via the Bethe ansatz and quantum computing via the Yang--Baxter equation.

Yong Zhang

2011-11-16T23:59:59.000Z

153

Extremal quantum protocols  

E-Print Network [OSTI]

Generalized quantum instruments correspond to measurements where the input and output are either states or more generally quantum circuits. These measurements describe any quantum protocol including games, communications, and algorithms. The set of generalized quantum instruments with a given input and output structure is a convex set. Here we investigate the extremal points of this set for the case of finite dimensional quantum systems and generalized instruments with finitely many outcomes. We derive algebraic necessary and sufficient conditions for extremality.

Giacomo Mauro D'Ariano; Paolo Perinotti; Michal Sedlak

2011-01-25T23:59:59.000Z

154

A New Ontological View of the Quantum Measurement Problem  

E-Print Network [OSTI]

A new ontological view of the quantum measurement processes is given, which has bearings on many broader issues in the foundations of quantum mechanics as well. In this scenario a quantum measurement is a non-equilibrium phase transition in a ``resonant cavity'' formed by the entire physical universe including all of its material and energy content. A quantum measurement involves the energy and matter exchange among not only the system being measured and the measuring apparatus but also the global environment of the universe resonant cavity, which together constrain the nature of the phase transition. Strict realism, including strict energy and angular momentum conservation, is recovered in this view of the quantum measurement process beyond the limit set by the uncertainty relations, which are themselves derived from the exact commutation relations for quantum conjugate variables. Both the amplitude and the phase of the quantum mechanical wavefunction acquire substantial meanings in the new ontology, and the probabilistic element is removed from the foundations of quantum mechanics, its apparent presence in the quantum measurement being solely a result of the sensitive dependence on initial/boundary conditions of the phase transitions of a many degree-of-freedom system which is effectively the whole universe. Vacuum fluctuations are viewed as the ``left over'' fluctuations after forming the whole numbers of nonequilibrium resonant modes in the universe cavity. This new view on the quantum processes helps to clarify many puzzles in the foundations of quantum mechanics.

Xiaolei Zhang

2005-06-13T23:59:59.000Z

155

Heat flux limiting sleeves  

DOE Patents [OSTI]

A heat limiting tubular sleeve extending over only a portion of a tube having a generally uniform outside diameter, the sleeve being open on both ends, having one end thereof larger in diameter than the other end thereof and having a wall thickness which decreases in the same direction as the diameter of the sleeve decreases so that the heat transfer through the sleeve and tube is less adjacent the large diameter end of the sleeve than adjacent the other end thereof.

Harris, William G. (Tampa, FL)

1985-01-01T23:59:59.000Z

156

Quantum Fusion of Domain Walls with Fluxes  

E-Print Network [OSTI]

We study how fluxes on the domain wall world volume modify quantum fusion of two distant parallel domain walls into a composite wall. The elementary wall fluxes can be separated into parallel and antiparallel components. The parallel component affects neither the binding energy nor the process of quantum merger. The antiparallel fluxes, instead, increase the binding energy and, against naive expectations, suppress quantum fusion. In the small flux limit we explicitly find the bounce solution and the fusion rate as a function of the flux. We argue that at large (antiparallel) fluxes there exists a critical value of the flux (versus the difference in the wall tensions), which switches off quantum fusion altogether. This phenomenon of flux-related wall stabilization is rather peculiar: it is unrelated to any conserved quantity. Our consideration of the flux-related all stabilization is based on substantiated arguments that fall short of complete proof.

S. Bolognesi; M. Shifman; M. B. Voloshin

2009-07-20T23:59:59.000Z

157

Processing Information in Quantum Decision Theory  

E-Print Network [OSTI]

A survey is given summarizing the state of the art of describing information processing in Quantum Decision Theory, which has been recently advanced as a novel variant of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intended actions. The theory characterizes entangled decision making, non-commutativity of subsequent decisions, and intention interference. The self-consistent procedure of decision making, in the frame of the quantum decision theory, takes into account both the available objective information as well as subjective contextual effects. This quantum approach avoids any paradox typical of classical decision theory. Conditional maximization of entropy, equivalent to the minimization of an information functional, makes it possible to connect the quantum and classical decision theories, showing that the latter is the limit of the former under vanishing interference terms.

V. I. Yukalov; D. Sornette

2008-02-25T23:59:59.000Z

158

Brownian parametric quantum oscillator with dissipation  

Science Journals Connector (OSTI)

We study the quantum fluctuational properties of a parametric oscillator with and without coupling to an Ohmic environment. After considering the momentum and coordinate variances as a function of initial squeezing for the undamped dynamics, we invoke the functional integral method to derive the fully exact reduced density matrix for parametric dissipative quantum Brownian motion, covering the whole temperature regime from T=0 up to the classical limit at room temperatures. Moreover, we present the exact result for the quantum master equation for both the density matrix and the corresponding Wigner function. The time evolution of the covariance matrix elements of damped quantum fluctuations is studied numerically. These variances undergo within the regime of global stability asymptotic, periodic oscillations. As an interesting result, we find that the minima of these oscillations fall below the corresponding thermal equilibrium values.

Christine Zerbe and Peter Hänggi

1995-08-01T23:59:59.000Z

159

Quantum computer of wire circuit architecture  

E-Print Network [OSTI]

First solid state quantum computer was built using transmons (cooper pair boxes). The operation of the computer is limited because of using a number of the rigit cooper boxes working with fixed frequency at temperatures of superconducting material. Here, we propose a novel architecture of quantum computer based on a flexible wire circuit of many coupled quantum nodes containing controlled atomic (molecular) ensembles. We demonstrate wide opportunities of the proposed computer. Firstly, we reveal a perfect storage of external photon qubits to multi-mode quantum memory node and demonstrate a reversible exchange of the qubits between any arbitrary nodes. We found optimal parameters of atoms in the circuit and self quantum modes for quantum processing. The predicted perfect storage has been observed experimentally for microwave radiation on the lithium phthalocyaninate molecule ensemble. Then also, for the first time we show a realization of the efficient basic two-qubit gate with direct coupling of two arbitrary nodes by using appropriate atomic frequency shifts in the circuit nodes. Proposed two-qubit gate runs with a speed drastically accelerated proportionally to the number of atoms in the node. The direct coupling and accelerated two-qubit gate can be realized for large number of the circuit nodes. Finally, we describe two and three-dimensional scalable architectures that pave the road to construction of universal multi-qubit quantum computer operating at room temperatures.

S. A. Moiseev; F. F. Gubaidullin; S. N. Andrianov

2010-01-07T23:59:59.000Z

160

Robust quantum data locking from phase modulation  

E-Print Network [OSTI]

Quantum data locking is a unique quantum phenomenon that allows a relatively short key to (un)lock an arbitrarily long message encoded in a quantum state, in such a way that an eavesdropper who measures the state but does not know the key has essentially no information about the encrypted message. The application of quantum data locking in cryptography would allow one to overcome the limitations of the one-time pad encryption, which requires the key to have the same length as the message. However, it is known that the strength of quantum data locking is also its Achilles heel, as the leakage of a few bits of the key or the message may in principle allow the eavesdropper to unlock a disproportionate amount of information. In this paper we show that there exist quantum data locking schemes that can be made robust against information leakage by increasing the length of the shared key by a proportionate amount. This implies that a constant size key can still encrypt an arbitrarily long message as long as a fraction of it remains secret to the eavesdropper. Moreover, we greatly simplify the structure of the protocol by proving that phase modulation suffices to generate strong locking schemes, paving the way to optical experimental realizations. Also, we show that successful data locking protocols can be constructed using random codewords, which very well could be helpful in discovering random codes for data locking over noisy quantum channels.

Cosmo Lupo; Mark M. Wilde; Seth Lloyd

2014-08-29T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Excess optical quantum noise in atomic sensors  

E-Print Network [OSTI]

Enhanced nonlinear optical response of a coherent atomic medium is the basis for many atomic sensors, and their performance is ultimately limited by the quantum fluctuations of the optical read-out. Here we demonstrate that off-resonant interactions can significantly modify the quantum noise of the optical field, even when their effect on the mean signal is negligible. We illustrate this concept by using an atomic magnetometer based on the nonlinear Faraday effect: the rotation of the light polarization is mainly determined by the resonant light-induced spin alignment, which alone does not change the photon statistics of the optical probe. Yet, we found that the minimum noise of output polarization rotation measurements is above the expected shot noise limit. This excess quantum noise is due to off-resonant coupling and grows with atomic density. We also show that the detection scheme can be modified to reduce the measured quantum noise (even below the shot-noise limit) but only at the expense of the reduced rotational sensitivity. These results show the existence of previously unnoticed factors in fundamental limitations in atomic magnetometry and could have impacts in many other atom-light based precision measurements.

Irina Novikova; Eugeniy E. Mikhailov; Yanhong Xiao

2014-10-14T23:59:59.000Z

162

Quantum theory of nonequilibrium processes, 1  

SciTech Connect (OSTI)

Green's function techniques for studying nonequilibrium quantum processes are discussed. Perturbation expansions and Green's function equations of motion are developed for noncorrelated and correlated initial states of a system. A transition, from the Kadanoff-Baym Green's function equations of motion to the Boltzmann equation, and specifications of the respective limit, are examined in detail.

Danielewicz, P.

1984-02-01T23:59:59.000Z

163

Extremely correlated quantum liquids B. Sriram Shastry  

E-Print Network [OSTI]

Extremely correlated quantum liquids B. Sriram Shastry Physics Department, University of California; published 20 January 2010 Extreme correlations arise as the limit of strong correlations, when the local-J model, embodying such extreme correlations. We formulate the picture of an extremely correlated electron

California at Santa Cruz, University of

164

Gaussian quantum information  

Science Journals Connector (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 teleportation are among the most celebrated ideas that have emerged from this new field. It was realized later on that using continuous-variable quantum information carriers, instead of qubits, constitutes an extremely powerful alternative approach to quantum information processing. This review focuses on continuous-variable quantum information processes that rely on any combination of Gaussian states, Gaussian operations, and Gaussian measurements. Interestingly, such a restriction to the Gaussian realm comes with various benefits, since on the theoretical side, simple analytical tools are available and, on the experimental side, optical components effecting Gaussian processes are readily available in the laboratory. Yet, Gaussian quantum information processing opens the way to a wide variety of tasks and applications, including quantum communication, quantum cryptography, quantum computation, quantum teleportation, and quantum state and channel discrimination. This review reports on the state of the art in this field, ranging from the basic theoretical tools and landmark experimental realizations to the most recent successful developments.

Christian Weedbrook; Stefano Pirandola; Raúl García-Patrón; Nicolas J. Cerf; Timothy C. Ralph; Jeffrey H. Shapiro; Seth Lloyd

2012-05-01T23:59:59.000Z

165

Experimental feedback control of quantum systems using weak measurements  

E-Print Network [OSTI]

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario--the stabilization of non-orthogonal states of a qubit against dephasing--we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems.

G. G. Gillett; R. B. Dalton; B. P. Lanyon; M. P. Almeida; M. Barbieri; G. J. Pryde; J. L. O'Brien; K. J. Resch; S. D. Bartlett; A. G. White

2010-03-01T23:59:59.000Z

166

Quantum Information Causality  

Science Journals Connector (OSTI)

How much information can a transmitted physical system fundamentally communicate? We introduce the principle of quantum information causality, which states the maximum amount of quantum information that a quantum system can communicate as a function of its dimension, independently of any previously shared quantum physical resources. We present a new quantum information task, whose success probability is upper bounded by the new principle, and show that an optimal strategy to perform it combines the quantum teleportation and superdense coding protocols with a task that has classical inputs.

Damián Pitalúa-García

2013-05-22T23:59:59.000Z

167

Feasible quantum engineering of quantum multiphoton superpositions  

E-Print Network [OSTI]

We examine an experimental setup implementing a family of quantum non-Gaussian filters. The filters can be applied to an arbitrary two-mode input state. We assume realistic photodetection in the filtering process and explore two different models of inefficient detection: a beam splitter of a small reflectivity located in front of a perfect detector and a Weierstrass transform applied to the unperturbed measurement outcomes. We explicitly give an operator which describes the coherent action of the filters in the realistic experimental conditions. The filtered states may find applications in quantum metrology, quantum communication and other quantum tasks.

Magdalena Stobi?ska

2014-09-03T23:59:59.000Z

168

Fault Current Limiters  

Broader source: Energy.gov (indexed) [DOE]

Fault Fault Current Limiters Superconducting & Solid-state Power Equipment Office of Electricity Delivery and Energy Reliability www.oe.energy.gov Office of Electricity Delivery and Energy Reliability, OE-1 U.S. Department of Energy - 1000 Independence Avenue, SW - Washington, DC 20585 Plugging America Into the Future of Power What are FCLs? A fault is an unintentional short circuit, or partial short-circuit, in an electric circuit. A variety of factors such as lightning, downed power lines, or crossed power lines cause faults. During a fault, excessive current-called fault current- flows through the electrical system often resulting in a failure of one section of that system by causing a

169

Efficient distributed quantum computing  

E-Print Network [OSTI]

We provide algorithms for efficiently moving and addressing quantum memory in parallel. These imply that the standard circuit model can be simulated with a low overhead by a more realistic model of a distributed quantum ...

Beals, Robert

170

Changing quantum reference frames  

E-Print Network [OSTI]

We consider the process of changing reference frames in the case where the reference frames are quantum systems. We find that, as part of this process, decoherence is necessarily induced on any quantum system described relative to these frames. We explore this process with examples involving reference frames for phase and orientation. Quantifying the effect of changing quantum reference frames serves as a first step in developing a relativity principle for theories in which all objects including reference frames are necessarily quantum.

Matthew C. Palmer; Florian Girelli; Stephen D. Bartlett

2014-05-21T23:59:59.000Z

171

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

172

Nonequilibrium quantum kinetics  

SciTech Connect (OSTI)

This paper contains viewgraphs on non-equilibrium quantum kinetics of nuclear reactions at the intermediate and high energy ranges.

Danielewicz, P.

1997-09-22T23:59:59.000Z

173

On the Nature of Quantum Phenomena  

E-Print Network [OSTI]

It is shown that a coherent understanding of all quantized phenomena, including those governed by unitary evolution equations as well as those related to irreversible quantum measurements, can be achieved in a scenario of successive nonequilibrium phase transitions, with the lowest hierarchy of these phase transitions occurring in a ``resonant cavity'' formed by the entire matter and energy content of the universe. In this formalism, the physical laws themselves are resonantly-selected and ordered in the universe cavity in a hierarchical manner, and the values of fundamental constants are determined through a Generalized Mach's Principle. The existence of a preferred reference frame in this scenario is shown to be consistent with the relational nature of the origin of physical laws. Covariant unitary evolution is shown to connect smoothly with the reduction of wavefunction in the preferred frame during quantum measurement. The superluminal nature of quantum processes in the lowest hierarchy coexists with the universal speed limit obeyed by processes in higher hierarchies. A natural quantum-to-classical transition is also obtained which is stable against the diffusive tendency of the unitary quantum evolution processes. In this formalism a realistic quasi-classical ontology is established for the foundations of quantum mechanics.

Xiaolei Zhang

2007-12-28T23:59:59.000Z

174

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

175

Efficient distributed quantum computing  

Science Journals Connector (OSTI)

...model of a distributed quantum computer. As a result, the circuit...algorithms and the way that quantum computers are likely to be implemented...W.H. was funded by NSF grant nos 0916400, 0829937, 0803478...Large scale modular quantum computer architecture with atomic memory...

2013-01-01T23:59:59.000Z

176

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

177

Quantum Circuits Architecture  

E-Print Network [OSTI]

We present a method for optimizing quantum circuits architecture. The method is based on the notion of "quantum comb", which describes a circuit board in which one can insert variable subcircuits. The method allows one to efficiently address novel kinds of quantum information processing tasks, such as storing-retrieving, and cloning of channels.

Giulio Chiribella; Giacomo Mauro D'Ariano; Paolo Perinotti

2007-12-09T23:59:59.000Z

178

Eavesdropping without quantum memory  

E-Print Network [OSTI]

In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that the best strategy is actually to adopt the simple intercept/resend strategy.

H. Bechmann-Pasquinucci

2005-04-01T23:59:59.000Z

179

FED pumped limiter configuration issues  

SciTech Connect (OSTI)

Impurity control in the Fusion Engineering Device (FED) is provided by a toroidal belt pumped limiter. Limiter design issues addressed in this paper are (1) poloidal location of the limiter belt, (2) shape of the limiter surface facing the plasma, and (3) whether the belt is pumped from one or both sides. The criteria used for evaluation of limiter configuration features were sensitivity to plasma-edge conditions and ease of maintenance and fabrication. The evaluation resulted in the selection of a baseline FED limiter that is located at the bottom of the device and has a flat surface with a single leading edge.

Haines, J.R.; Fuller, G.M.

1983-01-01T23:59:59.000Z

180

Quantum Physics and Nanotechnology  

E-Print Network [OSTI]

Experimental studies of infinite (unrestricted at least in one direction) quantum particle motion using probe nanotechnologies have revealed the necessity of revising previous concepts of their motion. Particularly, quantum particles transfer quantum motion nonlocality energy beside classical kinetic energy, in other words, they are in two different kinds of motion simultaneously. The quantum component of the motion energy may be quite considerable under certain circumstances. Some new effects were predicted and proved experimentally in terms of this phenomenon. A new prototype refrigerating device was tested, its principle of operation being based on the effect of transferring the quantum component of the motion energy.

Vladimir K. Nevolin

2011-06-06T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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 Catalysis of Magnetic Phase Transitions in a Quantum Simulator P. Richerme,1  

E-Print Network [OSTI]

a transverse magnetic field as a quantum catalyst to observe the first steps of the complete fractal devil's staircase, which emerges in the thermodynamic limit and can be mapped to a large number of many on to a number of energy minimization problems [25,26], and shows the first steps of the complete devil

Richerme, Phil

182

Success Stories: Quantum Dots  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum Dots Outshine the Competition for Biomedical Assays Quantum Dots Outshine the Competition for Biomedical Assays Quantum Dots (Qdots), nano-scale semiconductor crystals that emit a range of bright colors when excited by a light source such as a laser, are shining brightly these days. The Berkeley Lab developed technology has been licensed by Quantum Dot Corporation and is being used as fluorescence probes for biomedical assays. The technology just won an R & D 100 Award and Quantum Dot Corporation was named by Fortune magazine as one of 2004's "Cool Companies." Science honored the technology as one of the Top 10 Breakthroughs of the Year in 2003, and Nanotechnology Now named Quantum Dots as the Best Nanotech Product in 2003, among other honors. Quantum Dot Corporation (QDC) is a 1998 start-up biotechnology company

183

Adiabatic topological quantum computing  

E-Print Network [OSTI]

Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev's surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computation size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.

Chris Cesare; Andrew J. Landahl; Dave Bacon; Steven T. Flammia; Alice Neels

2014-06-10T23:59:59.000Z

184

Adiabatic Quantum Transistors  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

We describe a many-body quantum system that can be made to quantum compute by the adiabatic application of a large applied field to the system. Prior to the application of the field, quantum information is localized on one boundary of the device, and after the application of the field, this information propagates to the other side of the device, with a quantum circuit applied to the information. The applied circuit depends on the many-body Hamiltonian of the material, and the computation takes place in a degenerate ground space with symmetry-protected topological order. Such “adiabatic quantum transistors” are universal adiabatic quantum computing devices that have the added benefit of being modular. Here, we describe this model, provide arguments for why it is an efficient model of quantum computing, and examine these many-body systems in the presence of a noisy environment.

Bacon, Dave; Flammia, Steven T.; Crosswhite, Gregory M.

2013-06-01T23:59:59.000Z

185

Quantum Thermodynamic Cycles and Quantum Heat Engines (II)  

E-Print Network [OSTI]

We study the quantum mechanical generalization of force or pressure, and then we extend the classical thermodynamic isobaric process to quantum mechanical systems. Based on these efforts, we are able to study the quantum version of thermodynamic cycles that consist of quantum isobaric process, such as quantum Brayton cycle and quantum Diesel cycle. We also consider the implementation of quantum Brayton cycle and quantum Diesel cycle with some model systems, such as single particle in 1D box and single-mode radiation field in a cavity. These studies lay the microscopic (quantum mechanical) foundation for Szilard-Zurek single molecule engine.

Quan, H T

2008-01-01T23:59:59.000Z

186

Alliance fights limits on chlorofluorocarbons  

Science Journals Connector (OSTI)

Alliance fights limits on chlorofluorocarbons ... Efforts by the nascent Alliance for Responsible CFC Policy to curb the Environmental Protection Agency's plans to put more limits on chlorofluorocarbons are beginning to have results. ... The 400-member alliance was formed last August to fight EPA's avowed intention to limit production of CFC's in the U.S. to 30% of their present levels. ...

1981-03-02T23:59:59.000Z

187

The Quantum Field as a Quantum Computer  

E-Print Network [OSTI]

It is supposed that at very small scales a quantum field is an infinite homogeneous quantum computer. On a quantum computer the information cannot propagate faster than $c=a/\\tau$, $a$ and $\\tau$ being the minimum space and time distances between gates, respectively. It is shown that the information flow satisfies a Dirac equation, with speed $v=\\zeta c$ and $\\zeta=\\zeta(m)$ mass-dependent. For $a/\\tau=c$ the speed of light $\\zeta^{-1}$ is a vacuum refraction index increasing monotonically from $\\zeta^{-1}(0)=1$ to $\\zeta^{-1}(M)=\\infty$, $M$ being the Planck mass for $2a$ the Planck length.

Giacomo Mauro D'Ariano

2010-12-02T23:59:59.000Z

188

Quantum fields on closed timelike curves  

SciTech Connect (OSTI)

Recently, there has been much interest in the evolution of quantum particles on closed timelike curves (CTCs). However, such models typically assume pointlike particles with only two degrees of freedom; a very questionable assumption given the relativistic setting of the problem. We show that it is possible to generalize the Deutsch model of CTCs to fields using the equivalent circuit formalism. We give examples for coherent, squeezed, and single-photon states interacting with the CTC via a beamsplitter. The model is then generalized further to account for the smooth transition to normal quantum mechanics as the CTC becomes much smaller than the size of the modes interacting on it. In this limit, we find that the system behaves like a standard quantum-mechanical feedback loop.

Pienaar, J. L.; Myers, C. R.; Ralph, T. C. [School of Mathematics and Physics, The University of Queensland, Brisbane 4072, Queensland (Australia)

2011-12-15T23:59:59.000Z

189

Semiclassical Foundation of Universality in Quantum Chaos  

E-Print Network [OSTI]

We sketch the semiclassical core of a proof of the so-called Bohigas-Giannoni-Schmit conjecture: A dynamical system with full classical chaos has a quantum energy spectrum with universal fluctuations on the scale of the mean level spacing. We show how in the semiclassical limit all system specific properties fade away, leaving only ergodicity, hyperbolicity, and combinatorics as agents determining the contributions of pairs of classical periodic orbits to the quantum spectral form factor. The small-time form factor is thus reproduced semiclassically. Bridges between classical orbits and (the non-linear sigma model of) quantum field theory are built by revealing the contributing orbit pairs as topologically equivalent to Feynman diagrams.

Sebastian Müller; Stefan Heusler; Petr Braun; Fritz Haake; Alexander Altland

2005-03-23T23:59:59.000Z

190

Quantum Information: an invitation for mathematicians  

SciTech Connect (OSTI)

Quantum Information is the science that aims to use the unusual behavior of the microscopic world, governed by the laws of Quantum Mechanics, in order to improve the way in which we compute or communicate information. Though the first ideas in this direction come from the early 80's, it is in the last decade when Quantum Information has suffered an spectacular development. It is impossible to resume in a paper like this one the importance and complexity of the field. Therefore, I will limit to briefly explain some of the initial ideas (considered classical by now), and to briefly suggest some of the modern lines of research. By the nature of this exposition, I have decided to avoid rigor and to concentrate more in ideas and intuitions. Anyhow, I have tried to provide with enough references, in such a way that an interested reader could find there proper theorems and proofs.

Perez-Garcia, David [Departamento de Analisis Matematico. Universidad Complutense de Madrid. 28040 Madrid (Spain)

2009-05-06T23:59:59.000Z

191

Quantum Copy-Protection and Quantum Money  

E-Print Network [OSTI]

Forty years ago, Wiesner proposed using quantum states to create money that is physically impossible to counterfeit, something that cannot be done in the classical world. However, Wiesner's scheme required a central bank ...

Aaronson, Scott

192

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

193

Nested Quantum Walks with Quantum Data Structures  

E-Print Network [OSTI]

We develop a new framework that extends the quantum walk framework of Magniez, Nayak, Roland, and Santha, by utilizing the idea of quantum data structures to construct an efficient method of nesting quantum walks. Surprisingly, only classical data structures were considered before for searching via quantum walks. The recently proposed learning graph framework of Belovs has yielded improved upper bounds for several problems, including triangle finding and more general subgraph detection. We exhibit the power of our framework by giving a simple explicit constructions that reproduce both the $O(n^{35/27})$ and $O(n^{9/7})$ learning graph upper bounds (up to logarithmic factors) for triangle finding, and discuss how other known upper bounds in the original learning graph framework can be converted to algorithms in our framework. We hope that the ease of use of this framework will lead to the discovery of new upper bounds.

Stacey Jeffery; Robin Kothari; Frederic Magniez

2012-10-03T23:59:59.000Z

194

Testing integrability with a single bit of quantum information  

SciTech Connect (OSTI)

We show that deterministic quantum computing with a single bit can determine whether the classical limit of a quantum system is chaotic or integrable using O(N) physical resources, where N is the dimension of the Hilbert space of the system under study. This is a square-root improvement over all known classical procedures. Our study relies strictly on the random matrix conjecture. We also present numerical results for the nonlinear kicked top.

Poulin, David; Laflamme, Raymond [Perimeter Institute for Theoretical Physics, 35 King Street N., Waterloo, Ontario, N2J 2W9 (Canada); Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Milburn, G.J. [Centre for Quantum Computer Technology, School of Physical Science, University of Queensland, Queensland 4072 (Australia); Paz, Juan Pablo [Departamento de Fisica 'J.J. Giambiagi', FCEN, UBA, Pabell on 1, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Theory Division, MS B213, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2003-08-01T23:59:59.000Z

195

Systematic quantum corrections to screening in thermonuclear fusion  

E-Print Network [OSTI]

We develop a series expansion of the plasma screening length away from the classical limit in powers of $\\hbar^{2}$. It is shown that the leading order quantum correction increases the screening length in solar conditions by approximately 2% while it decreases the fusion rate by approximately $ 0.34%$. We also calculate the next higher order quantum correction which turns out to be approximately 0.05%.

Chitanvis, S M

2006-01-01T23:59:59.000Z

196

Systematic quantum corrections to screening in thermonuclear fusion  

E-Print Network [OSTI]

We develop a series expansion of the plasma screening length away from the classical limit in powers of $\\hbar^{2}$. It is shown that the leading order quantum correction increases the screening length in solar conditions by approximately 2% while it decreases the fusion rate by approximately $ 0.34%$. We also calculate the next higher order quantum correction which turns out to be approximately 0.05%.

Shirish M. Chitanvis

2006-06-13T23:59:59.000Z

197

Quantum Copy-Protection and Quantum Money  

E-Print Network [OSTI]

Forty years ago, Wiesner proposed using quantum states to create money that is physically impossible to counterfeit, something that cannot be done in the classical world. However, Wiesner's scheme required a central bank to verify the money, and the question of whether there can be unclonable quantum money that anyone can verify has remained open since. One can also ask a related question, which seems to be new: can quantum states be used as copy-protected programs, which let the user evaluate some function f, but not create more programs for f? This paper tackles both questions using the arsenal of modern computational complexity. Our main result is that there exist quantum oracles relative to which publicly-verifiable quantum money is possible, and any family of functions that cannot be efficiently learned from its input-output behavior can be quantumly copy-protected. This provides the first formal evidence that these tasks are achievable. The technical core of our result is a "Complexity-Theoretic No-Cloning Theorem," which generalizes both the standard No-Cloning Theorem and the optimality of Grover search, and might be of independent interest. Our security argument also requires explicit constructions of quantum t-designs. Moving beyond the oracle world, we also present an explicit candidate scheme for publicly-verifiable quantum money, based on random stabilizer states; as well as two explicit schemes for copy-protecting the family of point functions. We do not know how to base the security of these schemes on any existing cryptographic assumption. (Note that without an oracle, we can only hope for security under some computational assumption.)

Scott Aaronson

2011-10-24T23:59:59.000Z

198

Quantum computation of scattering in scalar quantum field theories  

Science Journals Connector (OSTI)

Quantum field theory provides the framework for the most fundamental physical theories to be confirmed experimentally and has enabled predictions of unprecedented precision. However, calculations of physical observables often require great computational ... Keywords: quantum algorithm, quantum field theory, simulation

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

2014-09-01T23:59:59.000Z

199

Quantum Copy-Protection and Quantum Money  

E-Print Network [OSTI]

Forty years ago, Wiesner proposed using quantum states to create money that is physically impossible to counterfeit, something that cannot be done in the classical world. However, Wiesner's scheme required a central bank to verify the money, and the question of whether there can be unclonable quantum money that anyone can verify has remained open since. One can also ask a related question, which seems to be new: can quantum states be used as copy-protected programs, which let the user evaluate some function f, but not create more programs for f? This paper tackles both questions using the arsenal of modern computational complexity. Our main result is that there exist quantum oracles relative to which publicly-verifiable quantum money is possible, and any family of functions that cannot be efficiently learned from its input-output behavior can be quantumly copy-protected. This provides the first formal evidence that these tasks are achievable. The technical core of our result is a "Complexity-Theoretic No-Clon...

Aaronson, Scott

2011-01-01T23:59:59.000Z

200

Spatially dependent decoherence and anomalous diffussion of quantum walks  

E-Print Network [OSTI]

We analyze the long time behavior of a discrete time quantum walk subject to decoherence with a strong spatial dependence, acting on one half of the lattice. We show that, except for limiting cases on the decoherence parameter, the quantum walk at late times behaves sub-ballistically, meaning that the characteristic features of the quantum walk are not completely spoiled. Contrarily to expectations, the asymptotic behavior is non Markovian, and depends on the amount of decoherence. This feature can be clearly shown on the long time value of the Generalized Chiral Distribution (GCD).

A. Perez; A. Romanelli

2012-03-30T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Amplified Quantum Transforms  

E-Print Network [OSTI]

In this thesis we investigate two new Amplified Quantum Transforms. In particular we create and analyze the Amplified Quantum Fourier Transform (Amplified-QFT) and the Amplified-Haar Wavelet Transform. First, we provide a brief history of quantum mechanics and quantum computing. Second, we examine the Amplified-QFT in detail and compare it against the Quantum Fourier Transform (QFT) and Quantum Hidden Subgroup (QHS) algorithms for solving the Local Period Problem. We calculate the probabilities of success of each algorithm and show the Amplified-QFT is quadratically faster than the QFT and QHS algorithms. Third, we examine the Amplified-QFT algorithm for solving The Local Period Problem with an Error Stream. Fourth, we produce an uncertainty relation for the Amplified-QFT algorithm. Fifth, we show how the Amplified-Haar Wavelet Transform can solve the Local Constant or Balanced Signal Decision Problem which is a generalization of the Deutsch-Jozsa algorithm.

David Cornwell

2014-06-01T23:59:59.000Z

202

Asymptotic representations of quantum affine superalgebras  

E-Print Network [OSTI]

We study representations of the $q$-Yangian, the upper Borel subalgebra with respect to RTT realization of the quantum affine superalgebra associated with the Lie superalgebra $\\mathfrak{gl}(M,N)$. Following the work of Hernandez-Jimbo, we construct inductive systems of Kirillov-Reshetikhin modules by using a cyclicity result of tensor products of these modules we established recently, and realize their inductive limits as modules over the $q$-Yangian, extending the asymptotic construction of Hernandez-Jimbo to the super case. Then, we propose a new asymptotic construction on the inductive limits of the same inductive systems, resulting in modules over the full quantum affine superalgebra depending on an additional parameter. $q$-character and Gelfand-Tsetlin basis for these two kinds of modules are also investigated.

Huafeng Zhang

2014-10-03T23:59:59.000Z

203

Quantum Imaging Technologies  

E-Print Network [OSTI]

Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum ghost imaging and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of methods for characterizing the elusive quantum state itself. In this document, we describe new technologies that use the quantum properties of light for security. The first is a technique that extends the principles behind QKD to the field of imaging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that are secure against intercept-resend jamming attacks. The second technology presented in this article is based on an extension of quantum ghost imaging. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this document is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. We discuss the development of two OAM-QKD protocols based on the BB84 and Ekert QKD protocols. The fourth and final technology presented in this article is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state. We use this technique to characterize the quantum state of a photon with a dimensionality of d=27, and measure its rotation in the natural basis of OAM.

Mehul Malik; Robert W. Boyd

2014-06-06T23:59:59.000Z

204

Reducing Quantum Errors and Improving Large Scale Quantum Cryptography  

E-Print Network [OSTI]

Noise causes severe difficulties in implementing quantum computing and quantum cryptography. Several schemes have been suggested to reduce this problem, mainly focusing on quantum computation. Motivated by quantum cryptography, we suggest a coding which uses $N$ quantum bits ($N=n^2$) to encode one quantum bit, and reduces the error exponentially with $n$. Our result suggests the possibility of distributing a secure key over very long distances, and maintaining quantum states for very long times. It also provides a new quantum privacy amplification against a strong adversary.

T. Mor

1996-08-15T23:59:59.000Z

205

Quantum Money with Classical Verification  

E-Print Network [OSTI]

We construct a quantum money scheme that allows verification through classical communication with bank. This is the first demonstration that a secure quantum money scheme exists that does not require quantum communication for coin verification.

Gavinsky, Dmitry

2011-01-01T23:59:59.000Z

206

Quantum-assisted biomolecular modelling  

Science Journals Connector (OSTI)

...incremental improvements. Quantum computing offers the possibility...might be addressed using quantum computation and speculate on the future importance of quantum-assisted biomolecular...self-organization and molecular motors are central to all cellular...

2010-01-01T23:59:59.000Z

207

Coherent control of quantum information  

E-Print Network [OSTI]

Quantum computation requires the ability to efficiently control quantum information in the presence of noise. In this thesis, NMR quantum information processors (QIPs) are used to study noise processes that compromise ...

Henry, Michael Kevin

2006-01-01T23:59:59.000Z

208

Instantaneous Quantum Computation  

E-Print Network [OSTI]

We examine theoretic architectures and an abstract model for a restricted class of quantum computation, called here instantaneous quantum computation because it allows for essentially no temporal structure within the quantum dynamics. Using the theory of binary matroids, we argue that the paradigm is rich enough to enable sampling from probability distributions that cannot, classically, be sampled from efficiently and accurately. This paradigm also admits simple interactive proof games that may convince a skeptic of the existence of truly quantum effects. Furthermore, these effects can be created using significantly fewer qubits than are required for running Shor's Algorithm.

Dan Shepherd; Michael J. Bremner

2008-09-04T23:59:59.000Z

209

Efficient Distributed Quantum Computing  

E-Print Network [OSTI]

We provide algorithms for efficiently addressing quantum memory in parallel. These imply that the standard circuit model can be simulated with low overhead by the more realistic model of a distributed quantum computer. As a result, the circuit model can be used by algorithm designers without worrying whether the underlying architecture supports the connectivity of the circuit. In addition, we apply our results to existing memory intensive quantum algorithms. We present a parallel quantum search algorithm and improve the time-space trade-off for the Element Distinctness and Collision problems.

Robert Beals; Stephen Brierley; Oliver Gray; Aram Harrow; Samuel Kutin; Noah Linden; Dan Shepherd; Mark Stather

2012-07-10T23:59:59.000Z

210

Quantum Metropolis Sampling  

E-Print Network [OSTI]

The original motivation to build a quantum computer came from Feynman who envisaged a machine capable of simulating generic quantum mechanical systems, a task that is believed to be intractable for classical computers. Such a machine would have a wide range of applications in the simulation of many-body quantum physics, including condensed matter physics, chemistry, and high energy physics. Part of Feynman's challenge was met by Lloyd who showed how to approximately decompose the time-evolution operator of interacting quantum particles into a short sequence of elementary gates, suitable for operation on a quantum computer. However, this left open the problem of how to simulate the equilibrium and static properties of quantum systems. This requires the preparation of ground and Gibbs states on a quantum computer. For classical systems, this problem is solved by the ubiquitous Metropolis algorithm, a method that basically acquired a monopoly for the simulation of interacting particles. Here, we demonstrate how to implement a quantum version of the Metropolis algorithm on a quantum computer. This algorithm permits to sample directly from the eigenstates of the Hamiltonian and thus evades the sign problem present in classical simulations. A small scale implementation of this algorithm can already be achieved with today's technology

K. Temme; T. J. Osborne; K. G. Vollbrecht; D. Poulin; F. Verstraete

2009-11-18T23:59:59.000Z

211

Rotational Quantum Friction  

E-Print Network [OSTI]

We investigate the frictional forces due to quantum fluctuations acting on a small sphere rotating near a surface. At zero temperature, we find the frictional force near a surface to be several orders of magnitude larger than that for the sphere rotating in vacuum. For metallic materials with typical conductivity, quantum friction is maximized by matching the frequency of rotation with the conductivity. Materials with poor conductivity are favored to obtain large quantum frictions. For semiconductor materials that are able to support surface plasmon polaritons, quantum friction can be further enhanced by several orders of magnitude due to the excitation of surface plasmon polaritons.

Rongkuo Zhao; Alejandro Manjavacas; F. Javier García de Abajo; J. B. Pendry

2012-08-21T23:59:59.000Z

212

Classical and Quantum Polyhedra  

E-Print Network [OSTI]

Quantum polyhedra constructed from angular momentum operators are the building blocks of space in its quantum description as advocated by Loop Quantum Gravity. Here we extend previous results on the semiclassical properties of quantum polyhedra. Regarding tetrahedra, we compare the results from a canonical quantization of the classical system with a recent wave function based approach to the large-volume sector of the quantum system. Both methods agree in the leading order of the resulting effective operator (given by an harmonic oscillator), while minor differences occur in higher corrections. Perturbative inclusion of such corrections improves the approximation to the eigenstates. Moreover, the comparison of both methods leads also to a full wave function description of the eigenstates of the (square of the) volume operator at negative eigenvalues of large modulus. For the case of general quantum polyhedra described by discrete angular momentum quantum numbers we formulate a set of quantum operators fulfilling in the semiclassical regime the standard commutation relations between momentum and position. Differently from previous formulations, the position variable here is chosen to have dimension of (Planck) length squared which facilitates the identification of quantum corrections. Finally, we provide expressions for the pentahedral volume in terms of Kapovich-Millson variables.

John Schliemann

2014-12-11T23:59:59.000Z

213

Terahertz Quantum Cascade Lasers  

Science Journals Connector (OSTI)

We provide an overview of terahertz quantum cascade lasers based on resonant-phonon depopulation and metal-metal waveguides, including two-phonon resonant-phonon depopulation...

Williams, Benjamin; Kumar, Sushil; Qin, Qi; Lee, Alan Wei Min; Hu, Qing; Reno, John L; Wasilewski, Z R; Liu, H C

214

Quantum spin dynamics  

E-Print Network [OSTI]

The classical Landau-Lifshitz equation has been derived from quantum mechanics. Starting point is the assumption of a non-Hermitian Hamilton operator to take the energy dissipation into account. The corresponding quantum mechanical time dependent Schr\\"odinger, Liouville and Heisenberg equation have been described and the similarities and differences between classical and quantum mechanical spin dynamics have been discussed. Furthermore, a time dependent Schr\\"odinger equation corresponding to the classical Landau-Lifshitz-Gilbert equation and two ways to include temperature into the quantum mechanical spin dynamics have been proposed.

Robert Wieser

2014-10-23T23:59:59.000Z

215

Quantum Field Theory & Gravity  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Field Theory & Gravity Quantum Field Theory & Gravity Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email...

216

Quantum Junction Solar Cells  

Science Journals Connector (OSTI)

Quantum Junction Solar Cells ... § Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario, M5S 3G4, Canada ...

Jiang Tang; Huan Liu; David Zhitomirsky; Sjoerd Hoogland; Xihua Wang; Melissa Furukawa; Larissa Levina; Edward H. Sargent

2012-08-10T23:59:59.000Z

217

Quantum random access memory  

E-Print Network [OSTI]

A random access memory (RAM) uses n bits to randomly address N=2^n distinct memory cells. A quantum random access memory (qRAM) uses n qubits to address any quantum superposition of N memory cells. We present an architecture that exponentially reduces the requirements for a memory call: O(log N) switches need be thrown instead of the N used in conventional (classical or quantum) RAM designs. This yields a more robust qRAM algorithm, as it in general requires entanglement among exponentially less gates, and leads to an exponential decrease in the power needed for addressing. A quantum optical implementation is presented.

Vittorio Giovannetti; Seth Lloyd; Lorenzo Maccone

2007-08-14T23:59:59.000Z

218

QUANTUM CONVERSION IN PHOTOSYNTHESIS  

E-Print Network [OSTI]

QUANTUM CONVERSION IN PHOTOSYNTHESIS Melvin Calvin Januaryas it occurs in modern photosynthesis can only take place inof the problem or photosynthesis, or any specific aspect of

Calvin, Melvin

2008-01-01T23:59:59.000Z

219

Nested Cluster Algorithm for Frustrated Quantum Antiferromagnets  

E-Print Network [OSTI]

Simulations of frustrated quantum antiferromagnets suffer from a severe sign problem. We solve the ergodicity problem of the loop-cluster algorithm in a natural way and apply a powerful strategy to address the sign problem. For the spin 1/2 Heisenberg antiferromagnet on a kagome and on a frustrated square lattice, a nested cluster algorithm eliminates the sign problem for large systems. The method is applicable to general lattice geometries but limited to moderate temperatures.

M. Nyfeler; F. -J. Jiang; F. Kämpfer; U. -J. Wiese

2008-03-25T23:59:59.000Z

220

Extreme commutative quantum observables are sharp  

E-Print Network [OSTI]

It is well known that, in the description of quantum observables, positive operator valued measures (POVMs) generalize projection valued measures (PVMs) and they also turn out be more optimal in many tasks. We show that a commutative POVM is an extreme point in the convex set of all POVMs if and only if it is a PVM. This results implies that non-commutativity is a necessary ingredient to overcome the limitations of PVMs.

Teiko Heinosaari; Juha-Pekka Pellonpää

2011-06-21T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Tropical Limit in Statistical Physics  

E-Print Network [OSTI]

Tropical limit for macroscopic systems in equilibrium defined as the formal limit of Boltzmann constant k going to 0 is discussed. It is shown that such tropical limit is well-adapted to analyse properties of systems with highly degenerated energy levels, particularly of frustrated systems like spin ice and spin glasses. Tropical free energy is a piecewise linear function of temperature, tropical entropy is a piecewise constant function and the system has energy for which tropical Gibbs' probability has maximum. Properties of systems in the points of jump of entropy are studied. Systems with finite and infinitely many energy levels and phenomena of limiting temperatures are discussed.

M. Angelelli; B. Konopelchenko

2015-02-04T23:59:59.000Z

222

Quantum Walk of Two Interacting Bosons  

E-Print Network [OSTI]

We study the effect of interactions on the bosonic two-particle quantum walk and its corresponding spatial correlations. The combined effect of interactions and Hanbury-Brown Twiss interference results in unique spatial correlations which depend on the strength of the interaction, but not on its sign. The results are explained in light of the two-particle spectrum and the physics of attractively and repulsively bound pairs. We experimentally measure the weak interaction limit of these effects in nonlinear photonic lattices. Finally, we discuss an experimental approach to observe the strong interaction limit using single atoms in optical lattices.

Yoav Lahini; Mor Verbin; Sebastian D. Huber; Yaron Bromberg; Rami Pugatch; Yaron Silberberg

2011-05-11T23:59:59.000Z

223

On the Interpretation of Energy as the Rate of Quantum Computation  

Science Journals Connector (OSTI)

Over the last few decades, developments in the physical limits of computing and quantum computing have increasingly taught us that it can be helpful to think about physics itself in computational terms. For example, work over the last decade has shown ... Keywords: 03.65 Ta, 03.67, Hamiltonian energy, Margolus---Levitin theorem, Time evolution operator, action of the Hamiltonian operator, energy as computing, geometric phase, physics as computation, quantum computational complexity, quantum logic gates

Michael P. Frank

2005-10-01T23:59:59.000Z

224

Majorization-preserving quantum channels  

E-Print Network [OSTI]

In this report, we give a characterization to those quantum channels that preserve majorization relationship between quantum states. Some remarks are presented as well.

Lin Zhang

2012-09-24T23:59:59.000Z

225

Sandia National Laboratories: Quantum Systems  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum Systems Sensors Sandia leverages quantum mechanics to enable exquisite metrology devices, such as inertial sensors and frequency standards that go beyond the capabilities...

226

The Quantum Side of Photosynthesis  

Science Journals Connector (OSTI)

The Quantum Side of Photosynthesis ... But evidence is mounting that photosynthetic organisms may, in fact, capitalize on quantum effects to harness the sun’s rays. ...

JYLLIAN KEMSLEY

2012-02-19T23:59:59.000Z

227

FUEL CASK IMPACT LIMITER VULNERABILITIES  

SciTech Connect (OSTI)

Cylindrical fuel casks often have impact limiters surrounding just the ends of the cask shaft in a typical 'dumbbell' arrangement. The primary purpose of these impact limiters is to absorb energy to reduce loads on the cask structure during impacts associated with a severe accident. Impact limiters are also credited in many packages with protecting closure seals and maintaining lower peak temperatures during fire events. For this credit to be taken in safety analyses, the impact limiter attachment system must be shown to retain the impact limiter following Normal Conditions of Transport (NCT) and Hypothetical Accident Conditions (HAC) impacts. Large casks are often certified by analysis only because of the costs associated with testing. Therefore, some cask impact limiter attachment systems have not been tested in real impacts. A recent structural analysis of the T-3 Spent Fuel Containment Cask found problems with the design of the impact limiter attachment system. Assumptions in the original Safety Analysis for Packaging (SARP) concerning the loading in the attachment bolts were found to be inaccurate in certain drop orientations. This paper documents the lessons learned and their applicability to impact limiter attachment system designs.

Leduc, D; Jeffery England, J; Roy Rothermel, R

2009-02-09T23:59:59.000Z

228

Quantum random number generator based on spin noise  

Science Journals Connector (OSTI)

We present an implementation of a robust quantum random number generator based on the quantum fluctuations of the collective spin of an alkali-metal vapor. The achieved bit rate is limited by the spin relaxation rate of the alkali-metal atoms 1/T2 to about 1 kbit/s. However, the same physical scheme, which is impervious to limitations posed by single-photon detectors used in current implementations and rests solely on threshold detection, can be extended to solid state systems with a bit rate higher than 1 Gbit/s.

G. E. Katsoprinakis; M. Polis; A. Tavernarakis; A. T. Dellis; I. K. Kominis

2008-05-19T23:59:59.000Z

229

Quantum motor and future  

E-Print Network [OSTI]

In a popular language, the possibilities of the Casimir expulsion effect are presented, which can be the basis of quantum motors. Such motors can be in the form of a special multilayer thin film with periodic and complex nanosized structures. Quantum motors of the type of the Casimir platforms can be the base of transportation, energy and many other systems in the future.

Fateev, Evgeny G

2013-01-01T23:59:59.000Z

230

Quantum motor and future  

E-Print Network [OSTI]

In a popular language, the possibilities of the Casimir expulsion effect are presented, which can be the basis of quantum motors. Such motors can be in the form of a special multilayer thin film with periodic and complex nanosized structures. Quantum motors of the type of the Casimir platforms can be the base of transportation, energy and many other systems in the future.

Evgeny G. Fateev

2013-01-20T23:59:59.000Z

231

Isotope - based Quantum Information  

E-Print Network [OSTI]

This paper is brief review of three aspects of the isotope - based quantum information: computation, teleportation and cryptography. Our results demonstrate not only that entanglement exists in elementary excitation of isotope - mixed solids but also it can be used for quantum information processing.

Vladimir G. Plekhanov

2009-09-04T23:59:59.000Z

232

Reliable quantum computers  

Science Journals Connector (OSTI)

...the performance of a useful quantum computer will need to be. And that in itself...by the Department of Energy under Grant No. DE- FG03-92-ER40701, and...Lond. A (1998) Reliable quantum computers 409 References Aharonov, D. & Ben-Or...

1998-01-01T23:59:59.000Z

233

Quantum Spacetime Phenomenology  

E-Print Network [OSTI]

I review the current status of phenomenological programs inspired by quantum-spacetime research. I stress in particular the significance of results establishing that certain data analyses provide sensitivity to effects introduced genuinely at the Planck scale. And my main focus is on phenomenological programs that managed to affect the directions taken by studies of quantum-spacetime theories.

Giovanni Amelino-Camelia

2013-06-18T23:59:59.000Z

234

Quantum dot cascade laser  

Science Journals Connector (OSTI)

We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode...??~?6.15 ?m and a bro...

Ning Zhuo; Feng Qi Liu; Jin Chuan Zhang; Li Jun Wang…

2014-03-01T23:59:59.000Z

235

Quantum Dots Monitor TrkA Receptor Dynamics in the Interior of Neural PC12 Cells  

Science Journals Connector (OSTI)

23 These TrkA vesicles are then loaded onto microtubule motor transport highways within the cell and shuttled to different subcellular sites for interaction with other signaling molecules. ... Limitations and potential future uses of quantum dot probes are also discussed. ... Tracking Individual Kinesin Motors in Living Cells Using Single Quantum-Dot Imaging ...

Sujata Sundara Rajan; Tania Q. Vu

2006-08-22T23:59:59.000Z

236

Reasoning about quantum knowledge  

E-Print Network [OSTI]

We construct a formal framework for investigating epistemic and temporal notions in the context of distributed quantum computation. While we rely on structures developed earlier, we stress that our notion of quantum knowledge makes sense more generally in any agent-based model for distributed quantum systems. Several arguments are given to support our view that an agent's possibility relation should not be based on the reduced density matrix, but rather on local classical states and local quantum operations. In this way, we are able to analyse distributed primitives such as superdense coding and teleportation, obtaining interesting conclusions as to how the knowledge of individual agents evolves. We show explicitly that the knowledge transfer in teleportation is essentially classical, in that eventually, the receiving agent knows that its state is equal to the initial state of the sender. The relevant epistemic statements for teleportation deal with this correlation rather than with the actual quantum state, which is unknown throughout the protocol.

Ellie D'Hondt; Prakash Panangaden

2005-07-19T23:59:59.000Z

237

An Invisible Quantum Tripwire  

E-Print Network [OSTI]

We present here a quantum tripwire, which is a quantum optical interrogation technique capable of detecting an intrusion with very low probability of the tripwire being revealed to the intruder. Our scheme combines interaction-free measurement with the quantum Zeno effect in order to interrogate the presence of the intruder without interaction. The tripwire exploits a curious nonlinear behaviour of the quantum Zeno effect we discovered, which occurs in a lossy system. We also employ a statistical hypothesis testing protocol, allowing us to calculate a confidence level of interaction-free measurement after a given number of trials. As a result, our quantum intruder alert system is robust against photon loss and dephasing under realistic atmospheric conditions and its design minimizes the probabilities of false positives and false negatives as well as the probability of becoming visible to the intruder.

Petr M. Anisimov; Daniel J. Lum; S. Blane McCracken; Hwang Lee; Jonathan P. Dowling

2010-02-17T23:59:59.000Z

238

Effective equations for the quantum pendulum from momentous quantum mechanics  

SciTech Connect (OSTI)

In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

Hernandez, Hector H.; Chacon-Acosta, Guillermo [Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120 (Mexico)

2012-08-24T23:59:59.000Z

239

Quantum Degrees of Freedom, Quantum Integrability and Entanglment Generators  

E-Print Network [OSTI]

Dynamical algebra notion of quantum degrees of freedom is utilized to study the relation between quantum dynamical integrability and generalized entanglement. It is argued that a quantum dynamical system generates generalized entanglement by internal dynamics if and only if it is quantum non-integrable. Several examples are used to illustrate the relation.

Nikola Buric

2010-03-26T23:59:59.000Z

240

Classical capacity of the free-space quantum-optical channel  

E-Print Network [OSTI]

Exploring the limits to reliable communication rates over quantum channels has been the primary focus of many researchers over the past few decades. In the present work, the classical information carrying capacity of the ...

Guha, Saikat, 1980-

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Nonlinear subcritical magnetohydrodynamic beta limit  

SciTech Connect (OSTI)

Published gyrokinetic simulations have had difficulty operating beyond about half the ideal magnetohydrodynamic (MHD) critical beta limit with stationary and low transport levels in some well-established reference cases. Here it is demonstrated that this limitation is unlikely due to numerical instability, but rather appears to be a nonlinear subcritical MHD beta limit[R. E. Waltz, Phys. Rev. Lett. 55, 1098 (1985)] induced by the locally enhanced pressure gradients from the diamagnetic component of the nonlinearly driven (zero frequency) zonal flows. Strong evidence that the zonal flow corrugated pressure gradient profiles can act as a MHD-like beta limit unstable secondary equilibrium is provided. It is shown that the addition of sufficient ExB shear or operation closer to drift wave instability threshold, thereby reducing the high-n drift wave turbulence nonlinear pumping of the zonal flows, can allow the normal high-n ideal MHD beta limit to be reached with low transport levels. Example gyrokinetic simulations of experimental discharges are provided: one near the high-n beta limit reasonably matches the low transport levels needed when the high experimental level of ExB shear is applied; a second experimental example at moderately high beta appears to be limited by the subcritical beta.

Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2010-07-15T23:59:59.000Z

242

Quantum Electrodynamical Density-Functional Theory: Bridging Quantum Optics and Electronic-Structure Theory  

E-Print Network [OSTI]

In this work we give a comprehensive derivation of an exact and numerically feasible method to perform ab-initio calculations of quantum particles interacting with a quantized electromagnetic field. We present a hierachy of density-functional-type theories that describe the interaction of charged particles with photons and introduce the appropriate Kohn-Sham schemes. We show how the evolution of a system described by quantum electrodynamics in Coulomb gauge is uniquely determined by its initial state and two reduced quantities. These two fundamental observables, the polarization of the Dirac field and the vector potential of the photon field, can be calculated by solving two coupled, non-linear evolution equations without the need to explicitly determine the (numerically infeasible) many-body wave function of the coupled quantum system. To find reliable approximations to the implicit functionals we present the according Kohn-Sham construction. In the non-relativistic limit this density-functional-type theory ...

Ruggenthaler, Michael; Pellegrini, Camilla; Appel, Heiko; Tokatly, Ilya V; Rubio, Angel

2014-01-01T23:59:59.000Z

243

Quantum universality by state distillation  

E-Print Network [OSTI]

Quantum universality can be achieved using classically controlled stabilizer operations and repeated preparation of certain ancilla states. Which ancilla states suffice for universality? This "magic states distillation" question is closely related to quantum fault tolerance. Lower bounds on the noise tolerable on the ancilla help give lower bounds on the tolerable noise rate threshold for fault-tolerant computation. Upper bounds show the limits of threshold upper-bound arguments based on the Gottesman-Knill theorem. We extend the range of single-qubit mixed states that are known to give universality, by using a simple parity-checking operation. For applications to proving threshold lower bounds, certain practical stability characteristics are often required, and we also show a stable distillation procedure. No distillation upper bounds are known beyond those given by the Gottesman-Knill theorem. One might ask whether distillation upper bounds reduce to upper bounds for single-qubit ancilla states. For multi-qubit pure states and previously considered two-qubit ancilla states, the answer is yes. However, we exhibit two-qubit mixed states that are not mixtures of stabilizer states, but for which every postselected stabilizer reduction from two qubits to one outputs a mixture of stabilizer states. Distilling such states would require true multi-qubit state distillation methods.

Ben W. Reichardt

2006-08-09T23:59:59.000Z

244

Nonlinear friction in quantum mechanics  

E-Print Network [OSTI]

The effect of nonlinear friction forces in quantum mechanics is studied via dissipative Madelung hydrodynamics. A new thermo-quantum diffusion equation is derived, which is solved for the particular case of quantum Brownian motion with a cubic friction. It is extended also by a chemical reaction term to describe quantum reaction-diffusion systems with nonlinear friction as well.

Roumen Tsekov

2010-03-01T23:59:59.000Z

245

AN INTRODUCTION TO QUANTUM OPTICS...  

E-Print Network [OSTI]

AN INTRODUCTION TO QUANTUM OPTICS... ...the light as you've never seen before... Optics:http://science.howstuffworks.com/laser5.htm #12;5 DEFINITION Quantum Optics: "Quantum optics is a field in quantum physics, dealing OPTICS OPERATORS Light is described in terms of field operators for creation and annihilation of photons

Palffy-Muhoray, Peter

246

Cognitive Limitations and Investment "Myopia"  

E-Print Network [OSTI]

Optimization of investment decisions in an uncertain and dynamically evolving environment is difficult due to the limitations of the decision maker’s cognitive capacity. Thus, actual investment decisions may deviate from ...

Chi, Tailan; Fan, Dashan

1997-01-01T23:59:59.000Z

247

Ecological Exposure Limits and Guidelines  

Science Journals Connector (OSTI)

Abstract Ecological exposure limits and guidelines represent the maximum level of a chemical substance that is considered to be safe or acceptable in environmental releases or compartments. The ecological exposure limits are established to protect the ecosystems and environmental resources and may refer to the emissions, e.g., effluents, atmospheric emissions or discharges, or to the final concentration in the receiving body, e.g., water, sediment, or soil. There are two main methods for setting these limits. One focuses on the identification of best available practices for different sectors and processes; the other is a particular case of risk assessment, named by some authors as reverse risk assessment, which establishes the maximum level in the emission or receiving compartment maintaining an acceptable level of risk. The term ‘exposure limit’ is rarely used in the ecological context; the most usual terms are criteria, standards, or objectives.

J.V. Tarazona

2014-01-01T23:59:59.000Z

248

Hudol Limited | Open Energy Information  

Open Energy Info (EERE)

1TN Sector: Biomass Product: Wales-based firm with a licence that allows cost efficient gas production from biomass and Refuse derived Fuels (RDF). References: Hudol Limited1...

249

Extremal Limits and Kerr Spacetime  

E-Print Network [OSTI]

The fact that one must evaluate the near-extremal and near-horizon limits of Kerr space-time in a specific order, is shown to a lead to discontinuity in the extremal limit, such that this limiting space-time differs nontrivially from the precisely extremal space-time. This is established by first showing a discontinuity in the extremal limit of the maximal analytic extension of the Kerr geometry, given by Carter. Next, we examine the ISCO of the exactly extremal Kerr geometry and show that on the event horizon of the extremal Kerr black hole, it coincides with the principal null geodesic generator of the horizon, having vanishing energy and angular momentum. We find that there is no such ISCO in the near-extremal geometry, thus garnering additional support for our primary contention. We relate this disparity between the two geometries to the lack of a trapping horizon in the extremal situation.

Parthapratim Pradhan; Parthasarathi Majumdar

2011-08-11T23:59:59.000Z

250

Spitzer White Dwarf Planet Limits  

E-Print Network [OSTI]

We present preliminary limits on the presence of planets around white dwarf stars using the IRAC photometer on the Spitzer space telescope. Planets emit strongly in the mid-infrared which allows their presence to be detected as an excess at these wavelengths. We place limits of $5 M_J$ for 8 stars assuming ages of $1 Gyr$, and $10 M_J$ for 23 stars.We describe our survey, present our results and comment on approaches to improve our methodology.

F. Mullally; Ted von Hippel; D. E. Winget

2006-10-28T23:59:59.000Z

251

Narrow spectral linewidth of single zinc-blende GaN/AlN self-assembled quantum dots  

SciTech Connect (OSTI)

We study by microphotoluminescence the optical properties of single self-assembled zinc-blende GaN/AlN quantum dots grown by plasma-assisted molecular beam epitaxy. As opposed to previous reports, the high quality of such zinc-blende GaN quantum dots allows us to evidence a weak acoustic phonon sideband as well as a limited spectral diffusion. As a result, we report on resolution-limited quantum dot linewidths as narrow as 500 ± 50 ?eV. We finally confirm the fast radiative lifetime and high-temperature operation of such quantum dots.

Sergent, S. [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)] [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Kako, S. [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)] [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Bürger, M.; As, D. J. [Department Physik, Universität Paderborn, Warburger Str. 100, 33098 Paderborn (Germany)] [Department Physik, Universität Paderborn, Warburger Str. 100, 33098 Paderborn (Germany); Arakawa, Y. [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan) [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

2013-10-07T23:59:59.000Z

252

Quantum Channels with Memory  

E-Print Network [OSTI]

We present a general model for quantum channels with memory, and show that it is sufficiently general to encompass all causal automata: any quantum process in which outputs up to some time t do not depend on inputs at times t' > t can be decomposed into a concatenated memory channel. We then examine and present different physical setups in which channels with memory may be operated for the transfer of (private) classical and quantum information. These include setups in which either the receiver or a malicious third party have control of the initializing memory. We introduce classical and quantum channel capacities for these settings, and give several examples to show that they may or may not coincide. Entropic upper bounds on the various channel capacities are given. For forgetful quantum channels, in which the effect of the initializing memory dies out as time increases, coding theorems are presented to show that these bounds may be saturated. Forgetful quantum channels are shown to be open and dense in the set of quantum memory channels.

Dennis Kretschmann; Reinhard F. Werner

2005-02-17T23:59:59.000Z

253

Layered architecture for quantum computing  

E-Print Network [OSTI]

We develop a layered quantum computer architecture, which is a systematic framework for tackling the individual challenges of developing a quantum computer while constructing a cohesive device design. We discuss many of the prominent techniques for implementing circuit-model quantum computing and introduce several new methods, with an emphasis on employing surface code quantum error correction. In doing so, we propose a new quantum computer architecture based on optical control of quantum dots. The timescales of physical hardware operations and logical, error-corrected quantum gates differ by several orders of magnitude. By dividing functionality into layers, we can design and analyze subsystems independently, demonstrating the value of our layered architectural approach. Using this concrete hardware platform, we provide resource analysis for executing fault-tolerant quantum algorithms for integer factoring and quantum simulation, finding that the quantum dot architecture we study could solve such problems on the timescale of days.

N. Cody Jones; Rodney Van Meter; Austin G. Fowler; Peter L. McMahon; Jungsang Kim; Thaddeus D. Ladd; Yoshihisa Yamamoto

2012-09-27T23:59:59.000Z

254

Quantum technology: the second quantum revolution  

Science Journals Connector (OSTI)

...be an electron or nuclear spin in a molecule...the Coulomb energy cost of adding one extra...1667 A B A' B' C D BS M M S - 0 2.0 1...resolution at low cost. In addition to writing...A silicon-based nuclear spin quantum computer...

2003-01-01T23:59:59.000Z

255

Intrinsic Time Quantum Geometrodynamics  

E-Print Network [OSTI]

Quantum Geometrodynamics with intrinsic time development and momentric variables is presented. An underlying SU(3) group structure at each spatial point regulates the theory. The intrinsic time behavior of the theory is analyzed, together with its ground state and primordial quantum fluctuations. Cotton-York potential dominates at early times when the universe was small; the ground state naturally resolves Penrose's Weyl Curvature Hypothesis, and thermodynamic and gravitational `arrows of time' point in the same direction. Ricci scalar potential corresponding to Einstein's General Relativity emerges as a zero-point energy contribution. A new set of fundamental canonical commutation relations without Planck's constant emerges from the unification of Gravitation and Quantum Mechanics.

Eyo Eyo Ita III; Chopin Soo; Hoi-Lai Yu

2015-01-26T23:59:59.000Z

256

Stabilizing quantum information  

Science Journals Connector (OSTI)

The dynamical-algebraic structure underlying all the schemes for quantum information stabilization is argued to be fully contained in the reducibility of the operator algebra describing the interaction with the environment of the coding quantum system. This property amounts to the existence of a nontrivial group of symmetries for the global dynamics. We provide a unified framework that allows us to build systematically additional classes of error correcting codes and noiseless subsystems. It is shown that by using symmetrization strategies one can artificially produce noiseless subsystems supporting universal quantum computation.

Paolo Zanardi

2000-12-05T23:59:59.000Z

257

Random unitary maps for quantum state reconstruction  

SciTech Connect (OSTI)

We study the possibility of performing quantum state reconstruction from a measurement record that is obtained as a sequence of expectation values of a Hermitian operator evolving under repeated application of a single random unitary map, U{sub 0}. We show that while this single-parameter orbit in operator space is not informationally complete, it can be used to yield surprisingly high-fidelity reconstruction. For a d-dimensional Hilbert space with the initial observable in su(d), the measurement record lacks information about a matrix subspace of dimension {>=}d-2 out of the total dimension d{sup 2}-1. We determine the conditions on U{sub 0} such that the bound is saturated, and show they are achieved by almost all pseudorandom unitary matrices. When we further impose the constraint that the physical density matrix must be positive, we obtain even higher fidelity than that predicted from the missing subspace. With prior knowledge that the state is pure, the reconstruction will be perfect (in the limit of vanishing noise) and for arbitrary mixed states, the fidelity is over 0.96, even for small d, and reaching F>0.99 for d>9. We also study the implementation of this protocol based on the relationship between random matrices and quantum chaos. We show that the Floquet operator of the quantum kicked top provides a means of generating the required type of measurement record, with implications on the relationship between quantum chaos and information gain.

Merkel, Seth T. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Riofrio, Carlos A.; Deutsch, Ivan H. [Center for Quantum Information and Control (CQuIC), Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico, 87131 (United States); Flammia, Steven T. [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)

2010-03-15T23:59:59.000Z

258

Projective Loop Quantum Gravity I. State Space  

E-Print Network [OSTI]

Instead of formulating the state space of a quantum field theory over one big Hilbert space, it has been proposed by Kijowski to describe quantum states as projective families of density matrices over a collection of smaller, simpler Hilbert spaces. Beside the physical motivations for this approach, it could help designing a quantum state space holding the states we need. In [Oko{\\l}\\'ow 2013, arXiv:1304.6330] the description of a theory of Abelian connections within this framework was developed, an important insight being to use building blocks labeled by combinations of edges and surfaces. The present work generalizes this construction to an arbitrary gauge group G (in particular, G is neither assumed to be Abelian nor compact). This involves refining the definition of the label set, as well as deriving explicit formulas to relate the Hilbert spaces attached to different labels. If the gauge group happens to be compact, we also have at our disposal the well-established Ashtekar-Lewandowski Hilbert space, which is defined as an inductive limit using building blocks labeled by edges only. We then show that the quantum state space presented here can be thought as a natural extension of the space of density matrices over this Hilbert space. In addition, it is manifest from the classical counterparts of both formalisms that the projective approach allows for a more balanced treatment of the holonomy and flux variables, so it might pave the way for the development of more satisfactory coherent states.

Suzanne Lanéry; Thomas Thiemann

2014-11-11T23:59:59.000Z

259

Galilei covariance and Einstein's equivalence principle in quantum reference frames  

E-Print Network [OSTI]

The covariance of the Schr\\"odinger equation under Galilei boosts and the compatibility of nonrelativistic quantum mechanics with Einstein's equivalence principle have been constrained for so long to the existence of a superselection rule which would prevent a quantum particle to be found in superposition states of different masses. In a effort to avoid this expedient, thus allowing for nonrelativistic quantum mechanics to account for unstable particles, recent works have suggested that usual Galilean transformations are inconsistent with the nonrelativistic limit of the Lorentz transformation. Here we approach the issue in a fundamentally different way. Using a formalism of unitary transformations and employing quantum reference frames rather than immaterial coordinate systems, we show that the Schr\\"odinger equation, although form-variant, is fully compatible with the aforementioned principles of relativity.

S. T. Pereira; R. M. Angelo

2014-04-10T23:59:59.000Z

260

Quantum-Secure Authentication with a Classical Key  

E-Print Network [OSTI]

Authentication provides the trust people need to engage in transactions. The advent of physical keys that are impossible to copy promises to revolutionize this field. Up to now, such keys have been verified by classical challenge-response protocols. Such protocols are in general susceptible to emulation attacks. Here we demonstrate Quantum-Secure Authentication ("QSA") of an unclonable classical physical key in a way that is inherently secure by virtue of quantum-physical principles. Our quantum-secure authentication operates in the limit of a large number of channels, represented by the more than thousand degrees of freedom of an optical wavefront shaped with a spatial light modulator. This allows us to reach quantum security with weak coherent pulses of light containing dozens of photons, too few for an adversary to determine their complex spatial shapes, thereby rigorously preventing emulation.

Sebastianus A. Goorden; Marcel Horstmann; Allard P. Mosk; Boris Škori?; Pepijn W. H. Pinkse

2014-06-03T23:59:59.000Z

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261

On a super-selection rule in quantum cosmology  

E-Print Network [OSTI]

The discarding of negative frequency solutions in a quantum field theory brings about the absence of antiparticles which, after all, means the violation of 4-inversion symmetry $(x \\rightarrow -x, t \\rightarrow-t)$ which is a (improper) Lorentz transformation. Suppose you have a theory of quantum gravity which lacks the negative frequency solutions (like usually people have in quantum cosmology, invoking a super-selection rule). Taking some limit in this theory in order to obtain the weak (or null) gravitational regime, the result is a theory that does not respect that symmetry and does not have place for antiparticles. That is, a theory of fields is not obtained, as it should be. For the case of a quantum cosmology model we show that if we ignore the negative frequency solutions, the rich processes of creation/annihilation of universes at the Planck scale, are lost.

E. Sergio Santini

2014-12-26T23:59:59.000Z

262

A graph-separation theorem for quantum causal models  

E-Print Network [OSTI]

A causal model is an abstract representation of a physical system as a directed acyclic graph (DAG), where the statistical dependencies are encoded using a graphical criterion called `d-separation'. Recent work by Wood & Spekkens shows that causal models cannot, in general, provide a faithful representation of quantum systems. Since d-separation encodes a form of Reichenbach's Common Cause Principle (RCCP), whose validity is questionable in quantum mechanics, we propose a generalised graph separation rule that does not assume the RCCP. We prove that the new rule faithfully captures the statistical dependencies between observables in a quantum network, encoded as a DAG, and is consistent with d-separation in a classical limit. We note that the resulting model is still unable to give a faithful representation of correlations stronger than quantum mechanics, such as the Popescu-Rorlich box.

Jacques Pienaar; Caslav Brukner

2014-10-31T23:59:59.000Z

263

Nanophotonic quantum phase switch with a single atom  

E-Print Network [OSTI]

In analogy to transistors in classical electronic circuits, a quantum optical switch is an important element of quantum circuits and quantum networks. Operated at the fundamental limit where a single quantum of light or matter controls another field or material system, it may enable fascinating applications such as long-distance quantum communication, distributed quantum information processing and metrology, and the exploration of novel quantum states of matter. Here, by strongly coupling a photon to a single atom trapped in the near field of a nanoscale photonic crystal cavity, we realize a system where a single atom switches the phase of a photon, and a single photon modifies the atom's phase. We experimentally demonstrate an atom-induced optical phase shift that is nonlinear at the two-photon level, a photon number router that separates individual photons and photon pairs into different output modes, and a single-photon switch where a single "gate" photon controls the propagation of a subsequent probe fiel...

Tiecke, T G; de Leon, N P; Liu, L R; Vuleti?, V; Lukin, M D

2014-01-01T23:59:59.000Z

264

Quantum Cellular Automaton Theory of Light  

E-Print Network [OSTI]

We present a quantum theory of light based on quantum cellular automata (QCA). This approach allows us to have a thorough quantum theory of free electrodynamics encompassing an hypothetical discrete Planck scale. The theory is particularly relevant because it provides predictions at the macroscopic scale that can be experimentally tested. We show how, in the limit of small wave-vector k, the free Maxwell's equations emerge from two Weyl QCAs derived from informational principles in Ref. [1]. Within this framework the photon is introduced as a composite particle made of a pair of correlated massless Fermions, and the usual Bosonic statistics is recovered in the low photon density limit. We derive the main phenomenological features of the theory, consisting in dispersive propagation in vacuum, the occurrence of a small longitudinal polarization, and a saturation effect originated by the Fermionic nature of the photon. We then discuss whether these effects can be experimentally tested, and observe that only the dispersive effects are accessible with current technology, from observations of arrival times of pulses originated at cosmological distances.

Alessandro Bisio; Giacomo Mauro D'Ariano; Paolo Perinotti

2014-07-25T23:59:59.000Z

265

Nonadiabatic quantum state engineering driven by fast quench dynamics  

E-Print Network [OSTI]

There are a number of tasks in quantum information science that exploit non-transitional adiabatic dynamics. Such a dynamics is bounded by the adiabatic theorem, which naturally imposes a speed limit in the evolution of quantum systems. Here, we investigate an approach for quantum state engineering exploiting a shortcut to the adiabatic evolution, which is based on rapid quenches in a continuous-time Hamiltonian evolution. In particular, this procedure is able to provide state preparation faster than the adiabatic brachistochrone. Remarkably, the evolution time in this approach is shown to be ultimately limited by its "thermodynamical cost,"provided in terms of the average work rate (average power) of the quench process. We illustrate this result in a scenario that can be experimentally implemented in a nuclear magnetic resonance setup.

Marcela Herrera; Marcelo S. Sarandy; Eduardo I. Duzzioni; Roberto M. Serra

2014-03-03T23:59:59.000Z

266

A Quantum Production Model  

E-Print Network [OSTI]

The production system is a theoretical model of computation relevant to the artificial intelligence field allowing for problem solving procedures such as hierarchical tree search. In this work we explore some of the connections between artificial intelligence and quantum computation by presenting a model for a quantum production system. Our approach focuses on initially developing a model for a reversible production system which is a simple mapping of Bennett's reversible Turing machine. We then expand on this result in order to accommodate for the requirements of quantum computation. We present the details of how our proposition can be used alongside Grover's algorithm in order to yield a speedup comparatively to its classical counterpart. We discuss the requirements associated with such a speedup and how it compares against a similar quantum hierarchical search approach.

Luís Tarrataca; Andreas Wichert

2015-02-06T23:59:59.000Z

267

Terahertz quantum cascade lasers  

E-Print Network [OSTI]

The development of the terahertz frequency range has long been impeded by the relative dearth of compact, coherent radiation sources of reasonable power. This thesis details the development of quantum cascade lasers (QCLs) ...

Williams, Benjamin S. (Benjamin Stanford), 1974-

2003-01-01T23:59:59.000Z

268

Parasupersymmetry in Quantum Graphs  

E-Print Network [OSTI]

We study hidden parasupersymmetry structures in purely bosonic quantum mechanics on compact equilateral graphs. We consider a single free spinless particle on the graphs and show that the Huang-Su parasupersymmetry algebra is hidden behind degenerate spectra.

Satoshi Ohya

2012-10-29T23:59:59.000Z

269

Parasupersymmetry in Quantum Graphs  

E-Print Network [OSTI]

We study hidden parasupersymmetry structures in purely bosonic quantum mechanics on compact equilateral graphs. We consider a single free spinless particle on the graphs and show that the Rubakov-Spiridonov-Khare-Tomiya parasupersymmetries are hidden behind degenerate spectra.

Ohya, Satoshi

2012-01-01T23:59:59.000Z

270

Integrable quantum mappings  

Science Journals Connector (OSTI)

A quantum R-matrix structure is presented for a family of exactly integrable multidimensional rational mappings related to lattice versions of the Korteweg–de Vries equation. It is shown that these mappings possess a commuting family of invariants.

F. W. Nijhoff; H. W. Capel; V. G. Papageorgiou

1992-08-15T23:59:59.000Z

271

Wires with Quantum Memory  

E-Print Network [OSTI]

We show that quantum particles constrained to move along curves undergoing cyclic deformations acquire, in general, geometric phases. We treat explicitly an example, involving particular deformations of a circle, and ponder on potential applications.

C. Chryssomalakos; H. Hernandez; D. Gelbwaser-Klimovsky; E. Okon

2008-04-19T23:59:59.000Z

272

Geometrically frustrated quantum magnets  

E-Print Network [OSTI]

(cont.) more general lessons on frustrated quantum magnetism. At the end, we demonstrate some new mathematical tools on two other frustrated two-dimensional systems, and summarize our conclusions, with an outlook to remaining ...

Nikolić , Predrag, 1974-

2004-01-01T23:59:59.000Z

273

QUANTUM ERGODICITY AND REDUCTION BENJAMIN KUSTER AND PABLO RAMACHER  

E-Print Network [OSTI]

with an isometric effective action of a compact connected Lie group G, relying on recent results on singular of - in the limit of large eigenvalues. Concretely, let {uj} be an orthonormal basis of L2 (M) of eigenfunctions mechanics, quantum observables correspond to self-adjoint operators A in the Hilbert space L2 (M

Ramacher, Pablo

274

Ablamp Limited | Open Energy Information  

Open Energy Info (EERE)

Ablamp Limited Ablamp Limited Jump to: navigation, search Name Ablamp Limited Place Nanhai, Guangdong Province, China Sector Solar Product Manufacturer of energy-saving Compact Fluorescent Light Bulbs, solar-powered lights, LED bulbs, auto lamps and other speciality lamps. Coordinates 23.049681°, 113.173737° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":23.049681,"lon":113.173737,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

275

Solfex Limited | Open Energy Information  

Open Energy Info (EERE)

Solfex Limited Solfex Limited Jump to: navigation, search Name Solfex Limited Address Energy Arena Bannister Hall Works Off Shop Lane, Higher Walton Preston, Lancashire PR5 4DZ Place Preston, United Kingdom Sector Solar Product Solar thermal collectors Phone number 01772 312847 Website http://www.solfex.co.uk/home.h Coordinates 53.743452°, -2.64416° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":53.743452,"lon":-2.64416,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

276

Bioethanol Limited | Open Energy Information  

Open Energy Info (EERE)

Bioethanol Limited Bioethanol Limited Jump to: navigation, search Name Bioethanol Limited Place London, United Kingdom Zip SE1 7TJ Sector Renewable Energy Product Aims to develop a global renewable transport fuel business supplying primarily bioethanol but also biodiesel. Coordinates 51.506325°, -0.127144° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":51.506325,"lon":-0.127144,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

277

Renpro Limited | Open Energy Information  

Open Energy Info (EERE)

Renpro Limited Renpro Limited Jump to: navigation, search Name Renpro Limited Place London, England, United Kingdom Zip WC2N 4JF Sector Renewable Energy Product String representation "Founded in 2005 ... newable energy." is too long. Coordinates 51.506325°, -0.127144° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":51.506325,"lon":-0.127144,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

278

Quantum Subcritical Bubbles  

E-Print Network [OSTI]

We quantize subcritical bubbles which are formed in the weakly first order phase transition. We find that the typical size of the thermal fluctuation reduces in the quantum-statistical physics. We estimate the typical size and the amplitude of thermal fluctuations near the critical temperature in the electroweak phase transition using quantum statistical average. Furthermore based on our study, we give implication on the dynamics of phase transition.

Tomoko Uesugi; Masahiro Morikawa; Tetsuya Shiromizu

1996-06-26T23:59:59.000Z

279

Quantum error control codes  

E-Print Network [OSTI]

QUANTUM ERROR CONTROL CODES A Dissertation by SALAH ABDELHAMID AWAD ALY AHMED Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2008 Major... Subject: Computer Science QUANTUM ERROR CONTROL CODES A Dissertation by SALAH ABDELHAMID AWAD ALY AHMED Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY...

Abdelhamid Awad Aly Ahmed, Sala

2008-10-10T23:59:59.000Z

280

Time in quantum mechanics  

E-Print Network [OSTI]

OF CONTENTS I. INTRODUCTION II. HISTORICAL DEVELOPMENT A. Classical Mechanics B. Quantum Theory . C. The Problem 3 4 6 III. TIME ATOMS AND DISCRETE TIME A. The Earliest Applications of Atomistic and Discrete Time . . . . . B. The Radiating Electron... . C. Quantum Field Theory 8 10 l2 IV. TIME OPERATOR FORMULATIONS 16 A. Advocates Against a Time Operator . B. The Possibility of a Time Operator C, Advocates in Favor of a Time Operator D. A Restricted Time Delay Operator: Scattering Theory...

Chapin, Kimberly R.

2012-06-07T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Optical Quantum Computation  

E-Print Network [OSTI]

We review the field of Optical Quantum Computation, considering the various implementations that have been proposed and the experimental progress that has been made toward realizing them. We examine both linear and nonlinear approaches and both particle and field encodings. In particular we discuss the prospects for large scale optical quantum computing in terms of the most promising physical architectures and the technical requirements for realizing them.

T. C. Ralph; G. J. Pryde

2011-03-31T23:59:59.000Z

282

Quantum robots and environments  

Science Journals Connector (OSTI)

Quantum robots and their interactions with environments of quantum systems are described, and their study justified. A quantum robot is a mobile quantum system that includes an on-board quantum computer and needed ancillary systems. Quantum robots carry out tasks whose goals include specified changes in the state of the environment, or carrying out measurements on the environment. Each task is a sequence of alternating computation and action phases. Computation phase activites include determination of the action to be carried out in the next phase, and recording of information on neighborhood environmental system states. Action phase activities include motion of the quantum robot and changes in the neighborhood environment system states. Models of quantum robots and their interactions with environments are described using discrete space and time. A unitary step operator T that gives the single time step dynamics is associated with each task. T=Ta+Tc is a sum of action phase and computation phase step operators. Conditions that Ta and Tc should satisfy are given along with a description of the evolution as a sum over paths of completed phase input and output states. A simple example of a task—carrying out a measurement on a very simple environment—is analyzed in detail. A decision tree for the task is presented and discussed in terms of the sums over phase paths. It is seen that no definite times or durations are associated with the phase steps in the tree, and that the tree describes the successive phase steps in each path in the sum over phase paths.

Paul Benioff

1998-08-01T23:59:59.000Z

283

Chiral Quantum Walks  

E-Print Network [OSTI]

Wigner separated the possible types of symmetries in quantum theory into those symmetries that are unitary and those that are antiunitary. Unitary symmetries have been well studied whereas antiunitary symmetries and the physical implications associated with time-reversal symmetry breaking have had little influence on quantum information science. Here we develop a quantum circuits version of time-reversal symmetry theory, classifying time-symmetric and time-asymmetric Hamiltonians and circuits in terms of their underlying network elements and geometric structures. These results reveal that many of the typical quantum circuit networks found across the field of quantum information science exhibit time-asymmetry. We then experimentally implement the most fundamental time-reversal asymmetric process, applying local gates in an otherwise time-symmetric circuit to induce time-reversal asymmetry and thereby achieve (i) directional biasing in the transition probability between basis states, (ii) the enhancement of and (iii) the suppression of these transport probabilities. Our results imply that the physical effect of time-symmetry breaking plays an essential role in coherent transport and its control represents an omnipresent yet essentially untapped resource in quantum transport science.

DaWei Lu; Jacob D. Biamonte; Jun Li; Hang Li; Tomi H. Johnson; Ville Bergholm; Mauro Faccin; Zoltán Zimborás; Raymond Laflamme; Jonathan Baugh; Seth Lloyd

2014-05-23T23:59:59.000Z

284

Turbocharging Quantum Tomography.  

SciTech Connect (OSTI)

Quantum tomography is used to characterize quantum operations implemented in quantum information processing (QIP) hardware. Traditionally, state tomography has been used to characterize the quantum state prepared in an initialization procedure, while quantum process tomography is used to characterize dynamical operations on a QIP system. As such, tomography is critical to the development of QIP hardware (since it is necessary both for debugging and validating as-built devices, and its results are used to influence the next generation of devices). But tomography su %7C ers from several critical drawbacks. In this report, we present new research that resolves several of these flaws. We describe a new form of tomography called gate set tomography (GST), which unifies state and process tomography, avoids prior methods critical reliance on precalibrated operations that are not generally available, and can achieve unprecedented accuracies. We report on theory and experimental development of adaptive tomography protocols that achieve far higher fidelity in state reconstruction than non-adaptive methods. Finally, we present a new theoretical and experimental analysis of process tomography on multispin systems, and demonstrate how to more e %7C ectively detect and characterize quantum noise using carefully tailored ensembles of input states.

Blume-Kohout, Robin J; Gamble, John King,; Nielsen, Erik; Maunz, Peter Lukas Wilhelm; Scholten, Travis L.; Rudinger, Kenneth Michael

2015-01-01T23:59:59.000Z

285

Quantum-noise quenching in atomic tweezers  

SciTech Connect (OSTI)

The efficiency of extracting single atoms or molecules from an ultracold bosonic reservoir is theoretically investigated for a protocol based on lasers, coupling the hyperfine state in which the atoms form a condensate to another stable state, in which the atom experiences a tight potential in the regime of collisional blockade, the quantum tweezers. The transfer efficiency into the single-atom ground state of the tight trap is fundamentally limited by the collective modes of the condensate, which are thermally and dynamically excited. The noise due to these excitations can be quenched for sufficiently long laser pulses, thereby achieving high efficiencies. These results show that this protocol can be applied to initializing a quantum register based on tweezer traps for neutral atoms.

Zippilli, Stefano [Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Theoretische Physik, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Fachbereich Physik and Research Center OPTIMAS, Technische Universitaet Kaiserslautern, D-67663 Kaiserslautern (Germany); Mohring, Bernd; Schleich, Wolfgang [Institut fuer Quantenphysik, Universitaet Ulm, D-89081 Ulm (Germany); Lutz, Eric [Department of Physics, University of Augsburg, D-86135 Augsburg (Germany); Morigi, Giovanna [Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Theoretische Physik, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)

2011-05-15T23:59:59.000Z

286

Quantum-noise quenching in atomic tweezers  

E-Print Network [OSTI]

The efficiency of extracting single atoms or molecules from an ultracold bosonic reservoir is theoretically investigated for a protocol based on lasers, coupling the hyperfine state in which the atoms form a condensate to another stable state, in which the atom experiences a tight potential in the regime of collisional blockade, the quantum tweezers. The transfer efficiency into the single-atom ground state of the tight trap is fundamentally limited by the collective modes of the condensate, which are thermally and dynamically excited. The noise due to these excitations can be quenched for sufficiently long laser pulses, thereby achieving high efficiencies. These results show that this protocol can be applied for initializing a quantum register based on tweezer traps for neutral atoms.

Stefano Zippilli; Bernd Mohring; Eric Lutz; Giovanna Morigi; Wolfgang Schleich

2011-04-15T23:59:59.000Z

287

Quantum Memory with a controlled homogeneous splitting  

E-Print Network [OSTI]

We propose a quantum memory protocol where a input light field can be stored onto and released from a single ground state atomic ensemble by controlling dynamically the strength of an external static and homogeneous field. The technique relies on the adiabatic following of a polaritonic excitation onto a state for which the forward collective radiative emission is forbidden. The resemblance with the archetypal Electromagnetically-Induced-Transparency (EIT) is only formal because no ground state coherence based slow-light propagation is considered here. As compared to the other grand category of protocols derived from the photon-echo technique, our approach only involves a homogeneous static field. We discuss two physical situations where the effect can be observed, and show that in the limit where the excited state lifetime is longer than the storage time, the protocols are perfectly efficient and noise-free. We compare the technique to other quantum memories, and propose atomic systems where the experiment c...

Hétet, G; Chanelière, T

2013-01-01T23:59:59.000Z

288

Performance bound for quantum absorption refrigerators  

E-Print Network [OSTI]

An implementation of quantum absorption chillers with three qubits has been recently proposed, that is ideally able to reach the Carnot performance regime. Here we study the working efficiency of such self-contained refrigerators, adopting a consistent treatment of dissipation effects. We demonstrate that the coefficient of performance at maximum cooling power is upper bounded by 3/4 of the Carnot performance. The result is independent of the details of the system and the equilibrium temperatures of the external baths. We provide design prescriptions that saturate the bound in the limit of a large difference between the operating temperatures. Our study suggests that delocalized dissipation, which must be taken into account for a proper modelling of the machine-baths interaction, is a fundamental source of irreversibility which prevents the refrigerator from approaching the Carnot performance arbitrarily closely in practice. The potential role of quantum correlations in the operation of these machines is also investigated.

Luis A. Correa; José P. Palao; Gerardo Adesso; Daniel Alonso

2012-12-18T23:59:59.000Z

289

Optimal performance of endoreversible quantum refrigerators  

E-Print Network [OSTI]

The derivation of general performance benchmarks is important in the design of highly optimized heat engines and refrigerators. To obtain them, one may model phenomenologically the leading sources of irreversibility ending up with results which are model-independent, but limited in scope. Alternatively, one can take a simple physical system realizing a thermodynamic cycle and assess its optimal operation from a complete microscopic description. We follow this approach in order to derive the coefficient of performance at maximum cooling rate for \\textit{any} endoreversible quantum refrigerator. At striking variance with the \\textit{universality} of the optimal efficiency of heat engines, we find that the cooling performance at maximum power is crucially determined by the details of the specific system-bath interaction mechanism. A closed analytical benchmark is found for endoreversible refrigerators weakly coupled to unstructured bosonic heat baths: an ubiquitous case study in quantum thermodynamics.

Luis A. Correa; José P. Palao; Gerardo Adesso; Daniel Alonso

2014-11-24T23:59:59.000Z

290

Quantum gravity effects in the Kerr spacetime  

SciTech Connect (OSTI)

We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the 'dressing' of the black hole's mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.

Reuter, M. [Institute of Physics, University of Mainz, Staudingerweg 7, D-55099 Mainz (Germany); Tuiran, E. [Departamento de Fisica, Universidad del Norte, Km 5 via a Puerto Colombia, AA-1569 Barranquilla (Colombia)

2011-02-15T23:59:59.000Z

291

Teleportation-Based Continuous Variable Quantum Cryptography  

E-Print Network [OSTI]

We show a continuous variable (CV) quantum key distribution (QKD) scheme based on the CV quantum teleportation of coherent states that yields a raw secret key made up of discrete variables for both Alice and Bob. This protocol preserves the efficient detection schemes of current CV technology (no single-photon detection techniques) and, at the same time, has efficient error correction and privacy amplification schemes due to its binary discrete key. In particular, it is secure for any value of the transmission efficiency of the optical line used by Alice to share entangled two-mode squeezed states with Bob (no 3 dB or 50% loss limitation characteristic of beam splitting attacks). The present CVQKD protocol works deterministically (no postselection needed) with efficient direct reconciliation techniques (no reverse reconciliation) in order to generate a secure key, even at the surprisingly 100% loss case.

F. S. Luiz; Gustavo Rigolin

2014-08-21T23:59:59.000Z

292

Quantum graph as a quantum spectral filter  

SciTech Connect (OSTI)

We study the transmission of a quantum particle along a straight input-output line to which a graph {Gamma} is attached at a point. In the point of contact we impose a singularity represented by a certain properly chosen scale-invariant coupling with a coupling parameter {alpha}. We show that the probability of transmission along the line as a function of the particle energy tends to the indicator function of the energy spectrum of {Gamma} as {alpha}{yields}{infinity}. This effect can be used for a spectral analysis of the given graph {Gamma}. Its applications include a control of a transmission along the line and spectral filtering. The result is illustrated with an example where {Gamma} is a loop exposed to a magnetic field. Two more quantum devices are designed using other special scale-invariant vertex couplings. They can serve as a band-stop filter and as a spectral separator, respectively.

Turek, Ondrej; Cheon, Taksu [Laboratory of Physics, Kochi University of Technology, Tosa Yamada, Kochi 782-8502 (Japan)] [Laboratory of Physics, Kochi University of Technology, Tosa Yamada, Kochi 782-8502 (Japan)

2013-03-15T23:59:59.000Z

293

Improving Quantum Algorithms for Quantum Chemistry  

E-Print Network [OSTI]

We present several improvements to the standard Trotter-Suzuki based algorithms used in the simulation of quantum chemistry on a quantum computer. First, we modify how Jordan-Wigner transformations are implemented to reduce their cost from linear or logarithmic in the number of orbitals to a constant. Our modification does not require additional ancilla qubits. Then, we demonstrate how many operations can be parallelized, leading to a further linear decrease in the parallel depth of the circuit, at the cost of a small constant factor increase in number of qubits required. Thirdly, we modify the term order in the Trotter-Suzuki decomposition, significantly reducing the error at given Trotter-Suzuki timestep. A final improvement modifies the Hamiltonian to reduce errors introduced by the non-zero Trotter-Suzuki timestep. All of these techniques are validated using numerical simulation and detailed gate counts are given for realistic molecules.

M. B. Hastings; D. Wecker; B. Bauer; M. Troyer

2014-03-23T23:59:59.000Z

294

Strong reactions in quantum super PDEs. III: Exotic quantum supergravity  

E-Print Network [OSTI]

Following the previous two parts, of a work devoted to encode strong reaction dynamics in the A. Pr\\'astaro's algebraic topology of quantum super PDE's, nonlinear quantum propagators in the observed quantum super Yang-Mills PDE, $\\hat{(YM)}[i]$, are further characterized. In particular, nonlinear quantum propagators with non-zero defect quantum electric-charge, are interpreted as {\\em exotic-quantum supergravity} effects. As an application, the recently discovered bound-state called $Zc(3900)$, is obtained as a neutral quasi-particle, generated in a $Q$-quantum exotic supergravity process. {\\em Quantum entanglement} is justified by means of the algebraic topologic structure of nonlinear quantum propagators. Quantum Cheshire cats are considered as examples of quantum entanglements. Existence theorem for solutions of $\\hat{(YM)}[i]$ admitting negative local temperatures ({\\em quantum thermodynamic-exotic solutions}) is obtained too and related to quantum entanglement. Such exotic solutions are used to encode Universe at the Planck-epoch. It is proved that the Universe's expansion at the Planck epoch is justified by the fact that it is encoded by a nonlinear quantum propagator having thermodynamic quantum exotic components in its boundary. This effect produces also an increasing of energy in the Universe at the Einstein epoch: {\\em Planck-epoch-legacy} on the boundary of our Universe. This is the main source of the Universe's expansion and solves the problem of the non-apparent energy-matter ({\\em dark-energy-matter}) in the actual Universe. Breit-Wheeler-type processes have been proved in the framework of the Pr\\'astaro's algebraic topology of quantum super Yang-Mills PDEs. Numerical comparisons of nonlinear quantum propagators with Weinberg-Salam electroweak theory in Standard Model are given.

Agostino Prástaro

2015-02-01T23:59:59.000Z

295

Quantum lattice gas model of Dirac particles in 1+1 dimensions  

E-Print Network [OSTI]

Presented is a quantum computing representation of Dirac particle dynamics. The approach employs an operator splitting method that is an analytically closed-form product decomposition of the unitary evolution operator. This allows the Dirac equation to be cast as a unitary finite-difference equation in a high-energy limit. The split evolution operator (with separate kinetic and interaction terms) is useful for efficient quantum simulation. For pedagogical purposes, here we restrict the treatment to Dirac particle dynamics in 1+1 spacetime dimensions. Independent derivations of the quantum algorithm are presented and the model's validity is tested in several quantum simulations by comparing the numerical results against analytical predictions. Using the relativistic quantum algorithm in the case when mc^2 >> pc, quantum simulations of a nonrelativistic particle in an external scalar square well and parabolic potential is presented.

Jeffrey Yepez

2013-07-12T23:59:59.000Z

296

Review and Exams Limited Certification  

E-Print Network [OSTI]

__________________________________ Check which exam you will be taking: Commercial Landscape Maintenance Lawn & Ornamental CEU's ONLY 8 Limited Certification for Commercial Landscape Maintenance A license is necessary for each commercial landscape maintenance person who applies pesticides to ornamental plant beds. Application available at: http

Watson, Craig A.

297

Quantum computation beyond the circuit model  

E-Print Network [OSTI]

The quantum circuit model is the most widely used model of quantum computation. It provides both a framework for formulating quantum algorithms and an architecture for the physical construction of quantum computers. However, ...

Jordan, Stephen Paul

2008-01-01T23:59:59.000Z

298

Influence of geometry and topology of quantum graphs on their nonlinear optical properties  

Science Journals Connector (OSTI)

We analyze the nonlinear optics of quasi-one-dimensional quantum graphs and manipulate their topology and geometry to generate nonlinearities in a simple system approaching the fundamental limits of the first and second hyperpolarizabilities. We explore a huge configuration space in order to determine whether the fundamental limits may be approached for specific topologies, independent of molecular details, when the geometry is manipulated to maximize the intrinsic response. Changes in geometry result in smooth variations of the nonlinearities. Topological changes between geometrically similar systems cause profound changes in the nonlinear susceptibilities that include a discontinuity due to abrupt changes in the boundary conditions. We demonstrate the same universal scaling behavior for quantum graphs that is predicted for general quantum nonlinear optical systems near their fundamental limits, indicating that our results for quantum graphs may reflect general structure-property relationships for globally optimized nonlinear optical systems.

Rick Lytel; Shoresh Shafei; Julian H. Smith; Mark G. Kuzyk

2013-04-17T23:59:59.000Z

299

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 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 estimate an upper bound for the typical energy and length scales where quantum effects are relevant. We 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

2014-02-15T23:59:59.000Z

300

An algorithm for minimization of quantum cost  

E-Print Network [OSTI]

A new algorithm for minimization of quantum cost of quantum circuits has been designed. The quantum cost of different quantum circuits of particular interest (eg. circuits for EPR, quantum teleportation, shor code and different quantum arithmetic operations) are computed by using the proposed algorithm. The quantum costs obtained using the proposed algorithm is compared with the existing results and it is found that the algorithm has produced minimum quantum cost in all cases.

Anindita Banerjee; Anirban Pathak

2009-10-12T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Exploiting locality in quantum computation for quantum chemistry  

E-Print Network [OSTI]

Accurate prediction of chemical and material properties from first principles quantum chemistry is a challenging task on traditional computers. Recent developments in quantum computation offer a route towards highly accurate solutions with polynomial cost, however this solution still carries a large overhead. In this perspective, we aim to bring together known results about the locality of physical interactions from quantum chemistry with ideas from quantum computation. We show that the utilization of spatial locality combined with the Bravyi-Kitaev transformation offers an improvement in the scaling of known quantum algorithms for quantum chemistry and provide numerical examples to help illustrate this point. We combine these developments to improve the outlook for the future of quantum chemistry on quantum computers.

Jarrod R. McClean; Ryan Babbush; Peter J. Love; Alán Aspuru-Guzik

2014-07-29T23:59:59.000Z

302

Quantum Algorithm for SAT Problem and Quantum Mutual Entropy  

E-Print Network [OSTI]

It is von Neumann who opened the window for today's Information epoch. He defined quantum entropy including Shannon's information more than 20 years ahead of Shannon, and he introduced a concept what computation means mathematically. In this paper I will report two works that we have recently done, one of which is on quantum algorithum in generalized sense solving the SAT problem (one of NP complete problems) and another is on quantum mutual entropy properly describing quantum communication processes.

Masanori Ohya

2004-06-29T23:59:59.000Z

303

Highlighting the mechanism of the quantum speedup by time-symmetric and relational quantum mechanics  

E-Print Network [OSTI]

Bob hides a ball in one of four drawers. Alice is to locate it. Classically she has to open up to three drawers, quantally just one. The fundamental reason for this quantum speedup is not known. We explain it by extending the usual representation of the quantum algorithm, limited to the process of solving the problem, to the process of setting the problem. The number of the drawer with the ball becomes a unitary transformation of the random outcome of the preparation measurement. This brings in relational quantum mechanics: the extension is with respect to Bob and cannot be with respect to Alice. It would tell her the drawer number before she opens any drawer. To Alice, the projection of the quantum state due to the preparation measurement should be retarded at the end of her search; in the input state of the search, the drawer number is determined to Bob and undetermined to Alice. A second consequence is the emergence of an ambiguity. Either the preparation measurement or the final one required to read the solution selects the solution. For reasons of symmetry, we assume that the selection shares evenly between the two measurements. All is as if Alice, by reading the solution, selected half of the information that specifies the drawer number. This selection leaves the input state to Bob unaltered and projects that to Alice on a state of lower entropy where she knows that half in advance. The quantum algorithm is a sum over histories in each of which Alice knows in advance that the ball is in a pair of drawers and locates it by opening one of the two. More in general, given an oracle problem, this explanation of the speedup predicts the number of queries required to solve it in an optimal quantum way.

Giuseppe Castagnoli

2014-12-11T23:59:59.000Z

304

Quantum ergodicity for graphs related to interval maps  

E-Print Network [OSTI]

We prove quantum ergodicity for a family of graphs that are obtained from ergodic one-dimensional maps of an interval using a procedure introduced by Pakonski et al (J. Phys. A, v. 34, 9303-9317 (2001)). As observables we take the L^2 functions on the interval. The proof is based on the periodic orbit expansion of a majorant of the quantum variance. Specifically, given a one-dimensional, Lebesgue-measure-preserving map of an interval, we consider an increasingly refined sequence of partitions of the interval. To this sequence we associate a sequence of graphs, whose directed edges correspond to elements of the partitions and on which the classical dynamics approximates the Perron-Frobenius operator corresponding to the map. We show that, except possibly for subsequences of density 0, the eigenstates of the quantum graphs equidistribute in the limit of large graphs. For a smaller class of observables we also show that the Egorov property, a correspondence between classical and quantum evolution in the semiclassical limit, holds for the quantum graphs in question.

G. Berkolaiko; J. P. Keating; U. Smilansky

2006-07-07T23:59:59.000Z

305

Quantum Terahertz Electrodynamics and Macroscopic Quantum Tunneling in Layered Superconductors  

E-Print Network [OSTI]

of macroscopic quantum tunneling (MQT) in stacks of intrinsic Josephson junctions. Because of the long numbers: 74.72.Hs, 74.78.Fk The recent surge of interest in stacks of intrinsic Josephson junctions of stacks of Josephson junctions in quantum electronics [6]. This requires a quantum theory capable

Nori, Franco

306

Microwave Quantum Illumination  

E-Print Network [OSTI]

Quantum illumination is a quantum-optical sensing technique in which an entangled source is exploited to improve the detection of a low-reflectivity object that is immersed in a bright thermal background. Here we describe and analyze a system for applying this technique at microwave frequencies, a more appropriate spectral region for target detection than the optical, due to the naturally-occurring bright thermal background in the microwave regime. We use an electro-optomechanical converter to entangle microwave signal and optical idler fields, with the former being sent to probe the target region and the latter being retained at the source. The microwave radiation collected from the target region is then phase conjugated and upconverted into an optical field that is combined with the retained idler in a joint-detection quantum measurement. The error probability of this microwave quantum-illumination system, or 'quantum radar', is shown to be superior to that of any classical microwave radar of equal transmitted energy.

Shabir Barzanjeh; Saikat Guha; Christian Weedbrook; David Vitali; Jeffrey H. Shapiro; Stefano Pirandola

2014-10-15T23:59:59.000Z

307

Microwave Quantum Illumination  

E-Print Network [OSTI]

Quantum illumination is a quantum-optical sensing technique in which an entangled source is exploited to improve the detection of a low-reflectivity object that is immersed in a bright thermal background. Here we describe and analyze a system for applying this technique at microwave frequencies, a more appropriate spectral region for target detection than the optical, due to the naturally-occurring bright thermal background in the microwave regime. We use an electro-optomechanical converter to entangle microwave signal and optical idler fields, with the former being sent to probe the target region and the latter being retained at the source. The microwave radiation collected from the target region is then phase conjugated and upconverted into an optical field that is combined with the retained idler in a joint-detection quantum measurement. The error probability of this microwave quantum-illumination system, or 'quantum radar', is shown to be superior to that of any classical microwave radar of equal transmit...

Barzanjeh, Shabir; Weedbrook, Christian; Vitali, David; Shapiro, Jeffrey H; Pirandola, Stefano

2014-01-01T23:59:59.000Z

308

Consistent Quantum Reasoning  

E-Print Network [OSTI]

Precise rules are developed in order to formalize the reasoning processes involved in standard non-relativistic quantum mechanics, with the help of analogies from classical physics. A classical or quantum description of a mechanical system involves a {\\it framework}, often chosen implicitly, and a {\\it statement} or assertion about the system which is either true or false within the framework with which it is associated. Quantum descriptions are no less ``objective'' than their classical counterparts, but differ from the latter in the following respects: (i) The framework employs a Hilbert space rather than a classical phase space. (ii) The rules for constructing meaningful statements require that the associated projectors commute with each other and, in the case of time-dependent quantum histories, that consistency conditions be satisfied. (iii) There are incompatible frameworks which cannot be combined, either in constructing descriptions or in making logical inferences about them, even though any one of these frameworks may be used separately for describing a particular physical system. A new type of ``generalized history'' is introduced which extends previous proposals by Omn\\`es, and Gell-Mann and Hartle, and a corresponding consistency condition which does not involve density matrices or single out a direction of time. Applications which illustrate the formalism include: measurements of spin, two-slit diffraction, and the emergence of the classical world from a fully quantum description.

Robert B. Griffiths

1995-05-17T23:59:59.000Z

309

Damped quantum harmonic oscillator  

E-Print Network [OSTI]

In the framework of the Lindblad theory for open quantum systems the damping of the harmonic oscillator is studied. A generalization of the fundamental constraints on quantum mechanical diffusion coefficients which appear in the master equation for the damped quantum oscillator is presented; the Schr\\"odinger and Heisenberg representations of the Lindblad equation are given explicitly. On the basis of these representations it is shown that various master equations for the damped quantum oscillator used in the literature are particular cases of the Lindblad equation and that the majority of these equations are not satisfying the constraints on quantum mechanical diffusion coefficients. Analytical expressions for the first two moments of coordinate and momentum are also obtained by using the characteristic function of the Lindblad master equation. The master equation is transformed into Fokker-Planck equations for quasiprobability distributions. A comparative study is made for the Glauber $P$ representation, the antinormal ordering $Q$ representation and the Wigner $W$ representation. It is proven that the variances for the damped harmonic oscillator found with these representations are the same. By solving the Fokker-Planck equations in the steady state, it is shown that the quasiprobability distributions are two-dimensional Gaussians with widths determined by the diffusion coefficients. The density matrix is represented via a generating function, which is obtained by solving a time-dependent linear partial differential equation derived from the master equation. Illustrative examples for specific initial conditions of the density matrix are provided.

A. Isar; A. Sandulescu

2006-02-17T23:59:59.000Z

310

Definition: System Operating Limit | Open Energy Information  

Open Energy Info (EERE)

Operating Limit Operating Limit Jump to: navigation, search Dictionary.png System Operating Limit The value (such as MW, MVar, Amperes, Frequency or Volts) that satisfies the most limiting of the prescribed operating criteria for a specified system configuration to ensure operation within acceptable reliability criteria. System Operating Limits are based upon certain operating criteria. These include, but are not limited to: Facility Ratings (Applicable pre- and post- Contingency equipment or facility ratings), Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits), Voltage Stability Ratings (Applicable pre- and post- Contingency Voltage Stability), System Voltage Limits (Applicable pre- and post- Contingency Voltage Limits)[1] Also Known As SOL

311

Heat Machines and Quantum Systems  

E-Print Network [OSTI]

Heat Machines and Quantum Systems: Towards the Third Law Thesis submitted for the degree of "Doctor Machines and Quantum Systems: Towards the Third Law Thesis submitted for the degree of "Doctor

Kosloff, Ronnie

312

Multiple Ising Spins Coupled to 2d Quantum Gravity  

E-Print Network [OSTI]

We study a model in which p independent Ising spins are coupled to 2d quantum gravity (in the form of dynamical planar phi-cubed graphs). Consideration is given to the p tends to infinity limit in which the partition function becomes dominated by certain graphs; we identify most of these graphs. A truncated model is solved exactly providing information about the behaviour of the full model in the limit of small beta. Finally, we derive a bound for the critical value of the coupling constant, beta_c and examine the magnetization transition in the limit p tends to zero.

M. G. Harris; J. F. Wheater

1994-04-28T23:59:59.000Z

313

Coarse grained open system quantum dynamics  

SciTech Connect (OSTI)

We show that the quantum dynamics of a system comprised of a subspace Q coupled to a larger subspace P can be recast as a reduced set of 'coarse grained' ordinary differential equations with constant coefficients. These equations can be solved by a single diagonalization of a general complex matrix. The method makes no assumptions about the strength of the couplings between the Q and the P subspaces, nor is there any limitation on the initial population in P. The utility of the method is demonstrated via computations in three following areas: molecular compounds, photonic materials, and condensed phases.

Thanopulos, Ioannis [Department of Chemistry, University of British Columbia, Vancouver V6T 1Z3 (Canada); Brumer, Paul [Chemical Physics Theory Group, Department of Chemistry, and Center of Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 (Canada); Shapiro, Moshe [Department of Chemistry, University of British Columbia, Vancouver V6T 1Z3 (Canada); Department of Chemical Physics, Weizmann Institute, Rehovot 76100 (Israel)

2008-11-21T23:59:59.000Z

314

Testing quantum correlations with nuclear probes  

E-Print Network [OSTI]

We investigated the feasibility of quantum-correlation measurements in nuclear physics experiments. In a first approach, we measured spin correlations of singlet-spin (1S0) proton pairs, which were generated in 1H(d,2He) and 12C(d,2He) nuclear charge-exchange reactions. The experiment was optimized for a clean preparation of the 2He singlet state and offered a 2pi detection geometry for both protons in the exit channel. Our results confirm the effectiveness of the setup for theses studies, despite limitations of a small data sample recorded during the feasibility studies.

S. Hamieh; H. J. Woertche; C. Baeumer; A. M. van den Berg; D. Frekers; M. N. Harakeh; J. Heyse; M. Hunyadi; M. A. de Huu; C. Polachic; S. Rakers; C. Rangacharyulu

2003-10-17T23:59:59.000Z

315

Quantum Money with Classical Verification  

E-Print Network [OSTI]

We propose and construct a quantum money scheme that allows verification through classical communication with a bank. This is the first demonstration that a secure quantum money scheme exists that does not require quantum communication for coin verification. Our scheme is secure against adaptive adversaries - this property is not directly related to the possibility of classical verification, nevertheless none of the earlier quantum money constructions is known to possess it.

Dmitry Gavinsky

2012-03-15T23:59:59.000Z

316

STOPPING TIMES IN QUANTUM MECHANICS  

E-Print Network [OSTI]

(Stinespring, Kraus). 3". Time-dependant case General time evolution of an open quantum sys- tem = (Pt)t0

Attal, Stéphane

317

ON QUANTUM ERGODICITY FOR LINEAR MAPS OF PAR KURLBERG AND ZEEV RUDNICK  

E-Print Network [OSTI]

one to look for an analogous statement about the semi-classical limit of expectation values will use the quantized cat map to illuminate one of the few rigorous results available on the semi-classical limit of eigen- states of classically chaotic systems, namely Quantum Ergodicity [18, 3, 21

Kurlberg, Par

318

QKD Quantum Channel Authentication  

E-Print Network [OSTI]

Several simple yet secure protocols to authenticate the quantum channel of various QKD schemes, by coupling the photon sender's knowledge of a shared secret and the QBER Bob observes, are presented. It is shown that Alice can encrypt certain portions of the information needed for the QKD protocols, using a sequence whose security is based on computational-complexity, without compromising all of the sequence's entropy. It is then shown that after a Man-in-the-Middle attack on the quantum and classical channels, there is still enough entropy left in the sequence for Bob to detect the presence of Eve by monitoring the QBER. Finally, it is shown that the principles presented can be implemented to authenticate the quantum channel associated with any type of QKD scheme, and they can also be used for Alice to authenticate Bob.

J. T. Kosloski

2006-04-02T23:59:59.000Z

319

Optical Quantum Computing  

E-Print Network [OSTI]

In 2001 all-optical quantum computing became feasible with the discovery that scalable quantum computing is possible using only single photon sources, linear optical elements, and single photon detectors. Although it was in principle scalable, the massive resource overhead made the scheme practically daunting. However, several simplifications were followed by proof-of-principle demonstrations, and recent approaches based on cluster states or error encoding have dramatically reduced this worrying resource overhead, making an all-optical architecture a serious contender for the ultimate goal of a large-scale quantum computer. Key challenges will be the realization of high-efficiency sources of indistinguishable single photons, low-loss, scalable optical circuits, high efficiency single photon detectors, and low-loss interfacing of these components.

Jeremy L. O'Brien

2008-03-11T23:59:59.000Z

320

Quantum cosmology: a review  

E-Print Network [OSTI]

In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity: De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting "microscopic" degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.

Bojowald, Martin

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

The Invisible Quantum Barrier  

E-Print Network [OSTI]

We construct the invisible quantum barrier which represents the phenomenon of quantum reflection using the available data. We use the Abel equation to invert the data. The resulting invisible quantum barrier is double-valued in both axes. We study this invisible barrier in the case of atom and Bose-Einstein Condensate reflection from a solid silicon surface. A time-dependent, one-spatial dimension Gross-Pitaevskii equation is solved for the BEC case. We found that the BEC behaves very similarly to the single atom except for size effects, which manifest themselves in a maximum in the reflectivity at small distances from the wall. The effect of the atom-atom interaction on the BEC reflection and correspondingly on the invisible barrier is found to be appreciable at low velocities and comparable to the finite size effect. The trapping of ultracold atoms or BEC between two walls is discussed.

J. X. de Carvalho; M. S. Hussein; Weibin Li

2008-02-06T23:59:59.000Z

322

The Quantum Mellin transform  

E-Print Network [OSTI]

We uncover a new type of unitary operation for quantum mechanics on the half-line which yields a transformation to ``Hyperbolic phase space''. We show that this new unitary change of basis from the position x on the half line to the Hyperbolic momentum $p_\\eta$, transforms the wavefunction via a Mellin transform on to the critial line $s=1/2-ip_\\eta$. We utilise this new transform to find quantum wavefunctions whose Hyperbolic momentum representation approximate a class of higher transcendental functions, and in particular, approximate the Riemann Zeta function. We finally give possible physical realisations to perform an indirect measurement of the Hyperbolic momentum of a quantum system on the half-line.

J. Twamley; G. J. Milburn

2007-02-12T23:59:59.000Z

323

Extremal generalized quantum measurements  

E-Print Network [OSTI]

A measurement on a section K of the set of states of a finite dimensional C*-algebra is defined as an affine map from K to a probability simplex. Special cases of such sections are used in description of quantum networks, in particular quantum channels. Measurements on a section correspond to equivalence classes of so-called generalized POVMs, which are called quantum testers in the case of networks. We find extremality conditions for measurements on K and characterize generalized POVMs such that the corresponding measurement is extremal. These results are applied to the set of channels. We find explicit extremality conditions for two outcome measurements on qubit channels and give an example of an extremal qubit 1-tester such that the corresponding measurement is not extremal.

Anna Jencova

2012-07-23T23:59:59.000Z

324

Viscosity of Quantum Hall Fluids  

Science Journals Connector (OSTI)

The viscosity of quantum fluids with an energy gap at zero temperature is related to the adiabatic curvature on the space parametrizing flat background metrics. For quantum Hall fluids on two-dimensional tori, the quantum viscosity is computed. It turns out to be isotropic, constant, and proportional to the magnetic field strength.

J. E. Avron; R. Seiler; P. G. Zograf

1995-07-24T23:59:59.000Z

325

Shared access to quantum information  

Science Journals Connector (OSTI)

It is shown that quantum mechanics allows a qubit to be transferred so that it can be accessed symmetrically by two observers. These can then decide later which one is to take possession of the quantum information. The process is not fully successful, but a failed experiment may allow the retention of the quantum information for use in a subsequent operation.

Stig Stenholm and Erika Andersson

2000-09-11T23:59:59.000Z

326

Quantum simulation I. M. Georgescu  

E-Print Network [OSTI]

, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar, Saitama, 351-0198, Japan and Qatar Environment and Energy Research Institute, Doha, Qatar Franco Nori CEMS, high-energy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could

Nori, Franco

327

Authentication of quantum messages.  

SciTech Connect (OSTI)

Authentication is a well-studied area of classical cryptography: a sender A and a receiver B sharing a classical private key want to exchange a classical message with the guarantee that the message has not been modified or replaced by a dishonest party with control of the communication line. In this paper we study the authentication of messages composed of quantum states. We give a formal definition of authentication in the quantum setting. Assuming A and B have access to an insecure quantum channel and share a private, classical random key, we provide a non-interactive scheme that both enables A to encrypt and authenticate (with unconditional security) an m qubit message by encoding it into m + s qubits, where the probability decreases exponentially in the security parameter s. The scheme requires a private key of size 2m + O(s). To achieve this, we give a highly efficient protocol for testing the purity of shared EPR pairs. It has long been known that learning information about a general quantum state will necessarily disturb it. We refine this result to show that such a disturbance can be done with few side effects, allowing it to circumvent cryptographic protections. Consequently, any scheme to authenticate quantum messages must also encrypt them. In contrast, no such constraint exists classically: authentication and encryption are independent tasks, and one can authenticate a message while leaving it publicly readable. This reasoning has two important consequences: On one hand, it allows us to give a lower bound of 2m key bits for authenticating m qubits, which makes our protocol asymptotically optimal. On the other hand, we use it to show that digitally signing quantum states is impossible, even with only computational security.

Barnum, Howard; Crépeau, Jean-Claude; Gottesman, D. (Daniel); Smith, A. (Adam); Tapp, Alan

2001-01-01T23:59:59.000Z

328

Electric Field effects on quantum correlations in semiconductor quantum dots  

E-Print Network [OSTI]

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

S. Shojaei; M. Mahdian; R. Yousefjani

2012-05-01T23:59:59.000Z

329

Development of Superconducting AC Fault Current Limiter  

Science Journals Connector (OSTI)

The authors have developed a new superconducting fault current limiter whose impedance during normal operation is very small. During fault conditions, the limiter behaves as a superconducting reactor. The limiter

Daisuke Ito; Eriko Yoneda; Tsutomu Fujioka…

1990-01-01T23:59:59.000Z

330

Test on Superconducting AC Fault Current Limiter  

Science Journals Connector (OSTI)

The authors have developed a new superconducting fault current limiter whose impedance during normal operation is very small. During fault conditions, the limiter behaves as a superconducting reactor. The limiter

Daisuke Ito; Eriko S. Yoneda…

1990-01-01T23:59:59.000Z

331

Quantum convolutional stabilizer codes  

E-Print Network [OSTI]

and computer scientists such as Charles H. Bennett of the IBM Thomas J. Watson Research Center, Paul A. Benio® of Argonne National Laboratory in Illinois, David Deutsch of the University of Oxford, and Richard P. Feynman of California Institute of Technology... are inherently quantum mechanical in nature, not classical. Feynman was among the ¯rst to attempt to provide an answer to this question by producing an abstract model in 1982 that showed how a quantum system could be used to do computations. Later, in 1985...

Chinthamani, Neelima

2004-09-30T23:59:59.000Z

332

Thermodynamics of quantum lightspheres  

E-Print Network [OSTI]

Lightspheres, surfaces where massless particles are confined in closed orbits, are expected to be common astrophysical structures surrounding ultra-compact objects. In this paper a semi-classical treatment to photons in a lightspheres is proposed. We consider the quantum Maxwell field and derive its energy spectra. A thermodynamic approach for the quantum lightsphere is explored. Within this treatment, an expression for the spectral energy density of the emitted radiation is presented. Our results suggest that lightspheres populated by photons, when thermalized with their environment, have non-usual thermodynamic properties, which could lead to distinct observational signatures.

M. C. Baldiotti; Walace S. Elias; C. Molina; Thiago S. Pereira

2014-10-07T23:59:59.000Z

333

Thermodynamics of quantum lightspheres  

E-Print Network [OSTI]

Lightspheres, surfaces where massless particles are confined in closed orbits, are expected to be common astrophysical structures surrounding ultra-compact objects. In this paper a semi-classical treatment to photons in a lightspheres is proposed. We consider the quantum Maxwell field and derive its energy spectra. A thermodynamic approach for the quantum lightsphere is explored. Within this treatment, an expression for the spectral energy density of the emitted radiation is presented. Our results suggest that lightspheres populated by photons, when thermalized with their environment, have non-usual thermodynamic properties, which could lead to distinct observational signatures.

Baldiotti, M C; Molina, C; Pereira, Thiago S

2014-01-01T23:59:59.000Z

334

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

335

Information and quantum nonseparability  

Science Journals Connector (OSTI)

An information-theoretic inequality analogous to the well-known result of Bell [Physics 1, 195 (1964)] is formulated using the concept of information distance. This inequality, like Bell’s, is true for all local-hidden-variable theories, but not for quantum mechanics. The metric space structure of this new inequality suggests a reformulation of familiar Bell inequalities in terms of a ‘‘covariance distance.’’ Quantum nonseparability can be demonstrated through violations of these inequalities even in cases where the correlation between two systems is extremely weak. The connection between nonseparability and complementarity is also briefly discussed in this paper.

B. W. Schumacher

1991-12-01T23:59:59.000Z

336

Types of quantum information  

Science Journals Connector (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

2007-12-21T23:59:59.000Z

337

Quantum thermodynamic cooling cycle  

E-Print Network [OSTI]

The quantum-mechanical and thermodynamic properties of a 3-level molecular cooling cycle are derived. An inadequacy of earlier models is rectified in accounting for the spontaneous emission and absorption associated with the coupling to the coherent driving field via an environmental reservoir. This additional coupling need not be dissipative, and can provide a thermal driving force - the quantum analog of classical absorption chillers. The dependence of the maximum attainable cooling rate on temperature, at ultra-low temperatures, is determined and shown to respect the recently-established fundamental bound based on the second and third laws of thermodynamics.

Palao, J P; Gordon, J M; Palao, Jose P.; Kosloff, Ronnie; Gordon, Jeffrey M.

2001-01-01T23:59:59.000Z

338

Quantum thermodynamic cooling cycle  

E-Print Network [OSTI]

The quantum-mechanical and thermodynamic properties of a 3-level molecular cooling cycle are derived. An inadequacy of earlier models is rectified in accounting for the spontaneous emission and absorption associated with the coupling to the coherent driving field via an environmental reservoir. This additional coupling need not be dissipative, and can provide a thermal driving force - the quantum analog of classical absorption chillers. The dependence of the maximum attainable cooling rate on temperature, at ultra-low temperatures, is determined and shown to respect the recently-established fundamental bound based on the second and third laws of thermodynamics.

Jose P. Palao; Ronnie Kosloff; Jeffrey M. Gordon

2001-06-08T23:59:59.000Z

339

Quantum Decision Theory  

E-Print Network [OSTI]

We argue that, contrary to conventional wisdom, decision theory is not invariant to the physical environment in which a decision is made. Specifically, we show that a decision maker (DM) with access to quantum information resources may be able to do strictly better than a DM with access only to classical information resources. In this respect, our findings are somewhat akin to those in computer science that have established the superiority of quantum over classical algorithms for certain problems. We treat three kinds of decision tree (Kuhn [1950], [1953]): Kuhn trees in which the DM does or does not have perfect recall, and non-Kuhn trees.

Adam Brandenburger; Pierfrancesco La Mura

2011-07-01T23:59:59.000Z

340

Fields and Quantum Mechanics  

E-Print Network [OSTI]

The quantum field theories (QFT) constructed in [1,2] include phenomenology of interest. The constructions approximate: scattering by $1/r$ and Yukawa potentials in non-relativistic approximations; and the first contributing order of the Feynman series for Compton scattering. To have a semi-norm, photon states are constrained to transverse polarizations and for Compton scattering, the constructed cross section deviates at large momentum exchanges from the cross section prediction of the Feynman rules. Discussion includes the incompatibility of canonical quantization with the constructed interacting fields, and the role of interpretations of quantum mechanics in realizing QFT.

Glenn Eric Johnson

2014-12-21T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Characterizing quantum coherence  

Science Journals Connector (OSTI)

For a system with canonical variables x and p, [x,p]=i?, we associate with each density operator ? an x coherence ?x and a p coherence ?p which specify, respectively, the characteristic distance and momentum range over which the underlying quantum-mechanical nature of the ensemble cannot be neglected. These coherences are less than or equal to the associated uncertainties ?x??x, ?p??p; so the ratios cx??x/?x, cp??p/?p give measures of the quantum character of the ensemble with respect to x and p. Examples are presented.

J. E. Sipe and N. Arkani-Hamed

1992-09-01T23:59:59.000Z

342

Optimal Quantum Pumps  

E-Print Network [OSTI]

We study adiabatic quantum pumps on time scales that are short relative to the cycle of the pump. In this regime the pump is characterized by the matrix of energy shift which we introduce as the dual to Wigner's time delay. The energy shift determines the charge transport, the dissipation, the noise and the entropy production. We prove a general lower bound on dissipation in a quantum channel and define optimal pumps as those that saturate the bound. We give a geometric characterization of optimal pumps and show that they are noiseless and transport integral charge in a cycle. Finally we discuss an example of an optimal pump related to the Hall effect.

J. E. Avron; A. Elgart; G. M. Graf; L. Sadun

2001-07-12T23:59:59.000Z

343

Universal Quantum Circuits  

E-Print Network [OSTI]

We define and construct efficient depth-universal and almost-size-universal quantum circuits. Such circuits can be viewed as general-purpose simulators for central classes of quantum circuits and can be used to capture the computational power of the circuit class being simulated. For depth we construct universal circuits whose depth is the same order as the circuits being simulated. For size, there is a log factor blow-up in the universal circuits constructed here. We prove that this construction is nearly optimal.

Debajyoti Bera; Stephen Fenner; Frederic Green; Steve Homer

2008-04-15T23:59:59.000Z

344

Energy diffusion in strongly driven quantum chaotic systems  

E-Print Network [OSTI]

The energy evolution of a quantum chaotic system under the perturbation that harmonically depends on time is studied for the case of large perturbation, in which the rate of transition calculated from the Fermi golden rule exceeds the frequency of perturbation. It is shown that the energy evolution retains its diffusive character, with the diffusion coefficient that is asymptotically proportional to the magnitude of perturbation and to the square root of the density of states. The results are supported by numerical calculation. They imply the absence of the quantum-classical correspondence for the energy diffusion and the energy absorption in the classical limit $\\hbar \\to 0$.

P. V. Elyutin

2005-04-14T23:59:59.000Z

345

Pure Phase Solubility Limits: LANL  

SciTech Connect (OSTI)

The natural and engineered system at Yucca Mountain (YM) defines the site-specific conditions under which one must determine to what extent the engineered and the natural geochemical barriers will prevent the release of radioactive material from the repository. Most important mechanisms for retention or enhancement of radionuclide transport include precipitation or co-precipitation of radionuclide-bearing solid phases (solubility limits), complexation in solution, sorption onto surfaces, colloid formation, and diffusion. There may be many scenarios that could affect the near-field environment, creating chemical conditions more aggressive than the conditions presented by the unperturbed system (such as pH changes beyond the range of 6 to 9 or significant changes in the ionic strength of infiltrated waters). For an extended period of time, the near-field water composition may be quite different and more extreme in pH, ionic strength, and CO{sub 2} partial pressure (or carbonate concentration) than waters at some distance from the repository. Reducing conditions, high pH (up to 11), and low carbonate concentration may be present in the near-field after reaction of infiltrating groundwater with engineered barrier systems, such as cementitious materials. In the far-field, conditions are controlled by the rock-mass buffer providing a near-neutral, oxidizing, low-ionic-strength environment that controls radionuclide solubility limits and sorption capacities. There is the need for characterization of variable chemical conditions that affect solubility, speciation, and sorption reactions. Modeling of the groundwater chemistry is required and leads to an understanding of solubility and speciation of the important radionuclides. Because experimental studies cannot be performed under the numerous potential chemical conditions, solubility limitations must rely on geochemical modeling of the radionuclide's chemistry. Fundamental thermodynamic properties, such as solubility products, complex stability constants, and redox potentials for radionuclides in different oxidation states, form the underlying database to be used for those calculations. The potentially low solubilities of many radionuclides in natural waters constitute the first barrier for their migration from the repository into the environment. Evaluation of this effect requires a knowledge of the site-specific water chemistry and the expected spatial and temporal ranges of its variability. Quantitative determinations of radionuclide solubility in waters within the range of chemistry must be made. Speciation and molecular complexation must be ascertained to interpret and apply solubility results. The solubilities thus determined can be used to assess the effectiveness of solubility in limiting radionuclide migration. These solubilities can also be used to evaluate the effectiveness of other retardation processes expected to occur once dissolution of the source material and migration begin. Understanding the solubility behavior of radionuclides will assist in designing valuable sorption experiments that must be conducted below the solubility limit since only soluble species participate in surface reactions and sorption processes. The present strategy for radionuclide solubility tasks has been to provide a solubility model from bulk-experiments that attempt to bracket the estimate made for this Analysis and Modeling Report (AMR) of water conditions on site. The long-term goal must be to develop a thermodynamic database for solution speciation and solid-state determination as a prerequisite for transport calculations and interpretation of empirical solubility data. The model has to be self-consistent and tested against known solubility studies in order to predict radionuclide solubilities over the continuous distribution ranges of potential water compositions for performance assessment of the site. Solubility studies upper limits for radionuclide concentrations in natural waters. The concentration in the aqueous phase is controlled by the radionuclide-bearing solid phase and by

C. Stockman

2001-01-26T23:59:59.000Z

346

Summary of Superconducting Fault Current Limiter Technology  

Science Journals Connector (OSTI)

In recent years, superconducting fault current limiter (SFCL) has become one of the forefront topics of current-limiting technology in the world. In this...

Linmang Wang; Pengzan Jiang; Dada Wang

2012-01-01T23:59:59.000Z

347

Colony Mills Limited | Open Energy Information  

Open Energy Info (EERE)

Limited Place: Lahore, Pakistan Sector: Solar Product: Yarn manufacturer, plans to set up solar thermal plant. References: Colony Mills Limited1 This article is a stub. You can...

348

Universal Carbon Credits Limited | Open Energy Information  

Open Energy Info (EERE)

Universal Carbon Credits Limited Jump to: navigation, search Name: Universal Carbon Credits Limited Place: London, England, United Kingdom Zip: EC3A6DF Sector: Carbon Product:...

349

Crionaig Power Limited | Open Energy Information  

Open Energy Info (EERE)

Crionaig Power Limited Jump to: navigation, search Name: Crionaig Power Limited Place: United Kingdom Sector: Wind energy Product: Edinburgh-based power company developing wind...

350

Local Generation Limited | Open Energy Information  

Open Energy Info (EERE)

Generation Limited Place: United Kingdom Sector: Biomass Product: UK-based biomass firm developing anaerobic digestion plants. References: Local Generation Limited1 This article...

351

Analogue model for quantum gravity phenomenology  

E-Print Network [OSTI]

So called "analogue models" use condensed matter systems (typically hydrodynamic) to set up an "effective metric" and to model curved-space quantum field theory in a physical system where all the microscopic degrees of freedom are well understood. Known analogue models typically lead to massless minimally coupled scalar fields. We present an extended "analogue space-time" programme by investigating a condensed-matter system - in and beyond the hydrodynamic limit - that is in principle capable of simulating the massive Klein-Gordon equation in curved spacetime. Since many elementary particles have mass, this is an essential step in building realistic analogue models, and an essential first step towards simulating quantum gravity phenomenology. Specifically, we consider the class of two-component BECs subject to laser-induced transitions between the components, and we show that this model is an example for Lorentz invariance violation due to ultraviolet physics. Furthermore our model suggests constraints on quantum gravity phenomenology in terms of the "naturalness problem" and "universality issue".

Silke Weinfurtner; Stefano Liberati; Matt Visser

2005-11-18T23:59:59.000Z

352

Quantum Robot: Structure, Algorithms and Applications  

E-Print Network [OSTI]

A kind of brand-new robot, quantum robot, is proposed through fusing quantum theory with robot technology. Quantum robot is essentially a complex quantum system and it is generally composed of three fundamental parts: MQCU (multi quantum computing units), quantum controller/actuator, and information acquisition units. Corresponding to the system structure, several learning control algorithms including quantum searching algorithm and quantum reinforcement learning are presented for quantum robot. The theoretic results show that quantum robot can reduce the complexity of O(N^2) in traditional robot to O(N^(3/2)) using quantum searching algorithm, and the simulation results demonstrate that quantum robot is also superior to traditional robot in efficient learning by novel quantum reinforcement learning algorithm. Considering the advantages of quantum robot, its some potential important applications are also analyzed and prospected.

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

2005-06-18T23:59:59.000Z

353

Quantum cost for sending entanglement  

E-Print Network [OSTI]

Establishing quantum entanglement between two distant parties is an essential step of many protocols in quantum information processing. One possibility for providing long-distance entanglement is to create an entangled composite state within a lab and then physically send one subsystem to a distant lab. However, is this the "cheapest" way? Here, we investigate the minimal "cost" that is necessary for establishing a certain amount of entanglement between two distant parties. We prove that this cost is intrinsically quantum, and is specified by quantum correlations. Our results provide an optimal protocol for entanglement distribution and show that quantum correlations are the essential resource for this task.

Alexander Streltsov; Hermann Kampermann; Dagmar Bruß

2012-03-06T23:59:59.000Z

354

Classicality of quantum information processing  

Science Journals Connector (OSTI)

The ultimate goal of the classicality program is to quantify the amount of quantumness of certain processes. Here, classicality is studied for a restricted type of process: quantum information processing (QIP). Under special conditions, one can force some qubits of a quantum computer into a classical state without affecting the outcome of the computation. The minimal set of conditions is described and its structure is studied. Some implications of this formalism are the increase of noise robustness, a proof of the quantumness of mixed state quantum computing, and a step forward in understanding the very foundation of QIP.

David Poulin

2002-04-04T23:59:59.000Z

355

Performance limits of heliostat fields  

SciTech Connect (OSTI)

Geometric and thermodynamic arguments are used to derive upper limits on the performance of a solar energy collection system, consisting of an axisymmetric heliostat field, a solar tower, secondary optics and a black receiver. Performance limits on collected power, concentration, and work output are presented. Performance of tower systems with several secondary optics options is compared: tower-top Compound Parabolic Concentrator (CPC), Tailored Edge-Ray Concentrator (TERC) approximated by a cone, and Cassegrainian with ground-level CPC or Compound Elliptic Concentrator (CEC). Optimized ray tracing is used to generate the design parameters of the secondary concentrators that yield the highest optical efficiency. The results show that the tower-top Cone provides the best performance regarding both concentration and efficiency, except for very large fields. The Cassegrainian designs come in second, but become equal and even better than the Cone for large fields. The results for the Cassegrainian are sensitive to the value of the reflectivity, due to the additional reflections incurred. The choice of a CEC is better than a CPC for the terminal concentration in a Cassegrainian system, but the difference is small. The suitability of the different design options for high-temperature solar applications is discussed. The recommendations regarding optical configuration depend on field size, as well as on application-specific constraints.

Kribus, A.; Krupkin, V.; Yogev, A. [Weizmann Inst. of Science, Rehovot (Israel). Environmental Sciences and Energy Research Dept.; Spirkl, W. [Ludwig-Maximilians-Univ. Muenchen (Germany). Sektion Physik

1998-11-01T23:59:59.000Z

356

New Quantum Structures  

Science Journals Connector (OSTI)

...the thermal diffusion ofthe deposited...this thermal diffusion. Thus, LSL...low-density electron gas is predicted...microscope image oflateral superlattice...producing highly anisotropic electrical...broad span of infrared energies with...These wells and gases constitute...enhanced quantum-based electronic...

MANI SUNDARAM; SCOTT A. CHALMERS; PETER F. HOPKINS; ARTHUR C. GOSSARD

1991-11-29T23:59:59.000Z

357

Quantum Gauss Jordan Elimination  

E-Print Network [OSTI]

In this paper we construct the Quantum Gau\\ss Jordan Elimination (QGJE) Algorithm and estimate the complexity time of computation of Reduced Row Echelon Form (RREF) of an $N\\times N$ matrix using QGJE procedure. The main theorem asserts that QGJE has computation time of order $2^{N/2}$.

Do Ngoc Diep; Do Hoang Giang

2005-11-07T23:59:59.000Z

358

Hybrid Quantum Computation  

E-Print Network [OSTI]

We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model part of a quantum circuit is simulated by unitary evolution and the rest by measurements on star graph states, thereby combining the advantages of the two standard quantum computation models. In the hybrid model, a complicated unitary gate under simulation is decomposed in terms of a sequence of single-qubit operations, the controlled-Z gates, and multi-qubit rotations around the z-axis. Every single-qubit- and the controlled-Z gate are realized by a respective unitary evolution, and every multi-qubit rotation is executed by a single measurement on a required star graph state. The classical information processing in our model only needs an information flow vector and propagation matrices. We provide the implementation of multi-control gates in the hybrid model. They are very useful for implementing Grover's search algorithm, which is studied as an illustrating example.

Arun Sehrawat; Daniel Zemann; Berthold-Georg Englert

2010-08-06T23:59:59.000Z

359

Compatibility of quantum states  

SciTech Connect (OSTI)

We introduce a measure of compatibility between quantum states--the likelihood that two density matrices describe the same object. Our measure is motivated by two elementary requirements, which lead to a natural definition. We list some properties of this measure, and discuss its relation to the problem of combining two observers' states of knowledge.

Poulin, David; Blume-Kohout, Robin [Theoretical Division, Los Alamos National Laboratory, MS-B210, Los Alamos, New Mexico 87545 (United States)

2003-01-01T23:59:59.000Z

360

Compatibility of quantum states  

Science Journals Connector (OSTI)

We introduce a measure of compatibility between quantum states—the likelihood that two density matrices describe the same object. Our measure is motivated by two elementary requirements, which lead to a natural definition. We list some properties of this measure, and discuss its relation to the problem of combining two observers’ states of knowledge.

David Poulin and Robin Blume-Kohout

2003-01-15T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Phenomenological Quantum Gravity  

E-Print Network [OSTI]

Planck scale physics represents a future challenge, located between particle physics and general relativity. The Planck scale marks a threshold beyond which the old description of spacetime breaks down and conceptually new phenomena must appear. In the last years, increased efforts have been made to examine the phenomenology of quantum gravity, even if the full theory is still unknown.

S. Hossenfelder

2006-11-01T23:59:59.000Z

362

Resummed Quantum Gravity  

E-Print Network [OSTI]

We present the current status of the a new approach to quantum general relativity based on the exact resummation of its perturbative series as that series was formulated by Feynman. We show that the resummed theory is UV finite and we present some phenomenological applications as well.

B. F. L. Ward

2006-10-18T23:59:59.000Z

363

Spatially indirect excitons in coupled quantum wells  

SciTech Connect (OSTI)

Microscopic quantum phenomena such as interference or phase coherence between different quantum states are rarely manifest in macroscopic systems due to a lack of significant correlation between different states. An exciton system is one candidate for observation of possible quantum collective effects. In the dilute limit, excitons in semiconductors behave as bosons and are expected to undergo Bose-Einstein condensation (BEC) at a temperature several orders of magnitude higher than for atomic BEC because of their light mass. Furthermore, well-developed modern semiconductor technologies offer flexible manipulations of an exciton system. Realization of BEC in solid-state systems can thus provide new opportunities for macroscopic quantum coherence research. In semiconductor coupled quantum wells (CQW) under across-well static electric field, excitons exist as separately confined electron-hole pairs. These spatially indirect excitons exhibit a radiative recombination time much longer than their thermal relaxation time a unique feature in direct band gap semiconductor based structures. Their mutual repulsive dipole interaction further stabilizes the exciton system at low temperature and screens in-plane disorder more effectively. All these features make indirect excitons in CQW a promising system to search for quantum collective effects. Properties of indirect excitons in CQW have been analyzed and investigated extensively. The experimental results based on time-integrated or time-resolved spatially-resolved photoluminescence (PL) spectroscopy and imaging are reported in two categories. (i) Generic indirect exciton systems: general properties of indirect excitons such as the dependence of exciton energy and lifetime on electric fields and densities were examined. (ii) Quasi-two-dimensional confined exciton systems: highly statistically degenerate exciton systems containing more than tens of thousands of excitons within areas as small as (10 micrometer){sup 2} were observed. The spatial and energy distributions of optically active excitons were used as thermodynamic quantities to construct a phase diagram of the exciton system, demonstrating the existence of distinct phases. Optical and electrical properties of the CQW sample were examined thoroughly to provide deeper understanding of the formation mechanisms of these cold exciton systems. These insights offer new strategies for producing cold exciton systems, which may lead to opportunities for the realization of BEC in solid-state systems.

Lai, Chih-Wei Eddy

2004-03-01T23:59:59.000Z

364

Synthesis of linear quantum stochastic systems via quantum feedback networks  

E-Print Network [OSTI]

Recent theoretical and experimental investigations of coherent feedback control, the feedback control of a quantum system with another quantum system, has raised the important problem of how to synthesize a class of quantum systems, called the class of linear quantum stochastic systems, from basic quantum optical components and devices in a systematic way. The synthesis theory sought in this case can be naturally viewed as a quantum analogue of linear electrical network synthesis theory and as such has potential for applications beyond the realization of coherent feedback controllers. In earlier work, Nurdin, James and Doherty have established that an arbitrary linear quantum stochastic system can be realized as a cascade connection of simpler one degree of freedom quantum harmonic oscillators, together with a direct interaction Hamiltonian which is bilinear in the canonical operators of the oscillators. However, from an experimental perspective and based on current methods and technologies, direct interaction Hamiltonians are challenging to implement for systems with more than just a few degrees of freedom. In order to facilitate more tractable physical realizations of these systems, this paper develops a new synthesis algorithm for linear quantum stochastic systems that relies solely on field-mediated interactions, including in implementation of the direct interaction Hamiltonian. Explicit synthesis examples are provided to illustrate the realization of two degrees of freedom linear quantum stochastic systems using the new algorithm.

H. I. Nurdin

2009-05-06T23:59:59.000Z

365

Quo Vadis Quantum Mechanics?  

Science Journals Connector (OSTI)

Quantum mechanics is one of the most successful theoretical structures in all of science. Developed between 1925-26 to explain the optical spectrum of atoms, the theory over the succeeding 80 years has been extended, first to quantum field theories, gauge field theories, and now even string theory. It is used every day by thousands of physicists to calculate physical phenomena to exquisite precision, with no ambiguity in the results. To claim that this is a theory which is not understood by those physicists is absurd. And yet, as eminent a physicist as Richard Feynman, who did as much as anyone else to extend quantum theory to field theories and was a master at producing those exquisite calculations, could say that anyone who claimed they understood quantum theory clearly did not understand quantum theory. One hundred years ago Einstein postulated one of the most unsettling features of the theory, the wave-particle duality, with his particulate explanation for light of the photoelectric effect, and an explanation which was in direct conflict with Maxwell's brilliant development of a wave, or field, theory of light. Einstein believed that the particulate nature would ultimately be explainable by some sort of non-linear theory of electromagnetism, and was outraged by the acceptance of the community of the probabilistic quantum theory. His programme was of course dealt a (near?) fatal blow by Bell's discovery that the three desiderata - a theory which agrees with experiment, a theory which is local in its effects, and a theory in which nature, at its heart, is not probabilistic - are incompatible. That discomfort felt by Einstein and by Feynman is felt by numerous other people as well. This discomfort is heightened by the fact that the theory of gravity, another of Einstein's great achievements, has resisted all efforts at reconciliation with quantum mechanics. This book explores that discomfort, and tries to pin down what the locus of that discomfort is. For many, the locus is in the probabilistic nature at the heart of the theory. Nature should surely, at some fundamental level, know what it is doing. The photon, despite our inability to measure it, should know where it is and how fast it is going. The papers by t'Hooft, Hiley, and Smolin fall into this camp. Some suspect that the macroscopic world of our immediate sense experiences, and the microscopic world of quantum phenomena, are genuinely different, that the fundamental conceptual nature of physics changes from one to the other, with some unknown boundary between them. Penrose, in his preface alludes to his speculations on this, as does Leggett to his own speculations in his paper. And a number of articles (e.g., by Hartle, Rovelli, and others) opine that if only everyone looked at quantum mechanics in the right way (their way), it would lose its mystery, and be as natural as Newton's world view. (I myself tend to this position, which is however somewhat tempered by the realization that the clarity and naturalness of my viewpoint is not shared by the others who believe equally firmly in their own natural, clear, but radically different, viewpoint). A number of articles simply examine the counterintuitive nature of quantum theory in general, using it to make sense of time travel (Greenberger and Svozil) and demonstrating the unusual features of induction about the past from present observations within quantum theory (Aharonov and Dolev). The book is not free from rather overblown titles (e.g., 'Liberation and Purification from Classical Prejudice', or 'A Quantum Theory of the Human Person') but those articles nevertheless contain at least amusing speculations. In quantum gravity, the incompatibilities between the two masterstrokes of the twentieth century are highlighted. There is a strong suspicion amongst many in this field that progress in understanding quantum gravity demands a deeper understanding of the great mystery of quantum theory which this book explores. This book is a useful and, at times, fascinating introduction to the flounderings which are taking pla

W G Unruh

2006-01-01T23:59:59.000Z

366

Precision bounds in noisy quantum metrology  

E-Print Network [OSTI]

In an idealistic setting, quantum metrology protocols allow to sense physical parameters with mean squared error that scales as $1/N^2$ with the number of particles involved---substantially surpassing the $1/N$-scaling characteristic to classical statistics. A natural question arises, whether such an impressive enhancement persists when one takes into account the decoherence effects that are unavoidable in any real-life implementation. In this thesis, we resolve a major part of this issue by describing general techniques that allow to quantify the attainable precision in metrological schemes in the presence of uncorrelated noise. We show that the abstract geometrical structure of a quantum channel describing the noisy evolution of a single particle dictates then critical bounds on the ultimate quantum enhancement. Our results prove that an infinitesimal amount of noise is enough to restrict the precision to scale classically in the asymptotic $N$ limit, and thus constrain the maximal improvement to a constant factor. Although for low numbers of particles the decoherence may be ignored, for large $N$ the presence of noise heavily alters the form of both optimal states and measurements attaining the ultimate resolution. However, the established bounds are then typically achievable with use of techniques natural to current experiments. In this work, we thoroughly introduce the necessary concepts and mathematical tools lying behind metrological tasks, including both frequentist and Bayesian estimation theory frameworks. We provide examples of applications of the methods presented to typical qubit noise models, yet we also discuss in detail the phase estimation tasks in Mach-Zehnder interferometry both in the classical and quantum setting---with particular emphasis given to photonic losses while analysing the impact of decoherence.

Jan Kolodynski

2015-01-02T23:59:59.000Z

367

Limited View Angle Iterative CT Reconstruction  

E-Print Network [OSTI]

;Some Prior Literature in Limited View Tomography CT with limited-angle data and few views IRR algorithm Iterative Reconstruction-Reprojection (IRR) : An Algorithm for Limited Data Cardiac- Computed-views and limited-angle data in divergent-beam CT by E. Y. Sidky, CM Kao, and X. Pan (2006) Few-View Projection

368

Limits to power system growth  

SciTech Connect (OSTI)

In the design of space nuclear power systems a variety of conversion techniques may be used, each with its own advantages and disadvantages. A study was performed which analyzed over 120 proposed system designs. The designs were compared to identify the optimum conversion system as a function of power level and find limits to specific mass (kg/kWe) for each power cycle. Furthermore, the component masses were studied to determine which component of the overall design contributes the most to total system mass over a variety of power levels. The results can provide a focus for future research efforts by selecting the best conversion technology for the desired power range, and optimizing the system component which contributes most to the total mass.

Slater, S.M.; Klein, A.C. (Department of Nuclear Engineering, Oregon State University, Corvallis, Oregon 97331 (United States)); Webb, B.J. (Umpqua Research, Inc., P.O. Box 791, Myrtle Creek, Oregon 97457 (United States)); Pauley, K.A. (Battelle Pacific Northwest Laboratory, P.O. Box 999, Richland, Washington 99352 (United States))

1993-01-15T23:59:59.000Z

369

Composite quantum systems and environment-induced heating  

E-Print Network [OSTI]

In recent years, much attention has been paid to the development of techniques which transfer trapped particles to very low temperatures. Here we focus our attention on a heating mechanism which contributes to the finite temperature limit in laser sideband cooling experiments with trapped ions. It is emphasized that similar heating processes might be present in a variety of composite quantum systems whose components couple individually to different environments. For example, quantum optical heating effects might contribute significantly to the very high temperatures which occur during the collapse phase in sonoluminescence experiments. It might even be possible to design composite quantum systems, like atom-cavity systems, such that they continuously emit photons even in the absence of external driving.

Almut Beige; Andreas Kurcz; Adam Stokes

2011-10-07T23:59:59.000Z

370

Topological Strings from Quantum Mechanics  

E-Print Network [OSTI]

We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized theta function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P2, local P1xP1 and local F1. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Phys...

Grassi, Alba; Marino, Marcos

2014-01-01T23:59:59.000Z

371

Topological Strings from Quantum Mechanics  

E-Print Network [OSTI]

We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized theta function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P2, local P1xP1 and local F1. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.

Alba Grassi; Yasuyuki Hatsuda; Marcos Marino

2014-10-13T23:59:59.000Z

372

Why the two-pulse photon echo is not a good quantum memory protocol  

SciTech Connect (OSTI)

We consider in this paper a two-pulse photon echo sequence in the prospect of quantum light storage. We analyze the conditions where quantum storage could be realistically performed. We simply and analytically calculate the efficiency in that limit, and clarify the role of the exactly {pi}-rephasing pulse in the sequence. Our physical interpretation of the process is well supported by its experimental implementation in a Tm{sup 3+}:yttrium aluminum garnet crystal thanks to an accurate control of the rephasing pulse area. We finally address independently the fundamental limitations of the quantum fidelity. Our work allows us to point out on one side the real drawbacks of this scheme for quantum storage and on the other side its specificities which can be a source of inspiration to conceive more promising procedures with rare-earth ion doped crystals.

Ruggiero, Jerome; Le Goueet, Jean-Louis; Chaneliere, Thierry [Laboratoire Aime Cotton, CNRS-UPR 3321, Universite Paris-Sud, Bat. 505, 91405 Orsay Cedex (France); Simon, Christoph [Group of Applied Physics, University of Geneva, CH-1211 Geneva 4 (Switzerland)

2009-05-15T23:59:59.000Z

373

Quantum Computing via The Bethe Ansatz  

E-Print Network [OSTI]

We recognize quantum circuit model of computation as factorisable scattering model and propose that a quantum computer is associated with a quantum many-body system solved by the Bethe ansatz. As an typical example to support our perspectives on quantum computation, we study quantum computing in one-dimensional nonrelativistic system with delta-function interaction, where the two-body scattering matrix satisfies the factorisation equation (the quantum Yang--Baxter equation) and acts as a parametric two-body quantum gate. We conclude by comparing quantum computing via the factorisable scattering with topological quantum computing.

Yong Zhang

2011-06-20T23:59:59.000Z

374

Computational Complexity of interacting electrons and fundamental limitations of Density Functional Theory  

E-Print Network [OSTI]

One of the central problems in quantum mechanics is to determine the ground state properties of a system of electrons interacting via the Coulomb potential. Since its introduction by Hohenberg, Kohn, and Sham, Density Functional Theory (DFT) has become the most widely used and successful method for simulating systems of interacting electrons, making their original work one of the most cited in physics. In this letter, we show that the field of computational complexity imposes fundamental limitations on DFT, as an efficient description of the associated universal functional would allow to solve any problem in the class QMA (the quantum version of NP) and thus particularly any problem in NP in polynomial time. This follows from the fact that finding the ground state energy of the Hubbard model in an external magnetic field is a hard problem even for a quantum computer, while given the universal functional it can be computed efficiently using DFT. This provides a clear illustration how the field of quantum computing is useful even if quantum computers would never be built.

Norbert Schuch; Frank Verstraete

2007-12-04T23:59:59.000Z

375

Enhanced optical limiting effects of graphene materials in polyimide  

SciTech Connect (OSTI)

Three different graphene nanostructure suspensions of graphene oxide nanosheets (GONSs), graphene oxide nanoribbons (GONRs), and graphene oxide quantum dots (GOQDs) are prepared and characterized. Using a typical two-step method, the GONSs, GONRs, and GOQDs are incorporated into a polyimide (PI) matrix to synthesize graphene/PI composite films, whose nonlinear optical (NLO) and optical limiting (OL) properties are investigated at 532?nm in the nanosecond regime. The GONR suspension exhibits superior NLO and OL effects compared with those of GONSs and GOQDs because of its stronger nonlinear scattering and excited-state absorption. The graphene/PI composite films exhibit NLO and OL performance superior to that of their corresponding suspensions, which is attributed primarily to a combination of nonlinear mechanisms, charge transfer between graphene materials and PI, and the matrix effect.

Gan, Yao; Feng, Miao; Zhan, Hongbing, E-mail: hbzhan@fzu.edu.cn [College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108 (China)

2014-04-28T23:59:59.000Z

376

Computational equivalence between quantum Turing machines  

E-Print Network [OSTI]

Computational equivalence between quantum Turing machines and quantum circuit families Christian Westergaard 21st November 2005 Contents 1 The quantum Turing machine model 5 1.1 Basics of quantum Turing machines . . . . . . . . . . . . . . . . . . . 5 1.2 Projections on the quantum state space

Møller, Jesper Michael

377

On Quantum Capacity and its Bound  

E-Print Network [OSTI]

The quantum capacity of a pure quantum channel and that of classical-quantum-classical channel are discussed in detail based on the fully quantum mechanical mutual entropy. It is proved that the quantum capacity generalizes the so-called Holevo bound.

Masanori Ohya; Igor V. Volovich

2004-06-29T23:59:59.000Z

378

Exploiting the randomness of the measurement basis in quantum cryptography: Secure Quantum Key Growing without Privacy Amplification  

E-Print Network [OSTI]

We suggest that the randomness of the choices of measurement basis by Alice and Bob provides an additional important resource for quantum cryptography. As a specific application, we present a novel protocol for quantum key distribution (QKD) which enhances the BB84 scheme by encrypting the information sent over the classical channel during key sifting. We show that, in the limit of long keys, this process prevents an eavesdropper from reproducing the sifting process carried out by the legitimate users. The inability of the eavesdropper to sift the information gathered by tapping the quantum channel reduces the amount of information that an eavesdropper can gain on the sifted key. We further show that the protocol proposed is self sustaining, and thus allows the growing of a secret key.

Hannes R. Böhm; Paul S. Böhm; Markus Aspelmeyer; ?aslav Brukner; Anton Zeilinger

2004-08-30T23:59:59.000Z

379

Electroluminescence of quantum-dash-based quantum cascade laser structures  

SciTech Connect (OSTI)

We developed two mid-infrared quantum cascade structures based on InAs quantum dashes. The dashes were embedded either in AlInGaAs lattice-matched to InP or in tensile-strained AlInAs. The devices emit between 7 and 11 {mu}m and are a step forward in the development of quantum cascade lasers based on 3-D confined active regions.

Liverini, V.; Bismuto, A.; Nevou, L.; Beck, M.; Faist, J. [Institute of Quantum Electronics, ETH Zurich, 8092 (Switzerland); Wolfgang-Pauli-Str. 16, HPT F 11, Zurich, CH-8093 (Switzerland)

2011-12-23T23:59:59.000Z

380

Mean field limit for Bosons with compact kernels interactions by Wigner measures transportation  

E-Print Network [OSTI]

We consider a class of many-body Hamiltonians composed of a free (kinetic) part and a multi-particle (potential) interaction with a compactness assumption on the latter part. We investigate the mean field limit of such quantum systems following the Wigner measures approach. We prove the propagation of these measures along the flow of a nonlinear (Hartree) field equation. This enhances and complements some previous results in the subject.

Boris Pawilowski; Quentin Liard

2014-02-18T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Limiting absorption principle for some long range perturbations of Dirac systems at threshold energies  

E-Print Network [OSTI]

We establish a limiting absorption principle for some long range perturbations of the Dirac systems at threshold energies. We cover multi-center interactions with small coupling constants. The analysis is reduced to study a family of non-self-adjoint operators. The technique is based on a positive commutator theory for non self-adjoint operators, which we develop in appendix. We also discuss some applications to the dispersive Helmholzt model in the quantum regime.

Nabile Boussaid; Sylvain Golénia

2009-06-08T23:59:59.000Z

382

A quantum algorithm for the quantum Schur-Weyl transform  

E-Print Network [OSTI]

We construct an efficient quantum algorithm to compute the quantum Schur-Weyl transform for any value of the quantum parameter $q \\in [0,\\infty]$. Our algorithm is a $q$-deformation of the Bacon-Chuang-Harrow algorithm, in the sense that it has the same structure and is identically equal when $q=1$. When $q=0$, our algorithm is the unitary realization of the Robinson-Schensted-Knuth (or RSK) algorithm, while when $q=\\infty$ it is the dual RSK algorithm together with phase signs. Thus, we interpret a well-motivated quantum algorithm as a generalization of a well-known classical algorithm.

Sonya Berg

2012-05-17T23:59:59.000Z

383

Preventing Quantum Hacking in Continuous Variable Quantum Key Distribution  

Science Journals Connector (OSTI)

Security loopholes have been shown for discrete-variable Quantum Key Distribution (QKD). Here, we propose and provide experimental evidence of an attack targeting a continuous-variable...

Jouguet, Paul; Diamanti, Eleni; Kunz-Jacques, Sébastien

384

Photon and graviton mass limits  

SciTech Connect (OSTI)

We review past and current studies of possible long-distance, low-frequency deviations from Maxwell electrodynamics and Einstein gravity. Both have passed through three phases: (1) Testing the inverse-square laws of Newton and Coulomb, (2) Seeking a nonzero value for the rest mass of photon or graviton, and (3) Considering more degrees of freedom, allowing mass while preserving gauge or general-coordinate invariance. For electrodynamics there continues to be no sign of any deviation. Since our previous review the lower limit on the photon Compton wavelength (associated with weakening of electromagnetic fields in vacuum over large distance scale) has improved by four orders of magnitude, to about one astronomical unit. Rapid current progress in astronomical observations makes it likely that there will be further advances. These ultimately could yield a bound exceeding galactic dimensions, as has long been contemplated. Meanwhile, for gravity there have been strong arguments about even the concept of a graviton rest mass. At the same time there are striking observations, commonly labeled 'dark matter' and 'dark energy' that some argue imply modified gravity. This makes the questions for gravity much more interesting. For dark matter, which involves increased attraction at large distances, any explanation by modified gravity would be qualitatively different from graviton mass. Because dark energy is associated with reduced attraction at large distances, it might be explained by a graviton-mass-like effect.

Nieto, Michael [Los Alamos National Laboratory; Goldhaber Scharff, Alfred [SUNY

2008-01-01T23:59:59.000Z

385

Fast Electrical Control of a Quantum Dot Strongly Coupled to a Nano-resonator  

E-Print Network [OSTI]

The resonance frequency of an InAs quantum dot strongly coupled to a GaAs photonic crystal cavity was electrically controlled via quantum confined Stark effect. Stark shifts up to 0.3meV were achieved using a lateral Schottky electrode that created a local depletion region at the location of the quantum dot. We report switching of a probe laser coherently coupled to the cavity up to speeds as high as 150MHz, limited by the RC constant of the transmission line. The coupling rate and the magnitude of the Stark shift with electric field were investigated while coherently probing the system.

Andrei Faraon; Arka Majumdar; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

2009-06-03T23:59:59.000Z

386

The Hydrogen Atom: a Review on the Birth of Modern Quantum Mechanics  

E-Print Network [OSTI]

The purpose of this work is to retrace the steps that were made by scientists of XIX century, like Bohr, Schrodinger, Heisenberg, Pauli, Dirac, for the formulation of what today represents the modern quantum mechanics and that, within two decades, put in question the classical physics. In this context, the study of the electronic structure of hydrogen atom has been the main starting point for the formulation of the theory and, till now, remains the only real case for which the quantum equation of motion can be solved exactly. The results obtained by each theory will be discussed critically, highlighting limits and potentials that allowed the further development of the quantum theory.

Nanni, Luca

2015-01-01T23:59:59.000Z

387

Frustrated quantum phase diffusion and increased coherence of solitons due to nonlocality  

SciTech Connect (OSTI)

We investigate the quantum properties of solitons with nonlocal self-interaction. We find significant changes when compared to the local interaction. Quantum phase diffusion of nonlocal solitons is always reduced with respect to the local interaction and vanishes in the strongly nonlocal limit. Thus, coherence is increased in the nonlocal case. Furthermore, we compare the intrinsic quantum wave packet spreading to the recently discussed classical Gordon-Haus effect for nonlocal solitons [V. Folli and C. Conti, Phys. Rev. Lett. 104, 193901 (2010)].

Batz, Sascha [Max Planck Institute for the Science of Light, D-91058, Erlangen (Germany); Institute of Optics, Information and Photonics, University Erlangen-Nuremberg, D-91058 Erlangen (Germany); Peschel, Ulf [Institute of Optics, Information and Photonics, University Erlangen-Nuremberg, D-91058 Erlangen (Germany)

2011-03-15T23:59:59.000Z

388

Entanglement as Measure of Electron-Electron Correlation in Quantum Chemistry Calculations  

E-Print Network [OSTI]

In quantum chemistry calculations, the correlation energy is defined as the difference between the Hartree-Fock limit energy and the exact solution of the nonrelativistic Schrodinger equation. With this definition, the electron correlation effects are not directly observable. In this report, we show that the entanglement can be used as an alternative measure of the electron correlation in quantum chemistry calculations. Entanglement is directly observable and it is one of the most striking properties of quantum mechanics. As an example we calculate the entanglement for He atom and H2 molecule with different basis sets.

Zhen Huang; Sabre Kais

2005-07-15T23:59:59.000Z

389

Hierarchical quantum Ising model  

Science Journals Connector (OSTI)

A quantum Ising chain with both the exchange couplings and the transverse fields arranged in a hierarchical way is considered. Exact analytical results for the critical line and dispersion relation of the low-energy excitations are obtained. It is shown that only when R1=R2>Rc, where R1 and R2 are the hierarchical parameters for the exchange couplings and the transverse fields, respectively, does the system preserve a logarithmic singularity in the specific heat.

Zhifang Lin and Ruibao Tao

1990-06-01T23:59:59.000Z

390

Quantum Dots in Graphene  

Science Journals Connector (OSTI)

We suggest a way of confining quasiparticles by an external potential in a small region of a graphene strip. Transversal electron motion plays a crucial role in this confinement. Properties of thus obtained graphene quantum dots are investigated theoretically for different types of the boundary conditions at the edges of the strip. The (quasi)bound states exist in all systems considered. At the same time, the dependence of the conductance on the gate voltage carries information about the shape of the edges.

P. G. Silvestrov and K. B. Efetov

2007-01-03T23:59:59.000Z

391

Quantum information with Rydberg atoms  

Science Journals Connector (OSTI)

Rydberg atoms with principal quantum number n?1 have exaggerated atomic properties including dipole-dipole interactions that scale as n4 and radiative lifetimes that scale as n3. It was proposed a decade ago to take advantage of these properties to implement quantum gates between neutral atom qubits. The availability of a strong long-range interaction that can be coherently turned on and off is an enabling resource for a wide range of quantum information tasks stretching far beyond the original gate proposal. Rydberg enabled capabilities include long-range two-qubit gates, collective encoding of multiqubit registers, implementation of robust light-atom quantum interfaces, and the potential for simulating quantum many-body physics. The advances of the last decade are reviewed, covering both theoretical and experimental aspects of Rydberg-mediated quantum information processing.

M. Saffman; T. G. Walker; K. Mølmer

2010-08-18T23:59:59.000Z

392

Coherence-Preserving Quantum Bits  

Science Journals Connector (OSTI)

Real quantum systems couple to their environment and lose their intrinsic quantum nature through the process known as decoherence. Here we present a method for minimizing decoherence by making it energetically unfavorable. We present a Hamiltonian made up solely of two-body interactions between four two-level systems (qubits) which has a 2-fold degenerate ground state. This degenerate ground state has the property that any decoherence process acting on an individual physical qubit must supply energy from the bath to the system. Quantum information can be encoded into the degeneracy of the ground state and such coherence-preserving qubits will then be robust to local decoherence at low bath temperatures. We show how this quantum information can be universally manipulated and indicate how this approach may be applied to a quantum dot quantum computer.

Dave Bacon; Kenneth R. Brown; K. Birgitta Whaley

2001-11-26T23:59:59.000Z

393

Optical levitation of microdroplet containing a single quantum dot  

E-Print Network [OSTI]

Semiconductor nanocrystals, also known as quantum dots (QDs), are key ingredients in current quantum optics experiments. They serve as quantum emitters and memories and have tunable energy levels that depend not only on the material but also, through the quantum confinement effect, on the size. The resulting strongly confined electron and hole wave functions lead to large transition dipole moments, which opens a path to ultra strong coupling and even deep strong coupling between light and matter. Such efficient coupling requires the precise positioning of the QD in an optical cavity with a high quality factor and small mode volume, such as micro-Fabry--Perot cavity, whispering-gallery-mode microcavity, or photonic-crystal cavity. However, the absence of a technique for free-space positioning has limited the further research on QD-based cavity quantum electrodynamics. In this paper, we present a technique to overcome this challenge by demonstrating the optical levitation or trapping in helium gas of a single Q...

Minowa, Yosuke; Ashida, Masaaki

2014-01-01T23:59:59.000Z

394

Quantum plasmon effects in epsilon-near-zero metamaterials  

E-Print Network [OSTI]

Dispersion properties of metals and propagation of quantum bulk plasmon in the high photon energy regime are studied. The nonlocal dielectric permittivity of a metal is determined by the quantum plasma effects and is calculated by applying the Wigner equation in the kinetic theory and taking into account the electron lattice collisions. The properties of epsilon near zero material are investigated in a thin gold film. The spectrum and the damping rate of the quantum bulk plasmon are obtained for a wide range of energies, and the electron wave function is analytically calculated in both classical and quantum limits. It is shown that the quantum bulk plasmons exist with a propagation length of 1 to 10nm, which strongly depends on the electron energy. The propagation length is found to be much larger than the propagation length in the classical regime which is comparable to the atomic radius and the average inter particle distance. It is found that the spatial localization of the electron wave function is extend...

Moaied, M; Ostrikov, K

2014-01-01T23:59:59.000Z

395

Longitudinal dielectric permettivity of quantum Maxwell collisional plasmas  

E-Print Network [OSTI]

The kinetic equation of Wigner -- Vlasov -- Boltzmann with collision integral in relaxation BGK (Bhatnagar, Gross and Krook) form in coordinate space for quantum non--degenerate (Maxwellian) collisional plasma is used. Exact expression (within the limits of considered model) is found. The analysis of longitudinal dielectric permeability is done. It is shown that in the limit when Planck's constant tends to zero of expression for dielectric permettivity transforms into the classical case of dielectric permettivity. At small values of wave number it has been received the solution of the dispersion equation. Damping of plasma oscillations has been analized. The analytical comparison with the dielectric Mermin' function received with the use of the kinetic equation in momentum space is done. Graphic comparison of the real and imaginary parts of dielectric permettivity of quantum and classical plasma is done also.

A. V. Latyshev; A. A. Yushkanov

2010-03-12T23:59:59.000Z

396

Proposal for a Quantum-Degenerate Electron Source  

Science Journals Connector (OSTI)

We propose a pulsed electron source capable of 6D brightness orders-of-magnitude greater than that of existing sources. It could deliver average current up to 0.5 pA and achieve an emittance approaching the quantum limit in each spatial dimension. It could be employed to advantage in electron microscopy, inverse photo-emission, precision low-energy scattering experiments, and electron holography. This source could make possible pump-probe experiments with Ångstrom spatial and subpicosecond time resolution. Here, we present the basic concepts of the source, including a generalized expression for the brightness that can be used in the quantum limited case and the analysis of the main issues that must be addressed for successful construction and operation. We have begun an experiment to demonstrate its essential features.

M. Zolotorev; E. D. Commins; F. Sannibale

2007-05-03T23:59:59.000Z

397

Extending quantum operations  

SciTech Connect (OSTI)

For a given set of input-output pairs of quantum states or observables, we ask the question whether there exists a physically implementable transformation that maps each of the inputs to the corresponding output. The physical maps on quantum states are trace-preserving completely positive maps, but we also consider variants of these requirements. We generalize the definition of complete positivity to linear maps defined on arbitrary subspaces, then formulate this notion as a semidefinite program, and relate it by duality to approximative extensions of this map. This gives a characterization of the maps which can be approximated arbitrarily well as the restriction of a map that is completely positive on the whole algebra, also yielding the familiar extension theorems on operator spaces. For quantum channel extensions and extensions by probabilistic operations we obtain semidefinite characterizations, and we also elucidate the special case of Abelian inputs or outputs. Finally, revisiting a theorem by Alberti and Uhlmann, we provide simpler and more widely applicable conditions for certain extension problems on qubits, and by using a semidefinite programming formulation we exhibit counterexamples to seemingly reasonable but false generalizations of the Alberti-Uhlmann theorem.

Heinosaari, Teiko [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku (Finland); Jivulescu, Maria A. [Department of Mathematics, University Politehnica Timisoara, 300006 Timisoara (Romania); Reeb, David; Wolf, Michael M. [Department of Mathematics, Technische Universitaet Muenchen, 85748 Garching (Germany)

2012-10-15T23:59:59.000Z

398

Quantum Heat Bath  

E-Print Network [OSTI]

A model for a quantum heat bath is introduced. When the bath molecules have finitely many degrees of freedom, it is shown that the assumption that the molecules are weakly interacting is sufficient to enable one to derive the canonical distribution for the energy of a small system immersed in the bath. While the specific form of the bath temperature, for which we provide an explicit formula, depends on (i) spectral properties of the bath molecules, and (ii) the choice of probability measure on the state space of the bath, we are in all cases able to establish the existence of a strictly positive lower bound on the temperature of the bath. The results can be used to test the merits of different hypotheses for the equilibrium states of quantum systems. Two examples of physically plausible choices for the probability measure on the state space of a quantum heat bath are considered in detail, and the associated lower bounds on the temperature of the bath are worked out.

Dorje C. Brody; Lane P. Hughston

2014-11-17T23:59:59.000Z

399

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

400

Informational power of quantum measurements  

SciTech Connect (OSTI)

We introduce the informational power of a quantum measurement as the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We prove the additivity by showing that the informational power corresponds to the classical capacity of a quantum-classical channel. We restate the problem of evaluating the informational power as the maximization of the accessible information of a suitable ensemble. We provide a numerical algorithm to find an optimal ensemble and quantify the informational power.

Dall'Arno, Michele; D'Ariano, Giacomo Mauro [Quit Group, Dipartimento di Fisica 'A. Volta', via A. Bassi 6, I-27100 Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo IV, via A. Bassi 6, I-27100 Pavia (Italy); Sacchi, Massimiliano F. [Quit Group, Dipartimento di Fisica 'A. Volta', via A. Bassi 6, I-27100 Pavia (Italy); Istituto di Fotonica e Nanotecnologie (INF-CNR), Piazza Leonardo da Vinci 32, I-20133, Milano (Italy)

2011-06-15T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Finite Quantum Measure Spaces Denise Schmitz  

E-Print Network [OSTI]

Finite Quantum Measure Spaces Denise Schmitz 4 June 2012 Contents 1 Introduction 2 2 Preliminaries 2 2.1 Finite Measure Spaces . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Quantum Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Quantum Measures 3 3.1 Grade-2 Additivity . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Morrow, James A.

402

Information flow in entangled quantum systems  

Science Journals Connector (OSTI)

...research-article Research Article Information flow in entangled quantum systems David...of Oxford, , Oxford OX1 3PU, UK All information in quantum systems is, notwithstanding...Heisenberg picture to analyse quantum information processing makes this locality explicit...

2000-01-01T23:59:59.000Z

403

Quantum money and scalable 21-cm cosmology  

E-Print Network [OSTI]

This thesis covers two unrelated topics. The first part of my thesis is about quantum money, a cryptographic protocol in which a mint can generate a quantum state that no one can copy. In public-key quantum money, anyone ...

Lutomirski, Andrew (Andrew Michael)

2011-01-01T23:59:59.000Z

404

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

405

Applied quantum mechanics 1 Applied Quantum Mechanics  

E-Print Network [OSTI]

t an t n e int­ n = . If an t can be expressed as a power series in the perturbing potential then W^ x) A particle of mass m0 is initially in the ground state of a one dimensional har- monic oscillator. At time limit, t . Problem 8.2 An electron is in the ground state of a one-dimensional rectangular potential

Levi, Anthony F. J.

406

Sandia National Laboratories: quantum electronics  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

electronics EFRC Scientist Weng Chow Awarded the Quantum Electronics Award On July 24, 2013, in Energy, Energy Efficiency, News, News & Events, Solid-State Lighting EFRC Sr....

407

Purification of noisy quantum measurements  

SciTech Connect (OSTI)

We consider the problem of improving noisy quantum measurements by suitable preprocessing strategies making many noisy detectors equivalent to a single ideal detector. For observables pertaining to finite-dimensional systems (e.g., qubits or spins) we consider preprocessing strategies that are reminiscent of quantum error correction procedures and allow one to perfectly measure an observable on a single quantum system for increasing number of inefficient detectors. For measurements of observables with an unbounded spectrum (e.g., photon number and homodyne and heterodyne detection), the purification of noisy quantum measurements can be achieved by preamplification as suggested by Yuen [Opt. Lett. 12, 789 (1987)].

Dall'Arno, Michele; D'Ariano, Giacomo Mauro [Quit Group, Dipartimento di Fisica 'A. Volta', via Bassi 6, I-27100 Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo IV, via Bassi 6, I-27100 Pavia (Italy); Sacchi, Massimiliano F. [Quit Group, Dipartimento di Fisica 'A. Volta', via Bassi 6, I-27100 Pavia (Italy); Istituto di Fotonica e Nanotecnologie (IFN-CNR), Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)

2010-10-15T23:59:59.000Z

408

Polarization preserving quantum nondemolition photodetector  

E-Print Network [OSTI]

A polarization preserving quantum nondemolition photodetector is proposed based on nonlinearities obtainable through quantum coherence effects. An atomic level scheme is devised such that in the presence of strong linearly polarized drive field a coherent weak probe field acquires a phase proportional to the number of photons in the signal mode immaterial of its polarization state. It is also shown that the unavoidable phase-kicks resulting due to the measurement process are insensitive to the polarization state of the incoming signal photon. It is envisioned that such a device would have tremendous applicability in photonic quantum information proposals where quantum information in the polarization qubit is to be protected.

K. T. Kapale

2006-03-30T23:59:59.000Z

409

Quantum Information Science and Nanotechnology  

E-Print Network [OSTI]

In this note is touched upon an application of quantum information science (QIS) in nanotechnology area. The laws of quantum mechanics may be very important for nano-scale objects. A problem with simulating of quantum systems is well known and quantum computer was initially suggested by R. Feynman just as the way to overcome such difficulties. Mathematical methods developed in QIS also may be applied for description of nano-devices. Few illustrative examples are mentioned and they may be related with so-called fourth generation of nanotechnology products.

Alexander Yu. Vlasov

2009-03-06T23:59:59.000Z

410

Quantum Optical State Comparison Amplifier  

E-Print Network [OSTI]

It is a fundamental principle of quantum theory that an unknown state cannot be copied or, as a consequence, an unknown optical signal cannot be amplified deterministically and perfectly. Here we describe a protocol that provides nondeterministic quantum optical amplification in the coherent state basis with high gain, high fidelity and which does not use quantum resources. The scheme is based on two mature quantum optical technologies, coherent state comparison and photon subtraction. The method compares favourably with all previous nondeterministic amplifiers in terms of fidelity and success probability.

Electra Eleftheriadou; Stephen M. Barnett; John Jeffers

2013-11-22T23:59:59.000Z

411

New Scheme of Quantum Teleportation  

E-Print Network [OSTI]

A new scheme for quantum teleportation is presented, in which the complete teleportation can be occurred even when an entangled state between Alice and Bob is not maximal.

A. Kossakowski; M. Ohya

2005-08-08T23:59:59.000Z

412

Three-graviton vertex function in thermal quantum gravity  

Science Journals Connector (OSTI)

The high-temperature limit of the three-graviton vertex function is studied in thermal quantum gravity, to one-loop order. The leading (T4) contributions arising from internal gravitons are calculated and shown to be twice the ones associated with internal scalar particles, in correspondence with the two helicity states of the graviton. The gauge invariance of this result follows as a consequence of the Ward and Weyl identities obeyed by the thermal loops, which are verified explicitly.

F. T. Brandt and J. Frenkel

1993-05-15T23:59:59.000Z

413

Definition: Fault Current Limiter | Open Energy Information  

Open Energy Info (EERE)

Limiter Limiter Jump to: navigation, search Dictionary.png Fault Current Limiter A fault current limiter prevents current in an electrical circuit from exceeding a predetermined level by increasing the electrical impedance of that circuit before the current through the circuit exceeds that level. Fault current limiters are designed so as to minimize the impedance of the circuit under normal conditions to reduce losses, but increase the impedance of the circuit under fault conditions to limit fault current.[1] View on Wikipedia Wikipedia Definition A Fault Current Limiter (FCL) is a device which limits the prospective fault current when a fault occurs (e.g. in a power transmission network). The term includes superconducting devices and non-superconducting devices, however some of the more simple non-superconducting devices (such

414

Gujarat Ambuja Cements Limited | Open Energy Information  

Open Energy Info (EERE)

Ambuja Cements Limited Ambuja Cements Limited Jump to: navigation, search Name Gujarat Ambuja Cements Limited Place Mumbai, India Zip 400 021 Sector Biomass Product Indian cement company. the company installed a 24MW biomass based captive electric generating stations that will provide electricity to Gujarat Ambuja Cements Limitedâ€(tm)s (“GACL”) facility in Ropar, Punjab. References Gujarat Ambuja Cements Limited[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Gujarat Ambuja Cements Limited is a company located in Mumbai, India . References ↑ "Gujarat Ambuja Cements Limited" Retrieved from "http://en.openei.org/w/index.php?title=Gujarat_Ambuja_Cements_Limited&oldid=346290

415

Definition: Fault Current Limiting | Open Energy Information  

Open Energy Info (EERE)

Limiting Limiting Jump to: navigation, search Dictionary.png Fault Current Limiting Fault current limiting can be achieved through sensors, communications, information processing, and actuators that allow the utility to use a higher degree of network coordination to reconfigure the system to prevent fault currents from exceeding damaging levels. Fault current limiting can also be achieved through the implementation of special stand alone devices known as Fault Current Limiters (FCLs) which act to automatically limit high through currents that occur during faults.[1] Related Terms fault, fault current limiter References ↑ SmartGrid.gov 'Description of Functions' Temp LikeLike UnlikeLike You like this.Sign Up to see what your friends like. late:ISGANAttributionsmart grid,smart grid,smart grid,smart grid,

416

DENSITY LIMITS IN TOROIDAL PLASMAS MARTIN GREENWALD  

E-Print Network [OSTI]

(RFP) ---- Spheromaks and FRCs · Physics basis for density limit ---- Neutrals ---- Radiation models as fast terminations · Spheromak and FRC don't have density limit data operation at "optimized" density

Greenwald, Martin

417

Gamma-ray free-electron lasers: Quantum fluid model  

E-Print Network [OSTI]

A quantum fluid model is used to describe the interacion of a nondegenerate cold relativistic electron beam with an intense optical wiggler taking into account the beam space-charge potential and photon recoil effect. A nonlinear set of coupled equations are obtained and solved numerically. The numerical results shows that in the limit of plasma wave-breaking an ultra-high power radiation pulse are emitted at the$\\gamma$-ray wavelength range which can reach an output intensity near the Schwinger limit depending of the values of the FEL parameters such as detuning and input signal initial phase at the entrance of the interaction region.

Silva, H M

2014-01-01T23:59:59.000Z

418

Limited Liability Companies and Corporate Business Structures  

E-Print Network [OSTI]

This publication describes limited liability companies and corporate forms of business organization, including S-Corporations and C-Corporations....

Thompson, Bill; Polk, Wade; Hayenga, Wayne

2009-01-07T23:59:59.000Z

419

Functionalized Graphene Nanoroads for Quantum Well Device. |...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Nanoroads for Quantum Well Device. Functionalized Graphene Nanoroads for Quantum Well Device. Abstract: Using density functional theory, a series of calculations of structural and...

420

Quantum Condensed Matter | More Science | ORNL  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum Condensed Matter SHARE Quantum Condensed Matter Neutron scattering is a uniquely powerful probe for measuring the structure and dynamics of condensed matter. As such it is...

Note: This page contains sample records for the topic "quantum limit outsmarting" 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 Information Science | ornl.gov  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

architectures is an open field. ASTEQC (Automated Software Tools for Engineering Quantum Computers) May 20, 2013 - The feasibility of quantum computing depends critically on the...

422

Quantum Condensed Matter | Neutron Science | ORNL  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum Condensed Matter SHARE Quantum Condensed Matter Neutron scattering is a uniquely powerful probe for measuring the structure and dynamics of condensed matter. As such it is...

423

Hybrid Rotaxanes: Interlocked Structures for Quantum Computing...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Hybrid Rotaxanes: Interlocked Structures for Quantum Computing? Print Wednesday, 26 August 2009 00:00 Rotaxanes are...

424

From Quantum Mechanics to Quantum Field Theory: The Hopf route  

E-Print Network [OSTI]

From Quantum Mechanics to Quantum Field Theory: The Hopf route A. I. Solomon1 2, G. E. H. Duchamp3. Eliasza-Radzikowskiego 152, PL 31-342 Krak´ow, Poland E-mail: a.i.solomon@open.ac.uk, gduchamp2@free solvable model (at least in the free boson case). On the basis of a combinatorial methodology, we show

Paris-Sud XI, Université de

425

From Quantum Mechanics to Quantum Field Theory: The Hopf route  

E-Print Network [OSTI]

From Quantum Mechanics to Quantum Field Theory: The Hopf route A. I. Solomon 1 2 , G. E. H. Duchamp. Eliasza­Radzikowskiego 152, PL 31­342 Krakâ??ow, Poland E­mail: a.i.solomon@open.ac.uk, gduchamp2@free solvable model (at least in the free boson case). On the basis of a combinatorial methodology, we show

Recanati, Catherine

426

Quantum metrology from a quantum information science perspective  

E-Print Network [OSTI]

We summarise important recent advances in quantum metrology, in connection to experiments in cold gases, trapped cold atoms and photons. First we review simple metrological setups, such as quantum metrology with spin squeezed states, with Greenberger-Horne-Zeilinger states, Dicke states and singlet states. We calculate the highest precision achievable in these schemes. Then, we present the fundamental notions of quantum metrology, such as shot-noise scaling, Heisenberg scaling, the quantum Fisher information and the Cramer-Rao bound. Using these, we demonstrate that entanglement is needed to surpass the shot-noise scaling in very general metrological tasks with a linear interferometer. We discuss some applications of the quantum Fisher information, such as how it can be used to obtain a criterion for a quantum state to be a macroscopic superposition. We show how it is related to the the speed of a quantum evolution, and how it appears in the theory of the quantum Zeno effect. Finally, we explain how uncorrela...

Toth, Geza

2015-01-01T23:59:59.000Z

427

Energy density matrix formalism for interacting quantum systems: a quantum Monte Carlo study  

SciTech Connect (OSTI)

We develop an energy density matrix that parallels the one-body reduced density matrix (1RDM) for many-body quantum systems. Just as the density matrix gives access to the number density and occupation numbers, the energy density matrix yields the energy density and orbital occupation energies. The eigenvectors of the matrix provide a natural orbital partitioning of the energy density while the eigenvalues comprise a single particle energy spectrum obeying a total energy sum rule. For mean-field systems the energy density matrix recovers the exact spectrum. When correlation becomes important, the occupation energies resemble quasiparticle energies in some respects. We explore the occupation energy spectrum for the finite 3D homogeneous electron gas in the metallic regime and an isolated oxygen atom with ground state quantum Monte Carlo techniques imple- mented in the QMCPACK simulation code. The occupation energy spectrum for the homogeneous electron gas can be described by an effective mass below the Fermi level. Above the Fermi level evanescent behavior in the occupation energies is observed in similar fashion to the occupation numbers of the 1RDM. A direct comparison with total energy differences demonstrates a quantita- tive connection between the occupation energies and electron addition and removal energies for the electron gas. For the oxygen atom, the association between the ground state occupation energies and particle addition and removal energies becomes only qualitative. The energy density matrix provides a new avenue for describing energetics with quantum Monte Carlo methods which have traditionally been limited to total energies.

Krogel, Jaron T [ORNL] [ORNL; Kim, Jeongnim [ORNL] [ORNL; Reboredo, Fernando A [ORNL] [ORNL

2014-01-01T23:59:59.000Z

428

LIMITING ABSORPTION PRINCIPLE FOR SINGULARLY PERTURBED OPERATORS  

E-Print Network [OSTI]

LIMITING ABSORPTION PRINCIPLE FOR SINGULARLY PERTURBED OPERATORS WALTER RENGER Abstract. Given an operator H 1 for which a limiting absorption principle holds, we study operators H 2 which are produced that (except for possibly a discrete set of eigenvalues) a limiting absorption principle holds for H 2 . We

429

Quantum interference within the complex quantum Hamilton-Jacobi formalism  

SciTech Connect (OSTI)

Quantum interference is investigated within the complex quantum Hamilton-Jacobi formalism. As shown in a previous work [Phys. Rev. Lett. 102 (2009) 250401], complex quantum trajectories display helical wrapping around stagnation tubes and hyperbolic deflection near vortical tubes, these structures being prominent features of quantum caves in space-time Argand plots. Here, we further analyze the divergence and vorticity of the quantum momentum function along streamlines near poles, showing the intricacy of the complex dynamics. Nevertheless, despite this behavior, we show that the appearance of the well-known interference features (on the real axis) can be easily understood in terms of the rotation of the nodal line in the complex plane. This offers a unified description of interference as well as an elegant and practical method to compute the lifetime for interference features, defined in terms of the average wrapping time, i.e., considering such features as a resonant process.

Chou, Chia-Chun, E-mail: chiachun@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Sanz, Angel S., E-mail: asanz@imaff.cfmac.csic.e [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Miret-Artes, Salvador, E-mail: s.miret@imaff.cfmac.csic.e [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Wyatt, Robert E., E-mail: wyattre@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712 (United States)

2010-10-15T23:59:59.000Z

430

Magnetic Field Control of the Quantum Chaotic Dynamics of Hydrogen Analogues in an Anisotropic Crystal Field  

E-Print Network [OSTI]

We report magnetic field control of the quantum chaotic dynamics of hydrogen analogues in an anisotropic solid state environment. The chaoticity of the system dynamics was quantified by means of energy level statistics. We analyzed the magnetic field dependence of the statistical distribution of the impurity energy levels and found a smooth transition between the Poisson limit and the Wigner limit, i.e. transition between regular Poisson and fully chaotic Wigner dynamics. Effect of the crystal field anisotropy on the quantum chaotic dynamics, which manifests itself in characteristic transitions between regularity and chaos for different field orientations, was demonstrated.

Weihang Zhou; Zhanghai Chen; Bo Zhang; C. H. Yu; Wei Lu; S. C. Shen

2010-03-09T23:59:59.000Z

431

Bose-Fermi solid and its quantum melting in a one-dimensional optical lattice  

Science Journals Connector (OSTI)

We investigate the quantum phase diagram of Bose-Fermi mixtures of ultracold dipolar particles trapped in one-dimensional optical lattices in the thermodynamic limit. With the presence of nearest-neighbor (NN) interactions, a long-ranged ordered crystalline phase (Bose-Fermi solid) is found stabilized in the limit of weak intersite tunneling (J). When J is increased, such a Bose-Fermi solid can be quantum melted into a Bose-Fermi liquid through different procedures, depending on whether the crystalline order is dominated by the NN interaction between fermions or bosons. These properties are qualitatively different from the classical picture of solid-liquid phase transition.

Bin Wang; Daw-Wei Wang; S. Das Sarma

2010-08-10T23:59:59.000Z

432

Multipartite entanglement in quantum algorithms  

SciTech Connect (OSTI)

We investigate the entanglement features of the quantum states employed in quantum algorithms. In particular, we analyze the multipartite entanglement properties in the Deutsch-Jozsa, Grover, and Simon algorithms. Our results show that for these algorithms most instances involve multipartite entanglement.

Bruss, D. [Institut fuer Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf, D-40225 Duesseldorf (Germany); Macchiavello, C. [Dipartimento di Fisica 'A. Volta' and INFN-Sezione di Pavia, Via Bassi 6, 27100 Pavia (Italy)

2011-05-15T23:59:59.000Z

433

Informational derivation of quantum theory  

SciTech Connect (OSTI)

We derive quantum theory from purely informational principles. Five elementary axioms - causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning - define a broad class of theories of information processing that can be regarded as standard. One postulate - purification - singles out quantum theory within this class.

Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Ontario, N2L 2Y5 (Canada); QUIT Group, Dipartimento di Fisica ''A. Volta'' and INFN Sezione di Pavia, via Bassi 6, I-27100 Pavia (Italy)

2011-07-15T23:59:59.000Z

434

Parrondo Games and Quantum Algorithms  

E-Print Network [OSTI]

We pursue the possible connections between classical games and quantum computation. The Parrondo game is one in which a random combination of two losing games produces a winning game. We introduce novel realizations of this Parrondo effect in which the player can `win' via random reflections and rotations of the state-vector, and connect these to known quantum algorithms.

Chiu Fan Lee; Neil Johnson

2002-03-10T23:59:59.000Z

435

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

436

Electric Time in Quantum Cosmology  

E-Print Network [OSTI]

Effective quantum cosmology is formulated with a realistic global internal time given by the electric vector potential. New possibilities for the quantum behavior of space-time are found, and the high-density regime is shown to be very sensitive to the specific form of state realized.

Stephon Alexander; Martin Bojowald; Antonino Marciano; David Simpson

2012-12-10T23:59:59.000Z

437

Non-Integer Quantum Transitions  

E-Print Network [OSTI]

We show that in the quantum transition of a system induced by the interaction with an intense laser of circular frequency $\\omega$, the energy difference between the initial and the final states of the system is not necessarily being an integer multiple of the quantum energy $\\hbar\\omega$.

Qi-Ren Zhang

2005-12-04T23:59:59.000Z

438

Dust time in quantum cosmology  

E-Print Network [OSTI]

We give a formulation of quantum cosmology with a pressureless dust and arbitrary additional matter fields. The dust provides a natural time gauge corresponding to a cosmic time, yielding a physical time independent Hamiltonian. The approach simplifies the analysis of both Wheeler-deWitt and loop quantum cosmology models, broadening the applicability of the latter.

Husain, Viqar

2013-01-01T23:59:59.000Z

439

Quantum–enhanced information processing  

Science Journals Connector (OSTI)

...conventional (classical) computing device. We will show how quantum...life. Anyone who has enjoyed listening to music on a CD, watching...quantum computer is any physical device that exploits the greatly enhanced...on any conceivable computing device. Multi- plying numbers or...

2000-01-01T23:59:59.000Z

440

Quantum computing: pro and con  

Science Journals Connector (OSTI)

...meeting knows well, building a quantum computer will be an enormous technical challenge...by the Department of Energy under Grant no. DE-FG03- 92-ER40701, and...fermi systems on a universal quantum computer. Online preprint quant-ph/9703054...

1998-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Quantum Computers, Factoring, and Decoherence  

E-Print Network [OSTI]

In a quantum computer any superposition of inputs evolves unitarily into the corresponding superposition of outputs. It has been recently demonstrated that such computers can dramatically speed up the task of finding factors of large numbers -- a problem of great practical significance because of its cryptographic applications. Instead of the nearly exponential ($\\sim \\exp L^{1/3}$, for a number with $L$ digits) time required by the fastest classical algorithm, the quantum algorithm gives factors in a time polynomial in $L$ ($\\sim L^2$). This enormous speed-up is possible in principle because quantum computation can simultaneously follow all of the paths corresponding to the distinct classical inputs, obtaining the solution as a result of coherent quantum interference between the alternatives. Hence, a quantum computer is sophisticated interference device, and it is essential for its quantum state to remain coherent in the course of the operation. In this report we investigate the effect of decoherence on the quantum factorization algorithm and establish an upper bound on a ``quantum factorizable'' $L$ based on the decoherence suffered per operational step.

I. Chuang; Raymond Laflamme; P. Shor; W. Zurek

1995-03-08T23:59:59.000Z

442

Quantum Probability from Decision Theory?  

E-Print Network [OSTI]

In a recent paper (quant-ph/9906015), Deutsch claims to derive the "probabilistic predictions of quantum theory" from the "non-probabilistic axioms of quantum theory" and the "non-probabilistic part of classical decision theory." We show that his derivation fails because it includes hidden probabilistic assumptions.

H. Barnum; C. M. Caves; J. Finkelstein; C. A. Fuchs; R. Schack

1999-07-07T23:59:59.000Z

443

Quantum Probability from Decision Theory?  

E-Print Network [OSTI]

Deutsch has recently (in quant-ph/9906015) offered a justification, based only on the non-probabilistic axioms of quantum theory and of classical decision theory, for the use of the standard quantum probability rules. In this note, this justification is examined.

J. Finkelstein

1999-07-01T23:59:59.000Z

444

Quantum ferroelectrics of mixed crystals  

Science Journals Connector (OSTI)

The inverse dielectric susceptibility for quantum ferroelectrics in mixed crystals is computed. As in the perfect crystals we find a logarithmic correction to the quantum mean-field theory. For mixed crystals the correction increases faster in the vicinity of the critical point.

D. Schmeltzer

1984-03-01T23:59:59.000Z

445

Quantum recoil and Bohm diffusion  

SciTech Connect (OSTI)

It is argued that the inclusion of the Bohm potential in quantum fluid equations is equivalent to inclusion of a nonrelativistic form of the quantum recoil in plasma kinetic theory. The Bohm term is incorrect when applied to waves with phase speed greater than the speed of light.

Melrose, D. B.; Mushtaq, A. [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia)

2009-09-15T23:59:59.000Z

446

Carbon Trust Enterprises Limited | Open Energy Information  

Open Energy Info (EERE)

Enterprises Limited Enterprises Limited Jump to: navigation, search Name Carbon Trust Enterprises Limited Place London, United Kingdom Zip WC2A 2AZ Sector Carbon Product Carbon Trust Enterprises creates and invests in new, high growth, carbon reducing businesses. Typically the company focuses on use of mature technologies rather than on technology innovations. References Carbon Trust Enterprises Limited[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Carbon Trust Enterprises Limited is a company located in London, United Kingdom . References ↑ "Carbon Trust Enterprises Limited" Retrieved from "http://en.openei.org/w/index.php?title=Carbon_Trust_Enterprises_Limited&oldid=343250"

447

Impact Capital Partners Limited | Open Energy Information  

Open Energy Info (EERE)

Limited Limited Jump to: navigation, search Name Impact Capital Partners Limited Place Los Angeles, California Zip CA 90067-1509 Product Los Angeles-based, investment intermediary that designs financial solutions and innovative strategies for achieving sustained growth and intrinsic value. References Impact Capital Partners Limited[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Impact Capital Partners Limited is a company located in Los Angeles, California . References ↑ "Impact Capital Partners Limited" Retrieved from "http://en.openei.org/w/index.php?title=Impact_Capital_Partners_Limited&oldid=346814" Categories: Clean Energy Organizations Companies

448

Bharat Electronics Limited BEL | Open Energy Information  

Open Energy Info (EERE)

Limited BEL Limited BEL Jump to: navigation, search Name Bharat Electronics Limited (BEL) Place Bangalore, India Zip 560015 Sector Solar Product Major supplier of products and turnkey systems with expertise in solar products and systems, defence communication, radars & sensors, telecommunication, broadcasting equipments, e-governance networks and other components. References Bharat Electronics Limited (BEL)[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Bharat Electronics Limited (BEL) is a company located in Bangalore, India . References ↑ "Bharat Electronics Limited (BEL)" Retrieved from "http://en.openei.org/w/index.php?title=Bharat_Electronics_Limited_BEL&oldid=342709

449

Quantum pumping in graphene  

Science Journals Connector (OSTI)

We show that graphene-based quantum pumps can tap into evanescent modes, which penetrate deeply into the device as a consequence of Klein tunneling. The evanescent modes dominate pumping at the Dirac point, and give rise to a universal response under weak driving for short and wide pumps, in close analogy to their role in the minimal conductivity in ballistic transport. In contrast, evanescent modes contribute negligibly to normal pumps. Our findings add an incentive for the exploration of graphene-based nanoelectronic devices.

E. Prada; P. San-Jose; H. Schomerus

2009-12-10T23:59:59.000Z

450

Quantum-secured imaging  

E-Print Network [OSTI]

We have built an imaging system that uses a photon's position or time-of-flight information to image an object, while using the photon's polarization for security. This ability allows us to obtain an image which is secure against an attack in which the object being imaged intercepts and resends the imaging photons with modified information. Popularly known as "jamming," this type of attack is commonly directed at active imaging systems such as radar. In order to jam our imaging system, the object must disturb the delicate quantum state of the imaging photons, thus introducing statistical errors that reveal its activity.

Mehul Malik; Omar S. Magaña-Loaiza; Robert W. Boyd

2012-12-11T23:59:59.000Z

451

A Description of Quantum Chaos  

E-Print Network [OSTI]

A measure describing the chaos of a dynamics was introduced by two complexities in information dynamics, and it is called the chaos degree. In particular, the entropic chaos degree has been used to characterized several dynamical maps such that logistis, Baker's, Tinckerbel's in classical or quantum systems. In this paper, we give a new treatment of quantum chaos by defining the entropic chaos degree for quantum transition dynamics, and we prove that every non-chaotic quantum dynamics, e.g., dissipative dynamics, has zero chaos degree. A quantum spin 1/2 system is studied by our chaos degree, and it is shown that this degree well describes the chaotic behavior of the spin system.

Kei Inoue; Andrzej Kossakowski; Masanori Ohya

2004-06-30T23:59:59.000Z

452

Non-adiabatic quantum pumping by a randomly moving quantum dot  

E-Print Network [OSTI]

We look at random time dependent fluctuations of the electrical charge in an open 1D quantum system represented by a quantum dot experiencing random lateral motion. In essentially non-adiabatic settings we study both diffusive and ballistic (Levy) regimes of the barrier motion. Here the electric current as well as the net pumped electric charge experience random fluctuations over the static background. We show that in the large-time limit $t \\to \\infty$ the wavefunction is naturally separated into the Berry-phase component (resulting from the singular part of the wave amplitude in the co-moving frame) and the non-adiabatic correction (arising from fast oscillating, slow decaying tails of the same amplitude). In the special limit of a delta-correlated continuous Gaussian random walk we obtain closed analytical expressions for the ensemble averaged amplitude in the co-moving frame and demonstrate that the main contribution to the average wavefunction and probability current comes from the Berry-phase component which leads to the saturation of the fluctuations of the electric current and the pumped charge. We also derive the exact expressions for the average propagator (in the co-moving basis representation) for both types of motion.

Stanislav Derevyanko; Daniel Waltner

2015-02-10T23:59:59.000Z

453

Quantum Szilard engines with arbitrary spin  

E-Print Network [OSTI]

The quantum Szilard engine (QSZE) is a conceptual quantum engine for understanding the fundamental physics of quantum thermodynamics and information physics. We generalize the QSZE to an arbitrary spin case, i.e., a spin QSZE (SQSZE), and we systematically study the basic physical properties of both fermion and boson SQSZEs in a low-temperature approximation. We give the analytic formulation of the total work. For the fermion SQSZE, the work might be absorbed from the environment, and the change rate of the work with temperature exhibits periodicity and even-odd oscillation, which is a generalization of a spinless QSZE. It is interesting that the average absorbed work oscillates regularly and periodically in a large-number limit, which implies that the average absorbed work in a fermion SQSZE is neither an intensive quantity nor an extensive quantity. The phase diagrams of both fermion and boson SQSZEs give the SQSZE doing positive or negative work in the parameter space of the temperature and the particle number of the system, but they have different behaviors because the spin degrees of the fermion and the boson play different roles in their configuration states and corresponding statistical properties. The critical temperature of phase transition depends sensitively on the particle number. By using Landauer's erasure principle, we give the erasure work in a thermodynamic cycle, and we define an efficiency (we refer to it as information-work efficiency) to measure the engine's ability of utilizing information to extract work. We also give the conditions under which the maximum extracted work and highest information-work efficiencies for fermion and boson SQSZEs can be achieved.

Zekun Zhuang; Shi-Dong Liang

2015-02-02T23:59:59.000Z

454

Quantum Horizons of the Standard Model Landscape  

E-Print Network [OSTI]

The long-distance effective field theory of our Universe--the Standard Model coupled to gravity--has a unique 4D vacuum, but we show that it also has a landscape of lower-dimensional vacua, with the potential for moduli arising from vacuum and Casimir energies. For minimal Majorana neutrino masses, we find a near-continuous infinity of AdS3xS1 vacua, with circumference ~20 microns and AdS3 length 4x10^25 m. By AdS/CFT, there is a CFT2 of central charge c~10^90 which contains the Standard Model (and beyond) coupled to quantum gravity in this vacuum. Physics in these vacua is the same as in ours for energies between 10^-1 eV and 10^48 GeV, so this CFT2 also describes all the physics of our vacuum in this energy range. We show that it is possible to realize quantum-stabilized AdS vacua as near-horizon regions of new kinds of quantum extremal black objects in the higher-dimensional space--near critical black strings in 4D, near-critical black holes in 3D. The violation of the null-energy condition by the Casimir energy is crucial for these horizons to exist, as has already been realized for analogous non-extremal 3D black holes by Emparan, Fabbri and Kaloper. The new extremal 3D black holes are particularly interesting--they are (meta)stable with an entropy independent of hbar and G_N, so a microscopic counting of the entropy may be possible in the G_N->0 limit. Our results suggest that it should be possible to realize the larger landscape of AdS vacua in string theory as near-horizon geometries of new extremal black brane solutions.

Nima Arkani-Hamed; Sergei Dubovsky; Alberto Nicolis; Giovanni Villadoro

2007-03-08T23:59:59.000Z

455

Quantum field theory solution for a short-range interacting SO(3) quantum spin-glass  

E-Print Network [OSTI]

We study the quenched disordered magnetic system, which is obtained from the 2D SO(3) quantum Heisenberg model, on a square lattice, with nearest neighbors interaction, by taking a Gaussian random distribution of couplings centered in an antiferromagnetic coupling, $\\bar J>0$ and with a width $\\Delta J$. Using coherent spin states we can integrate over the random variables and map the system onto a field theory, which is a generalization of the SO(3) nonlinear sigma model with different flavors corresponding to the replicas, coupling parameter proportional to $\\bar J$ and having a quartic spin interaction proportional to the disorder ($\\Delta J$). After deriving the CP$^1$ version of the system, we perform a calculation of the free energy density in the limit of zero replicas, which fully includes the quantum fluctuations of the CP$^1$ fields $z_i$. We, thereby obtain the phase diagram of the system in terms of ($T, \\bar J, \\Delta J$). This presents an ordered antiferromagnetic (AF) phase, a paramagnetic (PM) phase and a spin-glass (SG) phase. A critical curve separating the PM and SG phases ends at a quantum critical point located between the AF and SG phases, at T=0. The Edwards-Anderson order parameter, as well as the magnetic susceptibilities are explicitly obtained in each of the three phases as a function of the three control parameters. The magnetic susceptibilities show a Curie-type behavior at high temperatures and exhibit a clear cusp, characteristic of the SG transition, at the transition line. The thermodynamic stability of the phases is investigated by a careful analysis of the Hessian matrix of the free energy. We show that all principal minors of the Hessian are positive in the limit of zero replicas, implying in particular that the SG phase is stable.

C. M. S. da Conceição; E. C. Marino

2009-03-02T23:59:59.000Z

456

Quantum?mechanical derivation of the Bloch equations: Beyond the weak?coupling limit  

E-Print Network [OSTI]

and we simply use the relation that i OO dt e - i(x - xo)te -., = 11"fiJ (x - xo) - i9 (x - xo), (67) where fiJ (x - xo) is a generalized function such that lim€_ofiJ (x - xo) = 8(x - xo), the Dirac delta function, and 9 (x - xo) is a generalized... function defined by its ac­ tion under an integral sign: ~i~ f~ "" dxf(x) 9 (x - xo) = p f~ "" dx :<:~o ' (68) where f(x) is integrable on ( - 00,00) and P denotes the usual Cauchy principal value. Since, as we will see below, A- C I (cu) is real...

Laird, Brian Bostian; Budimir, Jane; Skinner, James L.

1991-01-01T23:59:59.000Z

457

Room-temperature quantum noise limited spectrometry and methods of the same  

DOE Patents [OSTI]

In one embodiment, a heterodyne detection system for detecting light includes a first input aperture adapted for receiving a first light from a scene input, a second input aperture adapted for receiving a second light from a local oscillator input, a broadband local oscillator adapted for providing the second light to the second input aperture, a dispersive element adapted for dispersing the first light and the second light, and a final condensing lens coupled to an infrared detector. The final condensing lens is adapted for concentrating incident light from a primary condensing lens onto the detector, and the detector is a square-law detector capable of sensing the frequency difference between the first light and the second light. More systems and methods for detecting light are disclosed according to more embodiments.

Stevens, Charles G; Tringe, Joseph W

2014-12-02T23:59:59.000Z

458

Optimization of superconducting flux qubit readout using near-quantum-limited amplifiers  

E-Print Network [OSTI]

1.3.2 Josephson junctions . . . . . . . 1.4 Superconductingpotential of a Josephson junction. . . . . . SQUID schematicSEM images of Josephson junctions. . . . . Double-angle

Johnson, Jedediah Edward Jensen

2012-01-01T23:59:59.000Z

459

Room-temperature quantum noise limited spectrometry and methods of the same  

DOE Patents [OSTI]

In one embodiment, a heterodyne detection system for detecting light includes a first input aperture adapted for receiving first light from a scene input, a second input aperture adapted for receiving second light from a local oscillator input, a broadband local oscillator adapted for providing the second light to the second input aperture, a dispersive element adapted for dispersing the first light and the second light, and a final condensing lens coupled to an infrared detector. The final condensing lens is adapted for concentrating incident light from a primary condensing lens onto the infrared detector, and the infrared detector is a square-law detector capable of sensing the frequency difference between the first light and the second light. More systems and methods for detecting light are described according to other embodiments.

Stevens, Charles G.; Tringe, Joseph W.; Cunningham, Christopher Thomas

2014-08-26T23:59:59.000Z

460

Lectures on Quantum Cosmology  

E-Print Network [OSTI]

The problems encountered in trying to quantize the various cosmological models, are brought forward by means of a concrete example. The Automorphism groups are revealed as the key element through which G.C.T.'s can be used for a general treatment of these problems. At the classical level, the time dependent automorphisms lead to significant simplifications of the line element for the generic spatially homogeneous geometry, without loss of generality. At the quantum level, the ''frozen'' automorphisms entail an important reduction of the configuration space --spanned by the 6 components of the scale factor matrix-- on which the Wheeler-DeWitt equation, is to be based. In this spirit the canonical quantization of the most general minisuperspace actions --i.e. with all six scale factor as well as the lapse function and the shift vector present-- describing the vacuum type II, I geometries, is considered. The reduction to the corresponding physical degrees of freedom is achieved through the usage of the linear constraints as well as the quantum version of the entire set of all classical integrals of motion.

T. Christodoulakis

2001-09-18T23:59:59.000Z

Note: This page contains sample records for the topic "quantum limit outsmarting" 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

Euclidean Quantum Electrodynamics  

Science Journals Connector (OSTI)

Quantum electrodynamics is transcribed into a Euclidean metric. A review is presented of the quantum action-principle approach to quantization, with its automatic emphasis on the dynamical variables associated with the physical degrees of freedom. Green's functions of the radiation gauge are defined, and then characterized by differential equations and boundary conditions. These Green's functions are of direct physical significance but involve a distinguished time-like direction. A gauge transformation is then performed to eliminate this dependence, introducing thereby the Green's functions of the Lorentz gauge, which lack immediate physical interpretation. The latter functions are now primarily defined by differential equations and boundary conditions, and form the basis for the analytic extension which is the change from space-time to Euclidean metric. Some properties of anticommuting matrices are discussed in relation to this metric transformation. Real Euclidean Green's functions are defined by correspondence with the Lorentz gauge functions and the appropriate differential equations obtained. Invariance properties of the Euclidean functions are discussed. The individual Euclidean Green's functions are given an operator construction and then combined into a generating Green's functional which is interpreted as the wave function, in a canonical field representation, of a state characterized by the Euclidean action operator. Differential operator realizations and some other benefits of a canonical variable description are exhibited.

Julian Schwinger

1959-08-01T23:59:59.000Z

462

Quantum fluctuations of axions  

SciTech Connect (OSTI)

We study the time evolution of the quantum fluctuations of the axion field for both the QCD axion as well as axions arising in the context of supergravity and string theories. We explicitly keep track not only of the coherently oscillating zero momentum mode of the axion but also of the higher non-zero momentum modes using the full axion potential. The full axion potential makes possible two kinds of instabilities: spinodal instabilities and parametric resonance instabilities. The presence of either of these instabilities can lead to a quasi-exponential increase in the occupation of non-zero momentum modes and the build-up of the quantum fluctuations of the axions. If either of these becomes a significant effect then axions would no longer be a suitable cold dark matter candidate. Our results confirm the conventional wisdom that these effects are not significant in the setting of an expanding FRW universe and hence axions are indeed cold dark matter candidates. {copyright} {ital 1998} {ital The American Physical Society}

Kolb, E.W. [NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)] [NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); [Department of Astronomy and Astrophysics, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Singh, A.; Srednicki, M. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)] [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

1998-11-01T23:59:59.000Z

463

Quantum Entanglement and Decoherence: Beyond Particle Models. A Farewell to Quantum Mechanics's Weirdness  

E-Print Network [OSTI]

Combining abstract to laboratory projected quantum states a general analysis of headline quantum phenomena is presented. Standard representation mode is replaced; instead quantum states sustained by elementary material constituents occupy its place. Renouncing to assign leading roles to language originated in classical physics when describing genuine quantum processes, together with sustainment concept most, if not all weirdness associated to Quantum Mechanics vanishes.

O. Tapia

2014-04-02T23:59:59.000Z

464

Quantum Stochastic Heating of a Trapped Ion  

E-Print Network [OSTI]

The resonant heating of a harmonically trapped ion by a standing-wave light field is described as a quantum stochastic process combining a coherent Schroedinger evolution with Bohr-Einstein quantum jumps. Quantum and semi-quantum treatments are compared.

L. Horvath; R. Fisher; M. J. Collett; H. J. Carmichael

2007-11-09T23:59:59.000Z

465

Interference and inequality in quantum decision theory  

E-Print Network [OSTI]

The quantum decision theory is examined in its simplest form of two-condition two-choice setting. A set of inequalities to be satisfied by any quantum conditional probability describing the decision process is derived. Experimental data indicating the breakdown of classical explanations are critically examined with quantum theory using the full set of quantum phases.

Taksu Cheon; Taiki Takahashi

2010-08-16T23:59:59.000Z

466

Quantum Enabled Security (QES) for Optical Communications  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum Enabled Security (QES) for Optical Communications Quantum Enabled Security (QES) for Optical Communications Quantum Enabled Security (QES) for Optical Communications Los Alamos National Laboratory has developed Quantum Enabled Security (QES), a revolutionary new cybersecurity capability using quantum (single-photon) communications integrated with optical communications to provide a strong, innate, security foundation at the photonic layer for optical fiber networks. July 10, 2013 Quantum Enabled Security (QES) for Optical Communications Available for thumbnail of Feynman Center (505) 665-9090 Email Quantum Enabled Security (QES) for Optical Communications Applications: Secure communication over optical or free space networks Financial networks Transparent access networks: fiber to the home (FTTH); fiber to the

467

Quantum Detection and Invisibility in Coherent Nanostructures  

SciTech Connect (OSTI)

We address quantum invisibility in the context of electronics in nanoscale quantum structures. In analogy with metamaterials, we use the freedom of design that quantum corrals provide and show that quantum mechanical objects can be hidden inside the corral, with respect to inelastic electron scattering spectroscopy in combination with scanning tunneling microscopy, and we propose a design strategy. A simple illustration of the invisibility is given in terms of an elliptic quantum corral containing a molecule, with a local vibrational mode, at one of the foci. Our work has implications to quantum information technology and presents new tools for nonlocal quantum detection and distinguishing between different molecules.

Fransson, J.

2010-04-28T23:59:59.000Z

468

EU Energy Wind Limited | Open Energy Information  

Open Energy Info (EERE)

energy Product: The company will be concentrating initially on bringing an innovative composite wind tower to market. References: EU Energy (Wind) Limited1 This article is a...

469

Power Projects Limited | Open Energy Information  

Open Energy Info (EERE)

Power Projects Limited Address: PO Box 25456 Panama Street Place: Wellington Zip: 6146 Region: New Zealand Sector: Marine and Hydrokinetic Year Founded: 2001 Website: http:...

470

Unionmet Singapore Limited | Open Energy Information  

Open Energy Info (EERE)

search Name: Unionmet (Singapore) Limited Place: Singapore Zip: 68805 Product: A manufacturer and recycler of indium - a raw material for CIGS PV and also for most transparent...

471

Quantum Money from Hidden Subspaces  

E-Print Network [OSTI]

Forty years ago, Wiesner pointed out that quantum mechanics raises the striking possibility of money that cannot be counterfeited according to the laws of physics. We propose the first quantum money scheme that is (1) public-key, meaning that anyone can verify a banknote as genuine, not only the bank that printed it, and (2) cryptographically secure, under a "classical" hardness assumption that has nothing to do with quantum money. Our scheme is based on hidden subspaces, encoded as the zero-sets of random multivariate polynomials. A main technical advance is to show that the "black-box" version of our scheme, where the polynomials are replaced by classical oracles, is unconditionally secure. Previously, such a result had only been known relative to a quantum oracle (and even there, the proof was never published). Even in Wiesner's original setting -- quantum money that can only be verified by the bank -- we are able to use our techniques to patch a major security hole in Wiesner's scheme. We give the first private-key quantum money scheme that allows unlimited verifications and that remains unconditionally secure, even if the counterfeiter can interact adaptively with the bank. Our money scheme is simpler than previous public-key quantum money schemes, including a knot-based scheme of Farhi et al. The verifier needs to perform only two tests, one in the standard basis and one in the Hadamard basis -- matching the original intuition for quantum money, based on the existence of complementary observables. Our security proofs use a new variant of Ambainis's quantum adversary method, and several other tools that might be of independent interest.

Scott Aaronson; Paul Christiano

2012-09-17T23:59:59.000Z

472

Severe Limits on Variations of the Speed of Light with Frequency  

E-Print Network [OSTI]

Explosive astrophysical events at high red shift can be used to place severe limits on the fractional variation in the speed of light ($\\Delta c/c$), the photon mass ($m_{\\gamma}$), and the energy scale of quantum gravity ($E_{QG}$). I find $\\Delta c/c < 6.3 \\times 10^{-21}$ based on the simultaneous arrival of a flare in GRB 930229 with a rise time of $220 \\pm 30 \\mu s$ for photons of 30 keV and 200 keV. The limit on $m_{\\gamma}$ is $4.2 \\times 10^{-44} g$ for GRB 980703 from radio to gamma ray observations. The limit on $E_{QG}$ is $8.3 \\times 10^{16}$ GeV for GRB 930131 from 30 keV to 80 MeV photons.

Bradley E. Schaefer

1998-10-29T23:59:59.000Z

473

Holonomic Quantum Computation via Adiabatic Shortcut  

E-Print Network [OSTI]

Fast quantum gates based on geometric phases provide a platform for performing robust quantum computation. In particular, non-adiabatic holonomic quantum computation, which involves non-Abelian geometric phases to achieve universality, has recently been demonstrated in several experiments. Here, we generalize the transitionless quantum driving algorithm to a degenerate Hilbert space, with which we propose a route towards fast holonomic quantum computation. We propose a proof-of-principle experiment in a superconducting circuit architecture to realize our scheme.

J. Zhang; Thi Ha Kyaw; D. M. Tong; Erik Sjöqvist; L. C. Kwek

2014-12-09T23:59:59.000Z

474

Quantum Theory and Spacelike Measurements  

E-Print Network [OSTI]

Experimentally observed violations of Bell inequalities rule out local realistic theories. Consequently, the quantum state vector becomes a strong candidate for providing an objective picture of reality. However, such an ontological view of quantum theory faces difficulties when spacelike measurements on entangled states have to be described, because time ordering of spacelike events can change under Lorentz-Poincar\\'e transformations. In the present paper it is shown that a necessary condition for consistency is to require state vector reduction on the backward light-cone. A fresh approach to the quantum measurement problem appears feasible within such a framework.

Bernd A. Berg

1998-01-04T23:59:59.000Z

475

Quantum metrology with molecular ensembles  

SciTech Connect (OSTI)

The field of quantum metrology promises measurement devices that are fundamentally superior to conventional technologies. Specifically, when quantum entanglement is harnessed, the precision achieved is supposed to scale more favorably with the resources employed, such as system size and time required. Here, we consider measurement of magnetic-field strength using an ensemble of spin-active molecules. We identify a third essential resource: the change in ensemble polarization (entropy increase) during the metrology experiment. We find that performance depends crucially on the form of decoherence present; for a plausible dephasing model, we describe a quantum strategy, which can indeed beat the standard strategy.

Schaffry, Marcus; Gauger, Erik M. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Morton, John J. L. [CAESR, Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU (United Kingdom); Fitzsimons, Joseph [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario (Canada); Benjamin, Simon C. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Lovett, Brendon W. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2010-10-15T23:59:59.000Z

476

Quantum modulation against electromagnetic interference  

E-Print Network [OSTI]

Periodic signals in electrical and electronic equipment can cause interference in nearby devices. Randomized modulation of those signals spreads their energy through the frequency spectrum and can help to mitigate electromagnetic interference problems. The inherently random nature of quantum phenomena makes them a good control signal. I present a quantum modulation method based on the random statistics of quantum light. The paper describes pulse width modulation schemes where a Poissonian light source acts as a random control that spreads the energy of the potential interfering signals. I give an example application for switching-mode power supplies and comment the further possibilities of the method.

Juan Carlos Garcia-Escartin

2014-11-26T23:59:59.000Z

477

Planck's quantum-driven integer quantum Hall effect in chaos  

E-Print Network [OSTI]

The integer quantum Hall effect (IQHE) and chaos are commonly conceived as being unrelated. Contrary to common wisdoms, we find in a canonical chaotic system, the kicked spin-$1/2$ rotor, a Planck's quantum($h_e$)-driven phenomenon bearing a firm analogy to IQHE but of chaos origin. Specifically, the rotor's energy growth is unbounded ('metallic' phase) for a discrete set of critical $h_e$-values, but otherwise bounded ('insulating' phase). The latter phase is topological in nature and characterized by a quantum number ('quantized Hall conductance'). The number jumps by unity whenever $h_e$ decreases passing through each critical value. Our findings, within the reach of cold-atom experiments, indicate that rich topological quantum phenomena may emerge from chaos.

Yu Chen; Chushun Tian

2014-09-18T23:59:59.000Z

478

Quantum walks and quantum search on graphene lattices  

E-Print Network [OSTI]

Quantum walks have been very successful in the development of search algorithms in quantum information, in particular in the development of spatial search algorithms. However, the construction of continuous-time quantum search algorithms in two-dimensional lattices has proved difficult, requiring additional degrees of freedom. Here, we demonstrate that continuous-time quantum walk search is possible in two-dimensions by changing the search topology to a graphene lattice, utilising the Dirac point in the energy spectrum. This is made possible by making a change to standard methods of marking a particular site in the lattice. Various ways of marking a site are shown to result in successful search protocols. We further establish that the search can be adapted to transfer probability amplitude across the lattice between specific lattice sites thus establishing a line of communication between these sites.

Iain Foulger; Sven Gnutzmann; Gregor Tanner

2015-01-29T23:59:59.000Z

479

Quantum Coherence Effects in Novel Quantum Optical Systems  

E-Print Network [OSTI]

Optical response of an active medium can substantially be modified when coherent superpositions of states are excited, that is, when systems display quantum coherence and interference. This has led to fascinating applications in atomic and molecular...

Sete, Eyob Alebachew

2012-10-19T23:59:59.000Z

480

Digital quantum simulation of fermionic models with a superconducting circuit  

E-Print Network [OSTI]

Simulating quantum physics with a device which itself is quantum mechanical, a notion Richard Feynman originated, would be an unparallelled computational resource. However, the universal quantum simulation of fermionic systems is daunting due to their particle statistics, and Feynman left as an open question whether it could be done, because of the need for non-local control. Here, we implement fermionic interactions with digital techniques in a superconducting circuit. Focusing on the Hubbard model, we perform time evolution with constant interactions as well as a dynamic phase transition with up to four fermionic modes encoded in four qubits. The implemented digital approach is universal and allows for the efficient simulation of fermions in arbitrary spatial dimensions. We use in excess of 300 single-qubit and two-qubit gates, and reach global fidelities which are limited by gate errors. This demonstration highlights the feasibility of the digital approach and opens a viable route towards analog-digital quantum simulation of interacting fermions and bosons in large-scale solid state systems.

R. Barends; L. Lamata; J. Kelly; L. García-Álvarez; A. G. Fowler; A. Megrant; E. Jeffrey; T. C. White; D. Sank; J. Y. Mutus; B. Campbell; Yu Chen; Z. Chen; B. Chiaro; A. Dunsworth; I. -C. Hoi; C. Neill; P. J. J. O'Malley; C. Quintana; P. Roushan; A. Vainsencher; J. Wenner; E. Solano; John M. Martinis

2015-01-30T23:59:59.000Z

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481

Fiber-based cryogenic and time-resolved spectroscopy of PbS quantum dots  

E-Print Network [OSTI]

PbS quantum dots are promising active emitters for use with high-quality Si nanophotonic devices in the telecommunications-band. Measurements of low quantum dot densities are limited both because of low fluorescence levels and the challenges of single photon detection at these wavelengths. Here, we report on methods using a fiber taper waveguide to efficiently extract PbS quantum dot photoluminescence. Temperature dependent ensemble measurements reveal an increase in emitted photons concomitant with an increase in excited-state lifetime from 58.9 ns at 293 K to 657 ns at 40 K. Measurements are also performed on quantum dots on high-$Q$ ($>10^5$) microdisks using cavity-resonant, pulsed excitation.

Matthew T. Rakher; Ranojoy Bose; Chee Wei Wong; Kartik Srinivasan

2010-12-01T23:59:59.000Z

482

Efficient and accurate surface hopping for long time nonadiabatic quantum dynamics  

E-Print Network [OSTI]

The quantum-classical Liouville equation offers a rigorous approach to nonadiabatic quantum dynamics based on surface hopping type trajectories. However, in practice the applicability of this approach has been limited to short times owing to unfavorable numerical scaling. In this paper we show that this problem can be alleviated by combining it with a formally exact generalized quantum master equation treatment. This allows dramatic improvements in the efficiency of the approach in nonadiabatic regimes, making it computationally tractable to treat the quantum dynamics of complex systems for long times. We demonstrate our approach by applying it to a model of condensed phase charge transfer where our method is shown to be numerically exact in regimes where fewest-switches surface hopping and mean field approaches fail to obtain the either the correct rates or long-time populations.

Aaron Kelly; Thomas E. Markland

2015-01-13T23:59:59.000Z

483

Density matrix and dynamical aspects of Quantum Mechanics with Fundamental Length  

E-Print Network [OSTI]

In this paper Quantum Mechanics with Fundamental Length is built as a deformation of Quantum Mechanics. To this aim an approach is used which does not take into account commutator deformation as usually it is done, but density matrix deformation. The corresponding deformed density matrix, which is called density pro-matrix is given explicitly. It properties have been investigated as well as some dynamical aspects of the theory. In particular, the deformation of Liouville equation is analyzed in detail. It was shown that Liouville equation in Quantum Mechanics appears as a low energy limit of deformed Liouville equation in Quantum Mechanics with Fundamental Length. Some implications of obtained results are presented as well as their application to the calculation of black hole entropy.

A. E. Shalyt-Margolin; J. G. Suarez

2002-11-25T23:59:59.000Z

484

Direct high-resolution characterization of quantum correlations via classical measurements  

E-Print Network [OSTI]

Quantum optics plays a central role in the study of fundamental concepts in quantum mechanics, and in the development of new technological applications. Typical experiments employ non-classical light, such as entangled photons, generated by parametric processes. The standard characterization of the sources by quantum tomography, which relies on detecting the pairs themselves and thus requires single photon detectors, limits both measurement speed and accuracy. Here we show that the spectral characterization of the quantum correlations generated by two-photon sources can be directly performed classically with an unprecedented spectral resolution. This streamlined technique has the potential to speed up design and testing of massively parallel integrated sources by providing a fast and reliable quality control procedure. Adapting our method to explore other degrees of freedom would allow the complete characterization of biphoton states generated by parametric processes.

Andreas Eckstein; Guillaume Boucher; Aristide Lemaître; Pascal Filloux; Ivan Favero; Giuseppe Leo; John E. Sipe; Marco Liscidini; Sara Ducci

2013-12-15T23:59:59.000Z

485

Quantum Optical Systems for the Implementation of Quantum Information Processing  

E-Print Network [OSTI]

We review the field of Quantum Optical Information from elementary considerations through to quantum computation schemes. We illustrate our discussion with descriptions of experimental demonstrations of key communication and processing tasks from the last decade and also look forward to the key results likely in the next decade. We examine both discrete (single photon) type processing as well as those which employ continuous variable manipulations. The mathematical formalism is kept to the minimum needed to understand the key theoretical and experimental results.

T. C. Ralph

2006-09-06T23:59:59.000Z

486

6.728 Applied Quantum and Statistical Physics, Fall 2002  

E-Print Network [OSTI]

Elementary quantum mechanics and statistical physics. Introduces applied quantum physics. Emphasizes experimental basis for quantum mechanics. Applies Schrodinger's equation to the free particle, tunneling, the harmonic ...

Bulovic, Vladimir, 1970-

487

Quantum cryptography put to work for electric grid security  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Quantum cryptography put to work Quantum cryptography put to work for electric grid security LANL's quantum cryptography team successfully completed the first-ever demonstration of...

488

Shiny quantum dots brighten future of solar cells  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Shiny quantum dots brighten future of solar cells Shiny quantum dots brighten future of solar cells The project demonstrates that superior light-emitting properties of quantum dots...

489

Optimal tunneling enhances the quantum photovoltaic effect in double quantum dots  

E-Print Network [OSTI]

We investigate the quantum photovoltaic effect in double quantum dots by applying the nonequilibrium quantum master equation. A drastic suppression of the photovoltaic current is observed near the open circuit voltage, ...

Wang, Chen

490

The Time Evolution of Quantum Universe in The Quantum Potential Picture  

E-Print Network [OSTI]

We use the quantum potential approach to analyse the quantum cosmological model of the universe. The quantum potential arises from exact solutions of the full Wheeler-De Witt equation.

A. Blaut; J. Kowalski-Glikman

1997-10-31T23:59:59.000Z

491

Scalable quantum computer architecture with coupled donor-quantum dot qubits  

DOE Patents [OSTI]

A quantum bit computing architecture includes a plurality of single spin memory donor atoms embedded in a semiconductor layer, a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, wherein a first voltage applied across at least one pair of the aligned quantum dot and donor atom controls a donor-quantum dot coupling. A method of performing quantum computing in a scalable architecture quantum computing apparatus includes arranging a pattern of single spin memory donor atoms in a semiconductor layer, forming a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, applying a first voltage across at least one aligned pair of a quantum dot and donor atom to control a donor-quantum dot coupling, and applying a second voltage between one or more quantum dots to control a Heisenberg exchange J coupling between quantum dots and to cause transport of a single spin polarized electron between quantum dots.

Schenkel, Thomas; Lo, Cheuk Chi; Weis, Christoph; Lyon, Stephen; Tyryshkin, Alexei; Bokor, Jeffrey

2014-08-26T23:59:59.000Z

492

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 descrip...

Fried, H M

2007-01-01T23:59:59.000Z

493

Principles of Quantum Universe  

E-Print Network [OSTI]

The present monograph is devoted to the theory of gravitation derived consequently as joint nonlinear realization of conformal and affine symmetries by means of Cartan differential forms. In the framework of the joint nonlinear realization of conformal and affine symmetries the interpretation of the last cosmological observational data of Ia Supernovae, anisotropy of the primordial radiation temperature and the mass spectrum of electroweak bosons, including the Higgs particle mass in the expected region ~ 125 GeV, is given. All these observational and experimental data testify to the vacuum energy dominance. The vacuum Casimir energy is a source of intensive cosmological quantum creation gravitons and electroweak bosons including Higgs particles from the empty Universe during the first 10^(-12) sec. The products of decay of the electroweak bosons give the matter content of the present day Universe, including primordial radiation and its baryon asymmetry.

V. N. Pervushin; A. E. Pavlov

2014-02-03T23:59:59.000Z

494

Quantum Non-Objectivity from Performativity of Quantum Phenomena  

E-Print Network [OSTI]

We analyze the logical foundations of quantum mechanics (QM) by stressing non-objectivity of quantum observables which is a consequence of the absence of logical atoms in QM. We argue that the matter of quantum non-objectivity is that, on the one hand, the formalism of QM constructed as a mathematical theory is self-consistent, but, on the other hand, quantum phenomena as results of experimenter's performances are not self-consistent. This self-inconsistency is an effect of that the langu