National Library of Energy BETA

Sample records for ultimate quantum limit

  1. Shear wall ultimate drift limits

    SciTech Connect (OSTI)

    Duffey, T.A.; Goldman, A.; Farrar, C.R.

    1994-04-01

    Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.

  2. The ultimate downscaling limit of FETs.

    SciTech Connect (OSTI)

    Mamaluy, Denis; Gao, Xujiao; Tierney, Brian David

    2014-10-01

    We created a highly efficient, universal 3D quant um transport simulator. We demonstrated that the simulator scales linearly - both with the problem size (N) and number of CPUs, which presents an important break-through in the field of computational nanoelectronics. It allowed us, for the first time, to accurately simulate and optim ize a large number of realistic nanodevices in a much shorter time, when compared to other methods/codes such as RGF[~N 2.333 ]/KNIT, KWANT, and QTBM[~N 3 ]/NEMO5. In order to determine the best-in-class for different beyond-CMOS paradigms, we performed rigorous device optimization for high-performance logic devices at 6-, 5- and 4-nm gate lengths. We have discovered that there exists a fundamental down-scaling limit for CMOS technology and other Field-Effect Transistors (FETs). We have found that, at room temperatures, all FETs, irre spective of their channel material, will start experiencing unacceptable level of thermally induced errors around 5-nm gate lengths.

  3. Shear wall ultimate drift limits for PRA applications

    SciTech Connect (OSTI)

    Duffey, T.A. [New Mexico Highlands Univ., Las Vegas, NM (United States); Farrar, C.R.; Goldman, A. [Los Alamos National Lab., NM (United States)

    1995-03-01

    Drift limits for reinforced concrete shear walls are investigated by reviewing the technical literature for appropriate experimental data. Based on the geometry of actual nuclear power plant structures (exclusive of containments) and concerns regarding their response during seismic loading, data are obtained from pertinent references where the wall aspect ratio is less than or equal to approximately 1, and for which the loading is cyclic. Lateral deflections at ultimate load, and at points in the softening region beyond ultimate, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of these statistics to estimate Probability of Failure for a shear wall structure is illustrated.

  4. Generalized Geometric Quantum Speed Limits

    E-Print Network [OSTI]

    Diego Paiva Pires; Marco Cianciaruso; Lucas C. Céleri; Gerardo Adesso; Diogo O. Soares-Pinto

    2015-09-30

    The attempt to gain a theoretical understanding of the concept of time in quantum mechanics has triggered significant progress towards the search for faster and more efficient quantum technologies. One of such advances consists in the interpretation of the time-energy uncertainty relations as lower bounds for the minimal evolution time between two distinguishable states of a quantum system, also known as quantum speed limits. We investigate how the non uniqueness of a bona fide measure of distinguishability defined on the quantum state space affects the quantum speed limits and can be exploited in order to derive improved bounds. Specifically, we establish an infinite family of quantum speed limits valid for unitary and nonunitary evolutions, based on an elegant information geometric formalism. Our work unifies and generalizes existing results on quantum speed limits, and provides instances of novel bounds which are tighter than any established one based on the conventional quantum Fisher information. We illustrate our findings with relevant examples, clarifying the role of classical populations versus quantum coherences in the determination and saturation of the speed limits. Our results can find applications in the optimization and control of quantum technologies such as quantum computation and metrology, and might provide new insights in fundamental investigations of quantum thermodynamics.

  5. Quantum Limits of Thermometry

    E-Print Network [OSTI]

    Thomas M. Stace

    2010-06-08

    The precision of typical thermometers consisting of $N$ particles is shot noise limited, improving as $\\sim1/\\sqrt{N}$. For high precision thermometry and thermometric standards this presents an important theoretical noise floor. Here it is demonstrated that thermometry may be mapped onto the problem of phase estimation, and using techniques from optimal phase estimation, it follows that the scaling of the precision of a thermometer may in principle be improved to $\\sim1/N$, representing a Heisenberg limit to thermometry.

  6. Finding Ultimate Limits of Performance for Hybrid Electric Edward D. Tate

    E-Print Network [OSTI]

    in a pure series hybrid vehicle over a fixed drive cycle subject to a number of practical constraints the given drive cycle. This optimal solution is the lower limit of fuel consumption that any control law can achieve for the given drive cycle and vehicle. In fact, this result provides a means to evaluate

  7. Quantum Computation--The Ultimate Frontier Chris Adami and Jonathan P. Dowling

    E-Print Network [OSTI]

    Dowling, Jonathan P.

    Technologies Group Jet Propulsion Laboratory MS 126-347, California Institute of Technology, Pasadena, CA 91109 of a polynomial quantum factoring algorithm would almost certainly have led us to that discovery. The "power to wave functions, not to individual objects. In classical mechanics, we do not usually make a distinction

  8. Polymer Quantum Mechanics and its Continuum Limit

    E-Print Network [OSTI]

    Alejandro Corichi; Tatjana Vukasinac; Jose A. Zapata

    2007-08-22

    A rather non-standard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle and a simple cosmological model.

  9. Quantum Cryptography Approaching the Classical Limit

    E-Print Network [OSTI]

    Weedbrook, Christian

    We consider the security of continuous-variable quantum cryptography as we approach the classical limit, i.e., when the unknown preparation noise at the sender’s station becomes significantly noisy or thermal (even by as ...

  10. Fundamental limitations for quantum and nano thermodynamics

    E-Print Network [OSTI]

    Micha? Horodecki; Jonathan Oppenheim

    2014-10-25

    The relationship between thermodynamics and statistical physics is valid in the thermodynamic limit - when the number of particles becomes very large. Here, we study thermodynamics in the opposite regime - at both the nano scale, and when quantum effects become important. Applying results from quantum information theory we construct a theory of thermodynamics in these limits. We derive general criteria for thermodynamical state transformations, and as special cases, find two free energies: one that quantifies the deterministically extractable work from a small system in contact with a heat bath, and the other that quantifies the reverse process. We find that there are fundamental limitations on work extraction from nonequilibrium states, owing to finite size effects and quantum coherences. This implies that thermodynamical transitions are generically irreversible at this scale. As one application of these methods, we analyse the efficiency of small heat engines and find that they are irreversible during the adiabatic stages of the cycle.

  11. Limits in high efficiency quantum frequency conversion

    E-Print Network [OSTI]

    Nicolás Quesada; J. E. Sipe

    2015-08-13

    Frequency conversion is an enabling process in many quantum information protocols. In this letter we study fundamental limits to high efficiency frequency conversion imposed by time ordering corrections. Using the Magnus expansion, we argue that these corrections, which are usually considered detrimental, can be used to increase the efficiency of conversion under certain circumstances. The corrections induce a nonlinear behaviour in the probability of upconversion as a function of the pump intensity, significantly modifying the sinusoidal Rabi oscillations that are otherwise expected. Finally, by using a simple scaling argument, we explain why cascaded frequency conversion devices attenuate time ordering corrections, allowing the construction of near ideal quantum pulse gates.

  12. Quantum Limits of Measurements and Uncertainty Principle

    E-Print Network [OSTI]

    Masanao Ozawa

    2015-05-19

    In this paper, we show how the Robertson uncertainty relation gives certain intrinsic quantum limits of measurements in the most general and rigorous mathematical treatment. A general lower bound for the product of the root-mean-square measurement errors arising in joint measurements of noncommuting observables is established. We give a rigorous condition for holding of the standard quantum limit (SQL) for repeated measurements, and prove that if a measuring instrument has no larger root-mean-square preparational error than the root-mean-square measurement errors then it obeys the SQL. As shown previously, we can even construct many linear models of position measurement which circumvent this condition for the SQL.

  13. Ultimate Energy Densities for Electromagnetic Pulses

    E-Print Network [OSTI]

    Mankei Tsang

    2008-03-06

    The ultimate electric and magnetic energy densities that can be attained by bandlimited electromagnetic pulses in free space are calculated using an ab initio quantized treatment, and the quantum states of electromagnetic fields that achieve the ultimate energy densities are derived. The ultimate energy densities also provide an experimentally accessible metric for the degree of localization of polychromatic photons.

  14. Standard Quantum Limit for Probing Mechanical Energy Quantization

    E-Print Network [OSTI]

    Corbitt, Thomas R.

    We derive a standard quantum limit for probing mechanical energy quantization in a class of systems with mechanical modes parametrically coupled to external degrees of freedom. To resolve a single mechanical quantum, it ...

  15. Quantum nonlocality with arbitrary limited detection efficiency

    E-Print Network [OSTI]

    Gilles Pütz; Nicolas Gisin

    2015-07-17

    The demonstration and use of nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detector inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only way to avoid this is to have detection efficiencies that are above a certain threshold. We introduce the intermediate assumption of limited detection efficiency, e.g. in each run of the experiment the overall detection efficiency is lower bounded by $\\eta_{min} > 0$. Hence, in an adversarial scenario, the adversaries have arbitrary large but not full control over the inefficiencies. We analyze the set of possible correlations that fulfil Limited Detection Locality (LDL) and show that they necessarily satisfy some linear Bell-like inequalities. We prove that quantum theory predicts violation of one of these inequalities for all $\\eta_{min} > 0$. Hence, nonlocality can be demonstrated with arbitrarily small limited detection efficiencies. Finally we propose a generalized scheme that uses this characterization to deal with detection inefficiencies, which interpolates between the two usual schemes, postselection and outcome assignment.

  16. Multivariate Central Limit Theorem in Quantum Dynamics

    E-Print Network [OSTI]

    Simon Buchholz; Chiara Saffirio; Benjamin Schlein

    2013-09-06

    We consider the time evolution of $N$ bosons in the mean field regime for factorized initial data. In the limit of large $N$, the many body evolution can be approximated by the non-linear Hartree equation. In this paper we are interested in the fluctuations around the Hartree dynamics. We choose $k$ self-adjoint one-particle operators $O_1, \\dots, O_k$ on $L^2 (\\R^3)$, and we average their action over the $N$-particles. We show that, for every fixed $t \\in \\R$, expectations of products of functions of the averaged observables approach, as $N \\to \\infty$, expectations with respect to a complex Gaussian measure, whose covariance matrix can be expressed in terms of a Bogoliubov transformation describing the dynamics of quantum fluctuations around the mean field Hartree evolution. If the operators $O_1, \\dots, O_k$ commute, the Gaussian measure is real and positive, and we recover a "classical" multivariate central limit theorem. All our results give explicit bounds on the rate of the convergence (we obtain therefore Berry-Ess{\\'e}en type central limit theorems).

  17. Anisotropic Fermi Surface and Quantum Limit Transport in High...

    Office of Scientific and Technical Information (OSTI)

    Anisotropic Fermi Surface and Quantum Limit Transport in High Mobility Three-Dimensional Dirac Semimetal Cd 3 As 2 Citation Details In-Document Search Title: Anisotropic Fermi...

  18. Cooling at the quantum limit and RF refrigeration

    E-Print Network [OSTI]

    Fominov, Yakov

    Cooling at the quantum limit and RF refrigeration Jukka Pekola Low Temperature Laboratory, Helsinki (electromagnetic) heat transport Cooling at the quantum limit: experiments RF refrigeration in a single as a refrigerator Optimum cooling power is reached at V 2/e: Cooling power of a NIS junction: Temperature TN

  19. Testing the limits of quantum mechanical superpositions

    E-Print Network [OSTI]

    Markus Arndt; Klaus Hornberger

    2014-10-01

    Quantum physics has intrigued scientists and philosophers alike, because it challenges our notions of reality and locality--concepts that we have grown to rely on in our macroscopic world. It is an intriguing open question whether the linearity of quantum mechanics extends into the macroscopic domain. Scientific progress over the last decades inspires hope that this debate may be decided by table-top experiments.

  20. Superconducting quantum interference device as a near-quantum-limited amplifier at 0.5 GHz

    E-Print Network [OSTI]

    Le Roy, Robert J.

    Superconducting quantum interference device as a near-quantum-limited amplifier at 0.5 GHz Michael 94720 Received 10 October 2000; accepted for publication 14 December 2000 A dc superconducting quantum, for example, superconducting transition-edge sensors for infrared, optical, and ultraviolet wavelengths,2

  1. Subdiffraction-limited quantum imaging within a living cell

    E-Print Network [OSTI]

    Michael A. Taylor; Jiri Janousek; Vincent Daria; Joachim Knittel; Boris Hage; Hans-A. Bachor; Warwick P. Bowen

    2014-02-05

    We report both sub-diffraction-limited quantum metrology and quantum enhanced spatial resolution for the first time in a biological context. Nanoparticles are tracked with quantum correlated light as they diffuse through an extended region of a living cell in a quantum enhanced photonic force microscope. This allows spatial structure within the cell to be mapped at length scales down to 10 nm. Control experiments in water show a 14% resolution enhancement compared to experiments with coherent light. Our results confirm the longstanding prediction that quantum correlated light can enhance spatial resolution at the nanoscale and in biology. Combined with state-of-the-art quantum light sources, this technique provides a path towards an order of magnitude improvement in resolution over similar classical imaging techniques.

  2. Discrimination of quantum observables using limited resources

    E-Print Network [OSTI]

    Mario Ziman; Teiko Heinosaari

    2008-02-18

    We address the problem of unambiguous discrimination and identification among quantum observables. We set a general framework and investigate in details the case of qubit observables. In particular, we show that perfect discrimination with two shots is possible only for sharp qubit observables (e.g. Stern-Gerlach apparatuses) associated with mutually orthogonal directions. We also show that for sharp qubit observables associated to nonorthogonal directions unambiguous discrimination with an inconclusive result is always possible.

  3. 2010 Macmillan Publishers Limited. All rights reserved. Towards quantum chemistry on a quantum computer

    E-Print Network [OSTI]

    White, Andrew G.

    © 2010 Macmillan Publishers Limited. All rights reserved. Towards quantum chemistry on a quantum computer B. P. Lanyon1,2 *, J. D. Whitfield4, G. G. Gillett1,2, M. E. Goggin1,5, M. P. Almeida1,2, I their computational cost grows exponentially with both the number of atoms and basis set size. A solution is to move

  4. Thermal Quantum Speed Limit for Classical-Driving Open Systems

    E-Print Network [OSTI]

    Wenjiong Wu; Kai Yan; Xiang Hao

    2015-10-21

    Quantum speed limit (QSL) time for open systems driven by classical fields is studied in the presence of thermal bosonic environments. The decoherence process is quantitatively described by the time-convolutionless master equation. The evolution speed of an open system is related not only to the strength of driving classical field but also to the environmental temperature. The energy-state population plays a key role in the thermal QSL. Comparing with the zero-temperature reservoir, we predict that the structural reservoir at low temperatures may contribute to the acceleration of quantum decoherence. The manifest oscillation of QSL time takes on under the circumstance of classical driving fields. We also investigate the scaling property of QSL time for multi-particle noninteracting entangled systems. It is demonstrated that entanglement of open systems can be considered as one resource for improving the potential capacity of thermal quantum speedup.

  5. Realization of Measurement and the Standard Quantum Limit

    E-Print Network [OSTI]

    Masanao Ozawa

    2015-05-05

    This paper, following [M. Ozawa, Phys. Rev. Lett. 60, 385 (1988)], reports a refutation of the claim that for monitoring the position of a free mass such as gravitational-wave interferometers the sensitivity is limited by the so called standard quantum limit (SQL) due to the uncertainty principle. The latest proof of the SQL is analyzed to revleal an unsupported assumption on quantum measurements. Quantum measurement theory is introduced to give a general criterion for physically realizable measurements in quantum mechanics. A theory of approximate position measurements is developed to obtain a rigorous condition for the SQL and also to show that a precise position measurement can leave the object in an arbitrary family of states independent of the input state. This concludes that Yuen's proposal of breaking the SQL by a contractive state measurement, a measurement of the position leaving the free mass in a state with the position uncertainty decreasing in time, is physically realizable in principle. To enforce this conclusion, a model for error-free position measurement that leaves the object in a contractive state is constructed with a solvable Hamiltonian for measuring interaction. Finally, this model is shown to break the SQL with arbitrary accuracy.

  6. The Weak-Coupling Limit of Simplicial Quantum Gravity

    E-Print Network [OSTI]

    G. Thorleifsson; P. Bialas; B. Petersson

    1998-12-23

    In the weak-coupling limit, kappa_0 going to infinity, the partition function of simplicial quantum gravity is dominated by an ensemble of triangulations with the ratio N_0/N_D close to the upper kinematic limit. For a combinatorial triangulation of the D--sphere this limit is 1/D. Defining an ensemble of maximal triangulations, i.e. triangulations that have the maximal possible number of vertices for a given volume, we investigate the properties of this ensemble in three dimensions using both Monte Carlo simulations and a strong-coupling expansion of the partition function, both for pure simplicial gravity and a with a suitable modified measure. For the latter we observe a continuous phase transition to a crinkled phase and we investigate the fractal properties of this phase.

  7. Private Database Queries Using Quantum States with Limited Coherence Times

    E-Print Network [OSTI]

    Tad Hogg; Li Zhang

    2009-03-31

    We describe a method for private database queries using exchange of quantum states with bits encoded in mutually incompatible bases. For technology with limited coherence time, the database vendor can announce the encoding after a suitable delay to allow the user to privately learn one of two items in the database without the ability to also definitely infer the second item. This quantum approach also allows the user to choose to learn other functions of the items, such as the exclusive-or of their bits, but not to gain more information than equivalent to learning one item, on average. This method is especially useful for items consisting of a few bits by avoiding the substantial overhead of conventional cryptographic approaches.

  8. Free fall onto evaporating black holes at the quantum limit

    E-Print Network [OSTI]

    Maurice H. P. M. van Putten

    2015-11-11

    Black hole space times evaporate in discrete steps due to remarkably slow Hawking radiation. We here identify evaporation with essentially extremal states at the limit of quantum computation, performing $2.7\\times 10^{79}$ bit calculations per photon emission in a one solar mass black hole. During evaporation, particles in free fall co-evolve satisfying $EM=$constant, where $E$ and $M$ denote the total mass energy-at-infinity of the particle and, respectively, black hole. Particles are hereby increasingly entangled with the black hole space-time over the course of its evaporation.

  9. Absolute Dynamical Limit to Cooling Weakly-Coupled Quantum Systems

    E-Print Network [OSTI]

    X. Wang; Sai Vinjanampathy; Frederick W. Strauch; Kurt Jacobs

    2012-05-15

    Cooling of a quantum system is limited by the size of the control forces that are available (the "speed" of control). We consider the most general cooling process, albeit restricted to the regime in which the thermodynamics of the system is preserved (weak coupling). Within this regime, we further focus on the most useful control regime, in which a large cooling factor, and good ground-state cooling can be achieved. We present a control protocol for cooling, and give clear structural arguments, as well as strong numerical evidence, that this protocol is globally optimal. From this we obtain simple expressions for the limit to cooling that is imposed by the speed of control.

  10. Reaching the quantum limit of sensitivity in electron spin resonance

    E-Print Network [OSTI]

    A. Bienfait; J. J. Pla; Y. Kubo; M. Stern; X. Zhou; C. C. Lo; C. D. Weis; T. Schenkel; M. L. W. Thewalt; D. Vion; D. Esteve; B. Julsgaard; K. Moelmer; J. J. L. Morton; P. Bertet

    2015-07-24

    We report pulsed electron-spin resonance (ESR) measurements on an ensemble of Bismuth donors in Silicon cooled at 10mK in a dilution refrigerator. Using a Josephson parametric microwave amplifier combined with high-quality factor superconducting micro-resonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly 4 orders of magnitude. We demonstrate the detection of 1700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise (SNR) ratio, reduced to just 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance.

  11. Dark Energy and Life's Ultimate Future

    E-Print Network [OSTI]

    Ruediger Vaas

    2007-03-19

    The discovery of the present accelerated expansion of space changed everything regarding cosmology and life's ultimate prospects. Both the optimistic scenarios of an ever (but decelerated) expanding universe and of a collapsing universe seem to be no longer available. The final future looks deadly dark. However, the fate of the universe and intelligence depends crucially on the nature of the still mysterious dark energy which drives the accelerated expansion. Depending on its - perhaps time-dependent - equation of state, there is a confusing number of different models now, popularly called Big Rip, Big Whimper, Big Decay, Big Crunch, Big Brunch, Big Splat, etc. This paper briefly reviews possibilities and problems. It also argues that even if our universe is finally doomed, perhaps that doesn't matter ultimately because there might be some kind of eternal recurrence. - Key words: Cosmology, Universe, Dark Energy, Cosmological Constant, Quintessence, Phantom Energy, Inflation, Quantum Gravity, Far Future, Life, Intelligence

  12. Conditional cooling limit for a quantum channel going through an incoherent environment

    E-Print Network [OSTI]

    Ivo Straka; Martina Miková; Michal Mi?uda; Miloslav Dušek; Miroslav Ježek; Radim Filip

    2015-11-24

    We propose and experimentally verify a cooling limit for a quantum channel going through an incoherent environment. The environment consists of a large number of independent non-interacting and non-interfering elementary quantum systems - qubits. The qubits travelling through the channel can only be randomly replaced by environmental qubits. We investigate a conditional cooling limit that exploits an additional probing output. The limit specifies when the single-qubit channel is quantum, i.e. it preserves entanglement. It is a fundamental condition for entanglement-based quantum technology.

  13. Limits on classical communication from quantum entropy power inequalities

    E-Print Network [OSTI]

    Robert Koenig; Graeme Smith

    2012-05-22

    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.

  14. Minimal evolution time and quantum speed limit of non-Markovian open systems

    E-Print Network [OSTI]

    Xiangyi Meng; Chengjun Wu; Hong Guo

    2015-10-01

    We derive a sharp bound as the quantum speed limit (QSL) for the minimal evolution time of quantum open systems in the non-Markovian strong-coupling regime with initial mixed states by considering the effects of both renormalized Hamiltonian and dissipator. For a non-Markovian quantum open system, the possible evolution time between two arbitrary states is not unique, among the set of which we find that the minimal one and its QSL can decrease more steeply by adjusting the coupling strength of the dissipator, which thus provides potential improvements of efficiency in many quantum physics and quantum information areas.

  15. Towards fully quantum second laws of thermodynamics: limitations on the evolution of quantum coherences

    E-Print Network [OSTI]

    Piotr ?wikli?ski; Micha? Studzi?ski; Micha? Horodecki; Jonathan Oppenheim

    2015-11-19

    The second law of thermodynamics places a limitation into which states a system can evolve into. For systems in contact with a heat bath, it can be combined with the law of energy conservation, and it says that a system can only evolve into another if the free energy goes down. Recently, it's been shown that there are actually many second laws, and that it is only for large macroscopic systems that they all become equivalent to the ordinary one. These additional second laws also hold for quantum systems, and are, in fact, often more relevant in this regime. They place a restriction on how the probabilities of energy levels can evolve. Here, we consider additional restrictions on how the coherences between energy levels can evolve. Coherences can only go down, and we provide a set of restrictions which limit the extent to which they can be maintained. We find that coherences over energy levels must decay at rates that are suitably adapted to the transition rates between energy levels. We show that the limitations are matched in the case of a single qubit, in which case we obtain the full characterization of state-to-state transformations. For higher dimensions, we conjecture that more severe constraints exist. We also introduce a new class of thermodynamical operations which allow for greater manipulation of coherences and study its power with respect to a class of operations known as thermal operations.

  16. Quantum spatial-periodic harmonic model for daily price-limited stock markets

    E-Print Network [OSTI]

    Meng, Xiangyi; Xu, Jingjing; Guo, Hong

    2015-01-01

    We investigate the behavior of stocks in daily price-limited stock markets by purposing a quantum spatial-periodic harmonic model. The stock price is presumed to oscillate and damp in a quantum spatial-periodic harmonic oscillator potential well. Complicated non-linear relations including inter-band positive correlation and intra-band negative correlation between the volatility and the trading volume of stocks are derived by considering the energy band structure of the model. The validity of price limitation is then examined and abnormal phenomena of a price-limited stock market (Shanghai Stock Exchange) of China are studied by applying our quantum model.

  17. Quantum-projection-noise-limited interferometry with coherent atoms in a Ramsey-type setup

    SciTech Connect (OSTI)

    Doering, D.; McDonald, G.; Debs, J. E.; Figl, C.; Altin, P. A.; Bachor, H.-A.; Robins, N. P.; Close, J. D. [Australian Research Council Centre of Excellence for Quantum-Atom Optics, Australian National University, Canberra, 0200 (Australia); Department of Quantum Science, Research School of Physics and Engineering, Australian National University, Canberra, 0200 (Australia)

    2010-04-15

    Every measurement of the population in an uncorrelated ensemble of two-level systems is limited by what is known as the quantum projection noise limit. Here, we present quantum-projection-noise-limited performance of a Ramsey-type interferometer using freely propagating coherent atoms. The experimental setup is based on an electro-optic modulator in an inherently stable Sagnac interferometer, optically coupling the two interfering atomic states via a two-photon Raman transition. Going beyond the quantum projection noise limit requires the use of reduced quantum uncertainty (squeezed) states. The experiment described demonstrates atom interferometry at the fundamental noise level and allows the observation of possible squeezing effects in an atom laser, potentially leading to improved sensitivity in atom interferometers.

  18. Towards fully quantum second laws of thermodynamics: limitations on the evolution of quantum coherences

    E-Print Network [OSTI]

    Piotr ?wikli?ski; Micha? Studzi?ski; Micha? Horodecki; Jonathan Oppenheim

    2015-01-30

    The second law of thermodynamics places a limitation on what states a system can evolve into. For closed systems, it says that a state can be transformed into another state, only if the course grained entropy increases. For systems in contact with a heat bath, it can be combined with the law of energy conservation, and it says that a system can only evolve into another if the free energy goes down. Here, the free energy is written in terms of the fine-grained entropy. Recently, it's been shown that there are actually many second laws, and that it is only for large macroscopic systems that they all become equivalent to the ordinary one. These additional second laws also hold for quantum systems, and are in fact, often more relevant in this regime. They place a restriction on how the probabilities of energy levels can evolve. Here, we consider additional restrictions on how the coherences between energy levels can evolve. Coherences can only go down, and we provide a set of restrictions which limit the extent to which they can be maintained. We find that coherences over energy levels must decay at rates that are suitably adapted to the transition rates between energy levels. We show that the limitations are matched in the case of single qubit, in which case we obtain the full characterization of state-to-state transformations. For higher dimensions, we conjecture more severe constraints exist. The results are obtained in the paradigm of Thermal Operations, and we introduce a new class of thermodynamical operations which allow for greater manipulation of coherences and study its power with respect to Thermal Operations.

  19. Laser cooling of a micromechanical membrane to the quantum backaction limit

    E-Print Network [OSTI]

    Peterson, R W; Kampel, N S; Andrews, R W; Yu, P -L; Lehnert, K W; Regal, C A

    2015-01-01

    The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator. In understanding the quantum limits of this cooling, one must consider the effect of shot noise fluctuations on the final thermal occupation. In optomechanical sideband cooling in a cavity, the finite Stokes Raman scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work we sideband cool to the quantum backaction limit by using a micromechanical membrane precooled in a dilution refrigerator. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath.

  20. Effects of Quantum Confinement on the Doping Limit of Semiconductor

    E-Print Network [OSTI]

    Wu, Junqiao

    . The magnitude of this effect in a given material is found to be determined by two material properties of semiconductor nanostructures in terms of their fundamental material parameters. Doping limits in various bulk are generated in semiconductor materials in response to extrinsic doping so as to pull EF back toward EFS

  1. Quasi-static Limits in Nonrelativistic Quantum Electrodynamics

    E-Print Network [OSTI]

    L. Tenuta

    2008-01-10

    We consider a system of N nonrelativistic particles of spin 1/2 interacting with the quantized Maxwell field (mass zero and spin one) in the limit when the particles have a small velocity, imposing to the interaction an ultraviolet cutoff, but no infrared cutoff. Two ways to implement the limit are considered: c going to infinity with the velocity v of the particles fixed, the case for which rigorous results have already been discussed in the literature, and v going to 0 with c fixed. The second case can be rephrased as the limit of heavy particles, m_{j} --> epsilon^{-2}m_{j}, observed over a long time, t --> epsilon^{-1}t, epsilon --> 0^{+}, with kinetic energy E_{kin} = Or(1). Focusing on the second approach we construct subspaces which are invariant for the dynamics up to terms of order epsilon sqrt{log(epsilon^{-1})} and describe effective dynamics, for the particles only, inside them. At the lowest order the particles interact through Coulomb potentials. At the second one, epsilon^{2}, the mass gets a correction of electromagnetic origin and a velocity dependent interaction, the Darwin term, appears. Moreover, we calculate the radiated piece of the wave function, i. e., the piece which leaks out of the almost invariant subspaces and calculate the corresponding radiated energy.

  2. Performance limits of multilevel and multipartite quantum heat machines

    E-Print Network [OSTI]

    Wolfgang Niedenzu; David Gelbwaser-Klimovsky; Gershon Kurizki

    2015-08-12

    We present the general theory of a quantum heat machine based on an $N$-level system (working medium) whose $N-1$ excited levels are degenerate, a prerequisite for steady-state interlevel coherence. Our goal is to find out: To what extent is coherence in the working medium an asset for heat machines? The performance bounds of such a machine are common to (reciprocating) cycles that consist of consecutive strokes and continuous cycles wherein the periodically driven system is constantly coupled to cold and hot heat baths. Intriguingly, we find that the machine's performance strongly depends on the relative orientations of the transition-dipole vectors in the system. Perfectly aligned (parallel) transition dipoles allow for steady-state coherence effects, but also give rise to dark states, which hinder steady-state thermalization and thus reduce the machine's performance. Similar thermodynamic properties hold for $N$ two-level atoms conforming to the Dicke model. We conclude that level degeneracy, but not necessarily coherence, is a thermodynamic resource, equally enhancing the heat currents and the power output of the heat machine. By contrast, the efficiency remains unaltered by this degeneracy and adheres to the Carnot bound.

  3. 16-QAM Quantum Receiver with Hybrid Structure Outperforming the Standard Quantum Limit

    E-Print Network [OSTI]

    Yuan Zuo; Ke Li; Bing Zhu

    2014-12-15

    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.

  4. Magnetic field sensing beyond the standard quantum limit under the effect of decoherence

    SciTech Connect (OSTI)

    Matsuzaki, Yuichiro; Benjamin, Simon C.; Fitzsimons, Joseph

    2011-07-15

    Entangled states can potentially be used to outperform the standard quantum limit by which every classical sensor is bounded. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents an investigation of how a quantum sensor composed of many spins is affected by independent dephasing. We adopt general noise models including non-Markovian effects, and in these noise models the performance of the sensor depends crucially on the exposure time of the sensor to the field. We have found that, by choosing an appropriate exposure time within the non-Markovian time region, an entangled sensor does actually beat the standard quantum limit. Since independent dephasing is one of the most typical sources of noise in many systems, our results suggest a practical and scalable approach to beating the standard quantum limit.

  5. Classical mechanics as the many-particle limit of quantum mechanics

    E-Print Network [OSTI]

    Gabriele Carcassi

    2009-02-02

    We derive the classical limit of quantum mechanics by describing the center of mass of a system constituted by a large number of particles. We will show that in that limit the commutator between the position and velocity of the center of mass is infinitesimal, which allows both to be known with great precision. We then show how the infinitesimal commutator allows for the definition of functions of position and velocity, and how the commutator reduces to a Poisson bracket.

  6. The classical limit of quantum optics: not what it seems at first sight

    E-Print Network [OSTI]

    Yakir Aharonov; Alonso Botero; Shmuel Nussinov; Sandu Popescu; Jeff Tollaksen; Lev Vaidman

    2013-05-01

    What is light and how to describe it has always been a central subject in physics. As our understanding has increased, so have our theories changed: Geometrical optics, wave optics and quantum optics are increasingly sophisticated descriptions, each referring to a larger class of phenomena than its predecessor. But how exactly are these theories related? How and when wave optics reduces to geometric optics is a rather simple problem. Similarly, how quantum optics reduces to wave optics has been considered to be a very simple business as well. It's not so. As we show here the classical limit of quantum optics is a far more complicated issue; it is in fact dramatically more involved and it requires a complete revision of all our intuitions. The revised intuitions can then serve as a guide to finding novel quantum effects.

  7. On the Mean-Field and Classical Limits of Quantum Mechanics

    E-Print Network [OSTI]

    François Golse; Clément Mouhot; Thierry Paul

    2015-08-10

    The main result in this paper is a new inequality bearing on solutions of the $N$-body linear Schr\\"{o}dinger equation and of the mean field Hartree equation. This inequality implies that the mean field limit of the quantum mechanics of $N$ identical particles is uniform in the classical limit and provides a quantitative estimate of the quality of the approximation. This result applies to the case of $C^{1,1}$ interaction potentials. The quantity measuring the approximation of the $N$-body quantum dynamics by its mean field limit is analogous to the Monge-Kantorovich (or Wasserstein) distance with exponent $2$. The inequality satisfied by this quantity is reminiscent of the work of Dobrushin on the mean field limit in classical mechanics [Func. Anal. Appl. 13 (1979), 115-123]. Our approach of this problem is based on a direct analysis of the $N$-particle Liouville equation, and avoids using techniques based on the BBGKY hierarchy or on second quantization.

  8. Quantum Speed Limit and Optimal Control of Many-Boson Dynamics

    E-Print Network [OSTI]

    Ioannis Brouzos; Alexej I. Streltsov; Antonio Negretti; Ressa S. Said; Tommaso Caneva; Simone Montangero; Tommaso Calarco

    2015-05-12

    We extend the concept of quantum speed limit -- the minimal time needed to perform a driven evolution -- to complex interacting many-body systems. We investigate a prototypical many-body system, a bosonic Josephson junction, at increasing levels of complexity: (a) within the two-mode approximation {corresponding to} a nonlinear two-level system, (b) at the mean-field level by solving the nonlinear Gross-Pitaevskii equation in a double well potential, and (c) at an exact many-body level by solving the time-dependent many-body Schr\\"odinger equation. We propose a control protocol to transfer atoms from the ground state of a well to the ground state of the neighbouring well. Furthermore, we show that the detrimental effects of the inter-particle repulsion can be eliminated by means of a compensating control pulse, yielding, quite surprisingly, an enhancement of the transfer speed because of the particle interaction -- in contrast to the self-trapping scenario. Finally, we perform numerical optimisations of both the nonlinear and the (exact) many-body quantum dynamics in order to further enhance the transfer efficiency close to the quantum speed limit.

  9. Fourth-order quantum master equation and its Markovian bath limit Seogjoo Jang, Jianshu Cao, and Robert J. Silbey

    E-Print Network [OSTI]

    Cao, Jianshu

    Fourth-order quantum master equation and its Markovian bath limit Seogjoo Jang, Jianshu Cao 02139 Received 14 September 2001; accepted 28 November 2001 Fourth-order quantum master equations FQMEs expressions for the fourth-order kernel, where the bath correlation functions are explicitly decoupled from

  10. Limiter

    DOE Patents [OSTI]

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

    1984-10-19

    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.

  11. Quantum Noise Limits in White-Light-Cavity-Enhanced Gravitational Wave Detectors

    E-Print Network [OSTI]

    Minchuan Zhou; Zifan Zhou; Selim M. Shahriar

    2015-09-03

    Previously, we had proposed a gravitational wave detector that incorporates the white light cavity (WLC) effect using a compound cavity for signal recycling (CC-SR). Here, we first use an idealized model for the negative dispersion medium (NDM), and use the Caves model for phase-insensitive linear amplifier to account for the quantum noise (QN) from the NDM, to determine the upper bound of the enhancement in the sensitivity-bandwidth product. We calculate the quantum noise limited sensitivity curves for the CC-SR design, and find that the broadening of sensitivity predicted by the classical analysis is also present in these curves, but is somewhat reduced. Furthermore, we find that the curves always stay above the standard quantum limit (SQL). To circumvent this limitation, we modify the dispersion to compensate the non-linear phase variation produced by the opto-mechanical (OM) resonance effects. We find that the upper bound of the factor by which the sensitivity-bandwidth product is increased, compared to the highest sensitivity result predicted by Bunanno and Chen [Phys. Rev. D 64, 042006 (2001)], is ~14. We also present a simpler scheme (WLC-SR) where a dispersion medium is inserted in the SR cavity. For this scheme, we found the upper bound of the enhancement factor to be ~18. We then consider an explicit system for realizing the NDM, which makes use of five energy levels in M-configuration to produce Gain, accompanied by Electromagnetically Induced Transparency (the GEIT system). For this explicit system, we employ the rigorous approach based on Master Equation (ME) to compute the QN contributed by the NDM, thus enabling us to determine the enhancement in the sensitivity-bandwidth product definitively rather than the upper bound thereof. Specifically, we identify a set of parameters for which the sensitivity-bandwidth product is enhanced by a factor of 17.66.

  12. Limiter

    DOE Patents [OSTI]

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

    1986-01-01

    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.

  13. Generalized Uncertainty Relations and Long Time Limits for Quantum Brownian Motion Models

    E-Print Network [OSTI]

    C. Anastopoulos; J. J. Halliwell

    1994-07-27

    We study the time evolution of the reduced Wigner function for a class of quantum Brownian motion models. We derive two generalized uncertainty relations. The first consists of a sharp lower bound on the uncertainty function, $U = (\\Delta p)^2 (\\Delta q)^2 $, after evolution for time $t$ in the presence of an environment. The second, a stronger and simpler result, consists of a lower bound at time $t$ on a modified uncertainty function, essentially the area enclosed by the $1-\\sigma$ contour of the Wigner function. In both cases the minimizing initial state is a non-minimal Gaussian pure state. These generalized uncertainty relations supply a measure of the comparative size of quantum and thermal fluctuations. We prove two simple inequalites, relating uncertainty to von Neumann entropy, and the von Neumann entropy to linear entropy. We also prove some results on the long-time limit of the Wigner function for arbitrary initial states. For the harmonic oscillator the Wigner function for all initial states becomes a Gaussian at large times (often, but not always, a thermal state). We derive the explicit forms of the long-time limit for the free particle (which does not in general go to a Gaussian), and also for more general potentials in the approximation of high temperature.

  14. Large gain quantum-limited qubit measurement using a two-mode nonlinear cavity

    E-Print Network [OSTI]

    Saeed Khan; R. Vijay; I. Siddiqi; Aashish A. Clerk

    2014-12-05

    We provide a thorough theoretical analysis of qubit state measurement in a setup where a driven, parametrically-coupled cavity system is directly coupled to the qubit, with one of the cavities having a weak Kerr nonlinearity. Such a system could be readily realized using circuit QED architectures. We demonstrate that this setup is capable in the standard linear-response regime of both producing a highly amplified output signal while at the same time achieving near quantum-limited performance: the measurement backaction on the qubit is near the minimal amount required by the uncertainty principle. This setup thus represents a promising route for performing efficient large-gain qubit measurement that is completely on-chip, and that does not rely on the use of circulators or complex non-reciprocal amplifiers.

  15. The ultimate disposition of depleted uranium

    SciTech Connect (OSTI)

    Lemons, T.R. [Uranium Enrichment Organization, Oak Ridge, TN (United States)

    1991-12-31

    Depleted uranium (DU) is produced as a by-product of the uranium enrichment process. Over 340,000 MTU of DU in the form of UF{sub 6} have been accumulated at the US government gaseous diffusion plants and the stockpile continues to grow. An overview of issues and objectives associated with the inventory management and the ultimate disposition of this material is presented.

  16. Ultimate storage ring based on fourth-order geometric achromats...

    Office of Scientific and Technical Information (OSTI)

    Ultimate storage ring based on fourth-order geometric achromats Citation Details In-Document Search Title: Ultimate storage ring based on fourth-order geometric achromats Authors:...

  17. An ultimate storage ring lattice with vertical emittance generated...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: An ultimate storage ring lattice with vertical emittance generated by damping wigglers Citation Details In-Document Search Title: An ultimate storage ring lattice...

  18. Graphene as the Ultimate Membrane for Gas Separation

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

    Graphene as the Ultimate Membrane for Gas Separation Graphene as the Ultimate Membrane for Gas Separation GraphenePore.jpg Key Challenges: Investigate the permeability and...

  19. Ultimate Fate of our Universe from Quantum Mechanics

    E-Print Network [OSTI]

    Antonio Alfonso-Faus

    2007-05-15

    It is conjectured that time intervals of any kind are proportional to the age of the Universe taken at the time we are considering the interval. If this is the case then the speed of light, in fact any speed, must decrease inversely proportional to this age. The immediate consequence is that energy is not conserved: the hypothesis that time is a homogeneous property implies conservation of energy (the theorem of Noether). Nonconservation of energy follows from the condition that any time interval is proportional to the cosmological time, and therefore time can not be homogeneous. From the uncertainty principle, taking the constant of Planck as a real constant, time independent, it follows that any energy in the Universe decreases linearly with time. We then prove that Schroedinger equation does not change, except for the potential energy term. The future of the Universe gives for the wave functions a long sinusoidal spatial solution, so that everything becomes unlocalized. The relativistic absolute interval remains the same, even with a changing speed of light, and the Universe turns out to be nonexpanding. A Mass-Boom effect is confirmed.

  20. Nonlinear Michelson interferometer for improved quantum metrology

    E-Print Network [OSTI]

    Alfredo Luis; Ángel Rivas

    2015-04-21

    We examine nonlinear quantum detection via a Michelson interferometer embedded in a gas with Kerr nonlinearity. The interferometer is illuminated by pulses of classical light. This strategy combines the robustness against practical imperfections of classical light with the improvement provided by nonlinear detection. Regarding ultimate quantum limits, we stress that, as a difference with linear schemes, the nonlinearity introduces pulse duration as a new variable into play along with the energy resources.

  1. Optical Spectrum Analyzer with Quantum-Limited Noise Floor M. Bishof, X. Zhang, M. J. Martin, and Jun Ye

    E-Print Network [OSTI]

    Optical Spectrum Analyzer with Quantum-Limited Noise Floor M. Bishof, X. Zhang, M. J. Martin with state-of-the-art stability. We demonstrate a technique that precisely measures the noise spectrum determine the laser noise spectrum from near dc to 100 Hz via the measured fluctuations in atomic excitation

  2. Ultimate stability of matter: Becoming a particle

    SciTech Connect (OSTI)

    Tsu, Raphael [ECE Department and Department of Optical Science and Engineering, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Datta, Timir [Department of Physics, University of South Carolina, Columbia, SC 29208 (United States)

    2014-05-15

    The de Broglie relation is a consequence of Planck-Einstein's energy quantization plus Lorentz invariance in describing any system of interaction. Once interaction results in a stable minimum energy configuration, the system, including low dimensional structures and devices, transforms into a particle, without further interactions. However any attempt to make observation of the particle, the interaction causes the entity to revert back to the realm of quantum mechanics. Certain steps may be described by the use of constitutive equations obtained by the use of RPA, Random Phase Approximation, resembling classical descriptions such as refractive index, deformation potentials, effective mass and others. All interactions are quantum mechanical, even appear to be classical.

  3. Linear Optical Quantum Metrology with Single Photons: Exploiting Spontaneously Generated Entanglement to Beat the Shot-Noise Limit

    E-Print Network [OSTI]

    Keith R. Motes; Jonathan P. Olson; Evan J. Rabeaux; Jonathan P. Dowling; S. Jay Olson; Peter P. Rohde

    2015-05-04

    Quantum number-path entanglement is a resource for super-sensitive quantum metrology and in particular provides for sub-shotnoise or even Heisenberg-limited sensitivity. However, such number-path entanglement has thought to have been resource intensive to create in the first place --- typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feed-forward, which are difficult to implement. Very recently, arising from the study of quantum random walks with multi-photon walkers, as well as the study of the computational complexity of passive linear optical interferometers fed with single-photon inputs, it has been shown that such passive linear optical devices generate a superexponentially large amount of number-path entanglement. A logical question to ask is whether this entanglement may be exploited for quantum metrology. We answer that question here in the affirmative by showing that a simple, passive, linear-optical interferometer --- fed with only uncorrelated, single-photon inputs, coupled with simple, single-mode, disjoint photodetection --- is capable of significantly beating the shotnoise limit. Our result implies a pathway forward to practical quantum metrology with readily available technology.

  4. Time-optimal bath-induced unitaries by Zermelo navigation: speed limit and non-Markovian quantum computation

    E-Print Network [OSTI]

    Jens Clausen

    2015-07-31

    The solution of the quantum Zermelo navigation problem is applied to the non-Markovian open system dynamics of a set of quantum systems interacting with a common environment. We consider a case allowing an exact time-optimal realization of environment-mediated non-local system unitaries. For a linear coupling to a harmonic bosonic bath, we derive a speed limit for the implementation time in terms of the fundamental frequency of the bath modes. As a product of two exponentials of the local free wind and the pairwise system-coupling, the Zermelo unitary forms a natural building block for reaching a general unitary by concatenation.

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

    E-Print Network [OSTI]

    Johnson, Jedediah Edward Jensen

    2012-01-01

    junctions . . . . . . . 1.4 Superconducting QuantumInterference 1.5 Superconducting qubits . . . . . . . . .2 Superconducting flux qubits 2.1 The one-junction flux

  6. The Phenix ultimate natural convection test

    SciTech Connect (OSTI)

    Gauthe, P.; Pialla, D.; Tenchine, D.; Vasile, A.; Rochwerger, D.

    2012-07-01

    The French sodium cooled fast reactor Phenix was shut down in 2009 after 35 years of operation. Before decommissioning, a final set of tests were performed by the CEA during 9 months. Several topics were involved such as thermal hydraulics, core physics and fuel behaviour. Among these ultimate experiments, two thermal hydraulic tests were performed: an asymmetrical test consisting in a trip of one secondary pump and a natural convection test in the primary circuit. Recognizing the unique opportunity offered by these Phenix ultimate tests, IAEA decided in 2007 to launch a Coordinated Research Project (CRP) devoted to benchmarking analyses with system codes on the Phenix natural convection test. One objective of the natural convection test in Phenix reactor is the assessment of the CATHARE system code for safety studies on future and advanced sodium cooled fast reactors. The aim of this paper is to describe this test, which was performed on June 22-23, 2009, and the associated benchmark specifications for the CRP work. The paper reminds briefly the Phenix reactor with the main physical parameters and the instrumentation used during the natural convection test. After that, the test scenario is described: - initial state at a power of 120 MWth, - test beginning resulting from a manual dry out of the two steam generators, - manual scram, - manual trip on the three primary pumps without back-up by pony motors, - setting and development of natural convection in the primary circuit, in a first phase without significant heat sink in the secondary circuits and in a second phase with significant heat sink in the secondary circuits, by opening the casing of steam generators to create an efficient heat sink, by air natural circulation in the steam generators casing. The benchmark case ends after this second phase, which corresponds to the experimental test duration of nearly 7 hours. The paper presents also the benchmark specifications data supplied by the CEA to all participants of this CRP in order to perform calculations (core, primary circuit, primary pumps, IHX, shutdown system, operating parameters, test scenario and real test conditions). Finally, main test results and analyses are presented including the evolution of the core and of the heat exchangers inlet and outlet temperatures, and some local temperature measurements. The natural convection has been easily set up in the pool type reactor Phenix with different boundary conditions at the secondary side, with or without heat sink. The data obtained during this unique test represent some very useful and precious results for the development of SFR in a wide range of thematic such as numerical methods dedicated to thermal-hydraulics safety analyses (system codes, CFD codes and coupling system and CFD codes) and instrumentation. (authors)

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

    E-Print Network [OSTI]

    Fahhad H Alharbi; Sabre Kais

    2014-02-09

    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.

  8. Quantum Photonic Interconnect

    E-Print Network [OSTI]

    Jianwei Wang; Damien Bonneau; Matteo Villa; Joshua W. Silverstone; Raffaele Santagati; Shigehito Miki; Taro Yamashita; Mikio Fujiwara; Masahide Sasaki; Hirotaka Terai; Michael G. Tanner; Chandra M. Natarajan; Robert H. Hadfield; Jeremy L. O'Brien; Mark G. Thompson

    2015-09-26

    Integrated photonics has enabled much progress towards quantum technologies. Many applications, including quantum communication, sensing, and distributed and cloud quantum computing, will require coherent photonic interconnection between separate chip-based sub-systems. Large-scale quantum computing systems and architectures may ultimately require quantum interconnects to enable scaling beyond the limits of a single wafer and towards "multi-chip" systems. However, coherently interconnecting separate chips is challenging due to the fragility of these quantum states and the demanding challenges of transmitting photons in at least two media within a single coherent system. Distribution and manipulation of qubit entanglement between multiple devices is one of the most stringent requirements of the interconnected system. Here, we report a quantum photonic interconnect demonstrating high-fidelity entanglement distribution and manipulation between two separate chips, implemented using state-of-the-art silicon photonics. Path-entangled states are generated and manipulated on-chip, and distributed between the chips by interconverting between path-encoding and polarisation-encoding. We use integrated state analysers to confirm a Bell-type violation of $S$=2.638+-0.039 between two chips. With improvements in loss, this quantum interconnect will provide new levels of flexible systems and architectures for quantum technologies.

  9. An Ultimate Target for Dark Matter Searches

    E-Print Network [OSTI]

    Kfir Blum; Yanou Cui; Marc Kamionkowski

    2014-12-10

    The combination of S-matrix unitarity and the dynamics of thermal freeze-out for massive relic particles (denoted here simply by WIMPs) implies a lower limit on the density of such particles, that provide a (potentially sub-dominant) contribution to dark matter. This then translates to lower limits to the signal rates for a variety of techniques for direct and indirect detection of dark matter. For illustration, we focus on models where annihilation is s-wave dominated. We derive lower limits to the flux of gamma-rays from WIMP annihilation at the Galactic center; direct detection of WIMPs; energetic neutrinos from WIMP annihilation in the Sun; and the effects of WIMPs on the angular power spectrum and frequency spectrum of the cosmic microwave background radiation. The results suggest that a variety of dark-matter-search techniques may provide interesting avenues to seek new physics, even if WIMPs do not constitute all the dark matter. While the limits are quantitatively some distance from the reach of current measurements, they may be interesting for long-range planning exercises.

  10. Engineering quantum pure states of a trapped cold ion beyond the Lamb-Dicke limit L. F. Wei,1,2

    E-Print Network [OSTI]

    Nori, Franco

    dimension of the motion of the ground state of the trapped ion should be much smaller than the effectiveEngineering quantum pure states of a trapped cold ion beyond the Lamb-Dicke limit L. F. Wei,1,2 Yu(s): 42.50.Dv, 42.50.Vk I. INTRODUCTION The engineering of quantum states has attracted consider- able

  11. T-shaped quantum wires in magnetic fields: Weakly confined magnetoexcitons beyond the diamagnetic limit

    E-Print Network [OSTI]

    Band, Yehuda B.

    T-shaped quantum wires in magnetic fields: Weakly confined magnetoexcitons beyond the diamagnetic at vanishing magnetic field26 to B 0. Exciton states for interacting electron-hole pairs confined to a T-particle states confined to the T intersection in a magnetic field and then using these single- particle states

  12. Non-Destructive Probing of Rabi Oscillations on the Cesium Clock Transition near the Standard Quantum Limit

    E-Print Network [OSTI]

    P. J. Windpassinger; D. Oblak; P. G. Petrov; M. Kubasik; M. Saffman; C. L. Garrido Alzar; J. Appel; J. H. Mueller; N. Kjaergaard; E. S. Polzik

    2008-01-27

    We report on non-destructive observation of Rabi oscillations on the Cs clock transition. The internal atomic state evolution of a dipole-trapped ensemble of cold atoms is inferred from the phase shift of a probe laser beam as measured using a Mach-Zehnder interferometer. We describe a single color as well as a two-color probing scheme. Using the latter, measurements of the collective pseudo-spin projection of atoms in a superposition of the clock states are performed and the observed spin fluctuations are shown to be close to the standard quantum limit.

  13. Functional Approach to Quantum Decoherence and the Classical Final Limit: the Mott and Cosmological problems

    E-Print Network [OSTI]

    Mario Castagnino; Roberto Laura

    2000-06-03

    Decoherence and the approach to the classical final limit are studied in two similar cases: the Mott and the Cosmological problems.

  14. Macroscopic quantum resonators (MAQRO): 2015 Update

    E-Print Network [OSTI]

    Rainer Kaltenbaek; Markus Arndt; Markus Aspelmeyer; Peter F. Barker; Angelo Bassi; James Bateman; Kai Bongs; Sougato Bose; Claus Braxmaier; ?aslav Brukner; Bruno Christophe; Michael Chwalla; Pierre-François Cohadon; Adrian M. Cruise; Catalina Curceanu; Kishan Dholakia; Klaus Döringshoff; Wolfgang Ertmer; Jan Gieseler; Norman Gürlebeck; Gerald Hechenblaikner; Antoine Heidmann; Sven Herrmann; Sabine Hossenfelder; Ulrich Johann; Nikolai Kiesel; Myungshik Kim; Claus Lämmerzahl; Astrid Lambrecht; Michael Mazilu; Gerard J. Milburn; Holger Müller; Lukas Novotny; Mauro Paternostro; Achim Peters; Igor Pikovski; André Pilan-Zanoni; Ernst M. Rasel; Serge Reynaud; C. Jess Riedel; Manuel Rodrigues; Loïc Rondin; Albert Roura; Wolfgang P. Schleich; Jörg Schmiedmayer; Thilo Schuldt; Keith C. Schwab; Martin Tajmar; Guglielmo M. Tino; Hendrik Ulbricht; Rupert Ursin; Vlatko Vedral

    2015-03-09

    Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schr\\"odinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission MAQRO may overcome these limitations and allow addressing those fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal of MAQRO is to probe the vastly unexplored "quantum-classical" transition for increasingly massive objects, testing the predictions of quantum theory for truly macroscopic objects in a size and mass regime unachievable in ground-based experiments. The hardware for the mission will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the (M4) Cosmic Vision call of the European Space Agency for a medium-size mission opportunity with a possible launch in 2025.

  15. Decoherence and the quantum-classical limit in the presence of chaos

    SciTech Connect (OSTI)

    Toscano, F.; Matos Filho, R.L. de; Davidovich, L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68.528, 21.941-972, Rio de Janeiro (Brazil)

    2005-01-01

    We investigate how decoherence affects the short-time separation between quantum and classical dynamics for classically chaotic systems, within the framework of a specific model. For a wide range of parameters, the distance between the corresponding phase-space distributions depends on a single parameter {chi} that relates an effective Planck constant ({Dirac_h}/2{pi}){sub eff}, the Lyapunov coefficient, and the diffusion constant. This distance peaks at a time that depends logarithmically on ({Dirac_h}/2{pi}){sub eff}, in agreement with previous estimations of the separation time for Hamiltonian systems. However, for {chi} < or approx. 1, the separation remains small, going down with ({Dirac_h}/2{pi}){sub eff}{sup 2}, so the concept of separation time loses its meaning.

  16. The ultimate rendezvous: microbial ecology meets industrial biotechnology

    E-Print Network [OSTI]

    McFall-Ngai, Margaret

    The ultimate rendezvous: microbial ecology meets industrial biotechnology Editorial overview about by the plethora of emissions associated with industrial growth. At the same time, economic, synthesis and degradation reactions that have been so far the near exclusive realm of industrial

  17. Light Nuclei and HyperNuclei from Quantum Chromodynamics in the Limit of SU(3) Flavor Symmetry

    SciTech Connect (OSTI)

    Beane, S R; Cohen, S D; Detmold, W; Lin, H W; Luu, T C; Orginos, K; Parreno, A; Savage, M J

    2013-02-01

    The binding energies of a range of nuclei and hypernuclei with atomic number A <= 4 and strangeness |s| <= 2, including the deuteron, di-neutron, H-dibaryon, {sup 3}He, {sub {Lambda}}{sup 3}He, {sub {Lambda}}{sup 4}He, and {sub {Lambda}{Lambda}}{sup 4}He, are calculated in the limit of flavor-SU(3) symmetry at the physical strange quark mass with quantum chromodynamics (without electromagnetic interactions). The nuclear states are extracted from Lattice QCD calculations performed with n{sub f}=3 dynamical light quarks using an isotropic clover discretization of the quark-action in three lattice volumes of spatial extent L ~ 3.4 fm, 4.5 fm and 6.7 fm, and with a single lattice spacing b ~ 0.145 fm.

  18. Quantum limit of the laser linewidth in chaotic cavities and statistics of residues of scattering matrix poles

    E-Print Network [OSTI]

    H. Schomerus; K. M. Frahm; M. Patra; C. W. J. Beenakker

    1999-11-01

    The quantum-limited linewidth of a laser cavity is enhanced above the Schawlow-Townes value by the Petermann factor K, due to the non-orthogonality of the cavity modes. We derive the relation between the Petermann factor and the residues of poles of the scattering matrix and investigate the statistical properties of the Petermann factor for cavities in which the radiation is scattered chaotically. For a single scattering channel we determine the complete probability distribution of K and find that the average Petermann factor $$ depends non-analytically on the area of the opening, and greatly exceeds the most probable value. For an arbitrary number N of scattering channels we calculate $$ as a function of the decay rate $\\Gamma$ of the lasing mode. We find for $N\\gg 1$ that for typical values of $\\Gamma$ the average Petermann factor $\\propto \\sqrt{N}\\gg 1$ is parametrically larger than unity.

  19. CENTRIFUGAL MODEL TESTS FOR ULTIMATE BEARING CAPACITY OF FOOTINGS ON STEEP SLOPES IN COHESIONLESS SOIL [abstract

    E-Print Network [OSTI]

    Gemperline, Mark

    1984-01-01

    Gemperline, Mark C. , Centrifugal ~odel Tests for UltimateDivision. ABSTRACTS II CENTRIFUGAL MODEL TESTS FOR ULTIMATE

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

    SciTech Connect (OSTI)

    Danel, J.-F.; Blottiau, P.; Kazandjian, L.; Piron, R.; Torrent, M.

    2014-10-15

    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.

  1. Ris-R-1111(EN) Ultimate Loading of Wind Turbines

    E-Print Network [OSTI]

    Risø-R-1111(EN) Ultimate Loading of Wind Turbines Gunner Chr. Larsen, Knut Ronold, Hans E-R-1111(EN) 2 Abstract An extreme loading study has been conducted comprising a general wind climate analysis as well as a wind turbine reliability study. In the wind climate analysis, the distribution

  2. Hybrid Dynamical Systems, or HDS: The Ultimate Switching Experience

    E-Print Network [OSTI]

    Branicky, Michael S.

    Hybrid Dynamical Systems, or HDS: The Ultimate Switching Experience Michael S. Branicky Laboratory concentrated on formalizing the notion of a hybrid system as switching among an indexed collection of dynamical give a quick overview of the area of hybrid systems. I also briefly review the formal definition

  3. Quantum Mechanical Pressure Frank Rioux

    E-Print Network [OSTI]

    Rioux, Frank

    Quantum Mechanical Pressure Frank Rioux CSB|SJU Quantum mechanics is based on the concept of wave it to its quantum mechanical equivalent. 2 2 2 2 2 p h KE m m = = Because objects with wave-like properties" character of quantum mechanical kinetic energy is the ultimate basis for the stability of matter. It also

  4. Monte Carlo simulation of a quantum noise limited ?erenkov detector based on air-spaced light guiding taper for megavoltage x-ray imaging

    SciTech Connect (OSTI)

    Teymurazyan, A.; Rowlands, J. A.; Thunder Bay Regional Research Institute , Thunder Bay P7A 7T1; Department of Radiation Oncology, University of Toronto, Toronto M5S 3E2 ; Pang, G.

    2014-04-15

    Purpose: Electronic Portal Imaging Devices (EPIDs) have been widely used in radiation therapy and are still needed on linear accelerators (Linacs) equipped with kilovoltage cone beam CT (kV-CBCT) or MRI systems. Our aim is to develop a new high quantum efficiency (QE) ?erenkov Portal Imaging Device (CPID) that is quantum noise limited at dose levels corresponding to a single Linac pulse. Methods: Recently a new concept of CPID for MV x-ray imaging in radiation therapy was introduced. It relies on ?erenkov effect for x-ray detection. The proposed design consisted of a matrix of optical fibers aligned with the incident x-rays and coupled to an active matrix flat panel imager (AMFPI) for image readout. A weakness of such design is that too few ?erenkov light photons reach the AMFPI for each incident x-ray and an AMFPI with an avalanche gain is required in order to overcome the readout noise for portal imaging application. In this work the authors propose to replace the optical fibers in the CPID with light guides without a cladding layer that are suspended in air. The air between the light guides takes on the role of the cladding layer found in a regular optical fiber. Since air has a significantly lower refractive index (?1 versus 1.38 in a typical cladding layer), a much superior light collection efficiency is achieved. Results: A Monte Carlo simulation of the new design has been conducted to investigate its feasibility. Detector quantities such as quantum efficiency (QE), spatial resolution (MTF), and frequency dependent detective quantum efficiency (DQE) have been evaluated. The detector signal and the quantum noise have been compared to the readout noise. Conclusions: Our studies show that the modified new CPID has a QE and DQE more than an order of magnitude greater than that of current clinical systems and yet a spatial resolution similar to that of current low-QE flat-panel based EPIDs. Furthermore it was demonstrated that the new CPID does not require an avalanche gain in the AMFPI and is quantum noise limited at dose levels corresponding to a single Linac pulse.

  5. Quantum technology and its applications

    SciTech Connect (OSTI)

    Boshier, Malcolm; Berkeland, Dana; Govindan, Tr; Abo - Shaeer, Jamil

    2010-12-10

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

  6. Photonic architecture for scalable quantum information processing in NV-diamond

    E-Print Network [OSTI]

    Kae Nemoto; Michael Trupke; Simon J. Devitt; Ashley M. Stephens; Kathrin Buczak; Tobias Nobauer; Mark S. Everitt; Jorg Schmiedmayer; William J. Munro

    2013-09-17

    Physics and information are intimately connected, and the ultimate information processing devices will be those that harness the principles of quantum mechanics. Many physical systems have been identified as candidates for quantum information processing, but none of them are immune from errors. The challenge remains to find a path from the experiments of today to a reliable and scalable quantum computer. Here, we develop an architecture based on a simple module comprising an optical cavity containing a single negatively-charged nitrogen vacancy centre in diamond. Modules are connected by photons propagating in a fiber-optical network and collectively used to generate a topological cluster state, a robust substrate for quantum information processing. In principle, all processes in the architecture can be deterministic, but current limitations lead to processes that are probabilistic but heralded. We find that the architecture enables large-scale quantum information processing with existing technology.

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

    E-Print Network [OSTI]

    Kobiela, Pawel Stanislaw

    1986-01-01

    conduction paths, one in the 2-DEG (medium 1) and the second an another medium (like AlGaAs), the conductivity tensor can be expressed as o' = rri + ap. Further analysis can be carried out by considering two separate limits: low and high magnetic fields.... The interval between the current pulses depended on the temperature and varied from 2-3 sec. at 10 K to about 1 min. at 15 mK. For each magnetic field scan between 0 and 7. 5 T about 500 readings were taken for l&oth current directions. As mentioned before...

  8. Ultrasensitive measurement of MEMS cantilever displacement sensitivity below the shot noise limit

    E-Print Network [OSTI]

    R. C. Pooser; B. J. Lawrie

    2015-06-29

    The displacement of micro-electro-mechanical-systems (MEMS) cantilevers is used to measure a broad variety of phenomena in devices ranging from force microscopes to biochemical sensors to thermal imaging systems. We demonstrate the first direct measurement of a MEMS cantilever displacement with a noise floor at 40% of the shot noise limit (SNL). By combining multi-spatial-mode quantum light sources with a simple ?differential measurement, we show that sub-SNL MEMS displacement sensitivity is highly accessible compared to previous efforts that measured the displacement of macroscopic mirrors with very distinct spatial structures crafted with multiple optical parametric amplifiers and locking loops. These results support a new class of quantum MEMS sensor with an ultimate signal to noise ratio determined by quantum correlations, enabling ultra-trace sensing, imaging, and microscopy applications in which signals were previously obscured by shot noise.

  9. Lattice Design for PEP-X Ultimate Storage Ring Light Source

    SciTech Connect (OSTI)

    Bane, K.L.F.; Cai, Y.; Nosochkov, Y.; Wang, M.-H.; Hettel, R.O.; /SLAC

    2011-12-13

    SLAC expertise in designing and operating high current storage rings and the availability of the 2.2-km PEP-II tunnel present an opportunity for building a next generation light source - PEP-X - that would replace the SPEAR3 storage ring in the future. The PEP-X 'baseline' design, with 164 pm-rad emittance at 4.5 GeV beam energy and a current of 1.5 A, was completed in 2010. As a next step, a so-called 'ultimate' PEP-X lattice, reducing the emittance to 11 pm-rad at zero current, has been designed. This emittance approaches the diffraction limited photon emittance for multi-keV photons, providing near maximum photon brightness and high coherence. It is achieved by using 7-bend achromat cells in the ring arcs and a 90-m damping wiggler in one of the 6 long straight sections. Details of the lattice design, dynamic aperture, and calculations of the intra-beam scattering effect and Touschek lifetime at a nominal 0.2 A current are presented. Accelerator-based light sources are in high demand for many experimental applications. The availability of the 2.2-km PEP-II tunnel at SLAC presents an opportunity for building a next generation light source - PEP-X - that would replace the existing SPEAR3 light source in the future. The PEP-X study started in 2008, and the 'baseline' design, yielding 164 pm-rad emittance at 4.5 GeV beam energy and a current of 1.5 A, was completed in 2010. This relatively conservative design can be built using existing technology. However, for a long term future, it is natural to investigate a more aggressive, so-called 'ultimate' ring design. The goal is to reduce the electron emittance in both x and y planes to near the diffraction limited photon emittance of 8 pm-rad at hard X-ray photon wavelength of 0.1 nm. This would provide a near maximum photon brightness and significant increase in photon coherence. This study was motivated by the advances in low emittance design at MAX-IV. The latter was used as a starting point for the PEP-X arc lattice, however new features were included into the design for better tuning capabilities and compensation of non-linear optics effects. Further emittance reduction is achieved with a 90-m damping wiggler. Finally, intra-beam scattering (IBS) and Touschek lifetime effects were estimated and cross-checked using various codes.

  10. Water-Walled Microfluidics Makes an Ultimate Optical Finesse

    E-Print Network [OSTI]

    Maayani, Shai; Carmon, Tal

    2015-01-01

    Liquids serve microcavity research ever since Ashkins studies on optical resonances in levitating droplets to recent optofluidic resonators. Droplets can provide optical quality factor (Q) in proximity to the limit restricted by water absorption and radiation loss. However, water micro-drops vaporize quickly due to their large area to volume ratio. Here we fabricate a water-air interface that almost entirely surrounds our device, allowing for more than 1,000,000 recirculations of light (finesse). We sustain the droplets for longer than 16 hours using a nano-water-bridge that extends from the droplet to a practically-unlimited distant-reservoir that compensates for evaporation. Our device exhibits surface tension 8000-times stronger than gravity that self-stabilizes its shape to a degree sufficient to maintain critical coupling as well as to resolve split modes. Our device has 98 percents of their surrounding walls made strictly of water-air interfaces with concave, convex or saddle geometries, suggesting an a...

  11. Expert: This GOP primary 'like ultimate fighting'; Will it leave general election wounds?

    E-Print Network [OSTI]

    Fernandez, Eduardo

    Expert: This GOP primary 'like ultimate fighting'; Will it leave general election wounds? By JOHN says. "It's more like ultimate fighting. There are no gentlemen's rules." #12;But "gentleman's rules to Obama. In 1976, Ronald Reagan took his fight against then-President Gerald Ford to the convention

  12. Tissue architecture: the ultimate regulator of breast epithelial function

    SciTech Connect (OSTI)

    Bissell, Mina J; Rizki, Aylin; Mian, Saira

    2003-10-20

    A problem in developmental biology that continues to take center stage is how higher organisms generate diverse tissues and organs given the same cellular genotype. In cell and tumor biology, the key question is not the production of form, but its preservation: how do tissues and organs maintain homeostasis, and how do cells within tissues lose or overcome these controls in cancer? Undoubtedly, mechanisms that maintain tissue specificity should share features with those employed to drive formation of the tissues. However, they are unlikely to be identical. At a simplistic level, developmental pathways may be thought of as a series of extremely rapid short-term events. Each new step depends on what came before, and the outcome is the organism itself at birth. All organs, with a few notable exceptions, such as the mammary gland and the brain, 'arrive' together and are complete when the organism is born. In mice and humans, these events occur in a mere 21 days and 9 months respectively. The stability of the differentiated state and the homeostasis of the organism, on the other hand, will last 40-110 times longer. How does the organism achieve this feat? How are tissues maintained? These questions also relate fundamentally to how tissues become malignant and, although not discussed here, to aging. While there is much literature on differentiation - loosely defined as the gain of a single or a series of functions - we know much less about the forces and the pathways that maintain organ morphology and function as a unit. This may be partly because it is difficult to study a tissue as a unit in vivo and there are few techniques that allow maintenance of organs in vitro long enough and in such a way as to make cell and molecular biology experiments possible. Techniques for culturing cells in three-dimensional gels (3D) as a surrogate for tissues, however, have been steadily improving and the method is now used by several laboratories. In this commentary we discuss the following: first, how our laboratory came to develop a model of the mammary gland acinus; second, what this model has told us about mechanisms that govern tissue specificity and malignancy; and third, possible directions for future studies. We summarize the evidence for the central role of ECM signaling in the maintenance of mammary function in culture and (more briefly) its role in tumorigenesis. This is followed by a discussion of the role that tissue architecture and tissue polarity (as opposed to cell polarity) may play in these processes. In an elegantly written and reasoned essay, Kirschner et al. coined the new science of developmental biology 'molecular vitalism'. They framed new concepts for self-organization as well as schemes for information flow in biological organization. Rao et al. reviewed and elaborated on differential-equation-based models of biochemical reaction networks and intracellular noise, with emphasis on bacteria and phage. Similarly, Hartwell et al. discussed the synergy between experiment and theory in elucidating 'modules' - collections of interacting molecules - and in unraveling how these modules collaborate to perform cellular functions such as signal transduction. We believe that many of these ideas will also be applicable to the maintenance of tissue specificity. As much as we agree with Kirschner et al. regarding the limitations of the machine analogy to biological systems, we conclude with thoughts on how we may proceed to model the complex tissue networks that govern breast tissue architecture. We suggest that our understanding of the structure and function of breast tissue would benefit from examining recent techniques for modeling large complex networks such as the World Wide Web and the Internet backbone among others.

  13. Quantum limit of photothermal cooling

    E-Print Network [OSTI]

    Simone De Liberato; Neill Lambert; Franco Nori

    2010-11-30

    We study the problem of cooling a mechanical oscillator using the photothermal (bolometric) force. Contrary to previous attempts to model this system, we take into account the noise effects due to the granular nature of photon absorption. This allows us to tackle the cooling problem down to the noise dominated regime and to find reasonable estimates for the lowest achievable phonon occupation in the cantilever.

  14. Effects of fracturing fluid recovery upon well performance and ultimate recovery of hydraulically fractured gas wells 

    E-Print Network [OSTI]

    Berthelot, Jan Marie

    1990-01-01

    EFFECTS OF FRACTURING FLUID RECOVERY UPON WELL PERFORMANCE AND ULTIMATE RECOVERY OF HYDRAULICALLY FRACTURED GAS WELLS A Thesis IAN MARIE BERTHELOT Submitted to the Office of Graduate Studies of Texas AdtM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE May 1990 Major Subject: Petroleum Engineering EFFECTS OF FRACTURING FLUID RECOVERY UPON WELL PERFORMANCE AND ULTIMATE RECOVERY OF HYDRAULICALLY FRACTURED GAS WELLS by JAN MARIE BERTIIELOT Appmved...

  15. Fast quantum control and light-matter interactions at the 10,000 quanta level

    E-Print Network [OSTI]

    J. Alonso; F. M. Leupold; Z. U. Soler; M. Fadel; M. Marinelli; B. C. Keitch; V. Negnevitsky; J. P. Home

    2015-09-23

    Fast control of quantum systems is essential in order to make use of quantum properties before they are degraded by decoherence. This is important for quantum-enhanced information processing, as well as for pushing quantum systems into macroscopic regimes at the boundary between quantum and classical physics. Bang-bang control attains the ultimate speed limit by making large changes to control fields on timescales much faster than the system can respond, however these methods are often challenging to implement experimentally. Here we demonstrate bang-bang control of a trapped-ion oscillator using nano-second switching of the trapping potentials. We perform controlled displacements which allow us to realize quantum states with up to 10,000 quanta of energy. We use these displaced states to verify the form of the ion-light interaction at high excitations which are far outside the usual regime of operation. These methods provide new possibilities for quantum-state manipulation and generation, alongside the potential for a significant increase in operational clock speed for ion-trap quantum information processing.

  16. Quantum Thermodynamics

    E-Print Network [OSTI]

    Sai Vinjanampathy; Janet Anders

    2015-08-25

    Quantum thermodynamics is an emerging research field aiming to extend standard thermodynamics and non-equilibrium statistical physics to ensembles of sizes well below the thermodynamic limit, in non-equilibrium situations, and with the full inclusion of quantum effects. Fuelled by experimental advances and the potential of future nanoscale applications this research effort is pursued by scientists with different backgrounds, including statistical physics, many-body theory, mesoscopic physics and quantum information theory, who bring various tools and methods to the field. A multitude of theoretical questions are being addressed ranging from issues of thermalisation of quantum systems and various definitions of "work", to the efficiency and power of quantum engines. This overview provides a perspective on a selection of these current trends accessible to postgraduate students and researchers alike.

  17. Ultimate Limit State Response of Reinforced Concrete Columns for Use in Performance-Based Analysis and Design 

    E-Print Network [OSTI]

    Urmson, Christopher R.

    2010-10-12

    and longitudinal bar buckling. The purpose of this research is to develop a model for the full compressive behavior of longitudinal steel including the effects of bar buckling. A computational algorithm is developed whereby experimental data can be rigorously...

  18. Bounds on Information and the Security of Quantum Cryptography

    E-Print Network [OSTI]

    E. Biahm; T. Mor

    1997-01-08

    Strong attacks against quantum key distribution use quantum memories and quantum gates to attack directly the final key. In this paper we extend a novel security result recently obtained, to demonstrate proofs of security against a wide class of such attacks. To reach this goal we calculate information-dependent reduced density matrices, we study the geometry of quantum mixed states, and we find bounds on the information leaked to an eavesdropper. Our result suggests that quantum cryptography is ultimately secure.

  19. Models of quantum computation and quantum programming languages

    E-Print Network [OSTI]

    J. A. Miszczak

    2011-12-03

    The goal of the presented paper is to provide an introduction to the basic computational models used in quantum information theory. We review various models of quantum Turing machine, quantum circuits and quantum random access machine (QRAM) along with their classical counterparts. We also provide an introduction to quantum programming languages, which are developed using the QRAM model. We review the syntax of several existing quantum programming languages and discuss their features and limitations.

  20. 02/03/2011 09:46The Last Word On Ultimate Explanations? | Evolutionary Psychology Blog Page 1 of 7http://www.epjournal.net/blog/2011/02/the-last-word-on-ultimate...1+Newsletter&utm_term=The+Last+Word+On+Ultimate+Explanations_3F

    E-Print Network [OSTI]

    West, Stuart

    02/03/2011 09:46The Last Word On Ultimate Explanations? | Evolutionary Psychology Blog Page 1 of 7http://www.epjournal.net/blog/2011/02/the-last-word-on-ultimate...1+Newsletter&utm_term=The+Last+Word, is now available. The Last Word On Ultimate Explanations? Posted on February 10, 2011 by Robert Kurzban

  1. Fast quantum control and light-matter interactions at the 10,000 quanta level

    E-Print Network [OSTI]

    Alonso, J; Soler, Z U; Fadel, M; Marinelli, M; Keitch, B C; Negnevitsky, V; Home, J P

    2015-01-01

    Fast control of quantum systems is essential in order to make use of quantum properties before they are degraded by decoherence. This is important for quantum-enhanced information processing, as well as for pushing quantum systems into macroscopic regimes at the boundary between quantum and classical physics. Bang-bang control attains the ultimate speed limit by making large changes to control fields on timescales much faster than the system can respond, however these methods are often challenging to implement experimentally. Here we demonstrate bang-bang control of a trapped-ion oscillator using nano-second switching of the trapping potentials. We perform controlled displacements which allow us to realize quantum states with up to 10,000 quanta of energy. We use these displaced states to verify the form of the ion-light interaction at high excitations which are far outside the usual regime of operation. These methods provide new possibilities for quantum-state manipulation and generation, alongside the poten...

  2. Quantum noise of non-ideal Sagnac speed meter interferometer with asymmetries

    E-Print Network [OSTI]

    S. L. Danilishin; C. Graef; S. S. Leavey; J. Hennig; E. A. Houston; D. Pascucci; S. Steinlechner; J. Wright; S. Hild

    2015-02-19

    The speed meter concept has been identified as a technique that can potentially provide laser-interferometric measurements at a sensitivity level which surpasses the Standard Quantum Limit (SQL) over a broad frequency range. As with other sub-SQL measurement techniques, losses play a central role in speed meter interferometers and they ultimately determine the quantum noise limited sensitivity that can be achieved. So far in the literature, the quantum noise limited sensitivity has only been derived for lossless or lossy cases using certain approximations (for instance that the arm cavity round trip loss is small compared to the arm cavity mirror transmission). In this article we present a generalised, analytical treatment of losses in speed meters that allows accurate calculation of the quantum noise limited sensitivity of Sagnac speed meters with arm cavities. In addition, our analysis allows us to take into account potential imperfections in the interferometer such as an asymmetric beam splitter or differences of the reflectivities of the two arm cavity input mirrors. Finally,we use the examples of the proof-of-concept Sagnac speed meter currently under construction in Glasgow and a potential implementation of a Sagnac speed meter in the Einstein Telescope (ET) to illustrate how our findings affect Sagnac speed meters with meter- and kilometre-long baselines.

  3. Minor in Management The student is ultimately responsible for knowing and completing all degree requirements.

    E-Print Network [OSTI]

    Kihara, Daisuke

    Information Systems (CS 23500 with a C- or higher) MGMT 45100* Strategic Management (MGMT 20100 with a CMinor in Management The student is ultimately responsible for knowing and completing all degree Management Minor available for students outside the School of Management Credit Hours: 15 Minor Requirements

  4. ULTIMATE BEHAVIOR OF HEAVY STEEL SECTION WELDED SPLICES AND DESIGN IMPLICATIONS

    E-Print Network [OSTI]

    Bruneau, Michel

    ULTIMATE BEHAVIOR OF HEAVY STEEL SECTION WELDED SPLICES AND DESIGN IMPLICATIONS By Michel Bruneau are tested. Test specimens are devised so splices are located in regions of pure bending. The partial) specifies special Charpy V-notch testing re- quirements, along with some other weld-preparation requirements

  5. Fusion Energy Research at The National Ignition Facility: The Pursuit of the Ultimate Clean, Inexhaustible

    E-Print Network [OSTI]

    Fusion Energy Research at The National Ignition Facility: The Pursuit of the Ultimate Clean, Inexhaustible Energy Source" John D. Moody, Lawrence Livermore National Laboratory" " Presented to: MIT ­ PSFC IAP 2014" " January 15, 2014" This work performed under the auspices of the U.S. Department of Energy

  6. he mobile world depends on lithium-ion batteries --today's ultimate

    E-Print Network [OSTI]

    Napp, Nils

    T he mobile world depends on lithium- ion batteries -- today's ultimate rechargeable energy store -- a performance roughly on a par with the best Li-ion batteries. His batteries are based on lithium­sulphur (Li is applied to reverse the electron flow, which also drives the lithium ions back. In a Li­S battery

  7. Predicting the ultimate bending capacity of concrete beams from the ``relaxation ratio'' analysis of AE signals

    E-Print Network [OSTI]

    Predicting the ultimate bending capacity of concrete beams from the ``relaxation ratio'' analysis Available online 26 July 2005 Abstract This paper presents an alternative approach to the problem, based the unloading and loading phases of a cycle test and it showed a clear correlation with the bending failure load

  8. Proposal for an RF roadmap towards Ultimate Intensity in the LHC

    E-Print Network [OSTI]

    Baudrenghien, P

    2012-01-01

    The LHC currently operates with 1380 bunches at 50 ns spacing and 1.4 1011 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 1011 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. One must also consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that can deal with ultimate bunch intensity. Only a minor upgrade of the Low Level RF is necessary: the field set point will be modulated according to the phase shift produced by the transient beam loading, thus minimizing the RF power while keeping the strong feedback for stability and reduction of the RF noise.

  9. ight-derived energy enters the biosphere through photosyn-thesis, and ultimately sustains virtually all living organisms.

    E-Print Network [OSTI]

    Sarhan, Fathey

    L ight-derived energy enters the biosphere through photosyn- thesis, and ultimately sustains transformation of the light into reducing power (NADPH) and chemical energy (ATP) and its ultimate utilization and metabolism, exposure of plants to light energy that is in excess of that required for photosynthesis re

  10. Key role of work hardening in superconductivity/superfluidity, heat conductivity and ultimate strain increase, evolution, cancer, aging and other phase transitions

    E-Print Network [OSTI]

    V. P. Kisel

    2009-05-27

    The shear/laminar flow of liquids/gas/plasma/biological cells (BC), etc. is equivalent to dislocation-like shear of solids. The turbulent flow is the next stage of deformation/ multiplication of dislocation-like defects and their ordering in sub-grains and grain-boundaries, then grains slip-rotation in the direction approximately perpendicular to the shear flow. It is shown that phase transitions are governed by unified deformation hardening/softening under hydrostatic pressure, particle irradiation and impurity (isotope) chemical pressure, hard confining conditions and cooling, etc. thus changing electric, magnetic, ferroelectric, thermal, optical properties.1-2 Dislocation-like work hardening, DWH, is determined by non-monotonous properties of dislocation double edge-cross-jog slip, and ultrastrong DWH gives the lowest drag for any dislocation-like plasticity at phase transitions. This provides the same micromechanisms of the ultimate stage of conventional deformation (superfluidity) of ordinary liquids, i.e., water, kerosene and glycerin, liquid and solid He, quasi-particle condensates. The key role of DWH is confirmed for superconductivity, integer and fractional quantum Hall effects and the enhancement of ultimate strain and diffusion under deformation down to nanostructures, etc. Phase transformations in biological cells (explosive events of diversity and population of species and diseases - for example, locust and plaque bacteria, evolution, aging and cancer,2 bursts in the development of human intellectual possibilities (languages, culture, arts and sciences, history, etc.) depend on the same deformation effects in biological evolution.

  11. Polymer crystals in Rydberg quantum gases with competing attractive and repulsive interactions

    E-Print Network [OSTI]

    Lan, Zhihao; Levi, Emanuele; Li, Weibin; Lesanovsky, Igor

    2015-01-01

    We study a quantum spin chain with density-density interactions, whose nearest-neighbor strength can be tuned freely while the long-range tail follows a repulsive (van-der-Waals) power-law. The classical limit of this many-body system with generally non-convex interactions possesses an exact solution. In the case of attractive nearest-neighbor interaction the ground state features two complete devil's staircases of crystals that --- depending on the filling fraction --- are either composed of dimer particles or dimer holes. The staircase structure is controlled by the values of the nearest-neighbor interaction rather than a chemical potential which would be typically the case for convex interactions. The introduction of quantum fluctuations through a transverse field melts the dimer crystalline structures and ultimately makes the system enter a paramagnetic phase. For intermediate transverse field strengths, however, we identify a region, where the density-density correlations suggest the emergence of quasi l...

  12. 1-nm-thick graphene tri-layer as the ultimate copper diffusion barrier

    SciTech Connect (OSTI)

    Nguyen, Ba-Son [Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Lin, Jen-Fin [Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Perng, Dung-Ching, E-mail: dcperng@ee.ncku.edu.tw [Institute of Microelectronics and Electrical Engineering Department, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China)

    2014-02-24

    We demonstrate the thinnest ever reported Cu diffusion barrier, a 1-nm-thick graphene tri-layer. X-ray diffraction patterns and Raman spectra show that the graphene is thermally stable at up to 750?°C against Cu diffusion. Transmission electron microscopy images show that there was no inter-diffusion in the Cu/graphene/Si structure. Raman analyses indicate that the graphene may have degraded into a nanocrystalline structure at 750?°C. At 800?°C, the perfect carbon structure was damaged, and thus the barrier failed. The results of this study suggest that graphene could be the ultimate Cu interconnect diffusion barrier.

  13. Sales to Ultimate Customers (Megawatthours) by State by Sector by Provider, 1990

    U.S. Energy Information Administration (EIA) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page| Open Energy Informationmonthly gasoline price toStocks 2009CubicAnalysis &V 1997Sales to Ultimate Customers

  14. Ultimate storage ring based on fourth-order geometric achromats (Journal

    Office of Scientific and Technical Information (OSTI)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.Theory of rare Kaon and(Conference) |Article) | SciTech Connect Ultimate storage

  15. The theoretical ultimate magnetoelectric coefficients of magnetoelectric composites by optimization design

    SciTech Connect (OSTI)

    Wang, H.-L.; Liu, B., E-mail: liubin@tsinghua.edu.cn [AML, CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2014-03-21

    This paper investigates what is the largest magnetoelectric (ME) coefficient of ME composites, and how to realize it. From the standpoint of energy conservation, a theoretical analysis is carried out on an imaginary lever structure consisting of a magnetostrictive phase, a piezoelectric phase, and a rigid lever. This structure is a generalization of various composite layouts for optimization on ME effect. The predicted theoretical ultimate ME coefficient plays a similar role as the efficiency of ideal heat engine in thermodynamics, and is used to evaluate the existing typical ME layouts, such as the parallel sandwiched layout and the serial layout. These two typical layouts exhibit ME coefficient much lower than the theoretical largest values, because in the general analysis the stress amplification ratio and the volume ratio can be optimized independently and freely, but in typical layouts they are dependent or fixed. To overcome this shortcoming and achieve the theoretical largest ME coefficient, a new design is presented. In addition, it is found that the most commonly used electric field ME coefficient can be designed to be infinitely large. We doubt the validity of this coefficient as a reasonable ME effect index and consider three more ME coefficients, namely the electric charge ME coefficient, the voltage ME coefficient, and the static electric energy ME coefficient. We note that the theoretical ultimate value of the static electric energy ME coefficient is finite and might be a more proper measure of ME effect.

  16. Weapons and commercial plutonium ultimate disposition choices: Destroy ``completely`` or store forever

    SciTech Connect (OSTI)

    Bowman, C.D.

    1994-07-01

    All of the options under consideration for weapons and commercial plutonium disposition ultimately boil down to the choices of either ``complete`` destruction or storage ``forever.`` None of the reactor-based plutonium burning systems demonstrated over the past 50 years of reactor development consume this material completely. Ultimately considerable unburned plutonium must be stored ``forever`` from those systems. Plutonium is considered to be dangerous both as a weapons material and as a health hazard. While properly stored plutonium might never make its way back by natural phenomena into the environment as a health hazard, stored plutonium is always accessible to recovery for malevolent purposes. It must be guarded wherever in the world it is stored for as long as it continues to exist. Complete destruction of the plutonium eliminates this material as a concern of future generations. Los Alamos National Laboratory accelerator-driven technology promises to allow safe and complete destruction of this material. Furthermore it appears that in the process of destruction the neutron rich features of the weapons plutonium provides benefits to society that place a value on weapons plutonium exceeding that of highly enriched uranium. A realistic time scale for development and deployment of burial technology either with or without partial burning in reactors is expected to be comparable with or to exceed the time for development and deployment of the accelerator-driven destruction method under study at Los Alamos.

  17. Quantum Time

    E-Print Network [OSTI]

    John Ashmead

    2010-05-05

    Normally we quantize along the space dimensions but treat time classically. But from relativity we expect a high level of symmetry between time and space. What happens if we quantize time using the same rules we use to quantize space? To do this, we generalize the paths in the Feynman path integral to include paths that vary in time as well as in space. We use Morlet wavelet decomposition to ensure convergence and normalization of the path integrals. We derive the Schr\\"odinger equation in four dimensions from the short time limit of the path integral expression. We verify that we recover standard quantum theory in the non-relativistic, semi-classical, and long time limits. Quantum time is an experiment factory: most foundational experiments in quantum mechanics can be modified in a way that makes them tests of quantum time. We look at single and double slits in time, scattering by time-varying electric and magnetic fields, and the Aharonov-Bohm effect in time.

  18. Quantum chaos algorithms and dissipative decoherence with quantum trajectories Jae Weon Lee and Dima L. Shepelyansky

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Quantum chaos algorithms and dissipative decoherence with quantum trajectories Jae Weon Lee algorithm simulating dynamics in various regimes of quantum chaos including dynamical localization of quantum chaos 24 . Such models describe a quantum dy- namics which is chaotic in the classical limit

  19. Assessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length

    SciTech Connect (OSTI)

    Stewart, G.; Lackner, M.; Haid, L.; Matha, D.; Jonkman, J.; Robertson, A.

    2013-07-01

    With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbines. One issue is the appropriate simulation length needed for floating turbines. This paper will discuss the results from a study assessing the impact of simulation length on the ultimate and fatigue loads of the structure, and will address uncertainties associated with changing the simulation length for the analyzed floating platform. Recommendations of required simulation length based on load uncertainty will be made and compared to current simulation length requirements.

  20. Quantum metrology in Lipkin-Meshkov-Glick critical systems

    E-Print Network [OSTI]

    Giulio Salvatori; Antonio Mandarino; Matteo G. A. Paris

    2015-04-01

    The Lipkin-Meshkov-Glick (LMG) model describes critical systems with interaction beyond the first-neighbor approximation. Here we address the characterization of LMG systems, i.e. the estimation of anisotropy, and show how criticality may be exploited to improve precision. In particular, we provide exact results for the Quantum Fisher Information of small-size LMG chains made of $N=2, 3$ and $4$ lattice sites and analyze the same quantity in the thermodynamical limit by means of a zero-th order approximation of the system Hamiltonian. We then show that the ultimate bounds to precision may be achieved by tuning the external field and by measuring the total magnetization of the system. We also address the use of LMG systems as quantum thermometers and show that: i) precision is governed by the gap between the lowest energy levels of the systems, ii) field-dependent level crossing provides a resource to extend the operating range of the quantum thermometer.

  1. Information and noise in quantum measurement

    E-Print Network [OSTI]

    Holger F. Hofmann

    2000-03-30

    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.

  2. Quantum Chaos & Quantum Computers

    E-Print Network [OSTI]

    D. L. Shepelyansky

    2000-06-15

    The standard generic quantum computer model is studied analytically and numerically and the border for emergence of quantum chaos, induced by imperfections and residual inter-qubit couplings, is determined. This phenomenon appears in an isolated quantum computer without any external decoherence. The onset of quantum chaos leads to quantum computer hardware melting, strong quantum entropy growth and destruction of computer operability. The time scales for development of quantum chaos and ergodicity are determined. In spite the fact that this phenomenon is rather dangerous for quantum computing it is shown that the quantum chaos border for inter-qubit coupling is exponentially larger than the energy level spacing between quantum computer eigenstates and drops only linearly with the number of qubits n. As a result the ideal multi-qubit structure of the computer remains rather robust against imperfections. This opens a broad parameter region for a possible realization of quantum computer. The obtained results are related to the recent studies of quantum chaos in such many-body systems as nuclei, complex atoms and molecules, finite Fermi systems and quantum spin glass shards which are also reviewed in the paper.

  3. Short seed extractors against quantum storage

    E-Print Network [OSTI]

    Amnon Ta-Shma

    2008-10-10

    Some, but not all, extractors resist adversaries with limited quantum storage. In this paper we show that Trevisan's extractor has this property, thereby showing an extractor against quantum storage with logarithmic seed length.

  4. Quantum Noise in Conventional Optical Heterodyne Devices

    E-Print Network [OSTI]

    Dechao He; Boya Xie; Yu Xiao; Sheng Feng

    2014-10-31

    By invoking the quantum theory of optical coherence, we theoretically show that the quantum noise in conventional optical heterodyne devices, which were previously identified as usual phase-insensitive amplifiers with additional quantum noise, is similar to that in optical homodyne devices, as verified by experimental data. Albeit more study is demanded to understand this result, it is certain that neither the uncertainty principle nor Caves's theorem for quantum noise of linear amplifiers sets a limit to the quantum noise of heterodyne devices.

  5. QUANTUM CHAOS IN QUANTUM NETWORKS()

    E-Print Network [OSTI]

    Shepelyansky, Dima

    QUANTUM CHAOS IN QUANTUM NETWORKS() Chepelianskii Alexei Lyc´ee Pierre de Fermat and Quantware MIPS Computers and Quantum Chaos", June 28 - 30, 2001, Villa Olmo, Como, Italy #12;SHORT DESCRIPTION OF THE RESULTS Quantum chaos in a quantum small world We introduce and study a quantum small world model

  6. Proximate and Ultimate Compositional Changes in Corn Stover during Torrefaction using Thermogravimetric Analyzer and Microwaves

    SciTech Connect (OSTI)

    Jaya Shankar Tumuluru

    2012-07-01

    Abstract The world is currently aiming to reduce the dependence on fossil fuels and to achieve a sustainable renewable supply. Renewable energies represent a diversity of energy sources that can help to maintain the equilibrium of different ecosystems. Among the various sources of renewable energy, biomass is considered carbon neutral because the carbon dioxide released during its use is already part of the carbon cycle. Increasing the use of biomass for energy can help to reduce the negative CO2 impact on the environment and help meet the targets established in the Kyoto Protocol. Energy from biomass can be produced from different processes, including thermochemical (direct combustion, gasification, and pyrolysis), biological (anaerobic digestion, fermentation), or chemical (esterification) technologies. There are lot challenges in using biomass for energy applications. To name few low bulk density, high moisture content, irregular size and shape, hydrophilic nature and low calorific value. In commercial scale operation large quantities of biomass are needed and this will create problems associated with storage and transportation. Furthermore, grinding raw biomass with high moisture content is very challenging as there are no specific equipments and can increase the costs and in some cases it becomes highly impossible. All of these drawbacks led to development of some pretreatment techniques to make biomass more suitable for fuel applications. One of the promising techniques is torrefaction. Torrefaction is heating the biomass in an inert environment or reduced environment. During torrefaction biomass losses moisture, becomes more brittle and with increased energy density values. There are different techniques used for torrefaction of biomass. Fixed bed, bubbling sand bed and moving bed are the most common ones used. The use of microwaves for torrefaction purposes has not been explored. In the present study we looked into the torrefaction of biomass using the regular and microwaves and their effect on proximate and ultimate composition. Studies indicated that microwave torrefaction is a good way to torrefy the biomass in short periods of time. A maximum calorific value of 21 MJ/kg is achievable at 6 min residence time compared to 15 min using the dry torrefaction technique. Increasing the residence time increased the carbon content where a maximum carbon content of 52.20 % was achievable at lower residence time. The loss of volatiles is comparatively lower compared to dry torrefaction technique. Moisture content of microwave torrefied samples was in between 2-2.5 % (w.b).

  7. Environmental, Economic, and Energy Assessment of the Ultimate Analysis and Moisture Content of Municipal Solid Waste in a Parallel

    E-Print Network [OSTI]

    Alvarez, Pedro J.

    -combustion is a waste-to-energy technology that can use MSW and coal as co-fuels, offering potential energy recoveryEnvironmental, Economic, and Energy Assessment of the Ultimate Analysis and Moisture Content ABSTRACT: Use of municipal solid waste (MSW) as fuel for electricity generation reduces landfill disposal

  8. Decoherence in adiabatic quantum computation

    E-Print Network [OSTI]

    Tameem Albash; Daniel A. Lidar

    2015-06-19

    Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time-scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit $T_2$ time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary cancellation methods, designed to improve the fidelity of adiabatic quantum computing in the closed system setting, remain beneficial in the open system setting. To address the high computational cost of master equation simulations, we also demonstrate that a quantum Monte Carlo algorithm that explicitly accounts for a thermal bosonic bath can be used to interpolate between classical and quantum annealing. Our study highlights and clarifies the significantly different role played by decoherence in the adiabatic and circuit models of quantum computing.

  9. Quantum coherent states in cosmology

    E-Print Network [OSTI]

    Houri Ziaeepour

    2015-02-15

    Coherent states consist of superposition of infinite number of particles and do not have a classical analogue. We study their evolution in a FLRW cosmology and show that only when full quantum corrections are considered, they may survive the expansion of the Universe and form a global condensate. This state of matter can be the origin of accelerating expansion of the Universe, generally called dark energy, and inflation in the early universe. Additionally, such a quantum pool may be the ultimate environment for decoherence at shorter distances. If dark energy is a quantum coherent state, its dominant contribution to the total energy of the Universe at present provides a low entropy state which may be necessary as an initial condition for a new Big Bang in the framework of bouncing cosmology models.

  10. Hybrid quantum-classical models as constrained quantum systems

    E-Print Network [OSTI]

    M. Radonjic; S. Prvanovic; N. Buric

    2012-06-07

    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.

  11. Theoretical framework for quantum networks Giulio Chiribella,* Giacomo Mauro D'Ariano,

    E-Print Network [OSTI]

    D'Ariano, Giacomo Mauro

    the design of quantum devices over all possibilities admitted by quantum mechanics, thus finding the ultimate are treated both from a constructive point of view-- based on connections of elementary circuits--and from but are irrelevant for the final purpose. Channels and POVMs provide an efficient description of elementary circuits

  12. Unconditional Room Temperature Quantum Memory

    E-Print Network [OSTI]

    M. Hosseini; G. Campbell; B. M. Sparkes; P. K. Lam; B. C. Buchler

    2015-02-10

    Just as classical information systems require buffers and memory, the same is true for quantum information systems. The potential that optical quantum information processing holds for revolutionising computation and communication is therefore driving significant research into developing optical quantum memory. A practical optical quantum memory must be able to store and recall quantum states on demand with high efficiency and low noise. Ideally, the platform for the memory would also be simple and inexpensive. Here, we present a complete tomographic reconstruction of quantum states that have been stored in the ground states of rubidium in a vapour cell operating at around 80$^o$C. Without conditional measurements, we show recall fidelity up to 98% for coherent pulses containing around one photon. In order to unambiguously verify that our memory beats the quantum no-cloning limit we employ state independent verification using conditional variance and signal transfer coefficients.

  13. Ultimate low system dark count rate for superconducting nanowire single-photon detector

    E-Print Network [OSTI]

    Hiroyuki Shibata; Kaoru Shimizu; Hiroki Takesue; Yasuhiro Tokura

    2015-07-07

    The dark count rate (DCR) is a key parameter of single-photon detectors. By introducing a bulk optical band-pass filter mounted on a fiber-to-fiber optical bench cooled at 3 K and blocking down to 5 micrometer, we suppressed the DCR of a superconducting nanowire single-photon detector by more than three orders of magnitude. The DCR is limited by the blackbody radiation through a signal passband of 20 nm bandwidth. The figure of merit, system detection efficiency, and DCR were 2.7 x 10^11, 2.3 %, and 0.001 Hz, respectively. Narrowing the bandwidth to 100 GHz suppresses the DCR to 0.0001 Hz and the figure of merit increases to 1.8 x 10^12.

  14. Ultimate low system dark count rate for superconducting nanowire single-photon detector

    E-Print Network [OSTI]

    Shibata, Hiroyuki; Takesue, Hiroki; Tokura, Yasuhiro

    2015-01-01

    The dark count rate (DCR) is a key parameter of single-photon detectors. By introducing a bulk optical band-pass filter mounted on a fiber-to-fiber optical bench cooled at 3 K and blocking down to 5 micrometer, we suppressed the DCR of a superconducting nanowire single-photon detector by more than three orders of magnitude. The DCR is limited by the blackbody radiation through a signal passband of 20 nm bandwidth. The figure of merit, system detection efficiency, and DCR were 2.7 x 10^11, 2.3 %, and 0.001 Hz, respectively. Narrowing the bandwidth to 100 GHz suppresses the DCR to 0.0001 Hz and the figure of merit increases to 1.8 x 10^12.

  15. Fundamental limit of nanophotonic light trapping in solar cells

    E-Print Network [OSTI]

    Fan, Shanhui

    Fundamental limit of nanophotonic light trapping in solar cells Zongfu Yu1 , Aaswath Raman and is becoming increasingly urgent for current solar cell research. The standard theory of light trapping-generation solar cells. The ultimate success of photovoltaic (PV) cell technology requires great advancements

  16. Exploring the limit of metazoan thermal tolerance via comparative proteomics

    E-Print Network [OSTI]

    Girguis, Peter R.

    around hydrothermal vents are highly variable, ranging from near freezing up to 3008C. Never- theless transport chain enable pronounced thermotolerance. Ultimately, oxidative stress may be the key factor instability [2], and limitations in gas transport have all been implicated as possible modes of physiological

  17. 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]

    Konstantin G. Zloshchastiev

    2009-11-30

    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.

  18. "Pushing the frontiers in spintronics and quantum information."

    E-Print Network [OSTI]

    Zhigilei, Leonid V.

    "Pushing the frontiers in spintronics and quantum information." Stuart Wolf Professor Director, and as reconfigurable logic, a potential replacement for conventional CMOS. The ultimate spintronic structure contains Spintronics and Nanomagnetics As conventional CMOS technologies are running into multiple "red brick walls

  19. Spectral problems in open quantum chaos

    E-Print Network [OSTI]

    Stéphane Nonnenmacher

    2011-11-03

    This review article will present some recent results and methods in the study of 1-particle quantum or wave scattering systems, in the semiclassical/high frequency limit, in cases where the corresponding classical/ray dynamics is chaotic. We will focus on the distribution of quantum resonances, and the structure of the corresponding metastable states. Our study includes the toy model of open quantum maps, as well as the recent quantum monodromy operator method.

  20. Spectral problems in open quantum chaos

    E-Print Network [OSTI]

    Nonnenmacher, Stéphane

    2011-01-01

    This review article will present some recent results and methods in the study of 1-particle quantum or wave scattering systems, in the semiclassical/high frequency limit, in cases where the corresponding classical/ray dynamics is chaotic. We will focus on the distribution of quantum resonances, and the structure of the corresponding metastable states. Our study includes the toy model of open quantum maps, as well as the recent quantum monodromy operator method.

  1. Quantum steady computation

    SciTech Connect (OSTI)

    Castagnoli, G. )

    1991-08-10

    This paper reports that current conceptions of quantum mechanical computers inherit from conventional digital machines two apparently interacting features, machine imperfection and temporal development of the computational process. On account of machine imperfection, the process would become ideally reversible only in the limiting case of zero speed. Therefore the process is irreversible in practice and cannot be considered to be a fundamental quantum one. By giving up classical features and using a linear, reversible and non-sequential representation of the computational process - not realizable in classical machines - the process can be identified with the mathematical form of a quantum steady state. This form of steady quantum computation would seem to have an important bearing on the notion of cognition.

  2. Mechanically Detecting and Avoiding the Quantum Fluctuations of a Microwave Field

    E-Print Network [OSTI]

    theme in physics has been about the untapped power and benefits of quantum phenomena, largely stemming, called the Standard Quantum Limit (SQL)[9] is not ben- eficial: back-action due to the quantum nature

  3. Quantum Chaos and Quantum Algorithms

    E-Print Network [OSTI]

    Daniel Braun

    2001-10-05

    It was recently shown (quant-ph/9909074) that parasitic random interactions between the qubits in a quantum computer can induce quantum chaos and put into question the operability of a quantum computer. In this work I investigate whether already the interactions between the qubits introduced with the intention to operate the quantum computer may lead to quantum chaos. The analysis focuses on two well--known quantum algorithms, namely Grover's search algorithm and the quantum Fourier transform. I show that in both cases the same very unusual combination of signatures from chaotic and from integrable dynamics arises.

  4. Local Power in Quantum Mechanics

    E-Print Network [OSTI]

    Guillermo Albareda; Fabio Lorenzo Traversa; Xavier Oriols

    2015-11-12

    A general expression for the local power of a quantum system is derived. Defined as the time rate of change of the kinetic energy evaluated in a finite volume $\\Omega$ of the physical space, the local power exhibits contributions from both many-body classical and quantum correlations. Significantly, quantum correlations are manifested through the presence of non-local sources/sinks of power and through the action of local forces with no classical counterpart. The soundness of our results is proved along three limits of particular relevance: the closed-system limit ($\\Omega \\to \\infty$), the limit of non-interacting particles, and invoking classicality. Interestingly, we show that quantum fingerprints arise on the local power expression only when the volume $\\Omega$ is finite. Otherwise we recover a classical-like expression. This work could be of particular interest in the field of nanoelectronics, where the realization of a zero-power technology constitutes a long standing challenge.

  5. Quantum Memristors

    E-Print Network [OSTI]

    P. Pfeiffer; I. L. Egusquiza; M. Di Ventra; M. Sanz; E. Solano

    2015-11-06

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.

  6. Quantum Algorithms

    E-Print Network [OSTI]

    Michele Mosca

    2008-08-04

    This article surveys the state of the art in quantum computer algorithms, including both black-box and non-black-box results. It is infeasible to detail all the known quantum algorithms, so a representative sample is given. This includes a summary of the early quantum algorithms, a description of the Abelian Hidden Subgroup algorithms (including Shor's factoring and discrete logarithm algorithms), quantum searching and amplitude amplification, quantum algorithms for simulating quantum mechanical systems, several non-trivial generalizations of the Abelian Hidden Subgroup Problem (and related techniques), the quantum walk paradigm for quantum algorithms, the paradigm of adiabatic algorithms, a family of ``topological'' algorithms, and algorithms for quantum tasks which cannot be done by a classical computer, followed by a discussion.

  7. Resource Limits and Conversion Efficiency with Implications for Climate Change

    E-Print Network [OSTI]

    Croft, Gregory Donald

    2009-01-01

    use an ultimate coal recovery of 1.3 trillion tonnes, butestimate of ultimate coal recovery. Where stable estimatesbetween our ultimate coal recoveries and those by Mohr and

  8. Quantum Thermodynamics

    E-Print Network [OSTI]

    Ronnie Kosloff

    2013-05-10

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

  9. Quantum chaos in the Lorenz equations with symmetry breaking

    SciTech Connect (OSTI)

    Sarkar, S.; Satchell, J.S.

    1987-01-01

    The role of phase diffusion for quantum chaos in the quantum-mechanical model of the laser in the Haken limit is discussed. Fractal properties of the support of the asymptotic attracting probability distribution for the system are studied.

  10. Superadiabatic Controlled Evolutions and Universal Quantum Computation

    E-Print Network [OSTI]

    Alan C. Santos; Marcelo S. Sarandy

    2015-10-31

    Adiabatic state engineering is a powerful technique in quantum information and quantum control. However, its performance is limited by the adiabatic theorem of quantum mechanics. In this scenario, shortcuts to adiabaticity, such as provided by the superadiabatic theory, constitute a valuable tool to speed up the adiabatic quantum behavior. Here, we propose a superadiabatic route to implement universal quantum computation. Our method is based on the realization of piecewise controlled superadiabatic evolutions. Remarkably, they can be obtained by simple time-independent counter-diabatic Hamiltonians. In particular, we discuss the implementation of fast rotation gates and arbitrary n-qubit controlled gates, which can be used to design different sets of universal quantum gates. Concerning the energy cost of the superadiabatic implementation, we show that it is dictated by the quantum speed limit, providing an upper bound for the corresponding adiabatic counterparts.

  11. Quantum optical technologies for metrology, sensing and imaging

    E-Print Network [OSTI]

    Jonathan P. Dowling; Kaushik P. Seshadreesan

    2015-02-27

    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.

  12. Quantum music

    E-Print Network [OSTI]

    Volkmar Putz; Karl Svozil

    2015-08-17

    We consider ways of conceptualizing, rendering and perceiving quantum music, and quantum art in general. Thereby, we give particular emphasis to its non-classical aspects, such as coherent superposition and entanglement.

  13. Quantum music

    E-Print Network [OSTI]

    Putz, Volkmar

    2015-01-01

    We consider ways of conceptualizing, rendering and perceiving quantum music, and quantum art in general. Thereby we give particular emphasis to its non-classical aspects, such as coherent superposition and entanglement.

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

    E-Print Network [OSTI]

    Paola Zizzi

    2009-05-28

    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.

  15. Quantum Communication

    E-Print Network [OSTI]

    Nicolas Gisin

    2015-07-18

    Quantum Communication is the art of transferring an unknown quantum state from one location, Alice, to a distant one, Bob. This is a non-trivial task because of the quantum no-cloning theorem which prevents one from merely using only classical means.

  16. Quantum Random Access Codes using Single $d$-level Systems

    E-Print Network [OSTI]

    Armin Tavakoli; Alley Hameedi; Breno Marques; Mohamed Bourennane

    2015-04-30

    Random access codes (RACs) are used by a party to despite limited communication access an arbitrary subset of information held by another party. Quantum resources are known to enable RACs that break classical limitations. Here, we study quantum and classical RACs with high-level communication. We derive average performances of classical RACs and present families of high-level quantum RACs. Our results show that high-level quantum systems can significantly increase the advantage of quantum RACs over the classical counterparts. We demonstrate our findings in an experimental realization of a quantum RAC with four-level communication.

  17. The ultimate biomass refinery

    SciTech Connect (OSTI)

    Bungay, H.R. )

    1988-01-01

    Bits and pieces of refining schemes and both old and new technology have been integrated into a complete biomass harvesting, processing, waste recycle, and marketing complex. These choices are justified with economic estimates and technology assessments.

  18. Ultimate crack and lack of any security in the statistical key exchange protocol with random signals and feedback

    E-Print Network [OSTI]

    Gingl, Zoltan

    2010-01-01

    We deterministically crack the secure, statistical key exchange protocol based on feedback proposed by Pao-Lo Liu [ J. Lightwave Techology 27 (2009) pp. 5230-34]. The crack is ultimate and absolute because it works under idealized conditions, and produces much higher data visibility for the eavesdropper than the protocol provides for Alice and Bob. Even with the most idealistic driving noise spectrum stated by Liu, during the most secure phase of the protocol, far away from the transients, where the system is already in its most secure steady-state, the eavesdropper has 100% success rate in identifying the key bits, at the same time when Alice and Bob have less than 100% success rate while using the Liu protocol. No statistics is needed, Eve can extract the secure bit from two samples of the signal in the two direction. Thus the Liu-protocol offers no security against the attack described in this paper.

  19. Ultimate crack and lack of any security in the statistical key exchange protocol with random signals and feedback

    E-Print Network [OSTI]

    Zoltan Gingl; Laszlo B. Kish

    2010-12-30

    We deterministically crack the secure, statistical key exchange protocol based on feedback proposed by Pao-Lo Liu [ J. Lightwave Techology 27 (2009) pp. 5230-34]. The crack is ultimate and absolute because it works under idealized conditions, and produces much higher data visibility for the eavesdropper than the protocol provides for Alice and Bob. Even with the most idealistic driving noise spectrum stated by Liu, during the most secure phase of the protocol, far away from the transients, where the system is already in its most secure steady-state, the eavesdropper has 100% success rate in identifying the key bits, at the same time when Alice and Bob have less than 100% success rate while using the Liu protocol. No statistics is needed, Eve can extract the secure bit from two samples of the signal in the two direction. Thus the Liu-protocol offers no security against the attack described in this paper.

  20. Decentralized Coherent Quantum Control Design for Translation Invariant Linear Quantum Stochastic Networks with Direct Coupling

    E-Print Network [OSTI]

    Arash Kh. Sichani; Igor G. Vladimirov; Ian R. Petersen

    2015-09-07

    This paper is concerned with coherent quantum control design for translation invariant networks of identical quantum stochastic systems subjected to external quantum noise. The network is modelled as an open quantum harmonic oscillator and is governed by a set of linear quantum stochastic differential equations. The dynamic variables of this quantum plant satisfy the canonical commutation relations. Similar large-scale systems can be found, for example, in quantum metamaterials and optical lattices. The problem under consideration is to design a stabilizing decentralized coherent quantum controller in the form of another translation invariant quantum system, directly coupled to the plant, so as to minimize a weighted mean square functional of the dynamic variables of the interconnected networks. We consider this problem in the thermodynamic limit of infinite network size and present first-order necessary conditions for optimality of the controller.

  1. Applications of quantum chaos to realistic quantum computations and sound treatment on quantum computers

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Applications of quantum chaos to realistic quantum computations and sound treatment on quantum speech and sound of complex quantum wavefunctions. Keywords: Quantum computers, quantum chaos

  2. Information Causality in the Quantum and Post-Quantum Regime

    E-Print Network [OSTI]

    Martin Ringbauer; Alessandro Fedrizzi; Dominic W. Berry; Andrew G. White

    2014-11-11

    Quantum correlations can be stronger than anything achieved by classical systems, yet they are not reaching the limit imposed by relativity. The principle of information causality offers a possible explanation for why the world is quantum and why there appear to be no even stronger correlations. Generalizing the no-signaling condition it suggests that the amount of accessible information must not be larger than the amount of transmitted information. Here we study this principle experimentally in the classical, quantum and post-quantum regimes. We simulate correlations that are stronger than allowed by quantum mechanics by exploiting the effect of polarization-dependent loss in a photonic Bell-test experiment. Our method also applies to other fundamental principles and our results highlight the special importance of anisotropic regions of the no-signalling polytope in the study of fundamental principles.

  3. Quantum curves

    E-Print Network [OSTI]

    Albert Schwarz

    2014-08-16

    One says that a pair (P,Q) of ordinary differential operators specify a quantum curve if [P,Q]=const. If a pair of difference operators (K,L) obey the relation KL=const LK we say that they specify a discrete quantum curve. This terminology is prompted by well known results about commuting differential and difference operators, relating pairs of such operators with pairs of meromorphic functions on algebraic curves obeying some conditions. The goal of this paper is to study the moduli spaces of quantum curves. We will show how to quantize a pair of commuting differential or difference operators (i.e. to construct the corresponding quantum curve or discrete quantum curve). The KP-hierarchy acts on the moduli space of quantum curves; we prove that similarly the discrete KP-hierarchy acts on the moduli space of discrete quantum curves.

  4. Grassmann Matrix Quantum Mechanics

    E-Print Network [OSTI]

    Dionysios Anninos; Frederik Denef; Ruben Monten

    2015-12-11

    We explore quantum mechanical theories whose fundamental degrees of freedom are rectangular matrices with Grassmann valued matrix elements. We study particular models where the low energy sector can be described in terms of a bosonic Hermitian matrix quantum mechanics. We describe the classical curved phase space that emerges in the low energy sector. The phase space lives on a compact Kahler manifold parameterized by a complex matrix, of the type discovered some time ago by Berezin. The emergence of a semiclassical bosonic matrix quantum mechanics at low energies requires that the original Grassmann matrices be in the long rectangular limit. We discuss possible holographic interpretations of such matrix models which, by construction, are endowed with a finite dimensional Hilbert space.

  5. Grassmann Matrix Quantum Mechanics

    E-Print Network [OSTI]

    Anninos, Dionysios; Monten, Ruben

    2015-01-01

    We explore quantum mechanical theories whose fundamental degrees of freedom are rectangular matrices with Grassmann valued matrix elements. We study particular models where the low energy sector can be described in terms of a bosonic Hermitian matrix quantum mechanics. We describe the classical curved phase space that emerges in the low energy sector. The phase space lives on a compact Kahler manifold parameterized by a complex matrix, of the type discovered some time ago by Berezin. The emergence of a semiclassical bosonic matrix quantum mechanics at low energies requires that the original Grassmann matrices be in the long rectangular limit. We discuss possible holographic interpretations of such matrix models which, by construction, are endowed with a finite dimensional Hilbert space.

  6. Weak Measurement and Feedback in Superconducting Quantum Circuits

    E-Print Network [OSTI]

    K. W. Murch; R. Vijay; I. Siddiqi

    2015-07-16

    We describe the implementation of weak quantum measurements in superconducting qubits, focusing specifically on transmon type devices in the circuit quantum electrodynamics architecture. To access this regime, the readout cavity is probed with on average a single microwave photon. Such low-level signals are detected using near quantum-noise-limited superconducting parametric amplifiers. Weak measurements yield partial information about the quantum state, and correspondingly do not completely project the qubit into an eigenstate. As such, we use the measurement record to either sequentially reconstruct the quantum state at a given time, yielding a quantum trajectory, or to close a direct quantum feedback loop, stabilizing Rabi oscillations indefinitely.

  7. Weak Measurement and Feedback in Superconducting Quantum Circuits

    E-Print Network [OSTI]

    K. W. Murch; R. Vijay; I. Siddiqi

    2015-07-28

    We describe the implementation of weak quantum measurements in superconducting qubits, focusing specifically on transmon type devices in the circuit quantum electrodynamics architecture. To access this regime, the readout cavity is probed with on average a single microwave photon. Such low-level signals are detected using near quantum-noise-limited superconducting parametric amplifiers. Weak measurements yield partial information about the quantum state, and correspondingly do not completely project the qubit into an eigenstate. As such, we use the measurement record to either sequentially reconstruct the quantum state at a given time, yielding a quantum trajectory, or to close a direct quantum feedback loop, stabilizing Rabi oscillations indefinitely.

  8. Joint system quantum descriptions arising from local quantumness

    E-Print Network [OSTI]

    Tom Cooney; Marius Junge; Miguel Navascues; David Perez-Garcia; Ignacio Villanueva

    2012-05-18

    Bipartite correlations generated by non-signalling physical systems that admit a finite-dimensional local quantum description cannot exceed the quantum limits, i.e., they can always be interpreted as distant measurements of a bipartite quantum state. Here we consider the effect of dropping the assumption of finite dimensionality. Remarkably, we find that the same result holds provided that we relax the tensor structure of space-like separated measurements to mere commutativity. We argue why an extension of this result to tensor representations seems unlikely.

  9. Quantum information science and complex quantum systems

    E-Print Network [OSTI]

    Michael A. Nielsen

    2002-10-01

    What makes quantum information science a science? This paper explores the idea that quantum information science may offer a powerful approach to the study of complex quantum systems.

  10. Dirac Quantum Cellular Automaton from Split-step Quantum Walk

    E-Print Network [OSTI]

    Mallick, Arindam

    2015-01-01

    Simulations of one quantum system by an other has an implications in realization of quantum machine that can imitate any quantum systems and solve problems that are not accessible to classical computers. One of the approach to engineer quantum simulations is to discretize the space-time degree of freedom in quantum dynamics and define the quantum cellular automata (QCA), a local unitary update rule on a lattice. Different models of QCA are constructed using different set of conditions which are not uniquely defined. The form of the operators in these model are not always in implementable configuration on an other system. Here, starting from a split-step discrete-time quantum walk (DTQW) which are uniquely defined for experimental implementation, we recover the Dirac quantum cellular automaton (DQCA). This will bridge the connection between Dirac equation(DE)-DQCA-DTQW and eliminate the explicit use of invariance, symmetries and limiting range of parameter to establish the connections. For a combination of par...

  11. Dirac Quantum Cellular Automaton from Split-step Quantum Walk

    E-Print Network [OSTI]

    Arindam Mallick; C. M. Chandrashekar

    2015-09-29

    Simulations of one quantum system by an other has an implications in realization of quantum machine that can imitate any quantum systems and solve problems that are not accessible to classical computers. One of the approach to engineer quantum simulations is to discretize the space-time degree of freedom in quantum dynamics and define the quantum cellular automata (QCA), a local unitary update rule on a lattice. Different models of QCA are constructed using different set of conditions which are not uniquely defined. The form of the operators in these model are not always in implementable configuration on an other system. Here, starting from a split-step discrete-time quantum walk (DTQW) which are uniquely defined for experimental implementation, we recover the Dirac quantum cellular automaton (DQCA). This will bridge the connection between Dirac equation(DE)-DQCA-DTQW and eliminate the explicit use of invariance, symmetries and limiting range of parameter to establish the connections. For a combination of parameters defining the split-step DTQW, we will show the recovery of all the fine oscillation of the probability distribution in position observed in DQCA but not in conventional DTQW. We will also present the Zitterbewegung oscillations and quantify the entanglement as a function of that parameters that define split-step DTQW. The unique definition of DTQW along with the parameter tuneability demonstrated in experimental implementation will establish it as an efficient tool to design quantum simulator with access to different physical regime and approach quantum field theory from principles of quantum information theory.

  12. The Three-mm Ultimate Mopra Milky Way Survey. I. Survey Overview, Initial Data Releases, and First Results

    E-Print Network [OSTI]

    Barnes, Peter J; Indermuehle, Balthasar; O'Dougherty, Stefan N; Lowe, Vicki; Cunningham, Maria R; Hernandez, Audra K; Fuller, Gary A

    2015-01-01

    We describe a new mm-wave molecular-line mapping survey of the southern Galactic Plane and its first data releases. The Three-mm Ultimate Mopra Milky Way Survey (ThrUMMS) maps a 60{\\deg}x2{\\deg} sector of our Galaxy's fourth quadrant, using a combination of fast mapping techniques with the Mopra radio telescope, simultaneously in the J=1-0 lines of $^{12}$CO, $^{13}$CO, C$^{18}$O, and CN near 112 GHz at ~arcminute and ~0.3 km s$^{-1}$ resolution, with ~2 K channel$^{-1}$ sensitivity for $^{12}$CO and ~1 K channel$^{-1}$ for the other transitions. The calibrated data cubes from these observations are made available to the community after processing through our pipeline. Here, we describe the motivation for ThrUMMS, the development of new observing techniques for Mopra, and how these techniques were optimised to the objectives of the survey. We showcase some sample data products and describe the first science results on CO-isotopologue line ratios. These vary dramatically across the Galactic Plane, indicating a...

  13. Gaussian quantum information

    E-Print Network [OSTI]

    Weedbrook, Christian

    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 ...

  14. Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity

    E-Print Network [OSTI]

    Unnikrishnan, C S

    2015-01-01

    Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitati...

  15. Low velocity limits of cold atom clocks

    E-Print Network [OSTI]

    J. Muñoz; I. Lizuain; J. G. Muga

    2009-09-08

    Fundamental low-energy limits to the accuracy of quantum clock and stopwatch models in which the clock hand motion is activated by the presence of a particle in a region of space have been studied in the past, but their relevance for actual atomic clocks had not been assessed. In this work we address the effect of slow atomic quantum motion on Rabi and Ramsey resonance fringe patterns, as a perturbation of the results based on classical atomic motion. We find the dependence of the fractional error of the corresponding atomic clocks on the atomic velocity and interaction parameters.

  16. Quantum Fourier transform and tomographic Renyi entropic inequalities

    E-Print Network [OSTI]

    M. A. Man'ko; V. I. Man'ko

    2009-02-25

    Renyi entropy associated with spin tomograms of quantum states is shown to obey to new inequalities containing the dependence on quantum Fourier transform. The limiting inequality for the von Neumann entropy of spin quantum states and a new kind of entropy associated with quantum Fourier transform are obtained. Possible connections with subadditivity and strong subadditivity conditions for tomographic entropies and von Neumann entropies are discussed.

  17. Quantum enhanced estimation of a multi-dimensional field

    E-Print Network [OSTI]

    Tillmann Baumgratz; Animesh Datta

    2015-07-10

    We present a framework for the quantum enhanced estimation of multiple parameters corresponding to non-commuting unitary generators. Our formalism provides a recipe for the simultaneous estimation of all three components of a magnetic field. We propose a probe state that surpasses the precision of estimating the three components individually and discuss measurements that come close to attaining the quantum limit. Our study also reveals that too much quantum entanglement may be detrimental to attaining the Heisenberg scaling in quantum metrology.

  18. Emergence of classical behavior from the quantum spin

    E-Print Network [OSTI]

    M. Radonjic; S. Prvanovic; N. Buric

    2012-02-09

    Classical Hamiltonian system of a point moving on a sphere of fixed radius is shown to emerge from the constrained evolution of quantum spin. The constrained quantum evolution corresponds to an appropriate coarse-graining of the quantum states into equivalence classes, and forces the equivalence classes to evolve as single units representing the classical states. The coarse-grained quantum spin with the constrained evolution in the limit of the large spin becomes indistinguishable from the classical system.

  19. Nanodiamond interferometry meets quantum gravity

    E-Print Network [OSTI]

    Albrecht, Andreas; Plenio, Martin B

    2014-01-01

    Interferometry with massive particles may have the potential to explore the limitations of standard quantum mechanics in particular where it concerns its boundary with general relativity and the yet to be developed theory of quantum gravity. This development is hindered considerably by the lack of experimental evidence and testable predictions. Analyzing effects that appear to be common to many of such theories, such as a modification of the energy dispersion and of the canonical commutation relation within the standard framework of quantum mechanics, has been proposed as a possible way forward. Here we analyze in some detail the impact of a modified energy-momentum dispersion in a Ramsey-Bord\\'e setup and provide achievable bounds of these correcting terms when operating such an interferometer with nanodiamonds. Thus, taking thermal and gravitational disturbances into account will show that without specific prerequisites, quantum gravity modifications may in general be suppressed requiring a revision of prev...

  20. Non-hermitian quantum thermodynamics

    E-Print Network [OSTI]

    Bart?omiej Gardas; Sebastian Deffner; Avadh Saxena

    2015-11-19

    Thermodynamics is a phenomenological theory of heat and work. Here we analyze to what extent quantum thermodynamic relations are immune to the underlying mathematical formulation of quantum mechanics. As a main result, we show that the Jarzynski equality holds true for all non-hermitian quantum systems with real spectrum. This equality expresses the second law of thermodynamics for isothermal processes arbitrarily far from equilibrium. In the quasistatic limit however, the second law is reflected in the Carnot bound and it is fulfilled even if some eigenenergies are complex provided they appear in conjugate pairs. Furthermore, we propose a setup to test our predictions. The quantum system in question consists of strongly interacting excitons and photons in a semiconductor microcavity.

  1. How Einstein's quantum hypothesis requires a departure from classical mechanics

    E-Print Network [OSTI]

    Gabriele Carcassi

    2009-02-16

    The aim of this work is to show how Einstein's quantum hypothesis leads immediately and necessarily to a departure from classical mechanics. First we note that the classical description and predictions are in terms of idealized measurements that are exact, instantaneous, non-perturbative, independent of each other and process agnostic. If we assume we cannot arbitrarily reduce the strength of a signal, measurements are ultimately perturbative to some degree. We show how a physical description in which the best measurement conceivable, i.e. the ideal measurement, perturbs the system leads to all the concepts present in quantum mechanics including conjugate variables, probabilistic predictions and measurements connected to symmetries.

  2. Introduction. The Snirelman theorem. Quantum unique ergodicity ? Pictures. Kolmogorov-Sinai entropy. About the proof. Entropy and the localization of eigenfunctions.

    E-Print Network [OSTI]

    Anantharaman, Nalini

    Introduction. The Snirelman theorem. Quantum unique ergodicity ? Pictures. Kolmogorov-Sinai entropy Polytechnique 16 octobre 2007 #12;Introduction. The Snirelman theorem. Quantum unique ergodicity ? Pictures) = 1 in the limit k - +. #12;Introduction. The Snirelman theorem. Quantum unique ergodicity ? Pictures

  3. Measuring Quantum Coherence with Entanglement

    E-Print Network [OSTI]

    Alexander Streltsov; Uttam Singh; Himadri Shekhar Dhar; Manabendra Nath Bera; Gerardo Adesso

    2015-06-18

    Quantum coherence is an essential ingredient in quantum information processing and plays a central role in emergent fields such as nanoscale thermodynamics and quantum biology. However, our understanding and quantitative characterization of coherence as an operational resource are still very limited. Here we show that any degree of coherence with respect to some reference basis can be converted to entanglement via incoherent operations. This finding allows us to define a novel general class of measures of coherence for a quantum system of arbitrary dimension, in terms of the maximum bipartite entanglement that can be generated via incoherent operations applied to the system and an incoherent ancilla. The resulting measures are proven to be valid coherence monotones satisfying all the requirements dictated by the resource theory of quantum coherence. We demonstrate the usefulness of our approach by proving that the fidelity-based geometric measure of coherence is a full convex coherence monotone, and deriving a closed formula for it on arbitrary single-qubit states. Our work provides a clear quantitative and operational connection between coherence and entanglement, two landmark manifestations of quantum theory and both key enablers for quantum technologies.

  4. Quantum optimality of photon counting for temperature measurement of thermal astronomical sources

    E-Print Network [OSTI]

    Ranjith Nair; Mankei Tsang

    2015-07-28

    Using the quantum Cram\\'{e}r-Rao bound from quantum estimation theory, we derive a fundamental quantum limit on the sensitivity of a temperature measurement of a thermal astronomical source. This limit is expressed in terms of the source temperature $T_s$, input spectral bandwidth $\\Delta \

  5. High-Performance Glazing for Energy-Efficient and Bird-Safe Buildings Objective: With the ultimate goal of reducing bird-window collisions, identify a short list

    E-Print Network [OSTI]

    Wolberg, George

    High-Performance Glazing for Energy-Efficient and Bird-Safe Buildings Objective: With the ultimate-- improving the energy efficiency of buildings, and preventing bird deaths. What brings them together energy-efficiency perspective, less glazing on buildings would be preferable. But it is unlikely that our

  6. About the Department of Energy's Basic Energy Sciences Program Basic Energy Sciences (BES) supports fundamental research to understand, predict, and ultimately control matter

    E-Print Network [OSTI]

    Zhigilei, Leonid V.

    at the electronic, atomic, and molecular levels. This research provides the foundations for new energy technologies#12;About the Department of Energy's Basic Energy Sciences Program Basic Energy Sciences (BES) supports fundamental research to understand, predict, and ultimately control matter and energy

  7. Quantum Chaos

    E-Print Network [OSTI]

    Frank Steiner

    1994-02-07

    A short historical overview is given on the development of our knowledge of complex dynamical systems with special emphasis on ergodicity and chaos, and on the semiclassical quantization of integrable and chaotic systems. The general trace formula is discussed as a sound mathematical basis for the semiclassical quantization of chaos. Two conjectures are presented on the basis of which it is argued that there are unique fluctuation properties in quantum mechanics which are universal and, in a well defined sense, maximally random if the corresponding classical system is strongly chaotic. These properties constitute the quantum mechanical analogue of the phenomenon of chaos in classical mechanics. Thus quantum chaos has been found.

  8. Physicalism versus quantum mechanics

    E-Print Network [OSTI]

    Stapp, Henry P; Theoretical Physics Group; Physics Division

    2009-01-01

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

  9. Liouville quantum gravity and KPZ

    E-Print Network [OSTI]

    Duplantier, Bertrand

    Consider a bounded planar domain D, an instance h of the Gaussian free field on D, with Dirichlet energy ... and a constant 0[less than or equal to]?<2. The Liouville quantum gravity measure on D is the weak limit as ...

  10. How detrimental is decoherence in adiabatic quantum computation?

    E-Print Network [OSTI]

    Albash, Tameem

    2015-01-01

    Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time-scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit $T_2$ time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary canc...

  11. Entropy of quantum channel in the theory of quantum information

    E-Print Network [OSTI]

    Wojciech Roga

    2011-10-03

    Quantum channels, also called quantum operations, are linear, trace preserving and completely positive transformations in the space of quantum states. Such operations describe discrete time evolution of an open quantum system interacting with an environment. The thesis contains an analysis of properties of quantum channels and different entropies used to quantify the decoherence introduced into the system by a given operation. Part I of the thesis provides a general introduction to the subject. In Part II, the action of a quantum channel is treated as a process of preparation of a quantum ensemble. The Holevo information associated with this ensemble is shown to be bounded by the entropy exchanged during the preparation process between the initial state and the environment. A relation between the Holevo information and the entropy of an auxiliary matrix consisting of square root fidelities between the elements of the ensemble is proved in some special cases. Weaker bounds on the Holevo information are also established. The entropy of a channel, also called the map entropy, is defined as the entropy of the state corresponding to the channel by the Jamiolkowski isomorphism. In Part III of the thesis, the additivity of the entropy of a channel is proved. The minimal output entropy, which is difficult to compute, is estimated by an entropy of a channel which is much easier to obtain. A class of quantum channels is specified, for which additivity of channel capacity is conjectured. The last part of the thesis contains characterization of Davies channels, which correspond to an interaction of a state with a thermal reservoir in the week coupling limit, under the condition of quantum detailed balance and independence of rotational and dissipative evolutions. The Davies channels are characterized for one-qubit and one-qutrit systems.

  12. Quantum time

    E-Print Network [OSTI]

    Giovannetti, Vittorio

    We give a consistent quantum description of time, based on Page and Wootters’s conditional probabilities mechanism, which overcomes the criticisms that were raised against similar previous proposals. In particular we show ...

  13. Quantum exam

    E-Print Network [OSTI]

    Nguyen Ba An

    2006-02-28

    Absolutely and asymptotically secure protocols for organizing an exam in a quantum way are proposed basing judiciously on multipartite entanglement. The protocols are shown to stand against common types of eavesdropping attack.

  14. Quantum conversion

    E-Print Network [OSTI]

    Michael Mazilu

    2015-08-06

    The electromagnetic momentum transferred transfered to scattering particles is proportional to the intensity of the incident fields, however, the momentum of single photons ($\\hbar k$) does not naturally appear in these classical expressions. Here, we discuss an alternative to Maxwell's stress tensor that renders the classical electromagnetic field momentum compatible to the quantum mechanical one. This is achieved through the introduction of the quantum conversion which allows the transformation, including units, of the classical fields to wave-function equivalent fields.

  15. Recent developments in mathematical Quantum Chaos

    E-Print Network [OSTI]

    S. Zelditch

    2009-11-23

    This is a survey of recent results on quantum ergodicity, specifically on the large energy limits of matrix elements relative to eigenfunctions of the Laplacian. It is mainly devoted to QUE (quantum unique ergodicity) results, i.e. results on the possible existence of a sparse subsequence of eigenfunctions with anomalous concentration. We cover the lower bounds on entropies of quantum limit measures due to Anantharaman, Nonnenmacher, and Rivi\\`ere on compact Riemannian manifolds with Anosov flow. These lower bounds give new constraints on the possible quantum limits. We also cover the non-QUE result of Hassell in the case of the Bunimovich stadium. We include some discussion of Hecke eigenfunctions and recent results of Soundararajan completing Lindenstrauss' QUE result, in the context of matrix elements for Fourier integral operators. Finally, in answer to the potential question `why study matrix elements' it presents an application of the author to the geometry of nodal sets.

  16. A semiclassical study of quantum maps

    SciTech Connect (OSTI)

    Guo, Y.

    1992-01-01

    The study of the behavior of quantum systems whose classical limit exhibits chaos defines the problem of quantum chaos. One would naturally ask how quantum mechanics approaches the classical limit [h bar] = 0, and how the chaotic motion in classical systems manifests itself in the corresponding quantum counterparts. Semiclassical mechanics is the bridge between quantum mechanics and classical mechanics. For studying the quantum mechanics corresponding to generic classical motion it is desirable to use the simplest possible model. The model system the authors use is the kicked rotator. Detailed computations of both classical and quantum mechanics are feasible for this system. The relationship between invariant classical phase space structures and quantum eigenfunctions has been the focus of recent semiclassical studies. The authors study the eigenstates of the quantum standard map associated with both integrable and non-integrable regions in classical phase space. The coherent-state representation is used to make the correspondence between the quantum eigenstates and the classical phase space structure. The importance of periodic orbits in the quantum eigenstates of classically chaotic Hamiltonians has become a popular topic in study of semiclassical limits of the systems. Periodic orbits arise without any assumption in the trace formula developed by Gutzwiller. The authors calculate the semiclassical coherent-state propagator. Since computing all the complex stationary orbits is not practical, the authors make a further assumption which the authors call the periodic point dominance (PPD). The authors present arguments and evidence to show that the PPD approximation works well in hard chaos regions where the full semiclassical approximation is not practical to use. The method fails in some boundary regions where both stable and unstable points are present, but the full semiclassical approximation is not a much better method than the PPD in many situations.

  17. Lead Telluride Quantum Dot Solar Cells Displaying External Quantum Efficiencies Exceeding 120%

    E-Print Network [OSTI]

    Böhm, Marcus L.; Jellicoe, Tom C.; Tabachnyk, Maxim; Davis, Nathaniel J. L. K.; Wisnivesky-Rocca-Rivarola, Florencia; Ducati, Caterina; Ehrler, Bruno; Bakulin, Artem A.; Greenham, Neil C.

    2015-10-21

    Multiple exciton generation (MEG) in semiconducting quantum dots is a process which produces multiple charge-carrier pairs from a single excitation. MEG is a possible route to bypass the Shockley-Queisser limit in single-junction solar cells...

  18. Quantum Non-Demolition Detection of Polar Molecule Complexes: Dimers, Trimers, Tetramers

    E-Print Network [OSTI]

    Mekhov, Igor B

    2011-01-01

    The optical nondestructive method for in situ detection of the bound states of ultracold polar molecules is developed. It promises a minimally destructive measurement scheme up to a physically exciting quantum non-demolition (QND) level. The detection of molecular complexes beyond simple pairs of quantum particles (dimers, known, e.g., from the BEC-BCS theory) is suggested, including three-body (trimers) and four-body (tertramers) complexes trapped by one-dimensional tubes. The intensity of scattered light is sensitive to the molecule number fluctuations beyond the mean-density approximation. Such fluctuations are very different for various complexes, which leads to radically different light scattering. This type of research extends "quantum optics of quantum gases" to the field of ultracold molecules. Merging the quantum optical and ultracold gas problems will advance the experimental efforts towards the study of the light-matter interaction at its ultimate quantum level, where the quantizations of both ligh...

  19. Sandia Energy - Quantum Optics

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

    Quantum Optics Home Energy Research EFRCs Solid-State Lighting Science EFRC Quantum Optics Quantum OpticsTara Camacho-Lopez2015-03-30T16:37:03+00:00 Quantum Optics with a Single...

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

    E-Print Network [OSTI]

    Wipf, Christopher (Christopher Conrad)

    2013-01-01

    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 ...

  1. Quantum Artificial Intelligence

    E-Print Network [OSTI]

    B. Aoun; M. Tarifi

    2011-06-04

    This report introduces researchers in AI to some of the concepts in quantum heurisitics and quantum AI.

  2. Quantum Biology

    E-Print Network [OSTI]

    Alessandro Sergi

    2009-07-11

    A critical assessment of the recent developments of molecular biology is presented. The thesis that they do not lead to a conceptual understanding of life and biological systems is defended. Maturana and Varela's concept of autopoiesis is briefly sketched and its logical circularity avoided by postulating the existence of underlying {\\it living processes}, entailing amplification from the microscopic to the macroscopic scale, with increasing complexity in the passage from one scale to the other. Following such a line of thought, the currently accepted model of condensed matter, which is based on electrostatics and short-ranged forces, is criticized. It is suggested that the correct interpretation of quantum dispersion forces (van der Waals, hydrogen bonding, and so on) as quantum coherence effects hints at the necessity of including long-ranged forces (or mechanisms for them) in condensed matter theories of biological processes. Some quantum effects in biology are reviewed and quantum mechanics is acknowledged as conceptually important to biology since without it most (if not all) of the biological structures and signalling processes would not even exist. Moreover, it is suggested that long-range quantum coherent dynamics, including electron polarization, may be invoked to explain signal amplification process in biological systems in general.

  3. Quantum Coding with Finite Resources

    E-Print Network [OSTI]

    Marco Tomamichel; Mario Berta; Joseph M. Renes

    2015-05-28

    The quantum capacity of a memoryless channel is often used as a single figure of merit to characterize its ability to transmit quantum information coherently. The capacity determines the maximal rate at which we can code reliably over asymptotically many uses of the channel. We argue that this asymptotic treatment is insufficient to the point of being irrelevant in the quantum setting where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. For all practical purposes we should instead focus on the trade-off between three parameters: the rate of the code, the number of coherent uses of the channel, and the fidelity of the transmission. The aim is then to specify the region determined by allowed combinations of these parameters. Towards this goal, we find approximate and exact characterizations of the region of allowed triplets for the qubit dephasing channel and for the erasure channel with classical post-processing assistance. In each case the region is parametrized by a second channel parameter, the quantum channel dispersion. In the process we also develop several general inner (achievable) and outer (converse) bounds on the coding region that are valid for all finite-dimensional quantum channels and can be computed efficiently. Applied to the depolarizing channel, this allows us to determine a lower bound on the number of coherent uses of the channel necessary to witness super-additivity of the coherent information.

  4. Waste Not, Want Not: Heisenberg-Limited Metrology With Information Recycling

    E-Print Network [OSTI]

    Haine, Simon A; Lang, Matthias D; Caves, Carlton M

    2014-01-01

    Information recycling has been shown to improve the sensitivity of interferometers when the input quantum state has been partially transferred from some donor system. In this paper we demonstrate that when the quantum state of this donor system is from a particular class of Heisenberg-limited states, information recycling yields a Heisenberg-limited phase measurement. Crucially, this result holds irrespective of the fraction of the quantum state transferred to the interferometer input and also for a general class of number-conserving quantum-state-transfer processes, including ones that destroy the first-order phase coherence between the branches of the interferometer. This result could have significant applications in Heisenberg-limited atom interferometry, where the quantum state is transferred from a Heisenberg-limited photon source, and in optical interferometry where the loss can be monitored.

  5. Quantum Locality?

    E-Print Network [OSTI]

    Stapp, Henry P

    2011-01-01

    Robert Griffiths has recently addressed, within the framework of a 'consistent quantum theory' 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 that the putative proofs of this property that involve hidden variables 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 establishing, instead, properties of a system modified by adding properties alien to the original 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...

  6. (Limiting the greenhouse effect)

    SciTech Connect (OSTI)

    Fulkerson, W.

    1991-01-10

    The Dahlem Conference on controlling CO{sub 2} in the atmosphere focused on research needs broadly defined. The RD D needs discussed tended to be social-institutional rather than technically oriented perhaps because of the propensity of most attendees, but many important ideas emerged, including those related to questions on technology adoption by both developed, emerging, or transition economics. The European attendees appeared to be strongly devoted to reducing emissions, and doing it soon using efficiency improvement and ultimately renewables. The importance of efficiency improvement was universally accepted, but the extent to which it can be relied upon is a major uncertainty for everyone except the most zealous. There was no detailed discussion of what could be done to encourage the more rapid adoption of renewables. Most attendees seemed to have discounted nuclear, but, at any rate, the problems of reviving nuclear worldwide were not discussed in detail.

  7. Quantum measurement of hyperfine interaction in nitrogen-vacancy center

    E-Print Network [OSTI]

    Kilhyun Bang; Wen Yang; L. J. Sham

    2012-05-23

    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.

  8. Surface code quantum communication

    E-Print Network [OSTI]

    Austin G. Fowler; David S. Wang; Charles D. Hill; Thaddeus D. Ladd; Rodney Van Meter; Lloyd C. L. Hollenberg

    2010-02-05

    Quantum communication typically involves a linear chain of repeater stations, each capable of reliable local quantum computation and connected to their nearest neighbors by unreliable communication links. The communication rate in existing protocols is low as two-way classical communication is used. We show that, if Bell pairs are generated between neighboring stations with a probability of heralded success greater than 0.65 and fidelity greater than 0.96, two-way classical communication can be entirely avoided and quantum information can be sent over arbitrary distances with arbitrarily low error at a rate limited only by the local gate speed. The number of qubits per repeater scales logarithmically with the communication distance. If the probability of heralded success is less than 0.65 and Bell pairs between neighboring stations with fidelity no less than 0.92 are generated only every T_B seconds, the logarithmic resource scaling remains and the communication rate through N links is proportional to 1/(T_B log^2 N).

  9. Notes on Deterministic Programming of Quantum Observables and Channels

    E-Print Network [OSTI]

    Teiko Heinosaari; Mikko Tukiainen

    2015-05-13

    We study the limitations of deterministic programmability of quantum circuits, e.g., quantum computer. More precisely, we analyse the programming of quantum observables and channels via quantum multimeters. We show that the programming vectors for any two different sharp observables are necessarily orthogonal, whenever post-processing is not allowed. This result then directly implies that also any two different unitary channels require orthogonal programming vectors. This approach generalizes the well-known orthogonality result first proven by Nielsen and Chuang. In addition, we give size-bounds for a multimeter to be efficient in quantum programming.

  10. A nonlinear Ramsey interferometer operating beyond the Heisenberg limit

    E-Print Network [OSTI]

    S. Choi; B. Sundaram

    2007-09-24

    We show that a dynamically evolving two-mode Bose-Einstein condensate (TBEC) with an adiabatic, time-varying Raman coupling maps exactly onto a nonlinear Ramsey interferometer that includes a nonlinear medium. Assuming a realistic quantum state for the TBEC, namely the SU(2) coherent spin state, we find that the measurement uncertainty of the ``path-difference'' phase shift scales as the standard quantum limit (1/N^{1/2}) where N is the number of atoms, while that for the interatomic scattering strength scales as 1/N^{7/5}, overcoming the Heisenberg limit of 1/N.

  11. Quantum arithmetic with the Quantum Fourier Transform

    E-Print Network [OSTI]

    Lidia Ruiz-Perez; Juan Carlos Garcia-Escartin

    2014-11-21

    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.

  12. Quantum chaos viewed from quantum action

    E-Print Network [OSTI]

    D. Huard; H. Kröger; G. Melkonyan; L. P. Nadeau; K. J. M. Moriarty

    2004-06-18

    We consider a mixed chaotic Hamiltonian system and compare classical with quantum chaos. As alternative to the methods of enegy level spacing statistics and trace formulas, we construct a quantum action and a quantum analogue phase space to analyse quantum chaos.

  13. Quantum Chaos via the Quantum Action

    E-Print Network [OSTI]

    H. Kröger

    2002-12-16

    We discuss the concept of the quantum action with the purpose to characterize and quantitatively compute quantum chaos. As an example we consider in quantum mechanics a 2-D Hamiltonian system - harmonic oscillators with anharmonic coupling - which is classically a chaotic system. We compare Poincar\\'e sections obtained from the quantum action with those from the classical action.

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

    E-Print Network [OSTI]

    Vlad Gheorghiu

    2014-12-15

    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.

  15. Quantum computing in a piece of glass

    E-Print Network [OSTI]

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

    2011-12-15

    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.

  16. Quantum Error Correction for Quantum Memories

    E-Print Network [OSTI]

    Barbara M. Terhal

    2015-04-10

    Active quantum error correction using qubit stabilizer codes has emerged as a promising, but experimentally challenging, engineering program for building a universal quantum computer. In this review we consider the formalism of qubit stabilizer and subsystem stabilizer codes and their possible use in protecting quantum information in a quantum memory. We review the theory of fault-tolerance and quantum error-correction, discuss examples of various codes and code constructions, the general quantum error correction conditions, the noise threshold, the special role played by Clifford gates and the route towards fault-tolerant universal quantum computation. The second part of the review is focused on providing an overview of quantum error correction using two-dimensional (topological) codes, in particular the surface code architecture. We discuss the complexity of decoding and the notion of passive or self-correcting quantum memories. The review does not focus on a particular technology but discusses topics that will be relevant for various quantum technologies.

  17. Electrical resistivity as quantum chaos

    SciTech Connect (OSTI)

    Laughlin, R.B.

    1987-08-01

    The physics of quantum transport is re-examined as a problem in quantum chaos. It is proposed that the ''random potential'' in which electrons in dirty metals move is not random at all, but rather any potential inducing the electron motion to be chaotic. The Liapunov characteristic exponent of classical electron motion in this potential is identified with the collision rate l/tau appearing in Ohm's law. A field theory for chaotic systems, analogous to that used to describe dirty metals, is developed and used to investigate the quantum Sinai billiard problem. It is shown that a noninteracting degenerate electron gas moving in this potential exhibits Drude conductivity in the limit h-bar ..-->.. 0. 15 refs., 4 figs.

  18. Quantum Averages of Weak Values

    E-Print Network [OSTI]

    Yakir Aharonov; Alonso Botero

    2005-08-23

    We re-examine the status of the weak value of a quantum mechanical observable as an objective physical concept, addressing its physical interpretation and general domain of applicability. We show that the weak value can be regarded as a \\emph{definite} mechanical effect on a measuring probe specifically designed to minimize the back-reaction on the measured system. We then present a new framework for general measurement conditions (where the back-reaction on the system may not be negligible) in which the measurement outcomes can still be interpreted as \\emph{quantum averages of weak values}. We show that in the classical limit, there is a direct correspondence between quantum averages of weak values and posterior expectation values of classical dynamical properties according to the classical inference framework.

  19. Quantum Structures of a Model-Universe: An Inconsistency with Everett Interpretation of Quantum Mechanics

    E-Print Network [OSTI]

    J. Jeknic-Dugic; M. Dugic; A. Francom

    2013-08-13

    We observe a Quantum Brownian Motion (QBM) Model Universe in conjunction with recently established Entanglement Relativity and Parallel Occurrence of Decoherence. The Parallel Occurrence of Decoherence establishes the simultaneous occurrence of decoherence for two mutually irreducible structures (decomposition into subsystems) of the total QBM model universe. First we find that Everett world branching for one structure excludes branching for the alternate structure and in order to reconcile this situation branching cannot be allowed for either of the structures considered. Second, we observe the non-existence of a third, "emergent structure", that could approximate both structures and also be allowed to branch. Ultimately we find unless world-branching requires additional criteria or conditions, or there is a privileged structure, that we provide a valid model that cannot be properly described by the Everett Interpretation of Quantum Mechanics.

  20. When is a quantum heat engine quantum?

    E-Print Network [OSTI]

    Alexander Friedenberger; Eric Lutz

    2015-08-17

    Quantum thermodynamics studies quantum effects in thermal machines. But when is a heat engine, which cyclically interacts with external reservoirs that unavoidably destroy its quantum coherence, really quantum? We here use the Leggett-Garg inequality to assess the nonclassical properties of a single two-level Otto engine. We provide the complete phase diagram characterizing the quantumness of the engine as a function of its parameters and identify three distinct phases. We further derive an explicit expression for the transition temperature.

  1. Quantum Heat Engines Using Superconducting Quantum Circuits

    E-Print Network [OSTI]

    H. T. Quan; Y. D. Wang; Yu-xi Liu; C. P. Sun; Franco Nori

    2006-09-14

    We propose a quantum analog of the internal combustion engine used in most cars. Specifically, we study how to implement the Otto-type quantum heat engine (QHE) with the assistance of a Maxwell's demon. Three steps are required: thermalization, quantum measurement, and quantum feedback controlled by the Maxwell demon. We derive the positive-work condition of this composite QHE. Our QHE can be constructed using superconducting quantum circuits. We explicitly demonstrate the essential role of the demon in this macroscopic QHE.

  2. A possible explanation of the clash for black hole entropy in the extremal limit

    E-Print Network [OSTI]

    Ru-Keng Su; Bin Wang; P. K. N. Yu; E. C. M. Young

    1997-11-24

    It is shown that the classical entropy of the extremal black hole depends on two different limits procedures. If we first take the extremal limit and then the boundary limit, the entropy is zero; if we do it the other way round, we get the Bekenstein-Hawking entropy. By means of the brick wall model, the quantum entropy of scalar field in the extremal black hole background has been calculated for the above two different limits procedures. A possible explanation which considers the quantum effect for the clash of black hole entropy in the extremal limit is given.

  3. Objectivisation In Simplified Quantum Brownian Motion Models

    E-Print Network [OSTI]

    J. Tuziemski; J. K. Korbicz

    2015-02-24

    Birth of objective properties from subjective quantum world has been one of the key questions in the quantum-to-classical transition. Basing on recent results in the field, we study it in a quantum mechanical model of a boson-boson interaction-quantum Brownian motion. Using various simplifications we prove a formation for thermal environments of, so called, spectrum broadcast structures, responsible for perceived objectivity. In the quantum measurement limit we prove that this structure is always formed, providing the characteristic timescales. Including self-Hamiltonians of the environment, we show the exponential scaling of the effect with the size of the environment. Finally, in the full model we numerically study the influence of squeezing in the initial state of the environment, showing broader regions of formation than for non-squeezed thermal states.

  4. Markovianizing Cost of Tripartite Quantum States

    E-Print Network [OSTI]

    Eyuri Wakakuwa; Akihito Soeda; Mio Murao

    2015-04-22

    We introduce and analyze a task that we call Markovianization, in which a tripartite quantum state is transformed to a quantum Markov chain by a randomizing operation on one of the three subsystems. We consider cases where the initial state is a tensor product of $n$ copies of a tripartite state $\\rho^{ABC}$, and is transformed to a quantum Markov chain conditioned by $B^n$ with a small error, by a random unitary operation on $A^n$. In an asymptotic limit of infinite copies and vanishingly small error, we analyze the Markovianizing cost, that is, the minimum cost of randomness per copy required for Markovianization. For tripartite pure states, we derive a single-letter formula for the Markovianizing costs. Counterintuitively, the Markovianizing cost is not a continuous function of states, and can be arbitrarily large even if the state is an approximate quantum Markov chain. Our results have an application for distributed quantum computation.

  5. Non-static Quantum Bit Commitment

    E-Print Network [OSTI]

    Jeong Woon Choi; Dowon Hong; Ku-Young Chang; Dong Pyo Chi; Soojoon Lee

    2009-09-15

    Quantum bit commitment has been known to be impossible by the independent proofs of Mayers, and Lo and Chau, under the assumption that the whole quantum states right before the unveiling phase are static to users. We here provide an unconditionally secure non-static quantum bit commitment protocol with a trusted third party, which is not directly involved in any communications between users and can be limited not to get any information of commitment without being detected by users. We also prove that our quantum bit commitment protocol is not secure without the help of the trusted third party. The proof is basically different from the Mayers-Lo-Chau's no-go theorem, because we do not assume the staticity of the finally shared quantum states between users.

  6. Time-optimal navigation through quantum wind

    E-Print Network [OSTI]

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

    2015-02-19

    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.

  7. Quantum Energy Regression using Scattering Transforms

    E-Print Network [OSTI]

    Matthew Hirn; Nicolas Poilvert; Stephane Mallat

    2015-02-06

    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.

  8. Quantum Energy Regression using Scattering Transforms

    E-Print Network [OSTI]

    Hirn, Matthew; Mallat, Stephane

    2015-01-01

    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.

  9. Quantum levitation by left-handed metamaterials

    E-Print Network [OSTI]

    U. Leonhardt; T. G. Philbin

    2007-07-19

    Left-handed metamaterials make perfect lenses that image classical electromagnetic fields with significantly higher resolution than the diffraction limit. Here we consider the quantum physics of such devices. We show that the Casimir force of two conducting plates may turn from attraction to repulsion if a perfect lens is sandwiched between them. For optical left-handed metamaterials this repulsive force of the quantum vacuum may levitate ultra-thin mirrors.

  10. 2T Physics and Quantum Mechanics

    E-Print Network [OSTI]

    W. Chagas-Filho

    2008-02-20

    We use a local scale invariance of a classical Hamiltonian and describe how to construct six different formulations of quantum mechanics in spaces with two time-like dimensions. All these six formulations have the same classical limit described by the same Hamiltonian. One of these formulations is used as a basis for a complementation of the usual quantum mechanics when in the presence of gravity.

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

    E-Print Network [OSTI]

    Maria Simonetta Bernabei; Horst Thaler

    2014-12-10

    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.

  12. Practical issues in quantum-key-distribution postprocessing

    SciTech Connect (OSTI)

    Fung, C.-H. Fred; Chau, H. F. [Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Ma Xiongfeng [Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Ave W., Waterloo, Ontario, Canada N2L 3G1 (Canada)

    2010-01-15

    Quantum key distribution (QKD) is a secure key generation method between two distant parties by wisely exploiting properties of quantum mechanics. In QKD, experimental measurement outcomes on quantum states are transformed by the two parties to a secret key. This transformation is composed of many logical steps (as guided by security proofs), which together will ultimately determine the length of the final secret key and its security. We detail the procedure for performing such classical postprocessing taking into account practical concerns (including the finite-size effect and authentication and encryption for classical communications). This procedure is directly applicable to realistic QKD experiments and thus serves as a recipe that specifies what postprocessing operations are needed and what the security level is for certain lengths of the keys. Our result is applicable to the BB84 protocol with a single or entangled photon source.

  13. Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits

    E-Print Network [OSTI]

    Ferdi Altintas; Ali Ü. C. Hardal; Özgür E. Müstecapl?o?lu

    2015-02-18

    We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygen's clocks. The engine operates in quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four stroke cycle; while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to Carnot bound when it operates at low temperatures and in the ultrastrong coupling regime. Interplay of quantum coherence and quantum correlations on the engine performance is discussed in terms of second order coherence, quantum mutual information and logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with the modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission line resonators.

  14. Complete positivity and contextuality of quantum dynamics

    E-Print Network [OSTI]

    Song Cheng; Dongsheng Wang

    2013-03-21

    Positivity or the stronger notion of complete positivity, and contextuality are central properties of quantum dynamics. In this work, we demonstrate that a physical unitary-universe dilation model could be employed to characterize the completely positive map, regardless of the initial correlation condition. Particularly, the problem of initial correlation can be resolved by a swap operation. Furthermore, we discuss the physical essence of completely positive map and highlights its limitations. Then we develop the quantum measurement-chain formula beyond the framework of completely positive map in order to describe much broader quantum dynamics, and therein the property of contextuality could be captured via measurement transfer matrix.

  15. Thermodynamic universality of quantum Carnot engines

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

    Gardas, Bart?omiej; Deffner, Sebastian

    2015-10-12

    The Carnot statement of the second law of thermodynamics poses an upper limit on the efficiency of all heat engines. Recently, it has been studied whether generic quantum features such as coherence and quantum entanglement could allow for quantum devices with efficiencies larger than the Carnot efficiency. The present study shows that this is not permitted by the laws of thermodynamic —independent of the model. We will show that rather the definition of heat has to be modified to account for the thermodynamic cost of maintaining non-Gibbsian equilibrium states. As a result, our theoretical findings are illustrated for two experimentallymore »relevant examples.« less

  16. Quantum thermal machines with single nonequilibrium environments

    E-Print Network [OSTI]

    Bruno Leggio; Bruno Bellomo; Mauro Antezza

    2015-01-08

    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.

  17. Quantum nonlocality

    SciTech Connect (OSTI)

    Stapp, H.P.

    1988-04-01

    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.

  18. Quantum Gravity at the LHC

    E-Print Network [OSTI]

    Xavier Calmet; Priscila de Aquino

    2009-10-08

    It has recently been shown that if there is a large hidden sector in Nature, the scale of quantum gravity could be much lower than traditionally expected. We study the production of massless gravitons at the LHC and compare our results to those obtained in extra dimensional models. The signature in both cases is missing energy plus jets. In case of non observation, the LHC could be used to put the tightest limit to date on the value of the Planck mass.

  19. Quantum chaos induced by measurements

    E-Print Network [OSTI]

    P. Facchi; S. Pascazio; A. Scardicchio

    1999-06-16

    We study the dynamics of a "kicked" quantum system undergoing repeated measurements of momentum. A diffusive behavior is obtained for a large class of Hamiltonians, even when the dynamics of the classical counterpart is not chaotic. These results can be interpreted in classical terms by making use of a "randomized" classical map. We compute the transition probability for the action variable and consider the semiclassical limit.

  20. Thermodynamics of discrete quantum processes

    E-Print Network [OSTI]

    Janet Anders; Vittorio Giovannetti

    2012-11-01

    We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency.

  1. Extractable work from ensembles of quantum batteries. Entanglement helps

    E-Print Network [OSTI]

    Robert Alicki; Mark Fannes

    2012-11-19

    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.

  2. Master equation for a quantum particle in a gas

    E-Print Network [OSTI]

    Klaus Hornberger

    2006-09-05

    The equation for the quantum motion of a Brownian particle in a gaseous environment is derived by means of S-matrix theory. This quantum version of the linear Boltzmann equation accounts non-perturbatively for the quantum effects of the scattering dynamics and describes decoherence and dissipation in a unified framework. As a completely positive master equation it incorporates both the known equation for an infinitely massive Brownian particle and the classical linear Boltzmann equation as limiting cases.

  3. Quantum Locality?

    SciTech Connect (OSTI)

    Stapp, Henry

    2011-11-10

    Robert Griffiths has recently addressed, within the framework of a ‘consistent quantum theory’ (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths’ rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his ‘consistent quantum theory’ shows that the cited proof is valid within that restrictive framework. This necessary existence, within the ‘consistent’ framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his ‘consistent’ framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths’ reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the vagaries that he cites do not upset the proof in question. It is show here in detail why the precise statement of this theorem justifies the specified application of CQT. It is also shown, in response to his challenge, why a putative proof of locality that he has proposed is not valid.

  4. Quest for the quantum limit in three dimensional metals

    SciTech Connect (OSTI)

    Brooks, J.S.; Qualls, J.S.; Engel, L.W. [Florida State Univ., Tallahassee, FL (United States)] [and others

    1996-11-01

    The purpose of this work is to exploit ultra-high, flux compression type magnetic fields to achieve magnetic energies which are on the same or greater scale of the electronic structure in metallic systems. Under such conditions a metal. may become an insulator, may acquire a completely new electronic structure, or may develop novel configurations of electronic order. In this paper we consider experiments on quasi-two dimensional molecular conductors in both non-destructive pulsed fields to 60 T and in destructive flux compression fields to 700 T at low temperatures. New results on the molecular conductors {alpha}-(BEDT-TTF) {sub 2}NH{sub 4}Hg(SCN){sub 4} and (TMTSF){sub 2}ClO{sub 4} are discussed in experiments up to 60 T at low temperatures, and preliminary results on {alpha}-(BEDT-TTF){sub 2}NH{sub 4}Hg(SON){sub 4} in the 700 T MC1 series flux compression generators are presented. We argue that true direct dc electrical transport measurements in these materials at low temperatures up to 700 T appear to be within reach.

  5. AN EXPERIMENT ON THE LIMITS OF QUANTUM ELECTRODYNAMICS HEPL-170

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

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  6. Anisotropic Fermi Surface and Quantum Limit Transport in High Mobility

    Office of Scientific and Technical Information (OSTI)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield MunicipalTechnicalInformation4563AbuseConnect Technicalofand(Conference) |

  7. Performance limits for exo-clutter Ground Moving Target Indicator (GMTI) radar.

    SciTech Connect (OSTI)

    Doerry, Armin Walter

    2010-09-01

    The performance of a Ground Moving Target Indicator (GMTI) radar system depends on a variety of factors, many which are interdependent in some manner. It is often difficult to 'get your arms around' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall GMTI radar system. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the 'seek time'.

  8. Quantum Learning Machine

    E-Print Network [OSTI]

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

    2008-03-31

    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.

  9. Statistics and Quantum Chaos

    E-Print Network [OSTI]

    F. Benatti; M. Fannes

    1998-11-26

    We use multi-time correlation functions of quantum systems to construct random variables with statistical properties that reflect the degree of complexity of the underlying quantum dynamics.

  10. Quantum Optimal Control Theory

    E-Print Network [OSTI]

    G. H. Gadiyar

    1994-05-10

    The possibility of control of phenomena at microscopic level compatible with quantum mechanics and quantum field theory is outlined. The theory could be used in nanotechnology.

  11. The Quantum Internet

    E-Print Network [OSTI]

    H. J. Kimble

    2008-06-25

    Quantum networks offer a unifying set of opportunities and challenges across exciting intellectual and technical frontiers, including for quantum computation, communication, and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for the generation and characterization of quantum coherence and entanglement. Fundamental to this endeavor are quantum interconnects that convert quantum states from one physical system to those of another in a reversible fashion. Such quantum connectivity for networks can be achieved by optical interactions of single photons and atoms, thereby enabling entanglement distribution and quantum teleportation between nodes.

  12. Entropy-energy balance in noisy quantum computers

    E-Print Network [OSTI]

    Maxim Raginsky

    2002-09-26

    We use entropy-energy arguments to assess the limitations on the running time and on the system size, as measured in qubits, of noisy macroscopic circuit-based quantum computers.

  13. QUANTUM CHAOS: LESSONS FROM DISORDERED METALS A. Altland, C. R. Offer and B. D. Simons

    E-Print Network [OSTI]

    Simons, Ben

    QUANTUM CHAOS: LESSONS FROM DISORDERED METALS A. Altland, C. R. Offer and B. D. Simons Cavendish are chaotic in their classical limit is the subject of ``Quantum Chaos''. A wide variety of physical systems encountered in the develop­ ment of a theory of quantum chaos. In the section ``Coherence Effects

  14. A Quantum Version of The Spectral Decomposition Theorem of Dynamical Systems, Quantum Chaos Hierarchy: Ergodic, Mixing and Exact

    E-Print Network [OSTI]

    Ignacio Gomez; Mario Castagnino

    2014-11-09

    In this paper we study Spectral Decomposition Theorem [1] and translate it to quantum language by means of the Wigner transform. We obtain a quantum version of Spectral Decomposition Theorem (QSDT) which enables us to achieve three distinct goals: First, to rank Quantum Ergodic Hierarchy levels [2,3]. Second, to analyze the classical limit in quantum ergodic systems and quantum mixing systems. And third, and maybe most important feature, to find a relevant and simple connection between the first three levels of quantum ergodic hierarchy (ergodic, exact and mixing) and quantum spectrum. Finally, we illustrate the physical relevance of QSDT applying it to two examples: Microwave billiards [4,5] and a phenomenological Gamow model type [6,7].

  15. Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity

    E-Print Network [OSTI]

    C. S. Unnikrishnan; George T. Gillies

    2015-08-03

    Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity.

  16. Investigation of Microscopic Materials Limitations of Superconducting RF Cavities

    SciTech Connect (OSTI)

    Anlage, Steven

    2014-07-23

    The high-field performance of SRF cavities is often limited by breakdown events below the intrinsic limiting surface fields of Nb, and there is abundant evidence that these breakdown events are localized in space inside the cavity. Also, there is a lack of detailed understanding of the causal links between surface treatments and ultimate RF performance at low temperatures. An understanding of these links would provide a clear roadmap for improvement of SRF cavity performance, and establish a cause-and-effect ‘RF materials science’ of Nb. We propose two specific microscopic approaches to addressing these issues. First is a spatially-resolved local microwave-microscope probe that operates at SRF frequencies and temperatures to discover the microscopic origins of breakdown, and produce quantitative measurements of RF critical fields of coatings and films. Second, RF Laser Scanning Microscopy (LSM) has allowed visualization of RF current flow and sources of nonlinear RF response in superconducting devices with micro-meter spatial resolution. The LSM will be used in conjunction with surface preparation and characterization techniques to create definitive links between physical and chemical processing steps and ultimate cryogenic microwave performance. We propose to develop RF laser scanning microscopy of small-sample Nb pieces to establish surface-processing / RF performance relations through measurement of RF current distributions on micron-length scales and low temperatures.

  17. Process Physics: From Quantum Foam to General Relativity

    E-Print Network [OSTI]

    Reginald T. Cahill

    2002-03-05

    Progress in the new information-theoretic process physics is reported in which the link to the phenomenology of general relativity is made. In process physics the fundamental assumption is that reality is to be modelled as self-organising semantic (or internal or relational) information using a self-referentially limited neural network model. Previous progress in process physics included the demonstration that space and quantum physics are emergent and unified, with time a distinct non-geometric process, that quantum phenomena are caused by fractal topological defects embedded in and forming a growing three-dimensional fractal process-space, which is essentially a quantum foam. Other features of the emergent physics were: quantum field theory with emergent flavour and confined colour, limited causality and the Born quantum measurement metarule, inertia, time-dilation effects, gravity and the equivalence principle, a growing universe with a cosmological constant, black holes and event horizons, and the emergence of classicality. Here general relativity and the technical language of general covariance is seen not to be fundamental but a phenomenological construct, arising as an amalgam of two distinct phenomena: the `gravitational' characteristics of the emergent quantum foam for which `matter' acts as a sink, and the classical `spacetime' measurement protocol, but with the later violated by quantum measurement processes. Quantum gravity, as manifested in the emergent Quantum Homotopic Field Theory of the process-space or quantum foam, is logically prior to the emergence of the general relativity phenomenology, and cannot be derived from it.

  18. Quantum Institute

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.Theory ofDid youOxygen Generation |Publications The NREL PublicationsPublishedQuantum

  19. Low-Energy Effective Theories of Quantum Link and Quantum Spin Models

    E-Print Network [OSTI]

    B. Schlittgen; U. -J. Wiese

    2000-12-11

    Quantum spin and quantum link models provide an unconventional regularization of field theory in which classical fields arise via dimensional reduction of discrete variables. This D-theory regularization leads to the same continuum theories as the conventional approach. We show this by deriving the low-energy effective Lagrangians of D-theory models using coherent state path integral techniques. We illustrate our method for the $(2+1)$-d Heisenberg quantum spin model which is the D-theory regularization of the 2-d O(3) model. Similarly, we prove that in the continuum limit a $(2+1)$-d quantum spin model with $SU(N)_L\\times SU(N)_R\\times U(1)_{L=R}$ symmetry is equivalent to the 2-d principal chiral model. Finally, we show that $(4+1)$-d SU(N) quantum link models reduce to ordinary 4-d Yang-Mills theory.

  20. Bohmian Mechanics with Complex Action: A New Trajectory-Based Formulation of Quantum Mechanics

    E-Print Network [OSTI]

    Yair Goldfarb; Ilan Degani; David J. Tannor

    2006-04-20

    In recent years there has been a resurgence of interest in Bohmian mechanics as a numerical tool because of its local dynamics, which suggest the possibility of significant computational advantages for the simulation of large quantum systems. However, closer inspection of the Bohmian formulation reveals that the nonlocality of quantum mechanics has not disappeared -- it has simply been swept under the rug into the quantum force. In this paper we present a new formulation of Bohmian mechanics in which the quantum action, S, is taken to be complex. This leads to a single equation for complex S, and ultimately complex x and p but there is a reward for this complexification -- a significantly higher degree of localization. The quantum force in the new approach vanishes for Gaussian wavepacket dynamics, and its effect on barrier tunneling processes is orders of magnitude lower than that of the classical force. We demonstrate tunneling probabilities that are in virtually perfect agreement with the exact quantum mechanics down to 10^{-7} calculated from strictly localized quantum trajectories that do not communicate with their neighbors. The new formulation may have significant implications for fundamental quantum mechanics, ranging from the interpretation of non-locality to measures of quantum complexity.

  1. C&EN: BOOKS -QUANTUM COMPUTERS MADE LUCID August 11, 2003

    E-Print Network [OSTI]

    Southern California, University of

    describes what may be the ultimate free lunch, spawned by our harnessing of the laws of nature is the mysterious and wonderful world of quantum mechanics, at a level of sophistication no higher than as taught. http://pubs.acs.org/isubscribe/journals/cen/81/i32/print/8132books.html (1 of 6)8/5/2003 6:53:08 PM #12

  2. Optical limiting materials

    DOE Patents [OSTI]

    McBranch, D.W.; Mattes, B.R.; Koskelo, A.C.; Heeger, A.J.; Robinson, J.M.; Smilowitz, L.B.; Klimov, V.I.; Cha, M.; Sariciftci, N.S.; Hummelen, J.C.

    1998-04-21

    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--1,100 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. 5 figs.

  3. Quantum correlations in spin chains at finite temperatures and quantum phase transitions

    E-Print Network [OSTI]

    Werlang, T; Ribeiro, G A P; Rigolin, Gustavo

    2010-01-01

    We compute the quantum correlation (quantum discord (QD)) and the entanglement (EoF) between nearest neighbor qubits (spin-1/2) in an infinite chain described by the Heisenberg model (XXZ Hamiltonian) at finite temperatures. The chain is in the thermodynamic limit and thermalized with a reservoir at temperature T (canonical ensemble). We show that QD, in contrast to EoF and other thermodynamic quantities, spotlight the critical points associated to quantum phase transitions (QPT) for this model even at finite T. This remarkable property of QD may have important implications for experimental characterization of QPTs when one is unable to reach temperatures below which a QPT can be seen.

  4. Quantum correlations in spin chains at finite temperatures and quantum phase transitions

    E-Print Network [OSTI]

    T. Werlang; C. Trippe; G. A. P. Ribeiro; Gustavo Rigolin

    2010-08-25

    We compute the quantum correlation (quantum discord (QD)) and the entanglement (EoF) between nearest neighbor qubits (spin-1/2) in an infinite chain described by the Heisenberg model (XXZ Hamiltonian) at finite temperatures. The chain is in the thermodynamic limit and thermalized with a reservoir at temperature T (canonical ensemble). We show that QD, in contrast to EoF and other thermodynamic quantities, spotlight the critical points associated to quantum phase transitions (QPT) for this model even at finite T. This remarkable property of QD may have important implications for experimental characterization of QPTs when one is unable to reach temperatures below which a QPT can be seen.

  5. Localized quantum walks as secured quantum memory

    E-Print Network [OSTI]

    C. M. Chandrashekar; Th. Busch

    2015-04-21

    We show that a quantum walk process can be used to construct and secure quantum memory. More precisely, we show that a localized quantum walk with temporal disorder can be engineered to store the information of a single, unknown qubit on a compact position space and faithfully recover it on demand. Since the localization occurss with a finite spread in position space, the stored information of the qubit will be naturally secured from the simple eavesdropper. Our protocol can be adopted to any quantum system for which experimental control over quantum walk dynamics can be achieved.

  6. Hybrid quantum devices and quantum engineering

    E-Print Network [OSTI]

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

    2009-11-19

    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.

  7. Quantum Annealing and Analog Quantum Computation

    E-Print Network [OSTI]

    Arnab Das; Bikas K. Chakrabarti

    2008-03-24

    We review here the recent success in quantum annealing, i.e., optimization of the cost or energy functions of complex systems utilizing quantum fluctuations. The concept is introduced in successive steps through the studies of mapping of such computationally hard problems to the classical spin glass problems. The quantum spin glass problems arise with the introduction of quantum fluctuations, and the annealing behavior of the systems as these fluctuations are reduced slowly to zero. This provides a general framework for realizing analog quantum computation.

  8. Quantum cards and quantum rods

    E-Print Network [OSTI]

    Milan Batista; Joze Peternelj

    2006-11-02

    Quantum mechanical analysis of a rigid rod with one end fixed to a flat table is presented. It is shown, that for a macroscopic rod the ground state is orientationally delocalized only if the table is absolutely horizontal. In this latter case the rod, assumed to be initally in the upright orientation, falls down symmetrically and simultaneously in both directions, as claimed by Tegmark and Wheeler. In addition, the time of fall is calculated using WKB wavefunctions representing energy eigenstates near the barrier summit.

  9. Quantum Matching Pennies Game

    E-Print Network [OSTI]

    Azhar Iqbal; Derek Abbott

    2008-10-21

    A quantum version of the Matching Pennies (MP) game is proposed that is played using an Einstein-Podolsky-Rosen-Bohm (EPR-Bohm) setting. We construct the quantum game without using the state vectors, while considering only the quantum mechanical joint probabilities relevant to the EPR-Bohm setting. We embed the classical game within the quantum game such that the classical MP game results when the quantum mechanical joint probabilities become factorizable. We report new Nash equilibria in the quantum MP game that emerge when the quantum mechanical joint probabilities maximally violate the Clauser-Horne-Shimony-Holt form of Bell's inequality.

  10. SEMICLASSICS OF THE QUANTUM CURRENT IN A STRONG CONSTANT MAGNETIC FIELD.

    E-Print Network [OSTI]

    there is no classical, persistent or diamagnetic current. In quantum mechanics, however, there may be a static current in the semiclassical limit. In the semiclassical limit one cannot expect to see a static current since to include the persistent quantum current. It should be noted that this paper deals solely with static

  11. Hybrid Quantum Cloning Machine

    E-Print Network [OSTI]

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

    2007-06-14

    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} $

  12. Solving the Graph Isomorphism Problem with a Quantum Annealer

    E-Print Network [OSTI]

    Itay Hen; A. P. Young

    2012-08-08

    We propose a novel method using a quantum annealer -- an analog quantum computer based on the principles of quantum adiabatic evolution -- to solve the Graph Isomorphism problem, in which one has to determine whether two graphs are isomorphic (i.e., can be transformed into each other simply by a relabeling of the vertices). We demonstrate the capabilities of the method by analyzing several types of graph families, focusing on graphs with particularly high symmetry called strongly regular graphs (SRG's). We also show that our method is applicable, within certain limitations, to currently available quantum hardware such as "D-Wave One".

  13. Deviation from the Knudsen law on quantum gases

    SciTech Connect (OSTI)

    Babac, Gulru

    2014-12-09

    Gas flow in micro/nano scale systems has been generally studied for the Maxwell gases. In the limits of very low temperature and very confined domains, the Maxwellian approximation can break down and the quantum character of the gases becomes important. In these cases, Knudsen law, which is one of the important equations to analyze rarefied gas flows is invalid and should be reanalyzed for quantum gases. In this work, the availability of quantum gas conditions in the high Knudsen number cases is discussed and Knudsen law is analyzed for quantum gases.

  14. A robust quantum receiver for phase shift keyed signals

    E-Print Network [OSTI]

    Christian R. Müller; Christoph Marquardt

    2014-12-19

    The impossibility of perfectly discriminating non orthogonal quantum states imposes far-reaching consequences both on quantum and classical communication schemes. We propose and numerically analyze an optimized quantum receiver for the discrimination of phase encoded signals. Our scheme outperforms the standard quantum limit and approaches the Helstrom bound for any signal power. The discrimination is performed via an optimized, feedback-mediated displacement prior to a photon counting detector. We provide a detailed analysis of the influence of excess noise and technical imperfections on the average error probability. The results demonstrate the receiver's robustness and show that it can outperform any classical receiver over a wide range of realistic parameters.

  15. Sensitivity to perturbations and quantum phase transitions

    E-Print Network [OSTI]

    D. A. Wisniacki; A. Roncaglia

    2013-05-15

    The local density of states or its Fourier transform, usually called fidelity amplitude, are important measures of quantum irreversibility due to imperfect evolution. In this Rapid Communication we study both quantities in a paradigmatic many body system, the Dicke Hamiltonian, where a single-mode bosonic field interacts with an ensemble of N two-level atoms. This model exhibits a quantum phase transition in the thermodynamic limit, while for finite instances the system undergoes a transition from quasi-integrability to quantum chaotic. We show that the width of the local density of states clearly points out the imprints of the transition from integrability to chaos but no trace remains of the quantum phase transition. The connection with the decay of the fidelity amplitude is also established.

  16. Dynamical Objectivity in Quantum Brownian Motion

    E-Print Network [OSTI]

    J. Tuziemski; J. K. Korbicz

    2015-01-05

    We analyze one of the fundamental models of decoherence and quantum-to-classical transition---Quantum Brownian Motion, and show formation of a, so called, spectrum broadcast structure. As recently shown, this is a specific structure of multi-partite quantum states responsible for appearance of classical objective features in quantum mechanics. Working in the limit of a very massive central system and in a weak-coupling regime, we derive a surprising time-evolving, rather than time-asymptotic, spectrum broadcast structure, leading to perceived objectivity of a state of motion. We do it for realistic, noisy random environment, modeled as a thermal bath, and present some generalization to arbitrary single-mode Gaussian states. We study numerically the formation of the spectrum broadcast structure as a function of the temperature, showing its certain noise-robustness.

  17. Electromagnetism in terms of quantum measurements

    E-Print Network [OSTI]

    Andreas Andersson

    2015-09-16

    We consider the question whether electromagnetism can be derived from quantum physics of measurements. It turns out that this is possible, both for quantum and classical electromagnetism, if we use more recent innovations such as smearing of observables and simultaneous measurability. In this way we justify the use of von Neumann-type measurement models for physical processes. We apply operational quantum measurement theory to gain insight in fundamental aspects of quantum physics. Interactions of von Neumann type make the Heisenberg evolution of observables describable using explicit operator deformations. In this way one can obtain quantized electromagnetism as a measurement of a system by another. The relevant deformations (Rieffel deformations) have a mathematically well-defined "classical" limit which is indeed classical electromagnetism for our choice of interaction.

  18. Quantum Fusion of Domain Walls with Fluxes

    E-Print Network [OSTI]

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

    2009-07-20

    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.

  19. Quantum Thermodynamic Cycles and quantum heat engines

    E-Print Network [OSTI]

    H. T. Quan; Yu-xi Liu; C. P. Sun; Franco Nori

    2007-04-03

    In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. Relations and mappings between these two quantum heat engines are also investigated by considering their respective quantum thermodynamic processes. In addition, we discuss the role of Maxwell's demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.

  20. Quantum Annealing for Constrained Optimization

    E-Print Network [OSTI]

    Itay Hen; Federico M. Spedalieri

    2015-08-18

    Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealers that could potentially solve certain quadratic unconstrained binary optimization problems faster than their classical analogues. The applicability of such devices for many theoretical and practical optimization problems, which are often constrained, is severely limited by the sparse, rigid layout of the devices' quantum bits. Traditionally, constraints are addressed by the addition of penalty terms to the Hamiltonian of the problem, which in turn requires prohibitively increasing physical resources while also restricting the dynamical range of the interactions. Here we propose a method for encoding constrained optimization problems on quantum annealers that eliminates the need for penalty terms and thereby removes many of the obstacles associated with the implementation of these. We argue the advantages of the proposed technique and illustrate its effectiveness. We then conclude by discussing the experimental feasibility of the suggested method as well as its potential to boost the encodability of other optimization problems.

  1. Quantum computer of wire circuit architecture

    E-Print Network [OSTI]

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

    2010-01-07

    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.

  2. Mean Field Analysis of Quantum Annealing Correction

    E-Print Network [OSTI]

    Shunji Matsuura; Hidetoshi Nishimori; Tameem Albash; Daniel A. Lidar

    2015-10-26

    Quantum annealing correction (QAC) is a method that combines encoding with energy penalties and decoding to suppress and correct errors that degrade the performance of quantum annealers in solving optimization problems. While QAC has been experimentally demonstrated to successfully error-correct a range of optimization problems, a clear understanding of its operating mechanism has been lacking. Here we bridge this gap using tools from quantum statistical mechanics. We study analytically tractable models using a mean-field analysis, specifically the $p$-body ferromagnetic infinite-range transverse-field Ising model as well as the quantum Hopfield model, in the zero temperature limit. We demonstrate that for $p=2$, where the quantum phase transition is of second order, QAC pushes the phase transition to infinite transverse field strength. For $p\\ge3$, where the quantum phase transition is of first order, QAC softens the closing of the gap for small energy penalty values and prevents its closure for sufficiently large energy penalty values. Thus QAC provides protection from excitations that occur near the quantum critical point.

  3. Consistent Evolution with Different Time-Slicings in Quantum Gravity

    E-Print Network [OSTI]

    R. Cosgrove

    1996-02-20

    Rovelli's `` quantum mechanics without time'' motivates an intrinsically time-slicing independent picture of reduced phase space quantum gravity, which may be described as ``quantization after evolution''. Sufficient criteria for carrying out quantization after evolution are developed in terms of a general concept of the classical limit of quantum mechanics. If these criteria are satisfied then it is possible to have consistent unitary evolution of operators, with respect to an infinite parameter family of time-slicings (and probably all time-slicings), with the correct classical limit. The criteria are particularly amenable to study in (2+1)-dimensional gravity, where the reduced phase space is finite dimensional.

  4. Quantum Phase Transition in a Graphene Model

    E-Print Network [OSTI]

    Simon Hands; Costas Strouthos

    2008-08-20

    We present results for the equation of state of a graphene-like model in an effort to understand the properties of its quantum phase transition. The N_f fermion species interact through a three dimensional instantaneous Coulomb potential. Since there are no reliable analytical tools that work for all values of N_f and the coupling constant g, we rely on Monte Carlo simulations to calculate the critical properties of the model near the phase transition. We consider the four-component formulation for the fermion fields, which arises naturally as the continuum limit of the staggered fermion construction in (2+1) dimensions. In the limit of infinitely strong Coulomb interaction, the system undergoes a quantum phase transition at a critical number of fermion species N_fc ~ 4.7. We also calculate the values of the critical exponents at the quantum phase transition.

  5. The Quantum Energy Density: Improved Efficiency for Quantum Monte Carlo

    E-Print Network [OSTI]

    Krogel, Jaron T; Kim, Jeongnim; Ceperley, David M

    2013-01-01

    We establish a physically meaningful representation of a quantum energy density for use in Quantum Monte Carlo calculations. The energy density operator, defined in terms of Hamiltonian components and density operators, returns the correct Hamiltonian when integrated over a volume containing a cluster of particles. This property is demonstrated for a helium-neon "gas," showing that atomic energies obtained from the energy density correspond to eigenvalues of isolated systems. The formation energies of defects or interfaces are typically calculated as total energy differences. Using a model of delta-doped silicon (where dopant atoms form a thin plane) we show how interfacial energies can be calculated more efficiently with the energy density, since the region of interest is small. We also demonstrate how the energy density correctly transitions to the bulk limit away from the interface where the correct energy is obtainable from a separate total energy calculation.

  6. Nonlinear Optical Galton Board: thermalization and continuous limit

    E-Print Network [OSTI]

    Giuseppe Di Molfetta; Fabrice Debbasch; Marc Brachet

    2015-06-13

    The nonlinear optical Galton board (NLOGB), a quantum walk like (but nonlinear) discrete time quantum automaton, is shown to admit a complex evolution leading to long time thermalized states. The continuous limit of the Galton Board is derived and shown to be a nonlinear Dirac equation (NLDE). The (Galerkin truncated) NLDE evolution is shown to thermalize toward states qualitatively similar to those of the NLOGB. The NLDE conserved quantities are derived and used to construct a stochastic differential equation converging to grand canonical distributions that are shown to reproduce the (micro canonical) NLDE thermalized statistics. Both the NLOGB and the Galerkin-truncated NLDE are thus demonstrated to exhibit spontaneous thermalization.

  7. Quantum correlations, quantum resource theories and exclusion game

    E-Print Network [OSTI]

    Liu, Zi-Wen

    2015-01-01

    This thesis addresses two topics in quantum information theory. The first topic is quantum correlations and quantum resource theory. The second is quantum communication theory. The first part summarizes an ongoing work ...

  8. A Causal Net Approach to Relativistic Quantum Mechanics

    E-Print Network [OSTI]

    R. D. Bateson

    2012-05-13

    In this paper we discuss a causal network approach to describing relativistic quantum mechanics. Each vertex on the causal net represents a possible point event or particle observation. By constructing the simplest causal net based on Reichenbach-like conjunctive forks in proper time we can exactly derive the 1+1 dimension Dirac equation for a relativistic fermion and correctly model quantum mechanical statistics. Symmetries of the net provide various quantum mechanical effects such as quantum uncertainty and wavefunction, phase, spin, negative energy states and the effect of a potential. The causal net can be embedded in 3+1 dimensions and is consistent with the conventional Dirac equation. In the low velocity limit the causal net approximates to the Schrodinger equation and Pauli equation for an electromagnetic field. Extending to different momentum states the net is compatible with the Feynman path integral approach to quantum mechanics that allows calculation of well known quantum phenomena such as diffraction.

  9. Alternative quantization of the Hamiltonian in isotropic loop quantum cosmology

    E-Print Network [OSTI]

    Jinsong Yang; You Ding; Yongge Ma

    2009-04-28

    Since there are quantization ambiguities in constructing the Hamiltonian constraint operator in isotropic loop quantum cosmology, it is crucial to check whether the key features of loop quantum cosmology, such as the quantum bounce and effective scenario, are robust against the ambiguities. In this paper, we consider a typical quantization ambiguity arising from the quantization of the field strength of the gravitational connection. An alternative Hamiltonian constraint operator is constructed, which is shown to have the correct classical limit by the semiclassical analysis. The effective Hamiltonian incorporating higher order quantum corrections is also obtained. In the spatially flat FRW model with a massless scalar field, the classical big bang is again replaced by a quantum bounce. Moreover, there are still great possibilities for the expanding universe to recollapse due to the quantum gravity effect. Thus, these key features are robust against this quantization ambiguity.

  10. Advances in Quantum Teleportation

    E-Print Network [OSTI]

    Pirandola, Stefano; Weedbrook, Christian; Furusawa, Akira; Braunstein, Samuel L

    2015-01-01

    Quantum teleportation is one of the most important protocols in quantum information. By exploiting the physical resource of entanglement, quantum teleportation serves as a key primitive in a variety of quantum information tasks and represents an important building block for quantum technologies, with a pivotal role in the continuing progress of quantum communication, quantum computing and quantum networks. Here we review the basic theoretical ideas behind quantum teleportation and its variant protocols. We focus on the main experiments, together with the technical advantages and disadvantages associated with the use of the various technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms, and solid-state systems. Analysing the current state-of-the-art, we finish by discussing open issues, challenges and potential future implementations.

  11. The Forbidden Quantum Adder

    E-Print Network [OSTI]

    U. Alvarez-Rodriguez; M. Sanz; L. Lamata; E. Solano

    2015-05-29

    Quantum information provides fundamentally different computational resources than classical information. We prove that there is no unitary protocol able to add unknown quantum states belonging to different Hilbert spaces. This is an inherent restriction of quantum physics that is related to the impossibility of copying an arbitrary quantum state, i.e., the no-cloning theorem. Moreover, we demonstrate that a quantum adder, in absence of an ancillary system, is also forbidden for a known orthonormal basis. This allows us to propose an approximate quantum adder that could be implemented in the lab. Finally, we discuss the distinct character of the forbidden quantum adder for quantum states and the allowed quantum adder for density matrices.

  12. Ancilla-Assisted Discrimination of Quantum Gates

    E-Print Network [OSTI]

    Jianxin Chen; Mingsheng Ying

    2008-09-02

    The intrinsic idea of superdense coding is to find as many gates as possible such that they can be perfectly discriminated. In this paper, we consider a new scheme of discrimination of quantum gates, called ancilla-assisted discrimination, in which a set of quantum gates on a $d-$dimensional system are perfectly discriminated with assistance from an $r-$dimensional ancilla system. The main contribution of the present paper is two-fold: (1) The number of quantum gates that can be discriminated in this scheme is evaluated. We prove that any $rd+1$ quantum gates cannot be perfectly discriminated with assistance from the ancilla, and there exist $rd$ quantum gates which can be perfectly discriminated with assistance from the ancilla. (2) The dimensionality of the minimal ancilla system is estimated. We prove that there exists a constant positive number $c$ such that for any $k\\leq cr$ quantum gates, if they are $d$-assisted discriminable, then they are also $r$-assisted discriminable, and there are $c^{\\prime}r\\textrm{}(c^{\\prime}>c)$ different quantum gates which can be discriminated with a $d-$dimensional ancilla, but they cannot be discriminated if the ancilla is reduced to an $r-$dimensional system. Thus, the order $O(r)$ of the number of quantum gates that can be discriminated with assistance from an $r-$dimensional ancilla is optimal. The results reported in this paper represent a preliminary step toward understanding the role ancilla system plays in discrimination of quantum gates as well as the power and limit of superdense coding.

  13. A Pedestrian Approach to the Measurement Problem in Quantum Mechanics

    E-Print Network [OSTI]

    Boughn, Stephen

    2013-01-01

    The quantum theory of measurement has been a matter of debate for over eighty years. Most of the discussion has focused on theoretical issues with the consequence that operational prescriptions, which are integral to experimental physics, have been largely ignored. This has undoubtedly exacerbated attempts to find a solution to the "measurement problem". In this paper, we fully embrace the ensemble interpretation of quantum mechanics that obviates the need to entertain reduction of the state vector, one of the primary dilemmas of the measurement problem. The other major aspect of the measurement problem, the necessity of describing measurements in terms of classical concepts, remains. However, we argue that the ultimate interface with experiments is described by operational prescriptions and not in terms of the concepts of classical theory. The pedestrian approach presented here suggests that the measurement problem is, in some sense, ill-posed and might never be resolved. This state of affairs is, in part, t...

  14. The Limit of Mental Structures

    E-Print Network [OSTI]

    Mandler, George

    2013-01-01

    of constructing such structures. References A cautionaryTHE LIMIT OF MENTAL STRUCTURES Asch, S. E. , & Ebenholtz, S.100. THE LIMIT OF MENTAL STRUCTURES Halford, G. S. , Cowan,

  15. Quantum Evolution and Anticipation

    E-Print Network [OSTI]

    Hans-Rudolf Thomann

    2010-03-04

    In a previous paper we have investigated quantum states evolving into mutually orthogonal states at equidistant times, and the quantum anticipation effect exhibited by measurements at one half step. Here we extend our analyzes of quantum anticipation to general type quantum evolutions and spectral measures and prove that quantum evolutions possessing an embedded orthogonal evolution are characterized by positive joint spectral measure. Furthermore, we categorize quantum evolution, assess anticipation strength and provide a framework of analytic tools and results, thus preparing for further investigation and experimental verification of anticipation in concrete physical situations such as the H-atom, which we have found to exhibit anticipation.

  16. The thermodynamics of creating correlations: Limitations and optimal protocols

    E-Print Network [OSTI]

    David Edward Bruschi; Martí Perarnau-Llobet; Nicolai Friis; Karen V. Hovhannisyan; Marcus Huber

    2015-03-11

    We establish a rigorous connection between fundamental resource theories at the quantum scale. Correlations and entanglement constitute indispensable resources for numerous quantum information tasks. However, their establishment comes at the cost of energy, the resource of thermodynamics, and is limited by the initial entropy. Here, the optimal conversion of energy into correlations is investigated. Assuming the presence of a thermal bath, we establish general bounds for arbitrary systems and construct a protocol saturating them. The amount of correlations, quantified by the mutual information, can increase at most linearly with the available energy, and we determine where the linear regime breaks down. We further consider the generation of genuine quantum correlations, focusing on the fundamental constituents of our universe: fermions and bosons. For fermionic modes, we find the optimal entangling protocol. For bosonic modes, we show that while Gaussian operations can be outperformed in creating entanglement, their performance is optimal for high energies.

  17. Ricci flow and quantum theory

    E-Print Network [OSTI]

    Robert Carroll

    2007-11-05

    We show some relations between Ricci flow and quantum theory via Fisher information and the quantum potential.

  18. Wave Packets in Discrete Quantum Phase Space

    E-Print Network [OSTI]

    Jang Young Bang; Micheal S Berger

    2008-11-06

    The properties of quantum mechanics with a discrete phase space are studied. The minimum uncertainty states are found, and these states become the Gaussian wave packets in the continuum limit. With a suitably chosen Hamiltonian that gives free particle motion in the continuum limit, it is found that full or approximate periodic time evolution can result. This represents an example of revivals of wave packets that in the continuum limit is the familiar free particle motion on a line. Finally we examine the uncertainty principle for discrete phase space and obtain the correction terms to the continuum case.

  19. Fault current limiter

    DOE Patents [OSTI]

    Darmann, Francis Anthony

    2013-10-08

    A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.

  20. Physical interpretation of Jeans instability in quantum plasmas

    SciTech Connect (OSTI)

    Akbari-Moghanjoughi, M.

    2014-08-15

    In this paper, we use the quantum hydrodynamics and its hydrostatic limit to investigate the newly posed problem of Jeans instability in quantum plasmas from a different point of view in connection with the well-known Chandrasekhar mass-limit on highly collapsed degenerate stellar configurations. It is shown that the hydrodynamic stability of a spherically symmetric uniform quantum plasma with a given fixed mass is achieved by increase in its mass-density or decrease in the radius under the action of gravity. It is also remarked that for masses beyond the limiting Jeans-mass, the plasma becomes completely unstable and the gravitational collapse would proceed forever. This limiting mass is found to depend strongly on the composition of the quantum plasma and the atomic-number of the constituent ions, where it is observed that heavier elements rather destabilize the quantum plasma hydrodynamically. It is also shown that the Chandrasekhar mass-limit for white dwarf stars can be directly obtained from the hydrostatic limit of our model.

  1. Steam turbine: Alternative emergency drive for the secure removal of residual heat from the core of light water reactors in ultimate emergency situation

    SciTech Connect (OSTI)

    Souza Dos Santos, R.

    2012-07-01

    In 2011 the nuclear power generation has suffered an extreme probation. That could be the meaning of what happened in Fukushima Nuclear Power Plants. In those plants, an earthquake of 8.9 on the Richter scale was recorded. The quake intensity was above the trip point of shutting down the plants. Since heat still continued to be generated, the procedure to cooling the reactor was started. One hour after the earthquake, a tsunami rocked the Fukushima shore, degrading all cooling system of plants. Since the earthquake time, the plant had lost external electricity, impacting the pumping working, drive by electric engine. When operable, the BWR plants responded the management of steam. However, the lack of electricity had degraded the plant maneuvers. In this paper we have presented a scheme to use the steam as an alternative drive to maintain operable the cooling system of nuclear power plant. This scheme adds more reliability and robustness to the cooling systems. Additionally, we purposed a solution to the cooling in case of lacking water for the condenser system. In our approach, steam driven turbines substitute electric engines in the ultimate emergency cooling system. (authors)

  2. (Limiting the greenhouse effect)

    SciTech Connect (OSTI)

    Rayner, S.

    1991-01-07

    Traveler attended the Dahlem Research Conference organized by the Freien Universitat, Berlin. The subject of the conference was Limiting the Greenhouse Effect: Options for Controlling Atmospheric CO{sub 2} Accumulation. Like all Dahlem workshops, this was a meeting of scientific experts, although the disciplines represented were broader than usual, ranging across anthropology, economics, international relations, forestry, engineering, and atmospheric chemistry. Participation by scientists from developing countries was limited. The conference was divided into four multidisciplinary working groups. Traveler acted as moderator for Group 3 which examined the question What knowledge is required to tackle the principal social and institutional barriers to reducing CO{sub 2} emissions'' The working rapporteur was Jesse Ausubel of Rockefeller University. Other working groups examined the economic costs, benefits, and technical feasibility of options to reduce emissions per unit of energy service; the options for reducing energy use per unit of GNP; and the significant of linkage between strategies to reduce CO{sub 2} emissions and other goals. Draft reports of the working groups are appended. Overall, the conference identified a number of important research needs in all four areas. It may prove particularly important in bringing the social and institutional research needs relevant to climate change closer to the forefront of the scientific and policy communities than hitherto.

  3. Reconfigurable quantum metamaterials

    E-Print Network [OSTI]

    James Q. Quach; Chun-Hsu Su; Andrew M. Martin; Andrew D. Greentree; Lloyd C. L. Hollenberg

    2011-06-04

    By coupling controllable quantum systems into larger structures we introduce the concept of a quantum metamaterial. Conventional meta-materials represent one of the most important frontiers in optical design, with applications in diverse fields ranging from medicine to aerospace. Up until now however, metamaterials have themselves been classical structures and interact only with the classical properties of light. Here we describe a class of dynamic metamaterials, based on the quantum properties of coupled atom-cavity arrays, which are intrinsically lossless, reconfigurable, and operate fundamentally at the quantum level. We show how this new class of metamaterial could be used to create a reconfigurable quantum superlens possessing a negative index gradient for single photon imaging. With the inherent features of quantum superposition and entanglement of metamaterial properties, this new class of dynamic quantum metamaterial, opens a new vista for quantum science and technology.

  4. Quantum convolutional stabilizer codes 

    E-Print Network [OSTI]

    Chinthamani, Neelima

    2004-09-30

    Quantum error correction codes were introduced as a means to protect quantum information from decoherance and operational errors. Based on their approach to error control, error correcting codes can be divided into two different classes: block codes...

  5. Quantum model of microcavity intersubband electroluminescent devices

    E-Print Network [OSTI]

    Simone De Liberato; Cristiano Ciuti

    2008-04-28

    We present a quantum theoretical analysis of the electroluminescence from an intersubband transition of a quantum well structure embedded in a planar microcavity. By using a cluster factorization method, we have derived a closed set of dynamical equations for the quantum well carrier and cavity photon occupation numbers, the correlation between the cavity field and the intersubband polarization, as well as polarization-polarization contributions. In order to model the electrical excitation, we have considered electron population tunneling from an injector and into an extractor contact. The tunneling rates have been obtained by considering the bare electronic states in the quantum well and the limit of validity of this approximation (broad-band injection) are discussed in detail. We apply the present quantum model to provide a comprehensive description of the electronic transport and optical properties of an intersubband microcavity light emitting diode, accounting for non-radiative carrier relaxation and Pauli blocking. We study the enhancement of the electroluminescence quantum efficiency passing from the weak to the strong polariton coupling regime.

  6. Superconducting Circuitry for Quantum Electromechanical Systems

    E-Print Network [OSTI]

    Matthew D. LaHaye; Francisco Rouxinol; Yu Hao; Seung-Bo Shim; Elinor K. Irish

    2015-04-11

    Superconducting systems have a long history of use in experiments that push the frontiers of mechanical sensing. This includes both applied and fundamental research, which at present day ranges from quantum computing research and efforts to explore Planck-scale physics to fundamental studies on the nature of motion and the quantum limits on our ability to measure it. In this paper, we first provide a short history of the role of superconducting circuitry and devices in mechanical sensing, focusing primarily on efforts in the last decade to push the study of quantum mechanics to include motion on the scale of human-made structures. This background sets the stage for the remainder of the paper, which focuses on the development of quantum electromechanical systems (QEMS) that incorporate superconducting quantum bits (qubits), superconducting transmission line resonators and flexural nanomechanical elements. In addition to providing the motivation and relevant background on the physical behavior of these systems, we discuss our recent efforts to develop a particular type of QEMS that is based upon the Cooper-pair box (CPB) and superconducting coplanar waveguide (CPW) cavities, a system which has the potential to serve as a testbed for studying the quantum properties of motion in engineered systems.

  7. Toy Model for a Relational Formulation of Quantum Theory

    E-Print Network [OSTI]

    David Poulin

    2005-07-07

    In the absence of an external frame of reference physical degrees of freedom must describe relations between systems. Using a simple model, we investigate how such a relational quantum theory naturally arises by promoting reference systems to the status of dynamical entities. Our goal is to demonstrate using elementary quantum theory how any quantum mechanical experiment admits a purely relational description at a fundamental level, from which the original "non-relational" theory emerges in a semi-classical limit. According to this thesis, the non-relational theory is therefore an approximation of the fundamental relational theory. We propose four simple rules that can be used to translate an "orthodox" quantum mechanical description into a relational description, independent of an external spacial reference frame or clock. The techniques used to construct these relational theories are motivated by a Bayesian approach to quantum mechanics, and rely on the noiseless subsystem method of quantum information science used to protect quantum states against undesired noise. The relational theory naturally predicts a fundamental decoherence mechanism, so an arrow of time emerges from a time-symmetric theory. Moreover, there is no need for a "collapse of the wave packet" in our model: the probability interpretation is only applied to diagonal density operators. Finally, the physical states of the relational theory can be described in terms of "spin networks" introduced by Penrose as a combinatorial description of geometry, and widely studied in the loop formulation of quantum gravity. Thus, our simple bottom-up approach (starting from the semi-classical limit to derive the fully relational quantum theory) may offer interesting insights on the low energy limit of quantum gravity.

  8. Quons in a Quantum Dissipative System

    E-Print Network [OSTI]

    Lee, Taejin

    2015-01-01

    String theory proves to be an imperative tool to explore the critical behavior of the quantum dissipative system. We discuss the quantum particles moving in two dimensions, in the presence of a uniform magnetic field, subject to a periodic potential and a dissipative force, which are described by the dissipative Wannier-Azbel-Hofstadter (DWAH) model. Using string theory formulation of the model, we find that the elementary excitations of the system at the generic points of the off-critical regions, in the zero temperature limit are quons, which satisfy q-deformed statistics.

  9. Quantum backgrounds and QFT

    E-Print Network [OSTI]

    Jae-Suk Park; John Terilla; Thomas Tradler

    2009-09-21

    We introduce the concept of a quantum background and a functor QFT. In the case that the QFT moduli space is smooth formal, we construct a flat quantum superconnection on a bundle over QFT which defines algebraic structures relevant to correlation functions in quantum field theory. We go further and identify chain level generalizations of correlation functions which should be present in all quantum field theories.

  10. Enhanced sequential carrier capture into individual quantum dots and quantum posts controlled by surface acoustic waves

    E-Print Network [OSTI]

    Stefan Völk; Florian J. R. Schülein; Florian Knall; Dirk Reuter; Andreas D. Wieck; Tuan A. Truong; Hyochul Kim; Pierre M. Petroff; Achim Wixforth; Hubert J. Krenner

    2010-11-19

    Individual self-assembled Quantum Dots and Quantum Posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For Quantum Posts, switching occurs continuously from predominantely charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent on whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is non-monotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which Quantum Dots nucleate. This limitation can be overcome for Quantum Posts where acoustically induced charge transport is highly efficient in a wide lateral Matrix-Quantum Well.

  11. Modes of asymmetry: the application of harmonic analysis to symmetric quantum dynamics and quantum reference frames

    E-Print Network [OSTI]

    Iman Marvian; Robert W. Spekkens

    2014-12-05

    Finding the consequences of symmetry for open system quantum dynamics is a problem with broad applications, including describing thermal relaxation, deriving quantum limits on the performance of amplifiers, and exploring quantum metrology in the presence of noise. The symmetry of the dynamics may reflect a symmetry of the fundamental laws of nature, a symmetry of a low-energy effective theory, or it may describe a practical restriction such as the lack of a reference frame. In this paper, we apply some tools of harmonic analysis together with ideas from quantum information theory to this problem. The central idea is to study the decomposition of quantum operations---in particular, states, measurements and channels---into different modes, which we call modes of asymmetry. Under symmetric processing, a given mode of the input is mapped to the corresponding mode of the output, implying that one can only generate a given output if the input contains all of the necessary modes. By defining monotones that quantify the asymmetry in a particular mode, we also derive quantitative constraints on the resources of asymmetry that are required to simulate a given asymmetric operation. We present applications of our results for deriving bounds on the probability of success in nondeterministic state transitions, such as quantum amplification, and a simplified formalism for studying the degradation of quantum reference frames.

  12. Stephen Hawking Quantum Gravity

    E-Print Network [OSTI]

    Visser, Matt

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

  13. Quantum Circuits Architecture

    E-Print Network [OSTI]

    Giulio Chiribella; Giacomo Mauro D'Ariano; Paolo Perinotti

    2007-12-09

    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.

  14. Quantum Control Theory

    E-Print Network [OSTI]

    Matthew James

    2014-06-20

    This paper explains some fundamental ideas of {\\em feedback} control of quantum systems through the study of a relatively simple two-level system coupled to optical field channels. The model for this system includes both continuous and impulsive dynamics. Topics covered in this paper include open and closed loop control, impulsive control, optimal control, quantum filtering, quantum feedback networks, and coherent feedback control.

  15. Introduction to Quantum Mechanics

    E-Print Network [OSTI]

    Eduardo J. S. Villaseñor

    2008-04-23

    The purpose of this contribution is to give a very brief introduction to Quantum Mechanics for an audience of mathematicians. I will follow Segal's approach to Quantum Mechanics paying special attention to algebraic issues. The usual representation of Quantum Mechanics on Hilbert spaces is also discussed.

  16. Enscription of Quantum Texts

    E-Print Network [OSTI]

    Randall Espinoza; Tom Imbo; Paul Lopata

    2004-03-30

    We investigate an entangled deformation of the deterministic quantum cloning process, called enscription, that can be applied to (certain) sets of distinct quantum states which are not necessarily orthogonal, called texts. Some basic theorems on enscribable texts are given, and a relationship to probabilistic quantum cloning is demonstrated.

  17. Vacuum energy: quantum hydrodynamics vs quantum gravity

    E-Print Network [OSTI]

    G. E. Volovik

    2005-09-09

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

  18. Quantum chaos in quantum Turing machines

    E-Print Network [OSTI]

    Ilki Kim; Guenter Mahler

    1999-10-18

    We investigate a 2-spin quantum Turing architecture, in which discrete local rotations \\alpha_m of the Turing head spin alternate with quantum controlled NOT-operations. We demonstrate that a single chaotic parameter input \\alpha_m leads to a chaotic dynamics in the entire Hilbert-space.

  19. Quantum Information Science | ornl.gov

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

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

  20. Quantum Dynamics of Nonlinear Cavity Systems

    E-Print Network [OSTI]

    Paul D. Nation

    2010-09-16

    We investigate the quantum dynamics of three different configurations of nonlinear cavity systems. To begin, we carry out a quantum analysis of a dc superconducting quantum interference device (SQUID) mechanical displacement detector comprised of a SQUID with a mechanically compliant loop segment. The SQUID is approximated by a nonlinear current-dependent inductor, inducing a flux tunable nonlinear Duffing term in the cavity equation of motion. Expressions are derived for the detector signal and noise response where it is found that a soft-spring Duffing self-interaction enables a closer approach to the displacement detection standard quantum limit, as well as cooling closer to the ground state. Next, we make use of a superconducting transmission line formed from an array of dc-SQUIDs for investigating analogue Hawking radiation. Biasing the array with a space-time varying flux modifies the propagation velocity of the transmission line, leading to an effective metric with a horizon. This setup allows for quantum effects such as backreaction and analogue space-time fluctuations on the Hawking process. Finally, we look at a quantum parametric amplifier with dynamical pump mode, viewed as a zero-dimensional model of Hawking radiation from an evaporating black hole. The conditions are derived under which the spectrum of particles generated from vacuum fluctuations deviates from the thermal spectrum predicted for the conventional parametric amplifier. We find that significant deviation occurs once the pump mode (black hole) has released nearly half of its initial energy in the signal (Hawking radiation) and idler (in-falling particle) modes. As a model of black hole dynamics, this finding lends support to the view that late-time Hawking radiation contains information about the quantum state of the black hole and is entangled with the black hole's quantum gravitational degrees of freedom.

  1. Quantum Riemannian geometry of phase space and nonassociativity

    E-Print Network [OSTI]

    Edwin J. Beggs; Shahn Majid

    2014-10-29

    Noncommutative or `quantum' differential geometry has emerged in recent years as a process for quantizing not only a classical space into a noncommutative algebra (as familiar in quantum mechanics) but also differential forms, bundles and Riemannian structures at this level. The data for the algebra quantisation is a classical Poisson bracket, the data for the quantum differential forms is a Poisson-compatible connection it was recently shown that after this, classical data such as classical bundles, metrics etc. all become quantised in a canonical `functorial' way at least to 1st order in deformation theory. There are, however, fresh compatibility conditions between the classical Riemannian and the Poisson structures as well as new physics such as nonassociativity at 2nd order. We give an introduction to this theory and some details for the case of CP${}^n$ where the commutation relations have the canonical form $[w^i,\\bar w^j]=\\mathrm{i}\\lambda\\delta_{ij}$ similar to the proposal of Penrose for quantum twistor space. Our work provides a canonical but ultimately nonassociative differential calculus on this algebra and quantises the metric and Levi-Civita connection at lowest order in $\\lambda$.

  2. On the hypothesis that quantum mechanism manifests classical mechanics: Numerical approach to the correspondence in search of quantum chaos

    SciTech Connect (OSTI)

    Lee, Sang-Bong

    1993-09-01

    Quantum manifestation of classical chaos has been one of the extensively studied subjects for more than a decade. Yet clear understanding of its nature still remains to be an open question partly due to the lack of a canonical definition of quantum chaos. The classical definition seems to be unsuitable in quantum mechanics partly because of the Heisenberg quantum uncertainty. In this regard, quantum chaos is somewhat misleading and needs to be clarified at the very fundamental level of physics. Since it is well known that quantum mechanics is more fundamental than classical mechanics, the quantum description of classically chaotic nature should be attainable in the limit of large quantum numbers. The focus of my research, therefore, lies on the correspondence principle for classically chaotic systems. The chaotic damped driven pendulum is mainly studied numerically using the split operator method that solves the time-dependent Schroedinger equation. For classically dissipative chaotic systems in which (multi)fractal strange attractors often emerge, several quantum dissipative mechanisms are also considered. For instance, Hoover`s and Kubo-Fox-Keizer`s approaches are studied with some computational analyses. But the notion of complex energy with non-Hermiticity is extensively applied. Moreover, the Wigner and Husimi distribution functions are examined with an equivalent classical distribution in phase-space, and dynamical properties of the wave packet in configuration and momentum spaces are also explored. The results indicate that quantum dynamics embraces classical dynamics although the classicalquantum correspondence fails to be observed in the classically chaotic regime. Even in the semi-classical limits, classically chaotic phenomena would eventually be suppressed by the quantum uncertainty.

  3. Quantum Physics and Nanotechnology

    E-Print Network [OSTI]

    Vladimir K. Nevolin

    2011-06-06

    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.

  4. Algorithms for Quantum Computers

    E-Print Network [OSTI]

    Jamie Smith; Michele Mosca

    2010-01-07

    This paper surveys the field of quantum computer algorithms. It gives a taste of both the breadth and the depth of the known algorithms for quantum computers, focusing on some of the more recent results. It begins with a brief review of quantum Fourier transform based algorithms, followed by quantum searching and some of its early generalizations. It continues with a more in-depth description of two more recent developments: algorithms developed in the quantum walk paradigm, followed by tensor network evaluation algorithms (which include approximating the Tutte polynomial).

  5. Scalable optical quantum computer

    SciTech Connect (OSTI)

    Manykin, E A; Mel'nichenko, E V [Institute for Superconductivity and Solid-State Physics, Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation)

    2014-12-31

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)

  6. Quantum Control Landscapes

    E-Print Network [OSTI]

    Raj Chakrabarti; Herschel Rabitz

    2007-10-03

    Numerous lines of experimental, numerical and analytical evidence indicate that it is surprisingly easy to locate optimal controls steering quantum dynamical systems to desired objectives. This has enabled the control of complex quantum systems despite the expense of solving the Schrodinger equation in simulations and the complicating effects of environmental decoherence in the laboratory. Recent work indicates that this simplicity originates in universal properties of the solution sets to quantum control problems that are fundamentally different from their classical counterparts. Here, we review studies that aim to systematically characterize these properties, enabling the classification of quantum control mechanisms and the design of globally efficient quantum control algorithms.

  7. Discrimination of the binary coherent signal: Gaussian-operation limit and simple non-Gaussian near-optimal receivers

    E-Print Network [OSTI]

    Masahiro Takeoka; Masahide Sasaki

    2008-08-14

    We address the limit of the Gaussian operations and classical communication in the problem of quantum state discrimination. We show that the optimal Gaussian strategy for the discrimination of the binary phase shift keyed (BPSK) coherent signal is a simple homodyne detection. We also propose practical near-optimal quantum receivers that beat the BPSK homodyne limit in all areas of the signal power. Our scheme is simple and does not require realtime electrical feedback.

  8. Superradiant Quantum Heat Engine

    E-Print Network [OSTI]

    Ali Ü. C. Hardal; Özgür E. Müstecapl?oglu

    2015-07-16

    Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.

  9. Superradiant Quantum Heat Engine

    E-Print Network [OSTI]

    Ali Ü. C. Hardal; Özgür E. Müstecapl?oglu

    2015-04-22

    Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.

  10. Getting Humans to do Quantum Optimization - User Acquisition, Engagement and Early Results from the Citizen Cyberscience Game Quantum Moves

    E-Print Network [OSTI]

    Andreas Lieberoth; Mads Kock Pedersen; Andreea Catalina Marin; Tilo Planke; Jacob Friis Sherson

    2015-06-26

    The game Quantum Moves was designed to pit human players against computer algorithms, combining their solutions into hybrid optimization to control a scalable quantum computer. In this midstream report, we open our design process and describe the series of constitutive building stages going into a quantum physics citizen science game. We present our approach from designing a core gameplay around quantum simulations, to putting extra game elements in place in order to frame, structure, and motivate players' difficult path from curious visitors to competent science contributors. The player base is extremely diverse - for instance, two top players are a 40 year old female accountant and a male taxi driver. Among statistical predictors for retention and in-game high scores, the data from our first year suggest that people recruited based on real-world physics interest and via real-world events, but only with an intermediate science education, are more likely to become engaged and skilled contributors. Interestingly, female players tended to perform better than male players, even though men played more games per day. To understand this relationship, we explore the profiles of our top players in more depth. We discuss in-world and in-game performance factors departing in psychological theories of intrinsic and extrinsic motivation, and the implications for using real live humans to do hybrid optimization via initially simple, but ultimately very cognitively complex games.

  11. Quantum Discord and its Role in Quantum Information Theory

    E-Print Network [OSTI]

    Alexander Streltsov

    2014-11-12

    Quantum entanglement is the most popular kind of quantum correlations, and its fundamental role in several tasks in quantum information theory like quantum cryptography, quantum dense coding, and quantum teleportation is undeniable. However, recent results suggest that various applications in quantum information theory do not require entanglement, and that their performance can be captured by a new type of quantum correlations which goes beyond entanglement. Quantum discord, introduced by Zurek more than a decade ago, is the most popular candidate for such general quantum correlations. In this work we give an introduction to this modern research direction. After a short review of the main concepts of quantum theory and entanglement, we present quantum discord and general quantum correlations, and discuss three applications which are based on this new type of correlations: remote state preparation, entanglement distribution, and transmission of correlations. We also give an outlook to other research in this direction.

  12. Quantum Thermodynamic Cycles and Quantum Heat Engines (II)

    E-Print Network [OSTI]

    H. T. Quan

    2009-03-09

    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.

  13. Fermion Doubling in Loop Quantum Gravity

    E-Print Network [OSTI]

    Jacob Barnett; Lee Smolin

    2015-07-05

    In this paper, we show that the Hamiltonian approach to loop quantum gravity has a fermion doubling problem. To obtain this result, we couple loop quantum gravity to a free massless scalar and a chiral fermion field, gauge fixing the many fingered time gauge invariance by interpreting the scalar field as a physical clock. We expand around a quantum gravity state based on a regular lattice and consider the limit where the bare cosmological constant is large but the fermonic excitations have energies low in Planck units. We then make the case for identifying the energy spectrum in this approximation with that of a model of lattice fermion theory which is known to double.

  14. QAM Adaptive Measurements Feedback Quantum Receiver Performance

    E-Print Network [OSTI]

    Tian Chen; Ke Li; Yuan Zuo; Bing Zhu

    2015-04-11

    We theoretically study the quantum receivers with adaptive measurements feedback for discriminating quadrature amplitude modulation (QAM) coherent states in terms of average symbol error rate. For rectangular 16-QAM signal set, with different stages of adaptive measurements, the effects of realistic imperfection parameters including the sub-unity quantum efficiency and the dark counts of on-off detectors, as well as the transmittance of beam splitters and the mode mismatch factor between the signal and local oscillating fields on the symbol error rate are separately investigated through Monte Carlo simulations. Using photon-number-resolving detectors (PNRD) instead of on-off detectors, all the effects on the symbol error rate due to the above four imperfections can be suppressed in a certain degree. The finite resolution and PNR capability of PNRDs are also considered. We find that for currently available technology, the receiver shows a reasonable gain from the standard quantum limit (SQL) with moderate stages.

  15. Dynamic trapping near a quantum critical point

    E-Print Network [OSTI]

    Michael Kolodrubetz; Emanuel Katz; Anatoli Polkovnikov

    2015-03-02

    The study of dynamics in closed quantum systems has recently been revitalized by the emergence of experimental systems that are well-isolated from their environment. In this paper, we consider the closed-system dynamics of an archetypal model: spins near a second order quantum critical point, which are traditionally described by the Kibble-Zurek mechanism. Imbuing the driving field with Newtonian dynamics, we find that the full closed system exhibits a robust new phenomenon -- dynamic critical trapping -- in which the system is self-trapped near the critical point due to efficient absorption of field kinetic energy by heating the quantum spins. We quantify limits in which this phenomenon can be observed and generalize these results by developing a Kibble-Zurek scaling theory that incorporates the dynamic field. Our findings can potentially be interesting in the context of early universe physics, where the role of the driving field is played by the inflaton or a modulus.

  16. Nonsingular cosmology from evolutionary quantum gravity

    E-Print Network [OSTI]

    Francesco Cianfrani; Giovanni Montani; Fabrizio Pittorino

    2014-10-30

    We provide a cosmological implementation of the evolutionary quantum gravity, describing an isotropic Universe, in the presence of a negative cosmological constant and a massive (preinflationary) scalar field. We demonstrate that the considered Universe has a nonsingular quantum behavior, associated to a primordial bounce, whose ground state has a high occupation number. Furthermore, in such a vacuum state, the super-Hamiltonian eigenvalue is negative, corresponding to a positive emerging dust energy density. The regularization of the model is performed via a polymer quantum approach to the Universe scale factor and the proper classical limit is then recovered, in agreement with a preinflationary state of the Universe. Since the dust energy density is redshifted by the Universe deSitter phase and the cosmological constant does not enter the ground state eigenvalue, we get a late-time cosmology, compatible with the present observations, endowed with a turning point in the far future.

  17. Parametric description of the quantum measurement process

    E-Print Network [OSTI]

    Pietro Liuzzo-Scorpo; Alessandro Cuccoli; Paola Verrucchi

    2015-05-12

    We present a description of the measurement process based on the parametric representation with environmental coherent states. This representation is specifically tailored for studying quantum systems whose environment needs being considered through the quantum-to-classical cross-over. Focusing upon projective measures, and exploiting the connection between large-$N$ quantum theories and the classical limit of related ones, we manage to push our description beyond the pre-measurement step. This allows us to show that the outcome production follows from a global-symmetry breaking, entailing the observed system's state reduction, and that the statistical nature of the process is brought about, together with the Born's rule, by the macroscopic character of the measuring apparatus.

  18. Quantum field theory as eigenvalue problem

    E-Print Network [OSTI]

    Arnold Neumaier

    2003-03-10

    A mathematically well-defined, manifestly covariant theory of classical and quantum field is given, based on Euclidean Poisson algebras and a generalization of the Ehrenfest equation, which implies the stationary action principle. The theory opens a constructive spectral approach to finding physical states both in relativistic quantum field theories and for flexible phenomenological few-particle approximations. In particular, we obtain a Lorentz-covariant phenomenological multiparticle quantum dynamics for electromagnetic and gravitational interaction which provides a representation of the Poincare group without negative energy states. The dynamics reduces in the nonrelativistic limit to the traditional Hamiltonian multiparticle description with standard Newton and Coulomb forces. The key that allows us to overcome the traditional problems in canonical quantization is the fact that we use the algebra of linear operators on a space of wave functions slightly bigger than traditional Fock spaces.

  19. Quantum Chaos and Quantum Computers D. L. Shepelyansky*

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Quantum Chaos and Quantum Computers D. L. Shepelyansky* Laboratoire de Physique Quantique, UMR 5626 analytically and numerically and the border for emergence of quantum chaos, induced by imperfections without any external decoherence. The onset of quantum chaos leads to quantum computer hard- ware melting

  20. COMMENTARY:Limits to adaptation

    SciTech Connect (OSTI)

    Preston, Benjamin L

    2013-01-01

    An actor-centered, risk-based approach to defining limits to social adaptation provides a useful analytic framing for identifying and anticipating these limits and informing debates over society s responses to climate change.

  1. Quantum Fisher Information as the Convex Roof of Variance

    E-Print Network [OSTI]

    Sixia Yu

    2013-02-21

    Quantum Fisher information places the fundamental limit to the accuracy of estimating an unknown parameter. Here we shall provide the quantum Fisher information an operational meaning: a mixed state can be so prepared that a given observable has the minimal averaged variance, which equals exactly to the quantum Fisher information for estimating an unknown parameter generated by the unitary dynamics with the given observable as Hamiltonian. In particular we shall prove that the quantum Fisher information is the convex roof of the variance, as conjectured by Toth and Petz based on numerical and analytical evidences, by constructing explicitly a pure-state ensemble of the given mixed state in which the averaged variance of a given observable equals to the quantum Fisher information.

  2. Quantum chaos with spin-chains in pulsed magnetic fields

    E-Print Network [OSTI]

    T. Boness; M. M. A. Stocklin; T. S. Monteiro

    2006-12-11

    Recently it was found that the dynamics in a Heisenberg spin-chain subjected to a sequence of periodic pulses from an external, parabolic, magnetic field can have a close correspondence with the quantum kicked rotor (QKR). The QKR is a key paradigm of quantum chaos; it has as its classical limit the well-known Standard Map. It was found that a single spin excitation could be converted into a pair of non-dispersive, counter-propagating spin coherent states equivalent to the accelerator modes of the Standard Map. Here we consider how other types of quantum chaotic systems such as a double-kicked quantum rotor or a quantum rotor with a double-well potential might be realized with spin chains; we discuss the possibilities regarding manipulation of the one-magnon spin waves.

  3. Systematic quantum corrections to screening in thermonuclear fusion

    E-Print Network [OSTI]

    Chitanvis, S M

    2006-01-01

    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%.

  4. Systematic quantum corrections to screening in thermonuclear fusion

    E-Print Network [OSTI]

    Shirish M. Chitanvis

    2006-06-13

    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%.

  5. Distinguishing decoherence from alternative quantum theories by dynamical decoupling

    E-Print Network [OSTI]

    Christian Arenz; Robin Hillier; Martin Fraas; Daniel Burgarth

    2015-08-03

    A longstanding challenge in the foundations of quantum mechanics is the veri?cation of alternative collapse theories despite their mathematical similarity to decoherence. To this end, we suggest a novel method based on dynamical decoupling. Experimental observation of nonzero saturation of the decoupling error in the limit of fast decoupling operations can provide evidence for alternative quantum theories. As part of the analysis we prove that unbounded Hamiltonians can always be decoupled, and provide novel dilations of Lindbladians.

  6. Optical, electronic, and structural properties of uncoupled and close-packed arrays of InP quantum dots

    SciTech Connect (OSTI)

    Micic, O.I.; Jones, K.M.; Cahill, A.; Nozik, A.J.

    1998-12-03

    Solid films consisting of close-packed arrays of InP quantum dots have been prepared by slowly evaporating colloidal solutions of InP quantum dots. The diameters of the quantum dots were controlled to be between about 30 to 60 {angstrom}; size-selective precipitation yielded a size distribution of about 10% about the mean diameter. The arrays show regions of hexagonal order, as well as disordered regions. Oxide layers can form irreversibly on the quantum dot surface and limit the effectiveness of the size-selective precipitation. Photoluminescence spectra obtained from close-packed films of InP quantum dots formed from quantum dots with a single mean diameter and from a mixture of two quantum dot sizes show that energy transfer occurs from the photoexcited smaller quantum dots to the larger quantum dots. The efficiency of this energy transfer process is high.

  7. Does quantum mechanics require non-locality?

    E-Print Network [OSTI]

    Ghenadie N. Mardari

    2014-10-29

    Non-commutative properties of single quanta must violate the limit of Bell's theorem, but not the boundary of Tsirelson's theorem. This is a consequence of three basic principles: superposition (every quantum is in many states at the same time), correspondence (only the net state of interference is real), and uncertainty (conjugate variables have inversely proportional spectra). The two conditions have only been verified with entangled pairs of quanta. It is not possible to perform incompatible measurements on the same entity. Hence, the principles of quantum mechanics cannot be verified directly. At least one of them could be wrong. Though, as shown by EPR, this can only be true if non-locality is at work. In light of the latest developments in quantum theory, even that assumption is insufficient. Non-local effects are either unable to cross Bell's limit, or forced to violate Tsirelson's bound. New layers of hidden variables are required to maintain belief in action-at-a-distance, but the three principles cannot be rejected in any case. Therefore, quantum mechanics is immune to this challenge. The hypothesis of non-locality is superfluous.

  8. Low-Noise Amplification of a Continuous Variable Quantum State

    E-Print Network [OSTI]

    R. C. Pooser; A. M. Marino; V. Boyer; K. M. Jones; P. D. Lett

    2009-06-27

    We present an experimental realization of a low-noise, phase-insensitive optical amplifier using a four-wave mixing interaction in hot Rb vapor. Performance near the quantum limit for a range of amplifier gains, including near unity, can be achieved. Such low-noise amplifiers are essential for so-called quantum cloning machines and are useful in quantum information protocols. We demonstrate that amplification and ``cloning'' of one half of a two-mode squeezed state is possible while preserving entanglement.

  9. Intrinsic linewidth of quantum cascade laser frequency combs

    E-Print Network [OSTI]

    Cappelli, Francesco; Riedi, Sabine; Faist, Jerome

    2015-01-01

    The frequency noise power spectral density of a free-running quantum cascade laser frequency comb is investigated. A plateau is observed at high frequencies, attributed to the quantum noise limit set by the Schawlow-Townes formula for the total laser power on all comb lines. In our experiment, a linewidth of 292 Hz is measured for a total power of 25 mW. This result proves that the four-wave mixing process, responsible for the comb operation, effectively correlates the quantum noise of the individual comb lines.

  10. Quantum Ergodicity and the Analysis of Semiclassical Pseudodifferential Operators

    E-Print Network [OSTI]

    Felix Wong

    2014-10-11

    This undergraduate thesis is concerned with developing the tools of differential geometry and semiclassical analysis needed to understand the the quantum ergodicity theorem of Schnirelman (1974), Zelditch (1987), and Colin de Verdi\\`ere (1985) and the quantum unique ergodicity conjecture of Rudnick and Sarnak (1994). The former states that, on any Riemannian manifold with negative curvature or ergodic geodesic flow, the eigenfunctions of the Laplace-Beltrami operator equidistribute in phase space with density 1. Under the same assumptions, the latter states that the eigenfunctions induce a sequence of Wigner probability measures on fibers of the Hamiltonian in phase space, and these measures converge in the weak-* topology to the uniform Liouville measure. If true, the conjecture implies that such eigenfunctions equidistribute in the high-eigenvalue limit with no exceptional "scarring" patterns. This physically means that the finest details of chaotic Hamiltonian systems can never reflect their quantum-mechanical behaviors, even in the semiclassical limit. The main contribution of this thesis is to contextualize the question of quantum ergodicity and quantum unique ergodicity in an elementary analytic and geometric framework. In addition to presenting and summarizing numerous important proofs, such as Colin de Verdi\\`ere's proof of the quantum ergodicity theorem, we perform graphical simulations of certain billiard flows and expositorily discuss several themes in the study of quantum chaos.

  11. Quantum-Mechanical Model of Spacetime

    E-Print Network [OSTI]

    Jarmo Makela

    2007-06-20

    We consider a possibility to construct a quantum-mechanical model of spacetime, where Planck size quantum black holes act as the fundamental constituents of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. Our model implies that area has a discrete spectrum with equal spacing. At macroscopic length scales our model reproduces Einstein's field equation with a vanishing cosmological constant as a sort of thermodynamical equation of state of spacetime and matter fields. In the low temperature limit, where most black holes are assumed to be in the ground state, our model implies the Unruh and the Hawking effects, whereas in the high temperature limit we find, among other things, that black hole entropy depends logarithmically on the event horizon area, instead of being proportional to the area.

  12. Dissipative Quantum Metrology with Spin Cat States

    E-Print Network [OSTI]

    Jiahao Huang; Xizhou Qin; Honghua Zhong; Yongguan Ke; Chaohong Lee

    2014-10-28

    The maximally entangled states are excellent candidates for achieving Heisenberg-limited measurements in ideal quantum metrology, however, they are fragile against dissipation such as particle losses and their achievable precisions may become even worse than the standard quantum limit (SQL). Here we present a robust high-precision measurement scheme via spin cat states (a kind of non-Gaussian entangled states in superposition of two spin coherent states) in the presence of particle losses. The input spin cat states are of excellent robustness against particle losses and their achievable precisions may still beat the SQL. For realistic measurements based upon our scheme, comparing with the population measurement, the parity measurement is more suitable for yielding higher precisions. In phase measurement with realistic dissipative systems of bosons, our scheme provides a robust and realizable way to achieve high-precision measurements beyond the SQL.

  13. Quantum chaos in small quantum networks

    E-Print Network [OSTI]

    Ilki Kim; Guenter Mahler

    1999-11-20

    We study a 2-spin quantum Turing architecture, in which discrete local rotations \\alpha_m of the Turing head spin alternate with quantum controlled NOT-operations. We show that a single chaotic parameter input \\alpha_m leads to a chaotic dynamics in the entire Hilbert space. The instability of periodic orbits on the Turing head and `chaos swapping' onto the Turing tape are demonstrated explicitly as well as exponential parameter sensitivity of the Bures metric.

  14. Liouville Quantum Gravity on the unit disk

    E-Print Network [OSTI]

    Yichao Huang; Rémi Rhodes; Vincent Vargas

    2015-02-15

    Our purpose is to pursue the rigorous construction of Liouville Quantum Field Theory on Riemann surfaces initiated by F. David, A. Kupiainen and the last two authors in the context of the Riemann sphere and inspired by the 1981 seminal work by Polyakov. In this paper, we investigate the case of simply connected domains with boundary. We also make precise conjectures about the relationship of this theory to scaling limits of random planar maps with boundary conformally embedded onto the disk.

  15. Blind quantum machine learning

    E-Print Network [OSTI]

    Yu-Bo Sheng; Lan Zhou

    2015-07-26

    Blind quantum machine learning (BQML) enables a classical client with little quantum technology to delegate a remote quantum machine learning to the quantum server in such a approach that the privacy data is preserved. Here we propose the first BQML protocol that the client can classify two-dimensional vectors to different clusters, resorting to a remote small-scale photon quantum computation processor. During the protocol, the client is only required to rotate and measure the single qubit. The protocol is secure without leaking any relevant information to the Eve. Any eavesdropper who attempts to intercept and disturb the learning process can be noticed. In principle, this protocol can be used to classify high dimensional vectors and may provide a new viewpoint and application for quantum machine learning.

  16. Quantum control in spintronics

    E-Print Network [OSTI]

    Ardavan, A

    2011-01-01

    Superposition and entanglement are uniquely quantum phenomena. Superposition incorporates a phase which contains information surpassing any classical mixture. Entanglement offers correlations between measurements in quantum systems that are stronger than any which would be possible classically. These give quantum computing its spectacular potential, but the implications extend far beyond quantum information processing. Early applications may be found in entanglement enhanced sensing and metrology. Quantum spins in condensed matter offer promising candidates for investigating and exploiting superposition and entanglement, and enormous progress is being made in quantum control of such systems. In GaAs, individual electron spins can be manipulated and measured, and singlet-triplet states can be controlled in double-dot structures. In silicon, individual electron spins can be detected by ionisation of phosphorous donors, and information can be transferred from electron spins to nuclear spins to provide long memor...

  17. Quantum physics meets biology

    E-Print Network [OSTI]

    Markus Arndt; Thomas Juffmann; Vlatko Vedral

    2009-11-01

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

  18. INSTITUTE for QUANTUM STRUCTURES AND DEVICES

    E-Print Network [OSTI]

    Plotkin, Steven S.

    , and #12;the design and fabrication of quantum devices based on magnetic, quantum dot, and superconducting

  19. Some topics in thermodynamics and quantum mechanics

    E-Print Network [OSTI]

    Robert Carroll

    2012-11-17

    We sketch some connecting relations involving fractional and quantum calculi, fractal structure, thermodynamics, and quantum mechanics.

  20. Quantum theory and Einstein's general relativity

    SciTech Connect (OSTI)

    v. Borzeszkowski, H.; Treder, H.

    1982-11-01

    We dicusss the meaning and prove the accordance of general relativity, wave mechanics, and the quantization of Einstein's gravitation equations themselves. Firstly, we have the problem of the influence of gravitational fields on the de Broglie waves, which influence is in accordance with Einstein's weak principle of equivalence and the limitation of measurements given by Heisenberg's uncertainty relations. Secondly, the quantization of the gravitational fields is a ''quantization of geometry.'' However, classical and quantum gravitation have the same physical meaning according to limitations of measurements given by Einstein's strong principle of equivalence and the Heisenberg uncertainties for the mechanics of test bodies.

  1. Motion in Quantum Gravity

    E-Print Network [OSTI]

    Karim Noui

    2010-03-31

    We tackle the question of motion in Quantum Gravity: what does motion mean at the Planck scale? Although we are still far from a complete answer we consider here a toy model in which the problem can be formulated and resolved precisely. The setting of the toy model is three dimensional Euclidean gravity. Before studying the model in detail, we argue that Loop Quantum Gravity may provide a very useful approach when discussing the question of motion in Quantum Gravity.

  2. Secure Quantum Key Distribution

    E-Print Network [OSTI]

    Hoi-Kwong Lo; Marcos Curty; Kiyoshi Tamaki

    2015-05-20

    Secure communication plays a crucial role in the Internet Age. Quantum mechanics may revolutionise cryptography as we know it today. In this Review Article, we introduce the motivation and the current state of the art of research in quantum cryptography. In particular, we discuss the present security model together with its assumptions, strengths and weaknesses. After a brief introduction to recent experimental progress and challenges, we survey the latest developments in quantum hacking and counter-measures against it.

  3. Are Quantum States Subjective?

    E-Print Network [OSTI]

    R. K. Pradhan

    2012-02-22

    The subjective nature of the quantum states is brought out and it is argued that the objective state assignment is subsequent to the subjective state of the observer regarding his state of knowledge about the system. The collapse postulate is examined in detail to bring out the inherent subjectivity of the quantum state. The role of doubt and faith in quantum state assignment is examined.

  4. Quantum information science as an approach to complex quantum systems

    E-Print Network [OSTI]

    Michael A. Nielsen

    2002-08-13

    What makes quantum information science a science? These notes explore the idea that quantum information science may offer a powerful approach to the study of complex quantum systems. We discuss how to quantify complexity in quantum systems, and argue that there are two qualitatively different types of complex quantum system. We also explore ways of understanding complex quantum dynamics by quantifying the strength of a quantum dynamical operation as a physical resource. This is the text for a talk at the ``Sixth International Conference on Quantum Communication, Measurement and Computing'', held at MIT, July 2002. Viewgraphs for the talk may be found at http://www.qinfo.org/talks/.

  5. Scalable cavity quantum electrodynamics system for quantum computing

    E-Print Network [OSTI]

    Mohammad Hasan Aram; Sina Khorasani

    2015-07-18

    We introduce a new scalable cavity quantum electrodynamics platform which can be used for quantum computing. This system is composed of coupled photonic crystal (PC) cavities which their modes lie on a Dirac cone in the whole super crystal band structure. Quantum information is stored in quantum dots that are positioned inside the cavities. We show if there is just one quantum dot in the system, energy as photon is exchanged between the quantum dot and the Dirac modes sinusoidally. Meanwhile the quantum dot becomes entangled with Dirac modes. If we insert more quantum dots into the system, they also become entangled with each other.

  6. Quantum gravity on the lattice

    E-Print Network [OSTI]

    Hamber, Herbert W.

    2009-01-01

    the Conference Quantum Gravity: Challenges and Perspectives.divergences in quantum gravity. In: Hawking, S.W. , Israel,f ) V n?1 ( f ) = Quantum gravity on the lattice Similarly,

  7. FOURIER TRANSFORM MULTIPLE QUANTUM NMR

    E-Print Network [OSTI]

    Drobny, G.

    2011-01-01

    of transition observed in Fourier transform multiple quantumDecember 18-19, 1979 FOURIER TRANSFORM MULTIPLE QUANTUM NMRof London, December 1978. FOURIER TRANSFO~~ MULTIPLE QUANTUM

  8. Vacuum Energy in Quantum Graphs 

    E-Print Network [OSTI]

    Wilson, Justin

    2007-07-14

    We calculate the vacuum energy in quantum graphs. Vacuum energy arose in quantum physics but has an independent mathematical interest as a functional carrying information about the eigenvalue spectrum of a system. A quantum graph is a metric graph...

  9. A quantum way for metamaterials

    E-Print Network [OSTI]

    Didier Felbacq

    2011-03-09

    A new future for metamaterials is suggested, involving the insertion of quantum degrees of freedom, under the guise of quantum dots or cold atoms, in an photonic matrix. It is argued that new emergent, quantum, properties could be obtained.

  10. Coherent control of quantum information

    E-Print Network [OSTI]

    Henry, Michael Kevin

    2006-01-01

    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 ...

  11. Reverse Engineering Quantum Field Theory

    E-Print Network [OSTI]

    Robert Oeckl

    2012-10-02

    An approach to the foundations of quantum theory is advertised that proceeds by "reverse engineering" quantum field theory. As a concrete instance of this approach, the general boundary formulation of quantum theory is outlined.

  12. Some Properties of Correlations of Quantum Lattice Systems in Thermal Equilibrium

    E-Print Network [OSTI]

    Juerg Froehlich; Daniel Ueltschi

    2015-05-27

    Simple proofs of uniqueness of the thermodynamic limit of KMS states and of the decay of equilibrium correlations are presented for a large class of quantum lattice systems at high temperatures. New quantum correlation inequalities for general Heisenberg models are described. Finally, a simplified derivation of a general result on power-law decay of correlations in 2D quantum lattice systems with continuous symmetries is given, extending results of Mc Bryan and Spencer for the 2D classical XY model.

  13. Quantum Walks and discrete Gauge Theories

    E-Print Network [OSTI]

    Pablo Arnault; Fabrice Debbasch

    2015-10-19

    A particular example is produced to prove that quantum walks can be used to simulate full-fledged discrete gauge theories. A new family of $(1 + 2)$-dimensional walks is introduced and its continuous limit is shown to coincide with the dynamics of a Dirac fermion coupled to arbitrary electromagnetic fields. The electromagnetic interpretation is extended beyond the continuous limit by proving that these DTQWs exhibit an exact discrete local $U(1)$ gauge invariance and possess a discrete gauge-invariant conserved current. A discrete gauge-invariant electromagnetic field is also constructed and that field is coupled to the conserved current by a discrete generalization of Maxwell equations. The dynamics of the DTQWs under crossed electric and magnetic fields is finally explored outside the continuous limit by numerical simulations. Bloch oscillations and the so-called ${\\bf E} \\times {\\bf B}$ drift are recovered in the weak-field limit. Localization is observed for some values of the gauge fields.

  14. Observables on Quantum Structures

    E-Print Network [OSTI]

    Anatolij Dvure?enskij; Mária Kuková

    2012-04-29

    An observable on a quantum structure is any $\\sigma$-homomorphism of quantum structures from the Borel $\\sigma$-algebra into the quantum structure. We show that our partial information on an observable known only for all intervals of the form $(-\\infty,t)$ is sufficient to determine uniquely the whole observable defined on quantum structures like $\\sigma$-MV-algebras, $\\sigma$-effect algebras, Boolean $\\sigma$-algebras, monotone $\\sigma$-complete effect algebras with the Riesz Decomposition Property, the effect algebra of effect operators of a Hilbert space, and a system of functions, and an effect-tribe.

  15. Criteria for quantum chaos

    SciTech Connect (OSTI)

    Heller, E.J. (Los Alamos National Lab., Albuquerque, NM); Davis, M.J.

    1982-06-10

    This paper reviews some of the opinions on quantum chaos put forth at the 1981 American Conference on Theoretical Chemistry and presents evidence to support the author's point of view. The degree of correspondence between classical and quantum onset and extent of chaos differs markedly according to the definition adopted for quantum chaos. At one extreme, a quantum generalization of the classical Kolmolgorov entropy which give zero entrophy for quantum systems with a discrete spectrum regardless of the classical properties, was a suitable foundation for the definition of quantum chaos. At the other, the quantum phase space definition shows generally excellent correspondence to the classical phase space measures. The authors preferred this approach. Another point of controversy is the question of whether the spectrum of energy levels (or its variation with some parameter of the Hamiltonian) is enough to characterize the quantum chaos (or lack of it), or whether more information is needed (i.e., eigenfunctions). The authors conclude that one does not want to rely upon eigenvalues alone to characterize the degree of chaos in the quantum dynamics.

  16. Generalizations of quantum statistics

    E-Print Network [OSTI]

    O. W. Greenberg

    2008-05-02

    We review generalizations of quantum statistics, including parabose, parafermi, and quon statistics, but not including anyon statistics, which is special to two dimensions.

  17. Quantum Mind from a Classical Field Theory of the Brain

    E-Print Network [OSTI]

    Paola Zizzi

    2011-04-13

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

  18. Signal Flows in Non-Markovian Linear Quantum Feedback Networks

    E-Print Network [OSTI]

    Re-Bing Wu; Jing Zhang; Yu-xi Liu; Tzyh-Jong Tarn

    2014-12-17

    Enabled by rapidly developing quantum technologies, it is possible to network quantum systems at a much larger scale in the near future. To deal with non-Markovian dynamics that is prevalent in solid-state devices, we propose a general transfer function based framework for modeling linear quantum networks, in which signal flow graphs are applied to characterize the network topology by flow of quantum signals. We define a noncommutative ring $\\mathbb{D}$ and use its elements to construct Hamiltonians, transformations and transfer functions for both active and passive systems. The signal flow graph obtained for direct and indirect coherent quantum feedback systems clearly show the feedback loop via bidirectional signal flows. Importantly, the transfer function from input to output field is derived for non-Markovian quantum systems with colored inputs, from which the Markovian input-output relation can be easily obtained as a limiting case. Moreover, the transfer function possesses a symmetry structure that is analogous to the well-know scattering transformation in \\sd picture. Finally, we show that these transfer functions can be integrated to build complex feedback networks via interconnections, serial products and feedback, which may include either direct or indirect coherent feedback loops, and transfer functions between quantum signal nodes can be calculated by the Riegle's matrix gain rule. The theory paves the way for modeling, analyzing and synthesizing non-Markovian linear quantum feedback networks in the frequency-domain.

  19. Quantum Non-Demolition Detection of Polar Molecule Complexes: Dimers, Trimers, Tetramers

    E-Print Network [OSTI]

    Igor B. Mekhov

    2011-11-16

    The optical nondestructive method for in situ detection of the bound states of ultracold polar molecules is developed. It promises a minimally destructive measurement scheme up to a physically exciting quantum non-demolition (QND) level. The detection of molecular complexes beyond simple pairs of quantum particles (dimers, known, e.g., from the BEC-BCS theory) is suggested, including three-body (trimers) and four-body (tertramers) complexes trapped by one-dimensional tubes. The intensity of scattered light is sensitive to the molecule number fluctuations beyond the mean-density approximation. Such fluctuations are very different for various complexes, which leads to radically different light scattering. This type of research extends "quantum optics of quantum gases" to the field of ultracold molecules. Merging the quantum optical and ultracold gas problems will advance the experimental efforts towards the study of the light-matter interaction at its ultimate quantum level, where the quantizations of both light and matter are equally important.

  20. Single-dot optical emission from ultralow density well-isolated InP quantum dots

    SciTech Connect (OSTI)

    Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.

    2008-10-06

    We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.

  1. Nash equilibrium in quantum superpositions

    E-Print Network [OSTI]

    Faisal Shah Khan; Simon. J. D. Phoenix

    2011-06-15

    A working definition of the term \\quantum game" is developed in an attempt to gain insights into aspects of quantum mechanics via game theory.

  2. Quantum Chaos and Statistical Mechanics

    E-Print Network [OSTI]

    Mark Srednicki

    1994-06-14

    We briefly review the well known connection between classical chaos and classical statistical mechanics, and the recently discovered connection between quantum chaos and quantum statistical mechanics.

  3. Quantum physics and human values

    SciTech Connect (OSTI)

    Stapp, H.P.

    1989-09-01

    This report discusses the following concepts: the quantum conception of nature; the quantum conception of man; and the impact upon human values. (LSP).

  4. Quantum Mechanics and Black Holes

    E-Print Network [OSTI]

    Jose N. Pecina-Cruz

    2005-11-27

    This paper discusses the existence of black holes from the foundations of quantum mechanics. It is found that quantum mechanics rule out a possible gravitational collapse.

  5. Quantum wave packets in space and time and an improved criterion for classical behavior

    E-Print Network [OSTI]

    C. L. Herzenberg

    2009-04-28

    An improved criterion for distinguishing conditions in which classical or quantum behavior occurs is developed by comparing classical and quantum mechanical measures of size while incorporating spatial and temporal restrictions on wave packet formation associated with limitations on spatial extent and duration.

  6. Quantum rejection sampling

    E-Print Network [OSTI]

    Maris Ozols; Martin Roetteler; Jérémie Roland

    2011-12-13

    Rejection sampling is a well-known method to sample from a target distribution, given the ability to sample from a given distribution. The method has been first formalized by von Neumann (1951) and has many applications in classical computing. We define a quantum analogue of rejection sampling: given a black box producing a coherent superposition of (possibly unknown) quantum states with some amplitudes, the problem is to prepare a coherent superposition of the same states, albeit with different target amplitudes. The main result of this paper is a tight characterization of the query complexity of this quantum state generation problem. We exhibit an algorithm, which we call quantum rejection sampling, and analyze its cost using semidefinite programming. Our proof of a matching lower bound is based on the automorphism principle which allows to symmetrize any algorithm over the automorphism group of the problem. Our main technical innovation is an extension of the automorphism principle to continuous groups that arise for quantum state generation problems where the oracle encodes unknown quantum states, instead of just classical data. Furthermore, we illustrate how quantum rejection sampling may be used as a primitive in designing quantum algorithms, by providing three different applications. We first show that it was implicitly used in the quantum algorithm for linear systems of equations by Harrow, Hassidim and Lloyd. Secondly, we show that it can be used to speed up the main step in the quantum Metropolis sampling algorithm by Temme et al.. Finally, we derive a new quantum algorithm for the hidden shift problem of an arbitrary Boolean function and relate its query complexity to "water-filling" of the Fourier spectrum.

  7. Quantum noise and radiation pressure effects in high power optical interferometers

    E-Print Network [OSTI]

    Corbitt, Thomas Randall

    2008-01-01

    In recent years, a variety of mechanical systems have been approaching quantum limits to their sensitivity of continuous position measurements imposed by the Heisenberg Uncertainty Principle. Most notably, gravitational ...

  8. Classical capacity of the free-space quantum-optical channel

    E-Print Network [OSTI]

    Guha, Saikat, 1980-

    2004-01-01

    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 ...

  9. Towards room-temperature Terahertz Quantum Cascade Lasers : directions and design

    E-Print Network [OSTI]

    Chan, Chun Wang Ivan

    2015-01-01

    Terahertz Quantum Cascade Lasers (THz QCLs) are arguably the most promising technology today for the compact, efficient generation of THz radiation. Their main limitation is that they require cryogenic cooling, which ...

  10. Quantum Gravity and Turbulence

    E-Print Network [OSTI]

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

    2010-05-18

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

  11. Quantum Physics Einstein's Gravity

    E-Print Network [OSTI]

    Visser, Matt

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

  12. Quantum motor and future

    E-Print Network [OSTI]

    Evgeny G. Fateev

    2013-01-20

    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.

  13. Quantum Dots: Theory

    SciTech Connect (OSTI)

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  14. Geometrization of Quantum Mechanics

    E-Print Network [OSTI]

    J. F. Carinena; J. Clemente-Gallardo; G. Marmo

    2007-03-23

    We show that it is possible to represent various descriptions of Quantum Mechanics in geometrical terms. In particular we start with the space of observables and use the momentum map associated with the unitary group to provide an unified geometrical description for the different pictures of Quantum Mechanics. This construction provides an alternative to the usual GNS construction for pure states.

  15. QUICK QUANTUM MECHANICS ---Introduction ---

    E-Print Network [OSTI]

    Jackson, Andrew D.

    QUICK QUANTUM MECHANICS --- Introduction --- The following notes are intended to be a supplement to your study of Liboff's ``Introductory Quantum Mechanics.'' They are not an alternative! My purpose here of Classical Mechanics After Newton found his equations of motion, physicists knew they would have to wait

  16. Topological quantum field theories

    E-Print Network [OSTI]

    Albert Schwarz

    2000-11-29

    Following my plenary lecture on ICMP2000 I review my results concerning two closely related topics: topological quantum field theories and the problem of quantization of gauge theories. I start with old results (first examples of topological quantum field theories were constructed in my papers in late seventies) and I come to some new results, that were not published yet.

  17. Quantum interfaces Karl Svozil

    E-Print Network [OSTI]

    Svozil, Karl

    Quantum interfaces Karl Svozil Institute for Theoretical Physics, Vienna University of Technology they consider to be objects. The cartesian cut or, in modern terminology, the interface mediating this exchange the necessary conceptual means. An attempt is made to formalize the interface, in particular the quantum

  18. FUEL CASK IMPACT LIMITER VULNERABILITIES

    SciTech Connect (OSTI)

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

    2009-02-09

    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.

  19. Quantum evolution across singularities

    E-Print Network [OSTI]

    Ben Craps; Oleg Evnin

    2008-01-21

    Attempts to consider evolution across space-time singularities often lead to quantum systems with time-dependent Hamiltonians developing an isolated singularity as a function of time. Examples include matrix theory in certain singular time-dependent backgounds and free quantum fields on the two-dimensional compactified Milne universe. Due to the presence of the singularities in the time dependence, the conventional quantum-mechanical evolution is not well-defined for such systems. We propose a natural way, mathematically analogous to renormalization in conventional quantum field theory, to construct unitary quantum evolution across the singularity. We carry out this procedure explicitly for free fields on the compactified Milne universe and compare our results with the matching conditions considered in earlier work (which were based on the covering Minkowski space).

  20. Quantum Data Fitting

    E-Print Network [OSTI]

    Nathan Wiebe; Daniel Braun; Seth Lloyd

    2012-07-03

    We provide a new quantum algorithm that efficiently determines the quality of a least-squares fit over an exponentially large data set by building upon an algorithm for solving systems of linear equations efficiently (Harrow et al., Phys. Rev. Lett. {\\bf 103}, 150502 (2009)). In many cases, our algorithm can also efficiently find a concise function that approximates the data to be fitted and bound the approximation error. In cases where the input data is a pure quantum state, the algorithm can be used to provide an efficient parametric estimation of the quantum state and therefore can be applied as an alternative to full quantum state tomography given a fault tolerant quantum computer.

  1. High Performance Quantum Computing

    E-Print Network [OSTI]

    Simon J. Devitt; William J. Munro; Kae Nemoto

    2008-10-14

    The architecture scalability afforded by recent proposals of a large scale photonic based quantum computer, utilizing the theoretical developments of topological cluster states and the photonic chip, allows us to move on to a discussion of massively scaled Quantum Information Processing (QIP). In this letter we introduce the model for a secure and unsecured topological cluster mainframe. We consider the quantum analogue of High Performance Computing, where a dedicated server farm is utilized by many users to run algorithms and share quantum data. The scaling structure of photonics based topological cluster computing leads to an attractive future for server based QIP, where dedicated mainframes can be constructed and/or expanded to serve an increasingly hungry user base with the ideal resource for individual quantum information processing.

  2. What quantum computers may tell us about quantum mechanics

    E-Print Network [OSTI]

    Monroe, Christopher

    17 What quantum computers may tell us about quantum mechanics Christopher R. Monroe University of Michigan, Ann Arbor Quantum mechanics occupies a unique position in the history of science. It has sur successes of quantum mechanics, its foundations are often questioned, owing to the glaring difficulties

  3. Quantum Techniques for Reaction Networks

    E-Print Network [OSTI]

    John C. Baez

    2013-06-14

    Reaction networks are a general formalism for describing collections of classical entities interacting in a random way. While reaction networks are mainly studied by chemists, they are equivalent to Petri nets, which are used for similar purposes in computer science and biology. As noted by Doi and others, techniques from quantum field theory can be adapted to apply to such systems. Here we use these techniques to study how the "master equation" describing stochastic time evolution for a reaction network reduces is related to the "rate equation" describing the deterministic evolution of the expected number of particles of each species in the large-number limit. We show that the relation is especially strong when a solution of master equation is a "coherent state", meaning that the numbers of entities of each kind are described by independent Poisson distributions.

  4. Lesson 8 Infinite Limits and One-sided Limits

    E-Print Network [OSTI]

    2013-09-06

    Sep 6, 2013 ... long-term behavior. A common model for the population of a species in an area is the logistic model: Lesson 8 Infinite Limits and One-sided ...

  5. Asymmetric Dual Axis Energy Recovery Linac for Ultra-High Flux sources of coherent X-ray/THz radiation: Investigations Towards its Ultimate Performance

    E-Print Network [OSTI]

    Ainsworth, R; Konoplev, I V; Seryi, A

    2015-01-01

    Truly compact and high current, efficient particle accelerators are required for sources of coherent high brightness and intensity THz and X-Ray radiation to be accepted by university or industrial R&D laboratories. The demand for compactness and efficiency can be satisfied by superconducting RF energy recovery linear accelerators (SRF ERL) allowing effectively minimising the footprint and maximising the efficiency of the system. However such set-ups are affected by regenerative beam-break up (BBU) instabilities which limit the beam current and may terminate the beam transport as well as energy recuperation. In this paper we suggest and discuss a SRF ERL with asymmetric configuration of accelerating and decelerating cavities resonantly coupled. In this model of SRF ERL we propose an electron bunch passing through accelerating and decelerating cavities each once and we show that in this case the regenerative BBU instability can be minimised allowing high currents to be achieved. We study the BBU start curr...

  6. Quantum estimation of physical parameters in the spacetime of a rotating planet

    E-Print Network [OSTI]

    Jan Kohlrus; David Edward Bruschi; Jorma Louko; Ivette Fuentes

    2015-11-13

    We employ quantum estimation techniques to obtain ultimate bounds on precision measurements of gravitational parameters of the spacetime outside a rotating planet. Spacetime curvature affects the frequency distribution of a photon sent from Earth to a satellite, and this change encodes parameters of the spacetime. This allows us to achieve precise measurements of parameters of Earth such as its Schwarzschild radius and equatorial angular velocity. We then are able to provide a comparison with the state-of-the-art in parameter estimation obtained through classical means. Extensions and future directions are also discussed.

  7. Quantum estimation of physical parameters in the spacetime of a rotating planet

    E-Print Network [OSTI]

    Kohlrus, Jan; Louko, Jorma; Fuentes, Ivette

    2015-01-01

    We employ quantum estimation techniques to obtain ultimate bounds on precision measurements of gravitational parameters of the spacetime outside a rotating planet. Spacetime curvature affects the frequency distribution of a photon sent from Earth to a satellite, and this change encodes parameters of the spacetime. This allows us to achieve precise measurements of parameters of Earth such as its Schwarzschild radius and equatorial angular velocity. We then are able to provide a comparison with the state-of-the-art in parameter estimation obtained through classical means. Extensions and future directions are also discussed.

  8. Quantum histories without contrary inferences

    SciTech Connect (OSTI)

    Losada, Marcelo; Laura, Roberto

    2014-12-15

    In the consistent histories formulation of quantum theory it was shown that it is possible to retrodict contrary properties. We show that this problem do not appear in our formalism of generalized contexts for quantum histories. - Highlights: • We prove ordinary quantum mechanics has no contrary properties. • Contrary properties in consistent histories are reviewed. • We prove generalized contexts for quantum histories have no contrary properties.

  9. Path Integral for Quantum Operations

    E-Print Network [OSTI]

    Vasily E. Tarasov

    2007-06-14

    In this paper we consider a phase space path integral for general time-dependent quantum operations, not necessarily unitary. We obtain the path integral for a completely positive quantum operation satisfied Lindblad equation (quantum Markovian master equation). We consider the path integral for quantum operation with a simple infinitesimal generator.

  10. ARITHMETIC QUANTUM CHAOS JENS MARKLOF

    E-Print Network [OSTI]

    Marklof, Jens

    ARITHMETIC QUANTUM CHAOS JENS MARKLOF 1. Introduction The central objective in the study of quantum (Berry and Tabor 1977; Bohigas, Giannoni and Schmit 1984). Arithmetic quantum chaos (AQC) refers chaos is to characterize universal properties of quantum systems that reflect the regular or chaotic

  11. QUANTUM MECHANICS II Physics 342

    E-Print Network [OSTI]

    Rosner, Jonathan L.

    QUANTUM MECHANICS II Physics 342 KPTC 103 9:00 ­ 10:20 a.m. 1 Tues., Thurs. ­ Winter Quarter 2011 quantum mechanics at the graduate level. The text for Quantum Mechanics II will be J. J. Sakurai and Jim Napolitano, Modern Quantum Mechanics, Second Edition (Addison-Wesley, San Francisco, 2011). For supplemental

  12. AN INTRODUCTION TO QUANTUM OPTICS...

    E-Print Network [OSTI]

    Palffy-Muhoray, Peter

    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

  13. Multivariable Optimization: Quantum Annealing & Computation

    E-Print Network [OSTI]

    Sudip Mukherjee; Bikas K. Chakrabarti

    2014-08-21

    Recent developments in quantum annealing techniques have been indicating potential advantage of quantum annealing for solving NP-hard optimization problems. In this article we briefly indicate and discuss the beneficial features of quantum annealing techniques and compare them with those of simulated annealing techniques. We then briefly discuss the quantum annealing studies of some model spin glass and kinetically constrained systems.

  14. Magmatic "Quantum-Like" Systems

    E-Print Network [OSTI]

    Elemer E Rosinger

    2008-12-16

    Quantum computation has suggested, among others, the consideration of "non-quantum" systems which in certain respects may behave "quantum-like". Here, what algebraically appears to be the most general possible known setup, namely, of {\\it magmas} is used in order to construct "quantum-like" systems. The resulting magmatic composition of systems has as a well known particular case the tensor products.

  15. STATEMENT OF CONSIDERATIONS STATEMENT OF CONSIDERATIONS FOR LIMITATION...

    Energy Savers [EERE]

    direction to deploy HPSS at computing centers for operational use in high performance computing environments. The ultimate goal is the continued viability of this...

  16. Quantum Spin Hall Eect May 9, 2011

    E-Print Network [OSTI]

    Hall Eect Quantum Spin Hall Eect in Graphene QSHE in quantum well QSHE in strained semiconductor Tim Quantum Spin Hall Eect in Graphene QSHE in quantum well QSHE in strained semiconductor Tim Hsieh Quantum Hsieh Quantum Spin Hall Eect #12;Integer Quantum Hall Eect (IQHE) 2D electron gas at low temperature

  17. Nuclear Structure at the Limits

    SciTech Connect (OSTI)

    Nazarewicz, W.

    1998-01-12

    One of the frontiers of today?s nuclear science is the ?journey to the limits? of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The tour to the limits is not only a quest for new, exciting phenomena, but the new data are expected, as well, to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this series of lectures, current developments in nuclear structure at the limits are discussed from a theoretical perspective, mainly concentrating on medium-mass and heavy nuclei.

  18. Nuclear Structure at the Limits

    SciTech Connect (OSTI)

    Nazarewicz, Witold

    1997-12-31

    One of the frontiers of today`s nuclear science is the ``journey to the limits``: of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The tour to the limits is not only a quest for new, exciting phenomena but the new data are expected, as well, to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this talk, current developments in nuclear structure at the limits are discussed from a theoretical perspective.

  19. Direct measure of quantum correlation

    SciTech Connect (OSTI)

    Yu, Chang-shui [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Zhao, Haiqing [School of Science, Dalian Jiaotong University, Dalian 116028 (China)

    2011-12-15

    The quantumness of the correlation known as quantum correlation is usually measured by quantum discord. So far various quantum discords can be roughly understood as indirect measure by some special discrepancy of two quantities. We present a direct measure of quantum correlation by revealing the difference between the structures of classically and quantum correlated states. Our measure explicitly includes the contributions of the inseparability and local nonorthogonality of the eigenvectors of a density matrix. Besides its relatively easy computability, our measure can provide a unified understanding of quantum correlation of all the present versions.

  20. Quantum noise effects with Kerr nonlinearity enhancement in coupled gain-loss waveguides

    E-Print Network [OSTI]

    Bing He; Shu-Bin Yan; Jing Wang; Min Xiao

    2015-05-26

    It is generally difficult to study the dynamical properties of a quantum system with both inherent quantum noises and non-perturbative nonlinearity. Due to the possibly drastic intensity increase of an input coherent light in the gain-loss waveguide couplers with parity-time (PT) symmetry, the Kerr effect from a nonlinearity added into the systems can be greatly enhanced, and is expected to create the macroscopic entangled states of the output light fields with huge photon numbers. Meanwhile, the quantum noises also coexist with the amplification and dissipation of the light fields. Under the interplay between the quantum noises and nonlinearity, the quantum dynamical behaviors of the systems become rather complicated. However, the important quantum noise effects have been mostly neglected in the previous studies about nonlinear PT-symmetric systems. Here we present a solution to this non-perturbative quantum nonlinear problem, showing the real-time evolution of the system observables. The enhanced Kerr nonlinearity is found to give rise to a previously unknown decoherence effect that is irrelevant to the quantum noises, and imposes a limit on the emergence of macroscopic nonclassicality. In contrast to what happen in the linear systems, the quantum noises exert significant impact on the system dynamics, and can create the nonclassical light field states in conjunction with the enhanced Kerr nonlinearity. This first study on the noise involved quantum nonlinear dynamics of the coupled gain-loss waveguides can help to better understand the quantum noise effects in the broad nonlinear systems.

  1. Quantum correlations of helicity entangled states in non-inertial frames beyond single mode approximation

    SciTech Connect (OSTI)

    Harsij, Zeynab Mirza, Behrouz

    2014-12-15

    A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation. - Highlights: • The helicity entangled states here are observer independent in non-inertial frames. • It is explicitly shown that Quantum Discord for these states is observer independent. • Geometric Quantum Discord is also not affected by acceleration increase. • Extending to beyond single mode does not change the degree of entanglement. • Beyond single mode approximation the degree of Quantum Discord is also preserved.

  2. Quantum teleportation using active feed-forward between two Canary Islands

    E-Print Network [OSTI]

    Xiao-song Ma; Thomas Herbst; Thomas Scheidl; Daqing Wang; Sebastian Kropatschek; William Naylor; Alexandra Mech; Bernhard Wittmann; Johannes Kofler; Elena Anisimova; Vadim Makarov; Thomas Jennewein; Rupert Ursin; Anton Zeilinger

    2012-05-17

    Quantum teleportation [1] is a quintessential prerequisite of many quantum information processing protocols [2-4]. By using quantum teleportation, one can circumvent the no-cloning theorem [5] and faithfully transfer unknown quantum states to a party whose location is even unknown over arbitrary distances. Ever since the first experimental demonstrations of quantum teleportation of independent qubits [6] and of squeezed states [7], researchers have progressively extended the communication distance in teleportation, usually without active feed-forward of the classical Bell-state measurement result which is an essential ingredient in future applications such as communication between quantum computers. Here we report the first long-distance quantum teleportation experiment with active feed-forward in real time. The experiment employed two optical links, quantum and classical, over 143 km free space between the two Canary Islands of La Palma and Tenerife. To achieve this, the experiment had to employ novel techniques such as a frequency-uncorrelated polarization-entangled photon pair source, ultra-low-noise single-photon detectors, and entanglement-assisted clock synchronization. The average teleported state fidelity was well beyond the classical limit of 2/3. Furthermore, we confirmed the quality of the quantum teleportation procedure (without feed-forward) by complete quantum process tomography. Our experiment confirms the maturity and applicability of the involved technologies in real-world scenarios, and is a milestone towards future satellite-based quantum teleportation.

  3. Quantum control in spintronics

    E-Print Network [OSTI]

    A. Ardavan; G. A. D. Briggs

    2011-02-08

    Superposition and entanglement are uniquely quantum phenomena. Superposition incorporates a phase which contains information surpassing any classical mixture. Entanglement offers correlations between measurements in quantum systems that are stronger than any which would be possible classically. These give quantum computing its spectacular potential, but the implications extend far beyond quantum information processing. Early applications may be found in entanglement enhanced sensing and metrology. Quantum spins in condensed matter offer promising candidates for investigating and exploiting superposition and entanglement, and enormous progress is being made in quantum control of such systems. In GaAs, individual electron spins can be manipulated and measured, and singlet-triplet states can be controlled in double-dot structures. In silicon, individual electron spins can be detected by ionisation of phosphorous donors, and information can be transferred from electron spins to nuclear spins to provide long memory times. Electron and nuclear spins can be manipulated in nitrogen atoms incarcerated in fullerene molecules, which in turn can be assembled in ordered arrays. Spin states of charged nitrogen vacancy centres in diamond can be manipulated and read optically. Collective spin states in a range of materials systems offer scope for holographic storage of information. Conditions are now excellent for implementing superposition and entanglement in spintronic devices, thereby opening up a new era of quantum technologies.

  4. Quantum field tomography

    E-Print Network [OSTI]

    A. Steffens; C. A. Riofrío; R. Hübener; J. Eisert

    2014-11-06

    We introduce the concept of quantum field tomography, the efficient and reliable reconstruction of unknown quantum fields based on data of correlation functions. At the basis of the analysis is the concept of continuous matrix product states, a complete set of variational states grasping states in quantum field theory. We innovate a practical method, making use of and developing tools in estimation theory used in the context of compressed sensing such as Prony methods and matrix pencils, allowing us to faithfully reconstruct quantum field states based on low-order correlation functions. In the absence of a phase reference, we highlight how specific higher order correlation functions can still be predicted. We exemplify the functioning of the approach by reconstructing randomised continuous matrix product states from their correlation data and study the robustness of the reconstruction for different noise models. We also apply the method to data generated by simulations based on continuous matrix product states and using the time-dependent variational principle. The presented approach is expected to open up a new window into experimentally studying continuous quantum systems, such as encountered in experiments with ultra-cold atoms on top of atom chips. By virtue of the analogy with the input-output formalism in quantum optics, it also allows for studying open quantum systems.

  5. Quantum Lyapunov Exponents

    E-Print Network [OSTI]

    P. Falsaperla; G. Fonte; G. Salesi

    2007-01-16

    We show that it is possible to associate univocally with each given solution of the time-dependent Schroedinger equation a particular phase flow ("quantum flow") of a non-autonomous dynamical system. This fact allows us to introduce a definition of chaos in quantum dynamics (quantum chaos), which is based on the classical theory of chaos in dynamical systems. In such a way we can introduce quantities which may be appelled "Quantum Lyapunov Exponents". Our approach applies to a non-relativistic quantum-mechanical system of n charged particles; in the present work numerical calculations are performed only for the hydrogen atom. In the computation of the trajectories we first neglect the spin contribution to chaos, then we consider the spin effects in quantum chaos. We show how the quantum Lyapunov exponents can be evaluated and give several numerical results which describe some properties found in the present approach. Although the system is very simple and the classical counterpart is regular, the most non-stationary solutions of the corresponding Schroeodinger equation are "chaotic" according to our definition.

  6. Layered architecture for quantum computing

    E-Print Network [OSTI]

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

    2012-09-27

    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.

  7. The Madelung Picture as a Foundation of Geometric Quantum Theory

    E-Print Network [OSTI]

    Maik Reddiger

    2015-09-01

    Despite its age quantum theory remains ill-understood, which is partially to blame on its deep interwovenness with the mysterious concept of quantization. In this article we argue that a quantum theory recoursing to quantization algorithms is necessarily incomplete. To provide a new axiomatic foundation, we give a rigorous proof showing how the Schr\\"odinger equation follows from the Madelung equations, which are formulated in the language of Newtonian mechanics. We show how the Schr\\"odinger picture relates to this Madelung picture and how the "classical limit" is directly obtained. This suggests a reformulation of the correspondence principle, stating that a quantum theory must reduce to a probabilistic version of Newtonian mechanics for large masses. We then enhance the stochastic interpretation developed by Tsekov, which speculates that quantum mechanical behavior is caused by random vibrations in spacetime. A new, yet incomplete model of particle creation and annihilation is also proposed.

  8. A Signed Particle Formulation of Non-Relativistic Quantum Mechanics

    E-Print Network [OSTI]

    Sellier, Jean Michel

    2015-01-01

    A formulation of non-relativistic quantum mechanics in terms of Newtonian particles is presented in the shape of a set of three postulates. In this new theory, quantum systems are described by ensembles of signed particles which behave as field-less classical objects which carry a negative or positive sign and interact with an external potential by means of creation and annihilation events only. This approach is shown to be a generalization of the signed particle Wigner Monte Carlo method which reconstructs the time-dependent Wigner quasi-distribution function of a system and, therefore, the corresponding Schroedinger time-dependent wave-function. Its classical limit is discussed and a physical interpretation, based on experimental evidences coming from quantum tomography, is suggested. Moreover, in order to show the advantages brought by this novel formulation, a straightforward extension to relativistic effects is discussed. To conclude, quantum tunnelling numerical experiments are performed to show the val...

  9. Atom-based coherent quantum-noise cancellation in optomechanics

    E-Print Network [OSTI]

    F. Bariani; H. Seok; S. Singh; M. Vengalattore; P. Meystre

    2015-08-24

    We analyze a quantum force sensor that uses coherent quantum noise cancellation (CQNC) to beat the Standard Quantum Limit (SQL). This sensor, which allows for the continuous, broad-band detection of feeble forces, is a hybrid dual-cavity system comprised of a mesoscopic mechanical resonator optically coupled to an ensemble of ultracold atoms. In contrast to the stringent constraints on dissipation typically associated with purely optical schemes of CQNC, the dissipation rate of the mechanical resonator only needs to be matched to the decoherence rate of the atomic ensemble -- a condition that is experimentally achievable even for the technologically relevant regime of low frequency mechanical resonators with large quality factors. The modular nature of the system further allows the atomic ensemble to aid in the cooling of the mechanical resonator, thereby combining atom-mediated state preparation with sensing deep in the quantum regime.

  10. Atom-based coherent quantum-noise cancellation in optomechanics

    E-Print Network [OSTI]

    Bariani, F; Singh, S; Vengalattore, M; Meystre, P

    2015-01-01

    We analyze a quantum force sensor that uses coherent quantum noise cancellation (CQNC) to beat the Standard Quantum Limit (SQL). This sensor, which allows for the continuous, broad-band detection of feeble forces, is a hybrid dual-cavity system comprised of a mesoscopic mechanical resonator optically coupled to an ensemble of ultracold atoms. In contrast to the stringent constraints on dissipation typically associated with purely optical schemes of CQNC, the dissipation rate of the mechanical resonator only needs to be matched to the decoherence rate of the atomic ensemble -- a condition that is experimentally achievable even for the technologically relevant regime of low frequency mechanical resonators with large quality factors. The modular nature of the system further allows the atomic ensemble to aid in the cooling of the mechanical resonator, thereby combining atom-mediated state preparation with sensing deep in the quantum regime.

  11. The Madelung Picture as a Foundation of Geometric Quantum Theory

    E-Print Network [OSTI]

    Maik Reddiger

    2015-10-01

    Despite its age quantum theory remains ill-understood, which is partially to blame on its deep interwovenness with the mysterious concept of quantization. In this article we argue that a quantum theory recoursing to quantization algorithms is necessarily incomplete. To provide a new axiomatic foundation, we give a rigorous proof showing how the Schr\\"odinger equation follows from the Madelung equations, which are formulated in the language of Newtonian mechanics. We show how the Schr\\"odinger picture relates to this Madelung picture and how the "classical limit" is directly obtained. This suggests a reformulation of the correspondence principle, stating that a quantum theory must reduce to a probabilistic version of Newtonian mechanics for large masses. We then enhance the stochastic interpretation developed by Tsekov, which speculates that quantum mechanical behavior is caused by random vibrations in spacetime. A new, yet incomplete model of particle creation and annihilation is also proposed.

  12. Random unitary maps for quantum state reconstruction

    SciTech Connect (OSTI)

    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)

    2010-03-15

    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.

  13. A quantum framework for likelihood ratios

    E-Print Network [OSTI]

    Rachael L. Bond; Yang-Hui He; Thomas C. Ormerod

    2015-08-04

    The ability to calculate precise likelihood ratios is fundamental to many STEM areas, such as decision-making theory, biomedical science, and engineering. However, there is no assumption-free statistical methodology to achieve this. For instance, in the absence of data relating to covariate overlap, the widely used Bayes' theorem either defaults to the marginal probability driven "naive Bayes' classifier", or requires the use of compensatory expectation-maximization techniques. Equally, the use of alternative statistical approaches, such as multivariate logistic regression, may be confounded by other axiomatic conditions, e.g., low levels of co-linearity. This article takes an information-theoretic approach in developing a new statistical formula for the calculation of likelihood ratios based on the principles of quantum entanglement. In doing so, it is argued that this quantum approach demonstrates: that the likelihood ratio is a real quality of statistical systems; that the naive Bayes' classifier is a special case of a more general quantum mechanical expression; and that only a quantum mechanical approach can overcome the axiomatic limitations of classical statistics.

  14. Interpretation of cosmological expansion effects on the quantum-classical transition

    E-Print Network [OSTI]

    C. L. Herzenberg

    2006-06-07

    Recently, what appears to be a fundamental limit associated with the size of an object that separates the quantum behavior characterizing small objects from the classical behavior characterizing large objects has been derived from the Hubble velocity spread in an extended object. This threshold is now examined further and interpreted in terms of diffusion processes in stochastic quantum mechanics. This limiting size that separates quantum behavior from classical behavior is shown to correspond approximately to the diffusion distance of the object over the Hubble time.

  15. Reducing collective quantum state rotation errors with reversible dephasing

    SciTech Connect (OSTI)

    Cox, Kevin C.; Norcia, Matthew A.; Weiner, Joshua M.; Bohnet, Justin G.; Thompson, James K.

    2014-12-29

    We demonstrate that reversible dephasing via inhomogeneous broadening can greatly reduce collective quantum state rotation errors, and observe the suppression of rotation errors by more than 21?dB in the context of collective population measurements of the spin states of an ensemble of 2.1×10{sup 5} laser cooled and trapped {sup 87}Rb atoms. The large reduction in rotation noise enables direct resolution of spin state populations 13(1) dB below the fundamental quantum projection noise limit. Further, the spin state measurement projects the system into an entangled state with 9.5(5) dB of directly observed spectroscopic enhancement (squeezing) relative to the standard quantum limit, whereas no enhancement would have been obtained without the suppression of rotation errors.

  16. Quantum Chaos at Finite Temperature

    E-Print Network [OSTI]

    L. A. Caron; H. Jirari; H. Kröger; X. Q. Luo; G. Melkonyan; K. J. M. Moriarty

    2001-06-23

    We use the quantum action to study quantum chaos at finite temperature. We present a numerical study of a classically chaotic 2-D Hamiltonian system - harmonic oscillators with anharmonic coupling. We construct the quantum action non-perturbatively and find temperature dependent quantum corrections in the action parameters. We compare Poincar\\'{e} sections of the quantum action at finite temperature with those of the classical action.

  17. On Quantum Integrable Systems

    SciTech Connect (OSTI)

    Danilov, Viatcheslav; /Oak Ridge; Nagaitsev, Sergei; /Fermilab

    2011-11-01

    Many quantum integrable systems are obtained using an accelerator physics technique known as Ermakov (or normalized variables) transformation. This technique was used to create classical nonlinear integrable lattices for accelerators and nonlinear integrable plasma traps. Now, all classical results are carried over to a nonrelativistic quantum case. In this paper we have described an extension of the Ermakov-like transformation to the Schroedinger and Pauli equations. It is shown that these newly found transformations create a vast variety of time dependent quantum equations that can be solved in analytic functions, or, at least, can be reduced to time-independent ones.

  18. Intrinsic Time Quantum Geometrodynamics

    E-Print Network [OSTI]

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

    2015-02-06

    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 commutation relations without Planck's constant emerges from the unification of Gravitation and Quantum Mechanics.

  19. Quantum Mechanics Without Observers

    E-Print Network [OSTI]

    W. H. Sulis

    2013-03-03

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

  20. Quantum measurement and decoherence

    E-Print Network [OSTI]

    G. W. Ford; J. T. Lewis; R. F. O'Connell

    2003-01-13

    Distribution functions defined in accord with the quantum theory of measurement are combined with results obtained from the quantum Langevin equation to discuss decoherence in quantum Brownian motion. Closed form expressions for wave packet spreading and the attenuation of coherence of a pair of wave packets are obtained. The results are exact within the context of linear passive dissipation. It is shown that, contrary to widely accepted current belief, decoherence can occur at high temperature in the absence of dissipation. Expressions for the decoherence time with and without dissipation are obtained that differ from those appearing in earlier discussions.

  1. Quantum Theory of Economics

    E-Print Network [OSTI]

    Vladimir I. Zverev; Alexander M. Tishin

    2009-01-29

    In the given work the first attempt to generalize quantum uncertainty relation on macro objects is made. Business company as one of economical process participants was chosen by the authors for this purpose. The analogies between quantum micro objects and the structures which from the first sight do not have anything in common with physics are given. The proof of generalized uncertainty relation is produced. With the help of generalized uncertainty relation the authors wanted to elaborate a new non-traditional approach to the description of companies' business activity and their developing and try to formulate some advice for them. Thus, our work makes the base of quantum theory of econimics

  2. Testing quantum physics in space using high-mass matter-wave interferometry

    E-Print Network [OSTI]

    Rainer Kaltenbaek

    2015-08-31

    Quantum superposition is central to quantum theory but challenges our concepts of reality and spacetime when applied to macroscopic objects like Schr\\"odinger's cat. For that reason, it has been a long-standing question whether quantum physics remains valid unmodified even for truly macroscopic objects. By now, the predictions of quantum theory have been confirmed via matter-wave interferometry for massive objects up to $10^4\\,$ atomic mass units (amu). The rapid development of new technologies promises to soon allow tests of quantum theory for significantly higher test masses by using novel techniques of quantum optomechanics and high-mass matter-wave interferometry. Such experiments may yield novel insights into the foundations of quantum theory, pose stringent limits on alternative theoretical models or even uncover deviations from quantum physics. However, performing experiments of this type on Earth may soon face principal limitations due to requirements of long times of flight, ultra-low vibrations, and extremely high vacuum. Here, we present a short overview of recent developments towards the implementation of the proposed space-mission MAQRO, which promises to overcome those limitations and to perform matter-wave interferometry in a parameter regime orders of magnitude beyond state-of-the-art.

  3. Hybrid Rotaxanes: Interlocked Structures for Quantum Computing...

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

    based on molecular magnets that may make them suitable as qubits for quantum computers. Chemistry Aids Quantum Computing Quantum bits or qubits are the fundamental...

  4. Giant Plasticity of a Quantum Crystal Ariel Haziot,1

    E-Print Network [OSTI]

    Balibar, Sébastien

    Giant Plasticity of a Quantum Crystal Ariel Haziot,1 Xavier Rojas,1 Andrew D. Fefferman,1 John R crystals may irreversibly deform. This phenomenon is known as plasticity and it is due to the motion and in the zero temperature limit, helium 4 crystals present a giant plasticity that is anisotropic and reversible

  5. Certifying quantumness: Benchmarks for the optimal processing of generalized coherent and squeezed states

    E-Print Network [OSTI]

    Yuxiang Yang; Giulio Chiribella; Gerardo Adesso

    2014-10-17

    Quantum technology promises revolutionary advantages in information processing and transmission compared to classical technology; however, determining which specific resources are needed to surpass the capabilities of classical machines often remains a nontrivial problem. To address such a problem, one first needs to establish the best classical solutions, which set benchmarks that must be beaten by any implementation claiming to harness quantum features for an enhanced performance. Here we introduce and develop a self-contained formalism to obtain the ultimate, generally probabilistic benchmarks for quantum information protocols including teleportation and approximate cloning, with arbitrary ensembles of input states generated by a group action, so-called Gilmore-Perelomov coherent states. This allows us to construct explicit fidelity thresholds for the transmission of multimode Gaussian and non-Gaussian states of continuous variable systems, as well as qubit and qudit pure states drawn according to nonuniform distributions on the Bloch hypersphere, which accurately model the current laboratory facilities. The performance of deterministic classical procedures such as square-root measurement strategies is further compared with the optimal probabilistic benchmarks, and the state-of-the-art performance of experimental quantum implementations against our newly derived thresholds is discussed. This work provides a comprehensive collection of directly useful criteria for the reliable certification of quantum communication technologies.

  6. TORSION AND QUANTUM GRAVITY

    E-Print Network [OSTI]

    Hanson, Andrew J.

    2011-01-01

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

  7. Nonlinear Quantum Gravity

    E-Print Network [OSTI]

    George Svetlichny

    2006-02-01

    Nonlinear quantum mechanics at the Planck scale can produce nonlocal effects contributing to resolution of singularities, to cosmic acceleration, and modified black-hole dynamics, while avoiding the usual causality issues.

  8. Geometrically frustrated quantum magnets

    E-Print Network [OSTI]

    Nikolić , Predrag, 1974-

    2004-01-01

    (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 ...

  9. Time in Quantum Mechanics

    E-Print Network [OSTI]

    Curt A. Moyer

    2013-05-23

    The failure of conventional quantum theory to recognize time as an observable and to admit time operators is addressed. Instead of focusing on the existence of a time operator for a given Hamiltonian, we emphasize the role of the Hamiltonian as the generator of translations in time to construct time states. Taken together, these states constitute what we call a timeline, or quantum history, that is adequate for the representation of any physical state of the system. Such timelines appear to exist even for the semi-bounded and discrete Hamiltonian systems ruled out by Pauli's theorem. However, the step from a timeline to a valid time operator requires additional assumptions that are not always met. Still, this approach illuminates the crucial issue surrounding the construction of time operators, and establishes quantum histories as legitimate alternatives to the familiar coordinate and momentum bases of standard quantum theory.

  10. Terahertz quantum cascade lasers

    E-Print Network [OSTI]

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

    2003-01-01

    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) ...

  11. quantum scattering calculations

    E-Print Network [OSTI]

    Ihee, Hyotcherl

    in a given quantum state per solid angle unit cross section : integral of the differential cross section) converged integral and differential cross sections geometriquantum scattering calculations on chemical reaction 1st Day #12;schedule day 1. 1.Introduction day

  12. On quantum Lyapunov exponents

    E-Print Network [OSTI]

    Wladyslaw A. Majewski; Marcin Marciniak

    2005-10-28

    It was shown that quantum analysis constitutes the proper analytic basis for quantization of Lyapunov exponents in the Heisenberg picture. Differences among various quantizations of Lyapunov exponents are clarified.

  13. Quantum physics motivated neurobiology 

    E-Print Network [OSTI]

    Mershin, Andreas

    2000-01-01

    This research addresses the question of what role might quantum phenomena play in the brain. Recent progress in understanding brain function in terms of its basic cellular and subcellular (microtubules) components will be ...

  14. Quantum-mimetic imaging

    E-Print Network [OSTI]

    Venkatraman, Dheera

    2015-01-01

    Many recent experiments have explored the use of nonclassical states of light to perform imaging or sensing. Although these experiments require quantum descriptions of light to explain their behavior, the advantages they ...

  15. Stiff Quantum Polymers

    E-Print Network [OSTI]

    H. Kleinert

    2007-05-01

    At ultralow temperatures, polymers exhibit quantum behavior, which is calculated here for the moments and of the end-to-end distribution in the large-stiffness regime. The result should be measurable for polymers in wide optical traps.

  16. Towards a quantum universe

    E-Print Network [OSTI]

    Jaume Giné

    2012-01-05

    In this short review we study the state of the art of the great problems in cosmology and their interrelationships. The reconciliation of these problems passes undoubtedly through the idea of a quantum universe.

  17. Quantum gravity effects in the Kerr spacetime

    SciTech Connect (OSTI)

    Reuter, M.; Tuiran, E.

    2011-02-15

    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.

  18. Performance bound for quantum absorption refrigerators

    E-Print Network [OSTI]

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

    2013-04-29

    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.

  19. The thermodynamics of quantum spacetime histories

    E-Print Network [OSTI]

    Smolin, Lee

    2015-01-01

    We show that the simplicity constraints, which define the dynamics of spin foam models, imply, and are implied by, the first law of thermodynamics, when the latter is applied to causal diamonds in the quantum spacetime. This result reveals an intimate connection between the holographic nature of gravity, as reflected by the Bekenstein entropy, and the fact that general relativity and other gravitational theories can be understood as constrained topological field theories. To state and derive this correspondence we describe causal diamonds in the causal structure of spin foam histories and generalize arguments given for the near horizon region of black holes by Frodden, Gosh and Perez and Bianchi. This allows us to apply a recent argument of Jacobson to show that if a spin foam history has a semiclassical limit described in terms of a smooth metric geometry, that geometry satisfies the Einstein equations. These results suggest also a proposal for a quantum equivalence principle.

  20. Multi-stage quantum absorption heat pumps

    E-Print Network [OSTI]

    Luis A. Correa

    2014-01-16

    It is well known that heat pumps, while being all limited by the same basic thermodynamic laws, may find realization on systems as "small" and "quantum" as a three-level maser. In order to quantitatively assess how the performance of these devices scales with their size, we design generalized $N$-dimensional ideal heat pumps by merging $N-2$ elementary three-level stages. We set them to operate in the absorption chiller mode between given hot and cold baths, and study their maximum achievable cooling power and the corresponding efficiency as a function of $N$. While the efficiency at maximum power is roughly size-independent, the power itself slightly increases with the dimension, quickly saturating to a constant. Thus, interestingly, scaling up autonomous quantum heat pumps does not render a significant enhancement beyond the optimal double-stage configuration.

  1. The Quantum Energy Density: Improved E

    SciTech Connect (OSTI)

    Krogel, Jaron; Yu, Min; Kim, Jeongnim; Ceperley, David M.

    2013-01-01

    We establish a physically meaningful representation of a quantum energy density for use in Quantum Monte Carlo calculations. The energy density operator, dened in terms of Hamiltonian components and density operators, returns the correct Hamiltonian when integrated over a volume containing a cluster of particles. This property is demonstrated for a helium-neon \\gas," showing that atomic energies obtained from the energy density correspond to eigenvalues of isolated systems. The formation energies of defects or interfaces are typically calculated as total energy dierences. Using a model of delta-doped silicon (where dopant atoms form a thin plane) we show how interfacial energies can be calculated more eciently with the energy density, since the region of interest is small. We also demonstrate how the energy density correctly transitions to the bulk limit away from the interface where the correct energy is obtainable from a separate total energy calculation.

  2. System identification for passive linear quantum systems

    E-Print Network [OSTI]

    Madalin Guta; Naoki Yamamoto

    2014-08-27

    System identification is a key enabling component for the implementation of quantum technologies, including quantum control. In this paper, we consider the class of passive linear input-output systems, and investigate several basic questions: (1) which parameters can be identified? (2) Given sufficient input-output data, how do we reconstruct system parameters? (3) How can we optimize the estimation precision by preparing appropriate input states and performing measurements on the output? We show that minimal systems can be identified up to a unitary transformation on the modes, and systems satisfying a Hamiltonian connectivity condition called "infecting" are completely identifiable. We propose a frequency domain design based on a Fisher information criterion, for optimizing the estimation precision for coherent input state. As a consequence of the unitarity of the transfer function, we show that the Heisenberg limit with respect to the input energy can be achieved using non-classical input states.

  3. Homogenization limit for a multiband effective mass model in heterostructures

    SciTech Connect (OSTI)

    Morandi, O.

    2014-06-15

    We study the homogenization limit of a multiband model that describes the quantum mechanical motion of an electron in a quasi-periodic crystal. In this approach, the distance among the atoms that constitute the material (lattice parameter) is considered a small quantity. Our model include the description of materials with variable chemical composition, intergrowth compounds, and heterostructures. We derive the effective multiband evolution system in the framework of the kp approach. We study the well posedness of the mathematical problem. We compare the effective mass model with the standard kp models for uniform and non-uniforms crystals. We show that in the limit of vanishing lattice parameter, the particle density obtained by the effective mass model, converges to the exact probability density of the particle.

  4. The Road From Classical to Quantum Codes: A Hashing Bound Approaching Design Procedure

    E-Print Network [OSTI]

    Zunaira Babar; Panagiotis Botsinis; Dimitrios Alanis; Soon Xin Ng; Lajos Hanzo

    2015-03-09

    Powerful Quantum Error Correction Codes (QECCs) are required for stabilizing and protecting fragile qubits against the undesirable effects of quantum decoherence. Similar to classical codes, hashing bound approaching QECCs may be designed by exploiting a concatenated code structure, which invokes iterative decoding. Therefore, in this paper we provide an extensive step-by-step tutorial for designing EXtrinsic Information Transfer (EXIT) chart aided concatenated quantum codes based on the underlying quantum-to-classical isomorphism. These design lessons are then exemplified in the context of our proposed Quantum Irregular Convolutional Code (QIRCC), which constitutes the outer component of a concatenated quantum code. The proposed QIRCC can be dynamically adapted to match any given inner code using EXIT charts, hence achieving a performance close to the hashing bound. It is demonstrated that our QIRCC-based optimized design is capable of operating within 0.4 dB of the noise limit.

  5. Turbocharging Quantum Tomography.

    SciTech Connect (OSTI)

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

    2015-01-01

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

  6. Classical and quantum chaos in atomic systems

    SciTech Connect (OSTI)

    Delande, D.; Buchleitner, A. [Universite Pierre et Marie Curie, Paris (France)

    1994-12-31

    Atomic systems played a major role in the birth and growth of quantum mechanics. One central idea was to relate the well-known classical motion of the electron of a hydrogen atom--an ellipsis around the nucleus--to the experimentally observed quantization of the energy levels. This is the aim of the Bohr and Bohr-Sommerfeld models. These simple semiclassical models were unable to make any reliable prediction on the energy spectrum of the next simplest atom, helium. Because of the great success of quantum mechanics, the problem of correspondence between the classical and the quantal dynamics has not received much attention in the last 60 years. The fundamental question is (Gutzwiller, 1990). How can classical mechanics be understood as a limiting case within quantum mechanics? For systems with time-independent one-dimensional dynamics like the harmonic oscillator and the hydrogen atom, the correspondence is well understood. The restriction to such simple cases creates the erroneous impression that the classical behavior of simple systems is entirely comprehensible and easily described. During the last 20 years it has been recognized that this in not true and that a complex behavior can be obtained from simple equations of motion. This usually happens when the motion is chaotic, that is, unpredictable on a long time scale although perfectly deterministic (Henon, 1983). A major problem is that of understanding how the regular or chaotic behavior of the classical system is manifest in its quantum properties, especially in the semiclassical limit. 53 refs., 15 figs., 1 tab.

  7. Manipulation of electron orbitals in hard-wall InAs/InP nanowire quantum dots

    E-Print Network [OSTI]

    Roddaro, Stefano; Ercolani, Daniele; Sorba, Lucia; Beltram, Fabio

    2010-01-01

    We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong electric dipole moment on the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed.

  8. Manipulation of electron orbitals in hard-wall InAs/InP nanowire quantum dots

    E-Print Network [OSTI]

    Stefano Roddaro; Andrea Pescaglini; Daniele Ercolani; Lucia Sorba; Fabio Beltram

    2010-12-22

    We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong electric dipole moment on the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed.

  9. Sparse Quantum Codes from Quantum Circuits

    E-Print Network [OSTI]

    Dave Bacon; Steven T. Flammia; Aram W. Harrow; Jonathan Shi

    2015-07-10

    We describe a general method for turning quantum circuits into sparse quantum subsystem codes. Using this prescription, we can map an arbitrary stabilizer code into a new subsystem code with the same distance and number of encoded qubits but where all the generators have constant weight, at the cost of adding some ancilla qubits. With an additional overhead of ancilla qubits, the new code can also be made spatially local. Applying our construction to certain concatenated stabilizer codes yields families of subsystem codes with constant-weight generators and with minimum distance $d = n^{1-\\varepsilon}$, where $\\varepsilon = O(1/\\sqrt{\\log n})$. For spatially local codes in $D$ dimensions we nearly saturate a bound due to Bravyi and Terhal and achieve $d = n^{1-\\varepsilon-1/D}$. Previously the best code distance achievable with constant-weight generators in any dimension, due to Freedman, Meyer and Luo, was $O(\\sqrt{n\\log n})$ for a stabilizer code.

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

    E-Print Network [OSTI]

    Agostino Prástaro

    2015-03-23

    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.

  11. Statistical anisotropy and cosmological quantum relaxation

    E-Print Network [OSTI]

    Antony Valentini

    2015-10-08

    We show that cosmological quantum relaxation predicts an anisotropic primordial power spectrum with a specific dependence on wavenumber k. We explore some of the consequences for precision measurements of the cosmic microwave background (CMB). Quantum relaxation is a feature of the de Broglie-Bohm pilot-wave formulation of quantum theory, which allows the existence of more general physical states that violate the Born probability rule. Recent work has shown that relaxation to the Born rule is suppressed for long-wavelength field modes on expanding space, resulting in a large-scale power deficit with a characteristic inverse-tangent dependence on k. Because the quantum relaxation dynamics is independent of the direction of the wave vector for the relaxing field mode, in the limit of weak anisotropy we are able to derive an expression for the anisotropic power spectrum that is determined by the power deficit function. As a result, the off-diagonal terms in the CMB covariance matrix are also determined by the power deficit. We show that the lowest-order l-(l+1) inter-multipole correlations have a characteristic scaling with multipole moment l. Our derived spectrum also predicts a residual statistical anisotropy at small scales, with an approximate consistency relation between the scaling of the l-(l+1) correlations and the scaling of the angular power spectrum at high l. We also predict a relationship between the l-(l+1) correlations at large and small scales. Cosmological quantum relaxation appears to provide a single physical mechanism that predicts both a large-scale power deficit and a range of statistical anisotropies, together with potentially testable relationships between them.

  12. Significant Quantum Effects in Hydrogen Activation

    SciTech Connect (OSTI)

    Kyriakou, Georgios; Davidson, Erlend R.; Peng, Guowen; Roling, Luke T.; Singh, Suyash; Boucher, Matthew B.; Marcinkowski, Matthew D.; Mavrikakis, Manos; Michaelides, Angelos; Sykes, E. Charles H.

    2014-05-27

    Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to 190 K and for D2 up to 140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.

  13. Quantum Mechanics and Representation Theory Columbia University

    E-Print Network [OSTI]

    Woit, Peter

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

  14. Quantum computation beyond the circuit model

    E-Print Network [OSTI]

    Jordan, Stephen Paul

    2008-01-01

    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, ...

  15. Quantum algorithms for algebraic problems

    E-Print Network [OSTI]

    Andrew M. Childs; Wim van Dam

    2008-12-02

    Quantum computers can execute algorithms that dramatically outperform classical computation. As the best-known example, Shor discovered an efficient quantum algorithm for factoring integers, whereas factoring appears to be difficult for classical computers. Understanding what other computational problems can be solved significantly faster using quantum algorithms is one of the major challenges in the theory of quantum computation, and such algorithms motivate the formidable task of building a large-scale quantum computer. This article reviews the current state of quantum algorithms, focusing on algorithms with superpolynomial speedup over classical computation, and in particular, on problems with an algebraic flavor.

  16. A functional quantum programming language

    E-Print Network [OSTI]

    Thorsten Altenkirch; Jonathan Grattage

    2005-04-19

    We introduce the language QML, a functional language for quantum computations on finite types. Its design is guided by its categorical semantics: QML programs are interpreted by morphisms in the category FQC of finite quantum computations, which provides a constructive semantics of irreversible quantum computations realisable as quantum gates. QML integrates reversible and irreversible quantum computations in one language, using first order strict linear logic to make weakenings explicit. Strict programs are free from decoherence and hence preserve superpositions and entanglement - which is essential for quantum parallelism.

  17. An algorithm for minimization of quantum cost

    E-Print Network [OSTI]

    Anindita Banerjee; Anirban Pathak

    2010-04-09

    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.

  18. On a New Form of Quantum Mechanics

    E-Print Network [OSTI]

    N. N. Gorobey; A. S. Lukyanenko

    2008-07-22

    We propose a new form of nonrelativistic quantum mechanics which is based on a quantum version of the action principle.

  19. Comparison of the attempts of quantum discord and quantum entanglement...

    Office of Scientific and Technical Information (OSTI)

    Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 1A7 (Canada) Publication Date: 2011-03-15 OSTI Identifier: 21537374 Resource...

  20. Quantum Equivalence and Quantum Signatures in Heat Engines

    E-Print Network [OSTI]

    Raam Uzdin; Amikam Levy; Ronnie Kosloff

    2015-04-15

    Quantum heat engines (QHE) are thermal machines where the working substance is quantum. In the extreme case the working medium can be a single particle or a few level quantum system. The study of QHE has shown a remarkable similarity with the standard thermodynamical models, thus raising the issue what is quantum in quantum thermodynamics. Our main result is thermodynamical equivalence of all engine type in the quantum regime of small action. They have the same power, the same heat, the same efficiency, and they even have the same relaxation rates and relaxation modes. Furthermore, it is shown that QHE have quantum-thermodynamic signature, i.e thermodynamic measurements can confirm the presence of quantum coherence in the device. The coherent work extraction mechanism enables power outputs that greatly exceed the power of stochastic (dephased) engines.

  1. Continuous Variable Quantum Key Distribution with a Noisy Laser

    E-Print Network [OSTI]

    Christian S. Jacobsen; Tobias Gehring; Ulrik L. Andersen

    2015-07-06

    Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement a theoretically proposed prepare-and-measure continuous-variable protocol and experimentally demonstrate the robustness of it against preparation noise stemming for instance from technical laser noise. Provided that direct reconciliation techniques are used in the post-processing we show that for small distances large amounts of preparation noise can be tolerated in contrast to reverse reconciliation where the key rate quickly drops to zero. Our experiment thereby demonstrates that quantum key distribution with non-shot-noise limited laser diodes might be feasible.

  2. Asymptotic properties of the Dirac quantum cellular automaton

    E-Print Network [OSTI]

    A. Pérez

    2015-04-28

    We show that the Dirac quantum cellular automaton [Ann. Phys. 354 (2015) 244] shares many properties in common with the discrete-time quantum walk. These similarities can be exploited to redefine the automaton as a unitary process that takes place at regular time steps on a one-dimensional lattice with an arbitrary lattice spacing. In this way, it becomes an alternative to the quantum walk, with a dispersion relation that can be controlled by a mass parameter, playing a similar role to the coin angle in the quantum walk. Moreover, the Dirac Hamiltonian is recovered under a suitable limit. We also provide two independent analytical approximations to the long term probability distribution. It is shown that, starting from localized conditions, the asymptotic value of the entropy of entanglement between internal and motional degrees of freedom overcomes the known limit that is approached by the quantum walk for the same initial conditions, and are similar to the ones achieved by highly localized states of the Dirac equation.

  3. Factory capacity limits Machine dependencies

    E-Print Network [OSTI]

    Foley, Simon

    Factory capacity limits Machine dependencies Employee scheduling Raw material availability Other internal operations (and also possibly the actions of other suppliers that supply raw materials) and at an international workshop at the multi-agent conference (AAMAS'06). Manufacturer Customer demand Penalties for non

  4. Suppression of quantum chaos in a quantum computer hardware

    SciTech Connect (OSTI)

    Lages, J.; Shepelyansky, D. L. [Laboratoire de Physique Theorique, UMR 5152 du CNRS, Universite Paul Sabatier, 31062 Toulouse Cedex 4 (France)

    2006-08-15

    We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.

  5. Suppression of quantum chaos in a quantum computer hardware

    E-Print Network [OSTI]

    J. Lages; D. L. Shepelyansky

    2005-10-14

    We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.

  6. Stationary States of Dissipative Quantum Systems

    E-Print Network [OSTI]

    Vasily E. Tarasov

    2011-07-29

    In this Letter we consider stationary states of dissipative quantum systems. We discuss stationary states of dissipative quantum systems, which coincide with stationary states of Hamiltonian quantum systems. Dissipative quantum systems with pure stationary states of linear harmonic oscillator are suggested. We discuss bifurcations of stationary states for dissipative quantum systems which are quantum analogs of classical dynamical bifurcations.

  7. An artificial Rb atom in a semiconductor with lifetime-limited linewidth

    E-Print Network [OSTI]

    Jan-Philipp Jahn; Mathieu Munsch; Lucas Béguin; Andreas V. Kuhlmann; Martina Renggli; Yongheng Huo; Fei Ding; Rinaldo Trotta; Marcus Reindl; Oliver G. Schmidt; Armando Rastelli; Philipp Treutlein; Richard J. Warburton

    2015-08-26

    We report results important for the creation of a best-of-both-worlds quantum hybrid system consisting of a solid-state source of single photons and an atomic ensemble as quantum memory. We generate single photons from a GaAs quantum dot (QD) frequency-matched to the Rb D2-transitions and then use the Rb transitions to analyze spectrally the quantum dot photons. We demonstrate lifetime-limited QD linewidths (1.48 GHz) with both resonant and non-resonant excitation. The QD resonance fluorescence in the low power regime is dominated by Rayleigh scattering, a route to match quantum dot and Rb atom linewidths and to shape the temporal wave packet of the QD photons. Noise in the solid-state environment is relatively benign: there is a blinking of the resonance fluorescence at MHz rates but negligible upper state dephasing of the QD transition. We therefore establish a close-to-ideal solid-state source of single photons at a key wavelength for quantum technologies.

  8. Displacement Echoes: Classical Decay and Quantum Freeze

    E-Print Network [OSTI]

    Cyril Petitjean; Diego V. Bevilaqua; Eric J. Heller; Philippe Jacquod

    2007-04-23

    Motivated by neutron scattering experiments, we investigate the decay of the fidelity with which a wave packet is reconstructed by a perfect time-reversal operation performed after a phase space displacement. In the semiclassical limit, we show that the decay rate is generically given by the Lyapunov exponent of the classical dynamics. For small displacements, we additionally show that, following a short-time Lyapunov decay, the decay freezes well above the ergodic value because of quantum effects. Our analytical results are corroborated by numerical simulations.

  9. Integer Quantum Hall Effect in Graphene

    E-Print Network [OSTI]

    Jellal, Ahmed

    2015-01-01

    We study the quantum Hall effect in a monolayer graphene by using an approach based on thermodynamical properties. This can be done by considering a system of Dirac particles in an electromagnetic field and taking into account of the edges effect as a pseudo-potential varying continuously along the $x$ direction. At low temperature and in the weak electric field limit, we explicitly determine the thermodynamical potential. With this, we derive the particle numbers in terms of the quantized flux and therefore the Hall conductivity immediately follows.

  10. Integer Quantum Hall Effect in Graphene

    E-Print Network [OSTI]

    Ahmed Jellal

    2015-04-24

    We study the quantum Hall effect in a monolayer graphene by using an approach based on thermodynamical properties. This can be done by considering a system of Dirac particles in an electromagnetic field and taking into account of the edges effect as a pseudo-potential varying continuously along the $x$ direction. At low temperature and in the weak electric field limit, we explicitly determine the thermodynamical potential. With this, we derive the particle numbers in terms of the quantized flux and therefore the Hall conductivity immediately follows.

  11. Displacement Echoes: Classical Decay and Quantum Freeze

    SciTech Connect (OSTI)

    Petitjean, Cyril [Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneva 4 (Switzerland); Bevilaqua, Diego V. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Heller, Eric J. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Jacquod, Philippe [Physics Department, University of Arizona, Tucson, Arizona 85721 (United States)

    2007-04-20

    Motivated by neutron scattering experiments, we investigate the decay of the fidelity with which a wave packet is reconstructed by a perfect time-reversal operation performed after a phase-space displacement. In the semiclassical limit, we show that the decay rate is generically given by the Lyapunov exponent of the classical dynamics. For small displacements, we additionally show that, following a short-time Lyapunov decay, the decay freezes well above the ergodic value because of quantum effects. Our analytical results are corroborated by numerical simulations.

  12. Bell Inequalities for Quantum Optical Fields

    E-Print Network [OSTI]

    Marek Zukowski; Marcin Wiesniak; Wieslaw Laskowski

    2015-06-29

    We show that the "practical" Bell inequalities, which use intensities as the observed variables, commonly used in quantum optics and widely accepted in the community, suffer from an inherent loophole, which severely limits the range of local hidden variable theories of light, which are invalidated by their violation. We present alternative inequalities which do not suffer from any (theoretical) loophole. The new inequalities use redefined correlation functions, which involve averaged products of local rates rather than intensities. Surprisingly, the new inequalities detect entanglement in situations in which the "practical" ones fail. Thus, we have two for the price on one: full consistency with Bell's Theorem, and better device-independent detection of entanglement.

  13. Static Quantum Games Revisited

    E-Print Network [OSTI]

    Marcin Markiewicz; Adrian Kosowski; Tomasz Tylec; Jaroslaw Pykacz; Cyril Gavoille

    2010-03-23

    The so called \\emph{quantum game theory} has recently been proclaimed as one of the new branches in the development of both quantum information theory and game theory. However, the notion of a quantum game itself has never been strictly defined, which has led to a lot of conceptual confusion among different authors. In this paper we introduce a new conceptual framework of a \\emph{scenario} and an \\emph{implementation} of a game. It is shown that the procedures of "quantization" of games proposed in the literature lead in fact to several different games which can be defined within the same scenario, but apart from this they may have nothing in common with the original game. Within the framework we put forward, a lot of conceptual misunderstandings that have arisen around "quantum games" can be stated clearly and resolved uniquely. In particular, the proclaimed essential role of entanglement in several static "quantum games", and their connection with Bell inequalities, is disproved.

  14. Physicalism versus quantum mechanics

    E-Print Network [OSTI]

    Henry P. Stapp

    2008-03-11

    In the context of theories of the connection between mind and brain, physicalism is the demand that all is basically purely physical. But the concept of "physical" embodied in this demand is characterized essentially by the properties of the physical that hold in classical physical theories. Certain of these properties contradict the character of the physical in quantum mechanics, which provides a better, more comprehensive, and more fundamental account of phenomena. It is argued that the difficulties that have plaged physicalists for half a century, and that continue to do so, dissolve when the classical idea of the physical is replaced by its quantum successor. The argument is concretized in a way that makes it accessible to non-physicists by exploiting the recent evidence connecting our conscious experiences to macroscopic measurable synchronous oscillations occurring in well-separated parts of the brain. A specific new model of the mind-brain connection that is fundamentally quantum mechanical but that ties conscious experiences to these macroscopic synchronous oscillations is used to illustrate the essential disparities between the classical and quantum notions of the physical, and in particular to demonstrate the failure in the quantum world of the principle of the causal closure of the physical, a failure that goes beyond what is entailed by the randomness in the outcomes of observations, and that accommodates the efficacy in the brain of conscious intent.

  15. Recoverability in quantum information theory

    E-Print Network [OSTI]

    Wilde, Mark M

    2015-01-01

    The fact that the quantum relative entropy is non-increasing with respect to quantum physical evolutions lies at the core of many optimality theorems in quantum information theory and has applications in other areas of physics. In this work, we establish improvements of this entropy inequality in the form of physically meaningful remainder terms. One of the main results can be summarized informally as follows: if the decrease in quantum relative entropy between two quantum states after a quantum physical evolution is relatively small, then it is possible to perform a recovery operation, such that one can perfectly recover one state while approximately recovering the other. This can be interpreted as quantifying how well one can reverse a quantum physical evolution. Our proof method is elementary, relying on the method of complex interpolation, basic linear algebra, and the recently introduced Renyi generalization of a relative entropy difference. The theorem has a number of applications in quantum information...

  16. Mathematical Aspects of Quantum Theory

    E-Print Network [OSTI]

    , Algeria Revised version: January 1, 2015 (This text is for personal use only) 1 #12;Acknowledgements Statistical Mechanics 3.1. The classical case 3.2. The quantum case 3.3. A second axiom system for quantum

  17. Quantum state fusion in photons

    E-Print Network [OSTI]

    Chiara Vitelli; Nicolò Spagnolo; Lorenzo Aparo; Fabio Sciarrino; Enrico Santamato; Lorenzo Marrucci

    2012-09-17

    Photons are the ideal carriers of quantum information for communication. Each photon can have a single qubit or even multiple qubits encoded in its internal quantum state, as defined by optical degrees of freedom such as polarization, wavelength, transverse modes, etc. Here, we propose and experimentally demonstrate a physical process, named "quantum state fusion", in which the two-dimensional quantum states (qubits) of two input photons are combined into a single output photon, within a four-dimensional quantum space. The inverse process is also proposed, in which the four-dimensional quantum state of a single photon is split into two photons, each carrying a qubit. Both processes can be iterated, and hence may be used to bridge multi-particle protocols of quantum information with the multi-degree-of-freedom ones, with possible applications in quantum communication networks.

  18. Quantum particles from classical statistics

    E-Print Network [OSTI]

    C. Wetterich

    2010-02-11

    Quantum particles and classical particles are described in a common setting of classical statistical physics. The property of a particle being "classical" or "quantum" ceases to be a basic conceptual difference. The dynamics differs, however, between quantum and classical particles. We describe position, motion and correlations of a quantum particle in terms of observables in a classical statistical ensemble. On the other side, we also construct explicitly the quantum formalism with wave function and Hamiltonian for classical particles. For a suitable time evolution of the classical probabilities and a suitable choice of observables all features of a quantum particle in a potential can be derived from classical statistics, including interference and tunneling. Besides conceptual advances, the treatment of classical and quantum particles in a common formalism could lead to interesting cross-fertilization between classical statistics and quantum physics.

  19. On Randomness in Quantum Mechanics

    E-Print Network [OSTI]

    Alberto C. de la Torre

    2007-07-19

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

  20. A quantum dot heterojunction photodetector

    E-Print Network [OSTI]

    Arango, Alexi Cosmos, 1975-

    2005-01-01

    This thesis presents a new device architecture for photodetectors utilizing colloidally grown quantum dots as the principle photo-active component. We implement a thin film of cadmium selenide (CdSe) quantum dot sensitizers, ...