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Sample records for model principle decoherence

  1. Quantum Internal Model Principle: Decoherence Control

    CERN Document Server

    Ganesan, Narayan; 10.1109/CDC.2007.4434706

    2010-01-01

    In this article, we study the problem of Decoherence Control for quantum systems by employing a novel construction termed "the bait" and with techniques from geometric control theory, in order to successfully and completely decouple an open quantum system from its environment. We re-formulate the problem of Decoherence Control as a disturbance rejection scheme which also leads us to the idea of Internal Model Principle for quantum control systems which is first of its kind in the literature. Classical internal model principle provides the guidelines for designing linear controllers for perfect tracking in the presence of external disturbances, with the help of the internal model of the disturbance generator. The theory of Disturbance Decoupling of the output from external noises is another problem that is well studied for classical systems. The two problems focus on different aspects viz. perfect output tracking and complete decoupling of output in the presence of the noise respectively. However for quantum s...

  2. Universal Decoherence under Gravity: A Perspective through the Equivalence Principle

    Science.gov (United States)

    Pang, Belinda H.; Chen, Yanbei; Khalili, Farid Ya.

    2016-08-01

    Pikovski et al. [Nat. Phys. 11, 668 (2015)] show that a composite particle prepared in a pure initial quantum state and propagated in a uniform gravitational field undergoes a decoherence process at a rate determined by the gravitational acceleration. By assuming Einstein's equivalence principle to be valid, we analyze a physical realization of the (1 +1 )D thought experiment of Pikovski et al. to demonstrate that the dephasing between the different internal states arises not from gravity but rather from differences in their rest mass, and the mass dependence of the de Broglie wave's dispersion relation. We provide an alternative view to the situation considered by Pikovski et al., where we propose that gravity plays a kinematic role by providing a relative velocity to the detector frame with respect to the particle; visibility can be easily recovered by giving the screen an appropriate uniform velocity. We then apply this insight to their thought experiment in (1 +1 )D to draw a direct correspondence, and obtain the same mathematical result for dephasing. We finally propose that dephasing due to gravity may in fact take place for certain modifications to the gravitational potential where the equivalence principle is violated.

  3. Models of decoherence with negative dephasing rate

    CERN Document Server

    Pernice, Ansgar; Strunz, Walter T

    2012-01-01

    We determine the total state dynamics of a dephasing open quantum system using the standard environment of harmonic oscillators. Of particular interest are random unitary approaches to the same reduced dynamics and system-environment correlations in the full model. Concentrating on a model with an at times negative dephasing rate, the issue of "non-Markovianity" will also be addressed with the emphasis on information obtained from the dynamics of the total state of system and environment: making use of criteria that allow us to distinguish between classically correlated and entangled total states, we employ a simple measure for the correlations emerging from the increase of the two local entropies, and relate it the nature of the correlations.

  4. Entanglement, decoherence and thermal relaxation in exactly solvable models

    CERN Document Server

    Lychkovskiy, Oleg

    2011-01-01

    Exactly solvable models provide an opportunity to study different aspects of reduced quantum dynamics in detail. We consider the reduced dynamics of a single spin in finite XX and XY spin 1/2 chains. First we introduce a general expression describing the evolution of the reduced density matrix. This expression proves to be tractable when the combined closed system (i.e. open system plus environment) is integrable. Then we focus on comparing decoherence and thermalization timescales in the XX chain. We find that for a single spin these timescales are comparable, in contrast to what should be expected for a macroscopic body. This indicates that the process of quantum relaxation of a system with few accessible states can not be separated in two distinct stages - decoherence and thermalization. Finally, we turn to finite-size effects in the time evolution of a single spin in the XY chain. We observe three consecutive stages of the evolution: regular evolution, partial revivals, irregular (apparently chaotic) evol...

  5. Numerical Simulation of the Two-State Decoherence Model of Nano-Spin Systems

    Institute of Scientific and Technical Information of China (English)

    蒋永进; 陶瑞宝

    2002-01-01

    We have studied the two-state random decoherence model of the V15 system (Phys. Rev. Lett. 84 (2000) 3458)time and the random dipolar interaction amplitude is verified. The distribution function of decoherence timespreads more widely as the amplitude of the random field is decreased, hence it is dirficult to define a decoherencetime for the system.

  6. Decoherence-induced conductivity in the one-dimensional Anderson model

    Energy Technology Data Exchange (ETDEWEB)

    Stegmann, Thomas; Wolf, Dietrich E. [Department of Physics, University of Duisburg-Essen and CENIDE, 47048 Duisburg (Germany); Ujsághy, Orsolya [Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1521 Budapest (Hungary)

    2014-08-20

    We study the effect of decoherence on the electron transport in the one-dimensional Anderson model by means of a statistical model [1, 2, 3, 4, 5]. In this model decoherence bonds are randomly distributed within the system, at which the electron phase is randomized completely. Afterwards, the transport quantity of interest (e.g. resistance or conductance) is ensemble averaged over the decoherence configurations. Averaging the resistance of the sample, the calculation can be performed analytically. In the thermodynamic limit, we find a decoherence-driven transition from the quantum-coherent localized regime to the Ohmic regime at a critical decoherence density, which is determined by the second-order generalized Lyapunov exponent (GLE) [4].

  7. Random unitary evolution model of quantum Darwinism with pure decoherence

    Science.gov (United States)

    Balanesković, Nenad

    2015-10-01

    We study the behavior of Quantum Darwinism [W.H. Zurek, Nat. Phys. 5, 181 (2009)] within the iterative, random unitary operations qubit-model of pure decoherence [J. Novotný, G. Alber, I. Jex, New J. Phys. 13, 053052 (2011)]. We conclude that Quantum Darwinism, which describes the quantum mechanical evolution of an open system S from the point of view of its environment E, is not a generic phenomenon, but depends on the specific form of input states and on the type of S- E-interactions. Furthermore, we show that within the random unitary model the concept of Quantum Darwinism enables one to explicitly construct and specify artificial input states of environment E that allow to store information about an open system S of interest with maximal efficiency.

  8. On universal decoherence under gravity: a perspective through the Equivalence Principle

    CERN Document Server

    Pang, B; Chen, Y

    2016-01-01

    In Nature Phys. 11, 668 (2015) (Ref. [1]), a composite particle prepared in a pure initial quantum state and propagated in a uniform gravitational field is shown to undergo a decoherence process at a rate determined by the gravitational acceleration. By assuming Einstein's Equivalence Principle to be valid, we demonstrate, first in a Lorentz frame with accelerating detectors, and then directly in the Lab frame with uniform gravity, that the dephasing between the different internal states arise not from gravity but rather from differences in their rest mass, and the mass dependence of the de Broglie wave's dispersion relation. We provide an alternative view to the situation considered by Ref. [1], where we propose that gravity plays a kinematic role in the loss of fringe visibility by giving the detector a transverse velocity relative to the particle beam; visibility can be easily recovered by giving the screen an appropriate uniform velocity. We finally propose that dephasing due to gravity may in fact take p...

  9. The Lee-Friedrichs Model: Continuous Limit and Decoherence

    Science.gov (United States)

    Laura, Roberto; Castagnino, Mario

    2007-09-01

    We analyze the thermodynamic limit of the Hamiltonian, states and observables, of a system containing an oscillator interacting with a thermal bath We use the results to a compare environment and self induced decoherence.

  10. Surface state decoherence in loop quantum gravity, a first toy model

    CERN Document Server

    Feller, Alexandre

    2016-01-01

    The quantum-to-classical transition through decoherence is a major facet of the semi-classical analysis of quantum models that are supposed to admit a classical regime, as quantum gravity should be. A particular problem of interest is the decoherence of black hole horizons and holographic screens induced by the bulk-boundary coupling with interior degrees of freedom. Here in this paper we present a first toy-model, in the context of loop quantum gravity, for the dynamics of a surface geometry as an open quantum system at fixed total area. We discuss the resulting decoherence and recoherence and compare the exact density matrix evolution to the commonly used master equation approximation {\\it \\`a la} Lindblad underlining its merits and limitations. The prospect of this study is to have a clearer understanding of the boundary decoherence of black hole horizons seen by outside observers.

  11. Quantum models of the mind: are they compatible with environment decoherence?

    Science.gov (United States)

    Rosa, Luiz Pinguelli; Faber, Jean

    2004-09-01

    Quantum models of the mind associate consciousness with coherent superposition of states in the brain. Some authors consider consciousness to be the result of a kind of internal quantum measurement process in the brain. In this paper we discuss the ideas of Hameroff-Penrose and Tegmark and their calculation for an estimate of decoherence time. We criticize the Hameroff-Penrose model in the context of a quantum brain model by gravitational collapse orchestrated objective reduction (OOR), assumed by Penrose, and we propose instead that the decoherence process is caused by interaction with the environment. We consider it useful to exploit this possibility because of the growing importance of the decoherence theory in quantum measurement, and also because quantum mechanics can be applied to brain study independently of the Hameroff-Penrose model for mind and consciousness. Our conclusion is that the Hameroff-Penrose model is not compatible with decoherence, but nevertheless the quantum brain can still be considered if we replace gravitational collapse OOR with decoherence. However, our result does not agree with Tegmark's conclusion of refuting not only the Hameroff-Penrose gravitational collapse but also the quantum brain, based on decoherence time calculations in specific cases in the brain. In spite of this fact we also disagree with some points of the response to Tegmark's article given by Hagan, Hameroff, and Tuszynski.

  12. Decoherence in quantum open systems revisited

    CERN Document Server

    Alicki, R

    2002-01-01

    The following statements belonging to the folklore of the theory of environmental decoherence are shown to be incorrect: 1) linear coupling to harmonic oscillator bath is a universal model of decoherence, 2) chaotic environments are more efficient decoherers.

  13. Gravitational decoherence

    Science.gov (United States)

    Bassi, Angelo; Großardt, André; Ulbricht, Hendrik

    2017-10-01

    We discuss effects of loss of coherence in low energy quantum systems caused by or related to gravitation, referred to as gravitational decoherence. These effects, resulting from random metric fluctuations, for instance, promise to be accessible by relatively inexpensive table-top experiments, way before the scales where true quantum gravity effects become important. Therefore, they can provide a first experimental view on gravity in the quantum regime. We will survey models of decoherence induced both by classical and quantum gravitational fluctuations; it will be manifest that a clear understanding of gravitational decoherence is still lacking. Next we will review models where quantum theory is modified, under the assumption that gravity causes the collapse of the wave functions, when systems are large enough. These models challenge the quantum-gravity interplay, and can be tested experimentally. In the last part we have a look at the state of the art of experimental research. We will review efforts aiming at more and more accurate measurements of gravity (G and g) and ideas for measuring conventional and unconventional gravity effects on nonrelativistic quantum systems.

  14. Exact solution of qubit decoherence models by a transfer matrix method

    CERN Document Server

    Nghiem, D; Joynt, Robert; Nghiem, Diu

    2005-01-01

    We present a new method for the solution of the behavior of an enesemble of qubits in a random time-dependent external field. The forward evolution in time is governed by a transfer matrix. The elements of this matrix determine the various decoherence times. The method provides an exact solution in cases where the noise is piecewise constant in time. We show that it applies, for example, to a realistic model of decoherence of electron spins in semiconductors. Results are obtained for the non-perturbative regimes of the models, and we see a transition from weak relaxation to overdamped behavior as a function of noise anisotropy.

  15. Random matrix models for decoherence and fidelity decay in quantum information systems

    Science.gov (United States)

    Pineda, Carlos; Seligman, Thomas H.

    2008-03-01

    This course aims to introduce the student to random matrix models for decoherence and fidelity decay. They present a very powerful alternate approach, that emphasizes the disordered character of many environments and uncontrollable perturbations/couplings. The inherent integrability of such models makes analytic studies possible. We limit our considerations to linear response treatment, as high fidelity and small decoherence are the backbone of quantum information processes. For fidelity decay, where experimental results are available, a comparison with experiments shows excellent agreement with random matrix theory predictions.

  16. Second Quantization of Cini Model for High Order Quantum Decoherence in Quantum Measurement

    CERN Document Server

    Zhou, D L; Sun, C P

    2001-01-01

    By making the second quantization for the Cini Model of quantum measurement without wave function collapse [M. Cini, Nuovo Cimento, B73 27(1983)], the second order quantum decoherence (SOQD) is studied with a two mode boson system interacting with an idealized apparatus composed by two quantum oscillators. In the classical limit that the apparatus is prepared in a Fock state with a very large quantum number, or in a coherent state with average quantum numbers large enough, the SOQD phenomenon appears similar to the first order case of quantum decoherence.

  17. Dense Coding in a Two-Spin Squeezing Model with Intrinsic Decoherence

    Science.gov (United States)

    Zhang, Bing-Bing; Yang, Guo-Hui

    2016-11-01

    Quantum dense coding in a two-spin squeezing model under intrinsic decoherence with different initial states (Werner state and Bell state) is investigated. It shows that dense coding capacity χ oscillates with time and finally reaches different stable values. χ can be enhanced by decreasing the magnetic field Ω and the intrinsic decoherence γ or increasing the squeezing interaction μ, moreover, one can obtain a valid dense coding capacity ( χ satisfies χ > 1) by modulating these parameters. The stable value of χ reveals that the decoherence cannot entirely destroy the dense coding capacity. In addition, decreasing Ω or increasing μ can not only enhance the stable value of χ but also impair the effects of decoherence. As the initial state is the Werner state, the purity r of initial state plays a key role in adjusting the value of dense coding capacity, χ can be significantly increased by improving the purity of initial state. For the initial state is Bell state, the large spin squeezing interaction compared with the magnetic field guarantees the optimal dense coding. One cannot always achieve a valid dense coding capacity for the Werner state, while for the Bell state, the dense coding capacity χ remains stuck at the range of greater than 1.

  18. Decoherence and Spin Transitions in Radical Pair Model of Avian Magnetoreception

    CERN Document Server

    Poonia, Vishvendra Singh

    2014-01-01

    The radical pair model for avian magnetoreception has been significantly efficacious in explaining the magnetosensitive behavior of chemical compass. In this model, we have a multi-spin system evolving under a specific Hamiltonian assisted by neurological spin-dependent recombination channels which give an elegant compass action that many species are belived to be using. In this study, we analyze the radical pair model form a microscopic spin transitional point of view and establish the role of nuclear and environmental decoherence in radical pair spin dynamics. We identify the spin interplay between singlet state and three triplet states of radical due to Zeeman and hyperfine and examine the distinctive roles of nuclear and environmental decoherence from this perspective. Additionally, we revisit some of the earlier results concerning radical pair model from this fresh outlook and provide more comprehensive explanation to those. The approach is aimed to equip us more for solid state emulation of avian compas...

  19. Alicki's model of scattering-induced decoherence derived from Hamiltonian dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hellmich, Mario [Faculty of Physics, University of Bielefeld, 33615 Bielefeld (Germany)

    2004-09-10

    We study a semiphenomenological model introduced by Alicki (2002 Phys. Rev. A 65 034104), describing environmental decoherence by scattering of a Brownian particle in a gas environment. For a slightly wider class of models, we prove that the semigroup describing the dynamics of the Brownian particle can be approximated by the reduced dynamics arising from a Hamiltonian interaction between the particle and an infinite fermionic thermal gas reservoir, provided the scattering process is isotropic.

  20. Strong decoherence

    CERN Document Server

    Gell-Mann, Murray; Gell-Mann, Murray; Hartle, James B

    1997-01-01

    We introduce a condition for the strong decoherence of a set of alternative histories of a closed quantum-mechanical system such as the universe. The condition applies, for a pure initial state, to sets of homogeneous histories that are chains of projections, generally branch-dependent. Strong decoherence implies the consistency of probability sum rules but not every set of consistent or even medium decoherent histories is strongly decoherent. Two conditions characterize a strongly decoherent set of histories: (1) At any time the operators that effectively commute with generalized records of history up to that moment provide the pool from which --- with suitable adjustment for elapsed time --- the chains of projections extending history to the future may be drawn. (2) Under the adjustment process, generalized record operators acting on the initial state of the universe are approximately unchanged. This expresses the permanence of generalized records. The strong decoherence conditions (1) and (2) guarantee wha...

  1. Kondo decoherence : finding the right spin model for iron impurities in gold and silver.

    Energy Technology Data Exchange (ETDEWEB)

    Costi, T. A.; Bergqvist, L.; Weichselbaum, A.; von Delft, J.; Micklitz, T.; Rosch, A.; Mavropoulos, P.; Dederichs, P. H.; Mallet, F.; Saminadayar, L.; Bauerle, C. (Materials Science Division); (Forschungszentrum Julich); (Ludwig-Maximilians-Univ. Munchen); (Univ. of Cologne); (CNRS); (Univ. Joseph Fourier); (Inst. Univ. de France)

    2009-02-01

    We exploit the decoherence of electrons due to magnetic impurities, studied via weak localization, to resolve a long-standing question concerning the classic Kondo systems of Fe impurities in the noble metals gold and silver: which Kondo-type model yields a realistic description of the relevant multiple bands, spin, and orbital degrees of freedom? Previous studies suggest a fully screened spin S Kondo model, but the value of S remained ambiguous. We perform density functional theory calculations that suggest S=3/2. We also compare previous and new measurements of both the resistivity and decoherence rate in quasi-one-dimensional wires to numerical renormalization group predictions for S=1/2, 1, and 3/2, finding excellent agreement for S=3/2.

  2. Lorentz invariant intrinsic decoherence

    CERN Document Server

    Milburn, G J

    2003-01-01

    Quantum decoherence can arise due to classical fluctuations in the parameters which define the dynamics of the system. In this case decoherence, and complementary noise, is manifest when data from repeated measurement trials are combined. Recently a number of authors have suggested that fluctuations in the space-time metric arising from quantum gravity effects would correspond to a source of intrinsic noise, which would necessarily be accompanied by intrinsic decoherence. This work extends a previous heuristic modification of Schr\\"{o}dinger dynamics based on discrete time intervals with an intrinsic uncertainty. The extension uses unital semigroup representations of space and time translations rather than the more usual unitary representation, and does the least violence to physically important invariance principles. Physical consequences include a modification of the uncertainty principle and a modification of field dispersion relations, in a way consistent with other modifications suggested by quantum grav...

  3. A universal test for gravitational decoherence

    Science.gov (United States)

    Pfister, C.; Kaniewski, J.; Tomamichel, M.; Mantri, A.; Schmucker, R.; McMahon, N.; Milburn, G.; Wehner, S.

    2016-10-01

    Quantum mechanics and the theory of gravity are presently not compatible. A particular question is whether gravity causes decoherence. Several models for gravitational decoherence have been proposed, not all of which can be described quantum mechanically. Since quantum mechanics may need to be modified, one may question the use of quantum mechanics as a calculational tool to draw conclusions from the data of experiments concerning gravity. Here we propose a general method to estimate gravitational decoherence in an experiment that allows us to draw conclusions in any physical theory where the no-signalling principle holds, even if quantum mechanics needs to be modified. As an example, we propose a concrete experiment using optomechanics. Our work raises the interesting question whether other properties of nature could similarly be established from experimental observations alone--that is, without already having a rather well-formed theory of nature to make sense of experimental data.

  4. Decoherence Spectroscopy for Atom Interferometry

    Directory of Open Access Journals (Sweden)

    Raisa Trubko

    2016-08-01

    Full Text Available Decoherence due to photon scattering in an atom interferometer was studied as a function of laser frequency near an atomic resonance. The resulting decoherence (contrast-loss spectra will be used to calibrate measurements of tune-out wavelengths that are made with the same apparatus. To support this goal, a theoretical model of decoherence spectroscopy is presented here along with experimental tests of this model.

  5. Decoherence in the Dirac equation

    CERN Document Server

    Meyer, D A

    1998-01-01

    A Dirac particle is represented by a unitarily evolving state vector in a Hilbert space which factors as $H_{spin} \\otimes H_{position}$. Motivated by the similarity to simple models of decoherence consisting of a two state system coupled to an environment, we investigate the occurence of decoherence in the Dirac equation upon tracing over position. We conclude that the physics of this mathematically exact model for decoherence is closely related to Zitterbewegung.

  6. Decoherence and localization in the double well model

    CERN Document Server

    Lemos, G B; De Faria, J G P; Terra-Cunha, M O; Nemes, M C; Lemos, Gabriela Barreto

    2005-01-01

    We use a spin-1/2 model to analyze tunnelling in a double well system coupled to an external reservoir. We consider different noise sources such as fluctuations on the height and central position of the barrier and propose an experiment to observe these effects in trapped ions or atoms.

  7. Decoherence, Entanglement and Cosmic Evolution

    CERN Document Server

    Capozziello, Salvatore

    2013-01-01

    The possible imprint of quantum decoherence, in the framework of cosmology, is here investigated. Particular attention is paid to the observational fact that entanglement could lead to the interaction of different eras of cosmic evolution. The role played by decoherence provides the existence of "quantum entanglement" between cosmological eras giving, as observational results, dynamical constraints on the corresponding cosmological models.

  8. Detecting gravitational decoherence with clocks: Limits on temporal resolution from a classical channel model of gravity

    CERN Document Server

    Khosla, Kiran

    2016-01-01

    The notion of time is given a different footing in Quantum Mechanics and General Relativity, treated as a parameter in the former and being an observer dependent property in the later. From a operational point of view time is simply the correlation between a system and a clock, where an idealized clock can be modelled as a two level systems. We investigate the dynamics of clocks interacting gravitationally by treating the gravitational interaction as a classical information channel. In particular, we focus on the decoherence rates and temporal resolution of arrays of $N$ clocks showing how the minimum dephasing rate scales with $N$, and the spatial configuration. Furthermore, we consider the gravitational redshift between a clock and massive particle and show that a classical channel model of gravity predicts a finite dephasing rate from the non-local interaction. In our model we obtain a fundamental limitation in time accuracy that is intrinsic to each clock.

  9. A comparison between models of gravity induced decoherence of the wavefunction

    Science.gov (United States)

    Bera, S.; Donadi, S.; Lochan, K.; Singh, TP

    2015-07-01

    It has already been suggested that quantum theory needs to be reformulated or modified in order to explain the measurement process and the successive collapse of the wave- function. However, there are also models of another type which keep quantum theory intact and instead modify the classical gravity by introducing stochasticity to it. These models suggest that there is a fluctuation in the background gravitational field which eventually results in the decoherence of the wavefunction. These fluctuations limit the precision with which one can measure the properties of a spacetime geometry with a quantum probe. Two similar models along this line have been suggested by Karolyhazy (K-model) and Diósi(D-model). They are based upon apparently different spacetime bounds. The results obtained for the coherence length are also somewhat different. In this article, we show that, given certain conditions apply, the minimal spacetime bounds in these two models are equivalent. We also derive the two-point correlation for the fluctuation potential in K-model which turns out to be non-white, unlike in D-model, where the corresponding correlation is white noise in time. In our opinion, this is the origin of discrepancy in the predictions of the two models. We argue that the noise correlation cannot be determined uniquely from a given spacetime bound.

  10. Quantum decoherence and neutrino data

    CERN Document Server

    Barenboim, G; Sarkar, S; Waldron-Lauda, A

    2006-01-01

    In this work we perform global fits of microscopic decoherence models of neutrinos to all available current data, including LSND and KamLAND spectral distortion results. In previous works on related issues the models used were supposed to explain LSND results by means of quantum gravity induced decoherence. However those models were purely phenomenological without any underlying microscopic basis. It is one of the main purposes of this article to use detailed microscopic decoherence models with complete positivity, to fit the data.The decoherence in these models has contributions not only from stochastic quantum gravity vacua operating as a medium, but also from conventional uncertainties in the energy of the (anti)neutrino beam. All these contributions lead to oscillation-length independent damping factors modulating the oscillatory terms from which one obtains an excellent fit to all available neutrino data, including LSND and Kamland spectral distortion.

  11. Exact expression for decoherence factor in the time-dependent generalized Cini model

    Institute of Scientific and Technical Information of China (English)

    Jianqi Shen(沈建其); Sanshui Xiao(肖三水); Qiang Wu(武强)

    2003-01-01

    The present letter finds the complete set of exact solutions of the time-dependent generalized Cini modelby making use of the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformationformulation and, based on this, the general explicit expression for the decoherence factor is thereforeobtained. This study provides us with a useful method to consider the geometric phase and topologicalproperties in the time-dependent quantum decoherence process.

  12. Principles of mathematical modeling

    CERN Document Server

    Dym, Clive

    2004-01-01

    Science and engineering students depend heavily on concepts of mathematical modeling. In an age where almost everything is done on a computer, author Clive Dym believes that students need to understand and "own" the underlying mathematics that computers are doing on their behalf. His goal for Principles of Mathematical Modeling, Second Edition, is to engage the student reader in developing a foundational understanding of the subject that will serve them well into their careers. The first half of the book begins with a clearly defined set of modeling principles, and then introduces a set of foundational tools including dimensional analysis, scaling techniques, and approximation and validation techniques. The second half demonstrates the latest applications for these tools to a broad variety of subjects, including exponential growth and decay in fields ranging from biology to economics, traffic flow, free and forced vibration of mechanical and other systems, and optimization problems in biology, structures, an...

  13. Spin decoherence in electron storage rings. More from a simple model

    Energy Technology Data Exchange (ETDEWEB)

    Barber, D.P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Heinemann, K. [The Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Mathematics and Statistics

    2015-06-15

    This is an addendum to the paper ''Some models of spin coherence and decoherence in storage rings'' by one of the authors (K. Heinemann, DESY Report 97-166 (1997)), in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, namely that the exact formalism of this article delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative ∂n/∂η. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring. For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of ∂n/∂η provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the exact rate of depolarisation can be obtained by replacing ∂n/∂η by another derivative, while giving a heuristic justification for the new derivative.

  14. Spin decoherence in electron storage rings --- more from a simple model

    CERN Document Server

    Barber, D P

    2015-01-01

    This is an addendum to the paper "Some models of spin coherence and decoherence in storage rings" by one of the authors [1] in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, a key implication in the Epilogue of [1], namely that the exact formalism of [1] delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative $\\partial \\hat n/\\partial\\eta$ [2,3,4]. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring (Machine II in [1]). For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation [5,6] for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of $\\partial \\hat n/\\partial\\eta$ provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the ...

  15. Effects of Dzyaloshinski-Moriya interaction and intrinsic decoherence on teleportation via a two-qubit Heisenberg XYZ model

    Institute of Scientific and Technical Information of China (English)

    Hu Xiao-Mian; Liu Jin-Ming

    2009-01-01

    Quantum teleportation via the entangled channel composed of a two-qubit Heisenberg XYZ model with Dzyaloshinski-Moriya (DM) interaction in the presence of intrinsic decoherenee has been investigated. We find that the initial state of the channel plays an important role in the teleported state and the average fidelity of teleportation. When the initial channel is in the state [ψ1(0)>=a|00> + b|11>, the average fidelity is equal to 1/3 constantly, which is independent of the DM interaction and the intrinsic decoherence effect. But when the channel is initially in the state [ψ2(0)> = c|01) + d|10>, the average fidelity is always larger than 2/3. Moreover, under a certain condition, the average fidelity can be enhanced by adjusting the DM interaction, and the intrinsic decoherence leads to a suppression of the fluctuation of the average fidelity.

  16. Investigations of the Quantum Correlation in Two-Qubit Heisenberg XYZ Model with Decoherence

    Science.gov (United States)

    Guo-Hui, Yang

    2016-12-01

    Quantum correlation dynamics in an anisotropic Heisenberg XYZ model under decoherence is investigated with the use of concurrence C and quantum discord (QD). With the Werner state as the initial state, we discuss the influence of mixture degree r on the dynamics. There are some difference between the time evolution behaviors of these two correlation measures with different value of r. For 0 ≤ r ≤ 1/3, there exists quantum discord but no entanglement; For 1/3

  17. Decoherence and the quantum-to-classical transition

    CERN Document Server

    Schlosshauer, Maximilian

    2007-01-01

    The ultimate introduction, textbook, and reference on decoherence and the quantum-to-classical transition. This detailed but accessible text describes the concepts, formalism, interpretation, and experimental observation of decoherence and explains how decoherence is responsible for the emergence, from the realm of quantum mechanics, of the classical world of our experience. Topics include: • Foundational problems at the quantum–classical border; • The role of the environment and entanglement; • Environment-induced loss of coherence and superselection; • Scattering-induced decoherence and spatial localization; • Master equations; • Decoherence models; • Experimental realization of "Schrödinger kittens" and their decoherence; • Quantum computing, quantum error correction, and decoherence-free subspaces; • Implications of decoherence for interpretations of quantum mechanics and for the "measurement problem"; • Decoherence in the brain. Written in a lucid and concise style that is accessib...

  18. Bootstrapping Time Dilation Decoherence

    CERN Document Server

    Gooding, Cisco

    2015-01-01

    We present a general relativistic model of a spherical shell of matter with a perfect fluid on its surface coupled to an internal oscillator, which generalizes a model recently introduced by the authors to construct a self-gravitating interferometer [1]. The internal oscillator evolution is defined with respect to the local proper time of the shell, allowing the oscillator to serve as a local clock that ticks differently depending on the shell's position and momentum. A Hamiltonian reduction is performed on the system, and an approximate quantum description is given to the reduced phase space. If we focus only on the external dynamics, we must trace out the clock degree of freedom, and this results in a form of intrinsic decoherence that shares some features with a proposed "universal" decoherence mechanism attributed to gravitational time dilation [2]. We show that the proposed decoherence remains present in the (gravity-free) limit of flat spacetime, indicating that the effect can be attributed entirely to ...

  19. Universal decoherence due to gravitational time dilation

    CERN Document Server

    Pikovski, Igor; Costa, Fabio; Brukner, Caslav

    2013-01-01

    Phenomena inherent to quantum theory on curved space-time, such as Hawking radiation, are typically assumed to be only relevant at extreme physical conditions: at high energies and in strong gravitational fields. Here we consider low-energy quantum mechanics in the presence of weak gravitational time dilation and show that the latter leads to universal decoherence of quantum superpositions. Time dilation induces a universal coupling between internal degrees-of-freedom and the centre-of-mass of a composite particle and we show that the resulting entanglement causes the particle's position to decohere. We derive the decoherence timescale and show that the weak time dilation on Earth is already sufficient to decohere micro-scale objects. No coupling to an external environment is necessary, thus even completely isolated composite systems will decohere on curved space-time. In contrast to gravitational collapse models, no modification of quantum theory is assumed. General relativity therefore can account for the e...

  20. Entanglement and decoherence: fragile and robust entanglement

    CERN Document Server

    Novotný, Jaroslav; Jex, Igor

    2011-01-01

    The destruction of entanglement of open quantum systems by decoherence is investigated in the asymptotic long-time limit. Starting from a general and analytically solvable decoherence model which does not involve any weak-coupling or Markovian assumption it is shown that two fundamentally different classes of entangled states can be distinguished. Quantum states of the first class are fragile against decoherence so that they can be disentangled asymptotically even if coherences between pointer states are still present. Quantum states of the second type are robust against decoherence. Asymptotically they can be disentangled only if also decoherence is perfect. A simple criterion for identifying these two classes on the basis of two-qubit entanglement is presented.

  1. Qubit Decoherence and Non-Markovian Dynamics at Low Temperatures via an Effective Spin-Boson Model

    CERN Document Server

    Shiokawa, K

    2004-01-01

    Quantum Brownian oscillator model (QBM), in the Fock-space representation, can be viewed as a multi-level spin-boson model. At sufficiently low temperature, the oscillator degrees of freedom are dynamically reduced to the lowest two levels and the system behaves effectively as a two-level (E2L) spin-boson model (SBM) in this limit. We discuss the physical mechanism of level reduction and analyze the behavior of E2L-SBM from the QBM solutions. The availability of close solutions for the QBM enables us to study the non-Markovian features of decoherence and leakage in a SBM in the non-perturbative regime (e.g. without invoking the Born approximation) in better details than before. Our result captures very well the characteristic non-Markovian short time low temperature behavior common in many models.

  2. Model Selection Principles in Misspecified Models

    CERN Document Server

    Lv, Jinchi

    2010-01-01

    Model selection is of fundamental importance to high dimensional modeling featured in many contemporary applications. Classical principles of model selection include the Kullback-Leibler divergence principle and the Bayesian principle, which lead to the Akaike information criterion and Bayesian information criterion when models are correctly specified. Yet model misspecification is unavoidable when we have no knowledge of the true model or when we have the correct family of distributions but miss some true predictor. In this paper, we propose a family of semi-Bayesian principles for model selection in misspecified models, which combine the strengths of the two well-known principles. We derive asymptotic expansions of the semi-Bayesian principles in misspecified generalized linear models, which give the new semi-Bayesian information criteria (SIC). A specific form of SIC admits a natural decomposition into the negative maximum quasi-log-likelihood, a penalty on model dimensionality, and a penalty on model miss...

  3. Quantum Samaritan's Dilemma Under Decoherence

    Science.gov (United States)

    Huang, Zhiming; Alonso-Sanz, Ramón; Situ, Haozhen

    2017-03-01

    We study how quantum noise affects the solution of quantum Samaritan's dilemma. Serval most common dissipative and nondissipative noise channels are considered as the model of the decoherence process. We find that the solution of quantum Samaritan's dilemma is stable under the influence of the amplitude damping, the bit flip and the bit-phase flip channel.

  4. Early transverse decoherence of bunches with space charge

    Science.gov (United States)

    Karpov, Ivan; Kornilov, Vladimir; Boine-Frankenheim, Oliver

    2016-12-01

    The transverse decoherence of injected bunches is an important phenomenon in synchrotrons and storage rings. The initial stage of this process determines the transverse emittance blowup, which should be taken into account for the design of feedback systems, for example. The interplay of different high-intensity effects can strongly affect the initial decoherence stage. We present a model that explains decoherence and emittance growth with chromaticity, space charge, and image charges within the first synchrotron period. We compare the model for different combinations of parameters with self-consistent particle tracking simulations and measurements in the SIS18 synchrotron at GSI Darmstadt. Generally, space charge slows down the decoherence process and can cause the loss of decoherence. Chromaticity and image charges can partly compensate this loss and restore the decoherence. We also analyze the single-particle excitation driven by space charge during the decoherence process. Particles gain large amplitudes from the coherent beam oscillation, which leads to halo buildup and losses.

  5. Does decoherence in the thermodynamic limit exist?

    CERN Document Server

    Frasca, M

    2002-01-01

    We consider the Jaynes-Cummings model for N particles in the thermodynamic limit showing how it can produce decoherence on a Schr\\"odinger cat state. This mechanism can be observed in current experiments with cavities.

  6. Decoherence in infinite quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, Philippe; Hellmich, Mario [Faculty of Physics, University of Bielefeld, Universitaetsstr. 25, 33615 Bielefeld (Germany); Bundesamt fuer Strahlenschutz (Federal Office for Radiation Protection), Willy-Brandt-Strasse 5, 38226 Salzgitter (Germany)

    2012-09-01

    We review and discuss a notion of decoherence formulated in the algebraic framework of quantum physics. Besides presenting some sufficient conditions for the appearance of decoherence in the case of Markovian time evolutions we provide an overview over possible decoherence scenarios. The framework for decoherence we establish is sufficiently general to accommodate quantum systems with infinitely many degrees of freedom.

  7. Decoherence and the quantum-to-classical transition

    Energy Technology Data Exchange (ETDEWEB)

    Schlosshauer, M.A. [Melbourne Univ., VIC (Australia). Dept. of Physics

    2007-07-01

    The ultimate introduction, textbook, and reference on decoherence and the quantum-to-classical transition. This detailed but accessible text describes the concepts, formalism, interpretation, and experimental observation of decoherence and explains how decoherence is responsible for the emergence, from the realm of quantum mechanics, of the classical world of our experience. Topics include: - Foundational problems at the quantum-classical border; - The role of the environment and entanglement; - Environment-induced loss of coherence and superselection; - Scattering-induced decoherence and spatial localization; - Master equations; - Decoherence models; - Experimental realization of ''Schroedinger's kittens'' and their decoherence; - Quantum computing, quantum error correction, and decoherence-free subspaces; - Implications of decoherence for interpretations of quantum mechanics and for the ''measurement problem''; - Decoherence in the brain. Written in a lucid and concise style that is accessible to all readers with a basic knowledge of quantum mechanics, this stimulating book tells the ''classical from quantum'' story in a comprehensive and coherent manner that brings together the foundational, technical, and experimental aspects of decoherence. It will be an indispensable resource for newcomers and experts alike. (orig.)

  8. Decoherence and dynamical entropy generation in quantum field theory

    Energy Technology Data Exchange (ETDEWEB)

    Koksma, Jurjen F., E-mail: J.F.Koksma@uu.nl [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands); Prokopec, Tomislav, E-mail: T.Prokopec@uu.nl [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands); Schmidt, Michael G., E-mail: M.G.Schmidt@thphys.uni-heidelberg.de [Institut fuer Theoretische Physik, Heidelberg University, Philosophenweg 16, D-69120 Heidelberg (Germany)

    2012-01-20

    We formulate a novel approach to decoherence based on neglecting observationally inaccessible correlators. We apply our formalism to a renormalised interacting quantum field theoretical model. Using out-of-equilibrium field theory techniques we show that the Gaussian von Neumann entropy for a pure quantum state increases to the interacting thermal entropy. This quantifies decoherence and thus measures how classical our pure state has become. The decoherence rate is equal to the single particle decay rate in our model. We also compare our approach to existing approaches to decoherence in a simple quantum mechanical model. We show that the entropy following from the perturbative master equation suffers from physically unacceptable secular growth.

  9. Decoherence: the view from the history and philosophy of science.

    Science.gov (United States)

    Hagar, Amit

    2012-09-28

    We present a brief history of decoherence, from its roots in the foundations of classical statistical mechanics, to the current spin bath models in condensed matter physics. We then analyse the philosophical importance of decoherence in three different foundational problems, and find that its role in their solutions is less than that commonly believed. What makes decoherence more philosophically interesting, we argue, are the methodological issues it draws attention to, and the question of the universality of quantum mechanics.

  10. Decoherence and the Branching of Chaos-less Classical Trajectory

    CERN Document Server

    Ishikawa, Takuji

    2016-01-01

    This study was started to know mysterious classicality of nuclei. This time, I found a new rule for decoherence. I used a model without chaos. As a result, it was shown that not only the intersection of classical trajectories but also branching of classical trajectories are needed for decoherence. In other words, it was shown that interactions between a main system and environments have to make enough branchings of classical trajectories of the main system for decoherence.

  11. Scanning Quantum Decoherence Microscopy

    OpenAIRE

    2008-01-01

    The use of qubits as sensitive magnetometers has been studied theoretically and recent demonstrated experimentally. In this paper we propose a generalisation of this concept, where a scanning two-state quantum system is used to probe the subtle effects of decoherence (as well as its surrounding electromagnetic environment). Mapping both the Hamiltonian and decoherence properties of a qubit simultaneously, provides a unique image of the magnetic (or electric) field properties at the nanoscale....

  12. Entropy squeezing for a two-level atom in two-mode Raman coupled model with intrinsic decoherence

    Institute of Scientific and Technical Information of China (English)

    Zhang Jian; Shao Bin; Zou Jian

    2009-01-01

    In this paper,we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling.We obtain the dynamical evolution of the total system under the influence of intrinsic decoherence when the two quantized fields are prepared in a two-mode squeezing vacuum state initially.The effects of the field squeezing factor,the two-level atomic transition frequency,the second field frequency and the intrinsic decoherence on the entropy squeezing are discussed.Without intrinsic decoherence,the increase of field squeezing factor can break the entropy squeezing.The two-level atomic transition frequency changes only the period of oscillation but not the strength of entropy squeezing.The influence of the second field frequency is complicated.With the intrinsic decoherence taken into consideration,the results show that the stronger the intrinsic decoherence is,the more quickly the entropy squeezing will disappear.The increase of the atomic transition frequency can hasten the disappearance of entropy squeezing.

  13. Equivalence principle in Chameleon models .

    Science.gov (United States)

    Kraiselburd, L.; Landau, S.; Salgado, M.; Sudarsky, D.

    Most theories that predict time and/or space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on WEP. We present a contrasting view based on an approximate calculation of the two body problem for the chameleon field and show that the force depends on the test body composition. Furthermore, we compare the prediction of the force on a test body with Eötvös type experiments and find that the chameleon field effect cannot account for current bounds.

  14. Equivalence Principle in Chameleon Models

    CERN Document Server

    Kraiselburd, Lucila; Salgado, Marcelo; Sudarsky, Daniel

    2013-01-01

    Most theories that predict time and/or space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on WEP. We present a contrasting view based on an approximate calculation of the two body problem for the chameleon field and show that the force depends on the test body composition. Furthermore, we compare the prediction of the force on a test body with E\\"otv\\"os type experiments and find that the chameleon field effect cannot account for current bounds.

  15. Time scale of stationary decoherence

    Science.gov (United States)

    Polonyi, Janos

    2017-07-01

    The decoherence of a test particle interacting with an ideal gas is studied by the help of the effective Lagrangian, derived in the leading order of the perturbation expansion and in order O (∂t2) . The stationary decoherence time is found to be comparable to or longer than the diffusion time. The decoherence time reaches its minimal value for classical, completely decohered environment, suggesting that physical decoherence is slowed down as compared with diffusion by the quantum coherence of the environment.

  16. Cosmic decoherence: massive fields

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Junyu [Department of Physics, California Institute of Technology,Pasadena, California 91125 (United States); School of the Gifted Young, University of Science and Technology of China,Hefei, Anhui 230026 (China); Sou, Chon-Man; Wang, Yi [Department of Physics, The Hong Kong University of Science and Technology,Clear Water Bay, Kowloon, Hong Kong (China)

    2016-10-14

    We study the decoherence of massive fields during inflation based on the Zurek’s density matrix approach. With the cubic interaction between inflaton and massive fields, the reduced density matrix for the massive fields can be calculated in the Schrödinger picture which is related to the variance of the non-Gaussian exponent in the wave functional. The decoherence rate is computed in the one-loop form from functional integration. For heavy fields with m≳O(H), quantum fluctuations will easily stay in the quantum state and decoherence is unlikely. While for light fields with mass smaller than O(H), quantum fluctuations are easily decohered within 5∼10 e-folds after Hubble crossing. Thus heavy fields can play a key role in studying problems involving inflationary quantum information.

  17. Cosmic Decoherence: Massive Fields

    CERN Document Server

    Liu, Junyu; Wang, Yi

    2016-01-01

    We study the decoherence of massive fields during inflation based on the Zurek's density matrix approach. With the cubic interaction between inflaton and massive fields, the reduced density matrix for the massive fields can be calculated in the Schr\\"odinger picture which is related to the variance of the non-Gaussian exponent in the wave functional. The decoherence rate is computed in the one-loop form from functional integration. For heavy fields with $m\\gtrsim \\mathcal{O}(H)$, quantum fluctuations will easily stay in the quantum state and decoherence is unlikely. While for light fields with mass smaller than $\\mathcal{O}(H)$, quantum fluctuations are easily decohered within $5\\sim10$ e-folds after Hubble crossing. Thus heavy fields can play a key role in studying problems involving inflationary quantum information.

  18. Parallel decoherence in composite quantum systems

    Indian Academy of Sciences (India)

    M Dugići; J Jeknić-Dugić

    2012-08-01

    For the standard quantum Brownian motion (QBM) model, we point out the occurrence of simultaneous (parallel), mutually irreducible and autonomous decoherence processes. Besides the standard Brownian particle, we show that there is at least another system undergoing the dynamics described by the QBM model. We do this by selecting the two mutually irreducible, global structures (decompositions into subsystems) of the composite system of the QBM model. The generalization of this observation is a new, challenging task in the foundations of the decoherence theory. We do not place our findings in any interpretational context.

  19. Quantum hydrodynamic analysis of decoherence: quantum trajectories and stress tensor

    Energy Technology Data Exchange (ETDEWEB)

    Na, Kyungsun; Wyatt, Robert E

    2002-12-30

    Quantum trajectories, obtained by integrating equations of motion for elements of the probability fluid, are used to analyze decoherence in a model two-mode system. Analysis of trajectories, flux maps, and the stress tensor for two composite systems, in one of which the system is uncoupled from the environment, leads to a hydrodynamic interpretation of the decoherence process.

  20. Short-Time Decoherence of Solid-State Qubit at Optimal Operation Points

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    We investigate the short-time decoherence of a solid-state qubit under Ohmic noise at optimal operation points. The decoherence is analyzed by maximum norm of the deviation density operator. It is shown that at the temperature T = 3 mK, the loss of the fidelity due to decoherence is much smaller than the DiVincenzo low decoherence criterion, which means that the model may be an optimal candidate of qubit for quantum computation.

  1. Realistic Decoherence Free Subspaces

    CERN Document Server

    Romero, K M F; Terra-Cunha, M O; Nemes, M C

    2003-01-01

    Decoherence free subspaces (DFS) is a theoretical tool towards experimental implementation of quantum information storage and processing. However, they represent an experimental challenge, since conditions for their existence are very stringent. This work explores the situation in which a system of $N$ oscillators coupled to a bath of harmonic oscillators is close to satisfy the conditions for the existence of DFS. We show, in the Born-Markov limit and for small deviations from separability and degeneracy conditions, that there are {\\emph{weak decoherence subspaces}} which resemble the original notion of DFS.

  2. Decoherence in Search Algorithms

    CERN Document Server

    Abal, G; Marquezino, F L; Oliveira, A C; Portugal, R

    2009-01-01

    Recently several quantum search algorithms based on quantum walks were proposed. Those algorithms differ from Grover's algorithm in many aspects. The goal is to find a marked vertex in a graph faster than classical algorithms. Since the implementation of those new algorithms in quantum computers or in other quantum devices is error-prone, it is important to analyze their robustness under decoherence. In this work we analyze the impact of decoherence on quantum search algorithms implemented on two-dimensional grids and on hypercubes.

  3. A general theoretical framework for decoherence in open and closed systems

    Science.gov (United States)

    Castagnino, Mario; Fortin, Sebastian; Laura, Roberto; Lombardi, Olimpia

    2008-08-01

    A general theoretical framework for decoherence is proposed, which encompasses formalisms originally devised to deal just with open or closed systems. The conditions for decoherence are clearly stated and the relaxation and decoherence times are compared. Finally, the spin-bath model is developed in detail from the new perspective.

  4. A general theoretical framework for decoherence in open and closed systems

    Energy Technology Data Exchange (ETDEWEB)

    Castagnino, Mario [CONICET, IAFE, Instituto de Fisica de Rosario, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Casilla de Correos 67, Sucursal 28, 1428, Buenos Aires (Argentina); Fortin, Sebastian [CONICET, IAFE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Casilla de Correos 67, Sucursal 28, 1428, Buenos Aires (Argentina); Laura, Roberto [Departamento de Fisica y Quimica, Facultad de Ciencias Exactas, IngenierIa y Agrimensura, Universidad Nacional de Rosario, Pellegrini 250, 2000, Rosario (Argentina); Lombardi, Olimpia [CONICET, Universidad de Buenos Aires, Crisologo Larralde 3440, 1430, Buenos Aires (Argentina)

    2008-08-07

    A general theoretical framework for decoherence is proposed, which encompasses formalisms originally devised to deal just with open or closed systems. The conditions for decoherence are clearly stated and the relaxation and decoherence times are compared. Finally, the spin-bath model is developed in detail from the new perspective.

  5. Decoherent Histories Analysis of Minisuperspace Quantum Cosmology

    CERN Document Server

    Halliwell, J J

    2011-01-01

    Recent results on the decoherent histories quantization of simple cosmological models (minisuperspace models) are described. The most important issue is the construction, from the wave function, of a probability distribution answering various questions of physical interest, such as the probability of the system entering a given region of configuration space at any stage in its entire history. A standard but heuristic procedure is to use the flux of (components of) the wave function in a WKB approximation as the probability. This gives sensible semiclassical results but lacks an underlying operator formalism. Here, we supply the underlying formalism by deriving probability distributions linked to the Wheeler-DeWitt equation using the decoherent histories approach to quantum theory, building on the generalized quantum mechanics formalism developed by Hartle. The key step is the construction of class operators characterizing questions of physical interest. Taking advantage of a recent decoherent histories analys...

  6. Quantum decoherence with holography

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Shih-Hao [Physics Division, National Center for Theoretical Sciences and Physics Department,National Tsing-Hua University, Hsin-Chu 300, Taiwan (China); Li, Wei [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut,Am Mühlenberg 1, 14476 Golm (Germany); Lin, Feng-Li; Ning, Bo [Department of Physics, National Taiwan Normal University,Taipei, 116, Taiwan (China)

    2014-01-30

    Quantum decoherence is the loss of a system’s purity due to its interaction with the surrounding environment. Via the AdS/CFT correspondence, we study how a system decoheres when its environment is a strongly-coupled theory. In the Feynman-Vernon formalism, we compute the influence functional holographically by relating it to the generating function of Schwinger-Keldysh propagators and thereby obtain the dynamics of the system’s density matrix. We present two exactly solvable examples: (1) a straight string in a BTZ black hole and (2) a scalar probe in AdS{sub 5}. We prepare an initial state that mimics Schrödinger’s cat and identify different stages of its decoherence process using the time-scaling behaviors of Rényi entropy. We also relate decoherence to local quantum quenches, and by comparing the time evolution behaviors of the Wigner function and Rényi entropy we demonstrate that the relaxation of local quantum excitations leads to the collapse of its wave-function.

  7. Decoherence free algebra

    CERN Document Server

    Ogata, Y

    2003-01-01

    We consider the decoherence free subalgebra which satisfies the minimal condition introduced by Alicki. We show the manifest form of it and relate the subalgebra with the Kraus representation. The arguments also provides a new proof for generalized L"{u}ders theorem.

  8. Composing decoherence functionals

    CERN Document Server

    Boes, Paul

    2016-01-01

    Quantum Measure Theory (QMT) is a generalization of quantum theory where physical predictions are computed from a matrix known as decoherence functional (DF). Previous works have noted that, in its original formulation, QMT exhibits a problem with composability, since the composition of two decoherence functionals is, in general, not a valid decoherence functional. This does not occur when the DFs in question happen to be positive semidefinite (a condition known as strong positivity). In this paper, we study the concept of composability of DFs and its consequences for QMT. First, using the notion of composability, we settle an old problem in QMT regarding the definition of decoherent histories. Then we show that the problem of composability is much deeper than originally envisaged, since, for any $n$, there exists a DF that can co-exist with $n-1$ copies of itself, but not with $n$. Finally, we prove that the set of strongly positive DFs cannot be enlarged while remaining closed under composition. Furthermore...

  9. Decoherence in atom-field interactions: A treatment using superoperator techniques

    Energy Technology Data Exchange (ETDEWEB)

    Moya-Cessa, Hector [Universitaet Ulm, Abteilung fuer Quantenphysik D-89069 Ulm (Germany) and INAOE, Coordinacion de Optica, Apdo. Postal 51 y 216, 72000 Puebla, Pue. (Mexico)]. E-mail: hmmc@inaoep.mx

    2006-09-15

    Decoherence is a subject of great importance in quantum mechanics, particularly in the fields of quantum optics, quantum information processing and quantum computing. Quantum computation relies heavily in the unitary character of each step carried out by a quantum computational device and this unitarity is affected by decoherence. An extensive study of master equations is therefore needed for a better understanding on how quantum information is processed when a system interacts with its environment. Master equations are usually studied by using Fokker-Planck and Langevin equations and not much attention has been given to the use of superoperator techniques. In this report we study in detail several approaches that lead to decoherence, for instance a variation of the Schroedinger equation that models decoherence as the system evolves through intrinsic mechanisms beyond conventional quantum mechanics rather than dissipative interaction with an environment. For the study of the dissipative interaction we use a correspondence principle approach. We solve the master equations for different physical systems, namely, Kerr and parametric down conversion. In the case of light-matter interaction we show that although dissipation destroys the quantumness of the field, information of the initial field may be obtained via the reconstruction of quasiprobability distribution functions.

  10. Equivalence Principle in Chameleon Models

    CERN Document Server

    Kraiselburd, Lucila; Salgado, Marcelo; Sudarsky, Daniel; Vucetich, Héctor

    2015-01-01

    Most theories that predict time and(or) space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltman proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on the WEP. In this paper we present a contrasting view based on the analysis of the force between two bodies induced by the chameleon field using a particular approach in which the field due to both the large and the small bodies is obtained by appropriate series expansions in the various regions of interest and the corresponding matching conditions. We found that resulting force depends on the test body\\'{}s composition even when the chameleon coupling constants $\\beta_{i}$ are universal. In particular, we compared the resulting differential acceleration of test bodies made of Be and Al with the corresponding bounds obtained from E\\"otv\\"os type experiments and find that the predictions of the chameleon model are, in general, various orders of magnitude a...

  11. 1/N-expansion for the Dicke model and the decoherence program

    CERN Document Server

    Frasca, M

    2004-01-01

    An analysis of the Dicke model, N two-level atoms interacting with a single radiation mode, is done using the Holstein-Primakoff transformation. The main aim of the paper is to show that, changing the quantization axis with respect to the common usage, it is possible to prove a general result either for N or the coupling constant going to infinity for the exact solution of the model. This completes the analysis, known in the current literature, with respect to the same model in the limit of N and volume going to infinity, keeping the density constant. For the latter the proper axis of quantization is given by the Hamiltonian of the two-level atoms and for the former the proper axis of quantization is defined by the interaction. The relevance of this result relies on the observation that a general measurement apparatus acts using electromagnetic interaction and so, one can states that the thermodynamic limit is enough to grant the appearance of classical effects. Indeed, recent experimental results give first ...

  12. Decoherence and determinism in a one-dimensional cloud-chamber model

    CERN Document Server

    Sparenberg, Jean-Marc

    2016-01-01

    A possible explanation for the seemingly random nature of the measurement result in quantum mechanics was recently proposed by Sparenberg et al. In this approach, a measurement result is simply determined by the microscopic state of the measuring device. This interpretation led to a new discussion of Mott's problem, i.e. the paradoxical appearance of linear tracks in a cloud-chamber measurement of a radioactive source emitting spherical waves. It was proposed that the appearance of particular linear tracks was actually determined by the (random) positions of atoms or molecules inside the chamber. In the present work, we further explore this hypothesis, both analytically and numerically, in the framework of a recently established one-dimensional model by Carlone et al. In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministicall...

  13. Scheme for Quantum Computing Immune to Decoherence

    Science.gov (United States)

    Williams, Colin; Vatan, Farrokh

    2008-01-01

    A constructive scheme has been devised to enable mapping of any quantum computation into a spintronic circuit in which the computation is encoded in a basis that is, in principle, immune to quantum decoherence. The scheme is implemented by an algorithm that utilizes multiple physical spins to encode each logical bit in such a way that collective errors affecting all the physical spins do not disturb the logical bit. The scheme is expected to be of use to experimenters working on spintronic implementations of quantum logic. Spintronic computing devices use quantum-mechanical spins (typically, electron spins) to encode logical bits. Bits thus encoded (denoted qubits) are potentially susceptible to errors caused by noise and decoherence. The traditional model of quantum computation is based partly on the assumption that each qubit is implemented by use of a single two-state quantum system, such as an electron or other spin-1.2 particle. It can be surprisingly difficult to achieve certain gate operations . most notably, those of arbitrary 1-qubit gates . in spintronic hardware according to this model. However, ironically, certain 2-qubit interactions (in particular, spin-spin exchange interactions) can be achieved relatively easily in spintronic hardware. Therefore, it would be fortunate if it were possible to implement any 1-qubit gate by use of a spin-spin exchange interaction. While such a direct representation is not possible, it is possible to achieve an arbitrary 1-qubit gate indirectly by means of a sequence of four spin-spin exchange interactions, which could be implemented by use of four exchange gates. Accordingly, the present scheme provides for mapping any 1-qubit gate in the logical basis into an equivalent sequence of at most four spin-spin exchange interactions in the physical (encoded) basis. The complexity of the mathematical derivation of the scheme from basic quantum principles precludes a description within this article; it must suffice to report

  14. Atomic entanglement and decoherence

    Science.gov (United States)

    Genes, Claudiu

    The generation of entanglement in atomic systems plays a central topic in the fields of quantum information storage and processing. Moreover, a special category of entangled states of multi-atom ensembles, spin squeezed states, have been proven to lead to considerable improvement in the sensitivity of precision measurements compared to systems involving uncorrelated atoms. A treatment of entanglement in open systems is, however, incomplete without a precise description of the process of decoherence which necessarily accompanies it. The theory of entanglement and decoherence are the two main topics of this thesis. Methods are described for the generation of strong correlations in large atomic ensembles using either cavity quantum electrodynamics or measurement outcome conditioned quantum dynamics. Moreover, the description of loss of entanglement resulting from the coupling to a noise reservoir (electromagnetic vacuum) is explored. A spin squeezing parameter is used throughout this thesis as both a measure of entanglement strength and as an indication of the sensitivity improvement above the so-called standard quantum limit (sensitivity obtained with uncorrelated particles) in metrology. The first scheme considered consists of a single mode cavity field interacting with a collection of atoms for which spin squeezing is produced in both resonant and off-resonant regimes. In the resonant case, transfer of squeezing from a field state to the atoms is analyzed, while in the off-resonant regime squeezing is produced via an effective nonlinear interaction (one-axis twisting Hamiltonian). A second, more experimentally realistic case, is one involving the interaction of free space atoms with laser pulses; a projective measurement of a source field originating from atomic fluctuations provides a means of preparing atomic collective states such as spin squeezed and Schrodinger cat states. A new "unravelling" is proposed, that employs the detection of photon number in a single

  15. Decoherence induced by fluctuating boundaries

    CERN Document Server

    De Lorenci, V A

    2012-01-01

    The effects of fluctuating boundaries on a superposition state of a quantum particle in a box is studied. We consider a model in one space dimension in which the initial state is a coherent superposition of two energy eigenstates. The locations of the walls of the box are assumed to undergo small fluctuation with a Gaussian probability distribution. The spatial probability density of the particle contains an interference term, which is found to decay in time due to the boundary fluctuations. At late times, this term vanishes and the quantum coherence is lost. The system is now described by a density matrix rather than a pure quantum state.This model gives a simple illustration of how environment-induced decoherence can take place in quantum systems. It can also serve as an analog model for the effects of spacetime geometry fluctuations on quantum systems.

  16. Centre of mass decoherence due to time dilation: paradoxical frame-dependence

    CERN Document Server

    Diósi, Lajos

    2015-01-01

    The recently proposed centre of mass decoherence of composite objects due to gravitational time-dilation [Pikovski et al., Nat.Phys. 15. June (2015); arXive:1311.1095] is confronted with the principle of equivalence between gravity and observer's acceleration. In the laboratory frame, a positional superposition $\\vert x_1\\rangle+\\vert x_2\\rangle$ can quickly decohere whereas in the free-falling frame, as I argue, the superposition can survive for almost arbitrary long times. The paradoxical result is explained by the so far unappreciated feature of the proposed model: the centre of mass canonical subsystem is ambiguous, it is different in the laboratory and the free-falling frames, respectively.

  17. Classical decoherence in a nanomechanical resonator

    Science.gov (United States)

    Maillet, O.; Vavrek, F.; Fefferman, A. D.; Bourgeois, O.; Collin, E.

    2016-07-01

    Decoherence is an essential mechanism that defines the boundary between classical and quantum behaviours, while imposing technological bounds for quantum devices. Little is known about quantum coherence of mechanical systems, as opposed to electromagnetic degrees of freedom. But decoherence can also be thought of in a purely classical context, as the loss of phase coherence in the classical phase space. Indeed the bridge between quantum and classical physics is under intense investigation, using, in particular, classical nanomechanical analogues of quantum phenomena. In the present work, by separating pure dephasing from dissipation, we quantitatively model the classical decoherence of a mechanical resonator: through the experimental control of frequency fluctuations, we engineer artificial dephasing. Building on the fruitful analogy introduced between spins/quantum bits and nanomechanical modes, we report on the methods available to define pure dephasing in these systems, while demonstrating the intrinsic almost-ideal properties of silicon nitride beams. These experimental and theoretical results, at the boundary between classical nanomechanics and quantum information fields, are prerequisite in the understanding of decoherence processes in mechanical devices, both classical and quantum.

  18. Einselection and decoherence from an information theory perspective

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, W.H. [Los Alamos National Lab., NM (United States)

    2000-07-01

    We introduce and investigate a simple model of conditional quantum dynamics. It allows for a discussion of the information-theoretic aspects of quantum measurements, decoherence, and environment-induced superselection (einselection). (orig.)

  19. Bounding quantum-gravity-inspired decoherence using atom interferometry

    Science.gov (United States)

    Minář, Jiří; Sekatski, Pavel; Sangouard, Nicolas

    2016-12-01

    Hypothetical models have been proposed in which explicit collapse mechanisms prevent the superposition principle from holding at large scales. In particular, the model introduced by Ellis et al. [J. Ellis et al., Phys. Lett. B 221, 113 (1989), 10.1016/0370-2693(89)91482-2] suggests that quantum gravity might be responsible for the collapse of the wave function of massive objects in spatial superpositions. We consider here a recent experiment reporting on interferometry with atoms delocalized over half a meter for a time scale of 1 s [T. Kovachy et al., Nature (London) 528, 530 (2015), 10.1038/nature16155] and show that the corresponding data strongly bound quantum-gravity-induced decoherence and rule it out in the parameter regime considered originally.

  20. Decoherence From an Unstable Environment

    CERN Document Server

    Blume-Kohout, R; Blume-Kohout, Robin; Zurek, Wojciech H.

    2002-01-01

    The exponential sensitivity of a quantum environment with a classically chaotic analogue to initial conditions suggests that even very small perturbations resulting from weak coupling to a system whose state is a superposition of eigenstates of the coupling Hamiltonian will compel the environment to evolve into very different states, dependent on the initial state of the system. In this letter, we analyze decoherence due to a ``toy'' quantum environment which is analytically solvable, yet displays the crucial phenomenon of sensitivity to perturbation. We show that such an environment, with a single degree of freedom, can be far more effective at decohering a harmonic oscillator than a heat bath with infinitely many degrees of freedom. In order to demonstrate this, we introduce a new method of obtaining the master equation for coupled linear systems. Finally, we indicate the shortcomings of our toy model, explain where it differs from physical systems, and comment on the applicability of our results to decoher...

  1. Multiple System-Decomposition Method for Avoiding Quantum Decoherence

    Institute of Scientific and Technical Information of China (English)

    J.Jekni(c)-Dugi(c); M.Dugi(c)

    2008-01-01

    Decomposition of a composite system C into different subsystems,A+B or D+ε,may help in avoiding decoherence.For example,the environment-induced decoherence for an A+B system need not destroy entanglement present in the D+ε system(A+B=C=D+ε).This new approach opens some questions also in the foundations of the quantum computation theory that might eventually lead to a new model of quantum computation.

  2. An example of the decoherence approach to quantum dissipative chaos

    CERN Document Server

    Brun, T A

    1995-01-01

    Quantum chaos---the study of quantized nonintegrable Hamiltonian systems---is an extremely well-developed and sophisticated field. By contrast, very little work has been done in looking at quantum versions of systems which classically exhibit {\\it dissipative} chaos. Using the decoherence formalism of Gell-Mann and Hartle, I find a quantum mechanical analog of one such system, the forced damped Duffing oscillator. I demonstrate the classical limit of the system, and discuss its decoherent histories. I show that using decoherent histories, one can define not only the quantum map of an entire density operator, but can find an analog to the Poincar\\'e map of the individual trajectory. Finally, I argue the usefulness of this model as an example of quantum dissipative chaos, as well as of a practical application of the decoherence formalism to an interesting problem.

  3. Parallel occurrence of decoherence in the composite quantum systems

    CERN Document Server

    Dugic, M

    2010-01-01

    A composite quantum system can be decomposed into subsystems in the different ways. For some relevant models of the decoherence theory, we investigate the occurrence of decoherence for the different decompositions of a composite system "system plus environment". The decompositions are mutually related by the proper linear canonical transformations that do not involve the comparatively trivial regrouping/coarse-graining or the permutations between the constituent subsystems. As a result, we obtain the parallel (simultaneous) occurrence of decoherence for the decompositions considered and give some arguments why this finding should not be an exceptional case. The parallel occurrence of decoherence suggests conceptually a new approach to investigating the non-completely positive maps for open quantum systems.

  4. Decoherence of two-qubit systems: a random matrix description

    Science.gov (United States)

    Pineda, C.; Gorin, T.; Seligman, T. H.

    2007-04-01

    We study decoherence of two non-interacting qubits. The environment and its interaction with the qubits are modelled by random matrices. Decoherence, measured in terms of purity, is calculated in linear response approximation. Monte Carlo simulations illustrate the validity of this approximation and of its extension by exponentiation. The results up to this point are also used to study one-qubit decoherence. Purity decay of entangled and product states are qualitatively similar though for the latter case it is slower. Numerical studies for a Bell pair as initial state reveal a one to one correspondence between its decoherence and its internal entanglement decay. For strong and intermediate coupling to the environment this correspondence agrees with the one for Werner states. In the limit of a large environment the evolution induces a unital channel in the two qubits, providing a partial explanation for the above relation.

  5. Decoherence of two qubit systems: A random matrix description

    CERN Document Server

    Pineda, C; Seligman, T H

    2007-01-01

    We study decoherence of two non-interacting qubits. The environment and its interaction with the qubits are modelled by random matrices. Decoherence, measured in terms of purity, is calculated in linear response approximation. Monte Carlo simulations illustrate the validity of this approximation and of its extension by exponentiation. The results up to this point are also used to study one qubit decoherence. Purity decay of entangled and product states are qualitatively similar though for the latter case it is slower. Numerical studies for a Bell pair as initial state reveal a one to one correspondence between its decoherence and its internal entanglement decay. For strong and intermediate coupling to the environment this correspondence agrees with the one for Werner states. In the limit of a large environment the evolution induces a unital channel in the two qubits, providing a partial explanation for the relation above.

  6. Measurement of decoherence of electron waves and visualization of the quantum-classical transition.

    Science.gov (United States)

    Sonnentag, Peter; Hasselbach, Franz

    2007-05-18

    Controlled decoherence of free electrons due to Coulomb interaction with a truly macroscopic environment, the electron (and phonon) gas inside a semiconducting plate, is studied experimentally. The quantitative results are compared with different theoretical models. The experiment confirms the main features of the theory of decoherence and can be interpreted in terms of which-path information. In contrast to previous model experiments on decoherence, the obtained interferograms directly visualize the transition from quantum to classical.

  7. Principles of models based engineering

    Energy Technology Data Exchange (ETDEWEB)

    Dolin, R.M.; Hefele, J.

    1996-11-01

    This report describes a Models Based Engineering (MBE) philosophy and implementation strategy that has been developed at Los Alamos National Laboratory`s Center for Advanced Engineering Technology. A major theme in this discussion is that models based engineering is an information management technology enabling the development of information driven engineering. Unlike other information management technologies, models based engineering encompasses the breadth of engineering information, from design intent through product definition to consumer application.

  8. Principles of Sonar Performance Modeling

    NARCIS (Netherlands)

    Ainslie, M.A.

    2010-01-01

    Sonar performance modelling (SPM) is concerned with the prediction of quantitative measures of sonar performance, such as probability of detection. It is a multidisciplinary subject, requiring knowledge and expertise in the disparate fields of underwater acoustics, acoustical oceanography, sonar sig

  9. CPT and Decoherence in Quantum Gravity

    CERN Document Server

    Mavromatos, N E

    2007-01-01

    In this review, I first discuss briefly some theoretical motivations for potential Lorentz Violation and deviation from ordinary quantum mechanical behavior (decoherence) of field theoretic systems in the background of some quantum gravity (QG) models. Both types of effects lead to CPT violation, but they can be disentangled experimentally. I, then, proceed to a description of precision tests of CPT symmetry using neutral and charged Kaons, which are of direct relevance to the main theme of this conference. I emphasize the potentially unique r\\^ole of neutral meson factories in providing ``smoking-gun'' evidence of some QG-decoherence models in which the CPT quantum mechanical operator is not well defined. This is achieved by means of potential observations of QG-induced modifications of the pertinent Einstein-Podolsky-Rosen (EPR) particle correlations.

  10. Decoherence of spin echoes

    Energy Technology Data Exchange (ETDEWEB)

    Prosen, Tomaz [Physics Department, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia)]. E-mail: prosen@fiz.uni-lj.si; Seligman, Thomas H. [Centro de Ciencias Fisicas, University of Mexico (UNAM), Cuernavaca (Mexico)]. E-mail: seligman@fis.unam.mx

    2002-06-07

    We define a quantity, the so-called purity fidelity, which measures the rate of dynamical irreversibility due to decoherence, observed e.g. in echo experiments, in the presence of an arbitrary small perturbation of the total (system + environment) Hamiltonian. We derive a linear response formula for the purity fidelity in terms of integrated time correlation functions of the perturbation. Our relation predicts, similar to the case of fidelity decay, that the faster the decay of purity fidelity the slower is the decay of time correlations. In particular, we find exponential decay in quantum mixing regime and faster, initially quadratic and later typically Gaussian decay in the regime of non-ergodic, e.g. integrable quantum dynamics. We illustrate our approach by an analytical calculation and numerical experiments in the Ising spin 1/2 chain kicked with tilted homogeneous magnetic field where part of the chain is interpreted as a system under observation and part as an environment. (author)

  11. Decoherence Free Neutron Interferometry

    CERN Document Server

    Pushin, Dmitry A; Cory, David G

    2016-01-01

    Perfect single-crystal neutron interferometers are adversely sensitive to environmental disturbances, particularly mechanical vibrations. The sensitivity to vibrations results from the slow velocity of thermal neutrons and the long measurement time that are encountered in a typical experiment. Consequently, to achieve a good interference solutions for reducing vibration other than those normally used in optical experiments must be explored. Here we introduce a geometry for a neutron interferometer that is less sensitive to low-frequency vibrations. This design may be compared with both dynamical decoupling methods and decoherence-free subspaces that are described in quantum information processing. By removing the need for bulky vibration isolation setups, this design will make it easier to adopt neutron interferometry to a wide range of applications and increase its sensitivity.

  12. A random matrix approach to decoherence

    CERN Document Server

    Gorin, T; Gorin, Thomas; Seligman, Thomas H.

    2001-01-01

    In order to analyze the effect of chaos or order on the rate of decoherence in a subsystem, we aim to distinguish effects of the two types of dynamics by choosing initial states as random product states from two factor spaces representing two subsystems. We introduce a random matrix model that permits to vary the coupling strength between the subsystems. The case of strong coupling is analyzed in detail, and we find no significant differences except for very low-dimensional spaces.

  13. Decoherence in Josephson Qubits from Dielectric Loss

    OpenAIRE

    Martinis, John M.; Cooper, K. B.; McDermott, R.; Steffen, Matthias; Ansmann, Markus; Osborn, K; Cicak, K.; Oh, S.; Pappas, D. P.; Simmonds, R. W.; Yu, Clare C

    2005-01-01

    Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the tunnel junction can lead to short coherence times. We show that a variety of microwave and qubit measurements are well modeled by loss from resonant absorption of two-level defects. Our results demonstrate that this loss can be significantly reduced by using better dielectrics and fabricating junctio...

  14. Two Qubits Entanglement Dynamics in 1D Heisenberg Chain with Intrinsic Decoherence

    Institute of Scientific and Technical Information of China (English)

    SHAO Bin; ZHANG Li-li; ZOU Jian

    2006-01-01

    To reveal how the decoherence modifies the time evolution of the entanglement of quantum system,the intrinsic decoherence approach and the entanglement of formation are used, and the time evolution of entanglement for two-qubit 1D quantum Heisenberg model in an external uniform magnetic field is derived. It is shown that the external magnetic field can strengthen the effects of the intrinsic decoherence on the entanglement of the system.

  15. Quantum Darwinism, Decoherence, and the Randomness of Quantum Jumps

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, Wojciech H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-06-05

    Tracing flows of information in our quantum Universe explains why we see the world as classical. Quantum principle of superposition decrees every combination of quantum states a legal quantum state. This is at odds with our experience. Decoherence selects preferred pointer states that survive interaction with the environment. They are localized and effectively classical. They persist while their superpositions decohere. Here we consider emergence of `the classical' starting at a more fundamental pre-decoherence level, tracing the origin of preferred pointer states and deducing their probabilities from the core quantum postulates. We also explore role of the environment as medium through which observers acquire information. This mode of information transfer leads to perception of objective classical reality.

  16. Principles of polymer processing modelling

    Directory of Open Access Journals (Sweden)

    Agassant Jean-François

    2016-01-01

    Full Text Available Polymer processing involves three thermo-mechanical stages: Plastication of solid polymer granules or powder to an homogeneous fluid which is shaped under pressure in moulds or dies and finally cooled and eventually drawn to obtain the final plastic part. Physical properties of polymers (high viscosity, non-linear rheology, low thermal diffusivity as well as the complex shape of most plastic parts make modelling a challenge. Several examples (film blowing extrusion dies, injection moulding, blow moulding are presented and discussed.

  17. Decoherence of rotational degrees of freedom

    Science.gov (United States)

    Zhong, Changchun; Robicheaux, F.

    2016-11-01

    The mechanism of decoherence for a mesoscopic quantum system with rotational degrees of freedom is studied. From a simple model of elastic scattering, we show that the nondiagonal density-matrix elements of the system exponentially decay. The decay rate depends on the difference of scattering amplitudes for different rotational configurations, leading to the gradual loss of quantum coherence between the pointer states in the orientational space. For a dielectric ellipsoid immersed in a photon-gas environment (assuming no absorption), the decay rate is found to be proportional to the seventh power of the temperature. For an ellipsoidal object interacting with massive particles, the decay rate is proportional to the 5/2 power of the temperature. Both are different from the case of translational decoherence induced by the same environment scattering. For photon scattering, the coherence time in the rotational degrees of freedom is shown to be much shorter than that in the translational degrees of freedom.

  18. Quantum Computation in Brain Microtubules? Decoherence and Biological Feasibility

    CERN Document Server

    Hagan, S; Tuszynski, J A

    2000-01-01

    The Penrose-Hameroff (`Orch OR') model of quantum computation in brain microtubules has been criticized as regards the issue of environmental decoherence. A recent report by Tegmark finds that microtubules can maintain quantum coherence for only $10^{-13}$ s, far too short to be neurophysiologically relevant. Here, we critically examine the assumptions behind Tegmark's calculation and find that: 1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the `Orch OR' theory with a soliton in superposition along the microtubule, 2) Tegmark predicts decreasing decoherence times at lower temperature, in direct contradiction of the observed behavior of quantum states, 3) recalculation after correcting Tegmark's equation for differences between his model and the `Orch OR' model (superposition separation, charge vs. dipole, dielectric constant) lengthens the decoherence time to $10^{-5} - 10^{-4}$ s and invalidates a criti...

  19. Decoherent Histories and Hydrodynamic Equations

    CERN Document Server

    Halliwell, J J

    1998-01-01

    For a system consisting of a large collection of particles, a set of variables that will generally become effectively classical are the local densities (number, momentum, energy). That is, in the context of the decoherent histories approach to quantum theory, it is expected that histories of these variables will be approximately decoherent, and that their probabilites will be strongly peaked about hydrodynamic equations. This possibility is explored for the case of the diffusion of the number density of a dilute concentration of foreign particles in a fluid. It is shown that, for certain physically reasonable initial states, the probabilities for histories of number density are strongly peaked about evolution according to the diffusion equation. Decoherence of these histories is also shown for a class of initial states which includes non-trivial superpositions of number density. Histories of phase space densities are also discussed. The case of histories of number, momentum and energy density for more general...

  20. Decoherence delays false vacuum decay

    Science.gov (United States)

    Bachlechner, Thomas C.

    2013-05-01

    We show that gravitational interactions between massless thermal modes and a nucleating Coleman-de Luccia bubble may lead to efficient decoherence and strongly suppress metastable vacuum decay for bubbles that are small compared to the Hubble radius. The vacuum decay rate including gravity and thermal photon interactions has the exponential scaling \\Gamma \\sim \\Gamma _{CDL}^{2}, where ΓCDL is the Coleman-de Luccia decay rate neglecting photon interactions. For the lowest metastable initial state an efficient quantum Zeno effect occurs due to thermal radiation of temperatures as low as the de Sitter temperature. This strong decoherence effect is a consequence of gravitational interactions with light external mode. We argue that efficient decoherence does not occur for the case of Hawking-Moss decay. This observation is consistent with requirements set by Poincaré recurrence in de Sitter space.

  1. Decoherence delays false vacuum decay

    CERN Document Server

    Bachlechner, Thomas C

    2012-01-01

    We show that gravitational interactions between thermal de Sitter photons and a nucleating Coleman-de Luccia bubble lead to efficient decoherence and strongly suppress metastable vacuum decay for bubbles that are small compared to the Hubble radius. The vacuum decay rate including gravity and photon interactions has the exponential scaling $\\Gamma\\sim \\Gamma_{0}^{2}$, where $\\Gamma_{0}$ is the Coleman-de Luccia decay rate neglecting photon interactions. This strong decoherence effect is a generic consequence of gravitational interactions with light external modes. We argue that efficient decoherence does not occur for the case of Hawking-Moss decay. This observation is consistent with requirements set by Poincare recurrence in de Sitter space.

  2. Decoherence in chaotic and integrable systems: a random matrix approach

    Science.gov (United States)

    Gorin, T.; Seligman, T. H.

    2003-03-01

    We study the influence of chaos and order on entanglement and decoherence. In view of applications in quantum computing and teleportation which should be able to work with arbitrarily complicated states, we pay particular attention to the behavior of random states. While studies with coherent states indicate that chaos accelerates decoherence and entanglement, we find that there is practically no difference between the chaotic and the integrable case, as far as random states are concerned. In the present studies we use unitary time evolution of the total system, and partial traces to emulate decoherence. Random matrix models are a natural choice to describe the dynamics of random states. The invariant aspects of chaos and order are then reflected in the different spectral statistics. We develop random matrix models for the evolution of entanglement for a large variety of situations, discussing the strong coupling case in full detail.

  3. Decoherence in chaotic and integrable systems: a random matrix approach

    Energy Technology Data Exchange (ETDEWEB)

    Gorin, T.; Seligman, T.H

    2003-03-17

    We study the influence of chaos and order on entanglement and decoherence. In view of applications in quantum computing and teleportation which should be able to work with arbitrarily complicated states, we pay particular attention to the behavior of random states. While studies with coherent states indicate that chaos accelerates decoherence and entanglement, we find that there is practically no difference between the chaotic and the integrable case, as far as random states are concerned. In the present studies we use unitary time evolution of the total system, and partial traces to emulate decoherence. Random matrix models are a natural choice to describe the dynamics of random states. The invariant aspects of chaos and order are then reflected in the different spectral statistics. We develop random matrix models for the evolution of entanglement for a large variety of situations, discussing the strong coupling case in full detail.

  4. Decoherence in quantum spin systems

    NARCIS (Netherlands)

    De Raedt, H; Dobrovitski, VV; Landau, DP; Lewis, SP; Schuttler, HB

    2003-01-01

    Computer simulations of decoherence in quantum spin systems require the solution of the time-dependent Schrodinger equation for interacting quantum spin systems over extended periods of time. We use exact diagonalization, the Chebyshev polynomial technique, four Suzuki-formula algorithms, and the sh

  5. Decoherence and Zeno time in quantum computations

    CERN Document Server

    Antoniou, I; Pronko, G; Yarevsky, E

    2003-01-01

    We analyze the short-time behaviour of the survival probability in the frame of the Friedrichs model for different form factors. We have shown that the probability may not be quadratic for the short times while the quantum Zeno effect (QZE) still exists in this case. We have found that the time when the QZE could be observed is much smaller than usually assumed. We have studied the anti-Zeno era and have estimated its duration. Related decoherence processes are also discussed.

  6. A random matrix approach to decoherence

    Energy Technology Data Exchange (ETDEWEB)

    Gorin, T [Theoretische Quantendynamik, Fakutaet fuer Physik, Universitaet Freiburg, Hermann-Herder-Strasse 3 D-79104 (Germany); Seligman, T H [Centro de Ciencias Fisicas, University of Mexico (UNAM), Avenida Universidad s/n, CP 62210 Cuernavaca (Mexico)

    2002-08-01

    In order to analyse the effect of chaos or order on the rate of decoherence in a subsystem, we aim to distinguish the effects of the two types of dynamics by choosing initial states as random product states from two factor spaces representing two subsystems. We introduce a random matrix model that allows us to vary the coupling strength between the subsystems. The case of strong coupling is analysed in detail, and we find no significant differences except for very low-dimensional spaces.

  7. Interaction-induced decoherence of atomic BLOCH oscillations.

    Science.gov (United States)

    Buchleitner, Andreas; Kolovsky, Andrey R

    2003-12-19

    We show that the energy spectrum of the Bose-Hubbard model amended by a static field exhibits Wigner-Dyson level statistics. In itself a characteristic signature of quantum chaos, this induces the irreversible decay of Bloch oscillations of cold, interacting atoms loaded into an optical lattice, and provides a Hamiltonian model for interaction-induced decoherence.

  8. Quantum Field Theory and Decoherence in the Early Universe

    Science.gov (United States)

    Koksma, J. F.

    2011-06-01

    Quantum field theory is indispensable for understanding many aspects of cosmology, both in the early Universe and today. For example, quantum processes could be paramount to understand the nature of the mysterious dark energy resulting in the Universe’s recently observed accelerated expansion. Inspired by these considerations, this PhD thesis is concerned with two aspects of quantum field theory relevant to cosmology: quantum backreaction and decoherence. Quantum backreaction is a line of research where the impact of quantum fluctuations on the background spacetime geometry in perturbative quantum gravity is investigated. The cosmological constant problem and the process of quantum backreaction are intimately related: quantum backreaction might provide us with a dynamical mechanism to effectively make the cosmological constant almost vanish. We investigate the quantum backreaction of the trace anomaly and of fermions. We find that the trace anomaly does not dynamically influence the effective value of the cosmological constant. We furthermore evaluate the fermion propagator in FLRW spacetimes with constant deceleration. Although the dynamics resulting from the one-loop stress-energy tensor need yet to be investigated, we find that we certainly cannot exclude a significant effect due to the quantum backreaction on the Universe’s expansion. Decoherence is a quantum theory which addresses the quantum-to-classical transition of a particular system. The idea of the decoherence formalism is that a macroscopic system cannot be separated from its environment. The framework of decoherence is widely used, e.g. in quantum computing, black hole physics, inflationary perturbation theory, and in elementary particle physics, such as electroweak baryogenesis models. We formulate a novel “correlator approach” to decoherence: neglecting observationally inaccessible correlators gives rise to an increase in entropy of the system, as perceived by an observer. This is inspired

  9. Emergence of Decoherence as Phenomenon in Quantum Phase Transition

    CERN Document Server

    Quan, H T; Liu, X F; Sun, C P

    2005-01-01

    We consider the intrinsic relation between the appearance of classicality of a quantum system and the occurrence of quantum phase transition (QPT) in the environment surrounding this system, and study in detail the novel mechanism of quantum decoherence based on QPT with a generalized Hepp-Coleman model where the quantum system is a two level system and the environment is the Ising spin chain interacting with the quantum system. It is discovered that, the quantum decoherence of the quantum system can be accompanied by the quantum critical phenomenon induced by the effective transverse back-action of the quantum system on the environment.

  10. Decoherence in Field Theory General Couplings and Slow Quenches

    CERN Document Server

    Lombardo, F C; Rivers, R J

    2003-01-01

    We study the onset of a classical order parameter after a second-order phase transition in quantum field theory. We consider a quantum scalar field theory in which the system-field (long-wavelength modes), interacts with its environment, represented both by a set of scalar fields and by its own short-wavelength modes. We compute the decoherence times for the system-field modes and compare them with the other time scales of the model. We analyze different couplings between the system and the environment for both instantaneous and slow quenches. Within our approximations decoherence is in general a short time event.

  11. Decoherence of an $n$-qubit quantum memory

    CERN Document Server

    Gorin, T; Seligman, T H; Gorin, Thomas; Pineda, Carlos; Seligman, Thomas H.

    2007-01-01

    We analyze decoherence of a quantum register in the absence of non-local operations i.e. of $n$ non-interacting qubits coupled to an environment. The problem is solved in terms of a sum rule which implies linear scaling in the number of qubits. Each term involves a single qubit and its entanglement with the remaining ones. Two conditions are essential: first decoherence must be small and second the coupling of different qubits must be uncorrelated in the interaction picture. We apply the result to a random matrix model, and illustrate its reach considering a GHZ state coupled to a spin bath.

  12. Decoherence of an n-Qubit Quantum Memory

    Science.gov (United States)

    Gorin, Thomas; Pineda, Carlos; Seligman, Thomas H.

    2007-12-01

    We analyze decoherence of a quantum register in the absence of nonlocal operations, i.e., n noninteracting qubits coupled to an environment. The problem is solved in terms of a sum rule which implies linear scaling in the number of qubits. Each term involves a single qubit and its entanglement with the remaining ones. Two conditions are essential: first, decoherence must be small, and second, the coupling of different qubits must be uncorrelated in the interaction picture. We apply the result to a random matrix model, and illustrate its reach considering a Greenberger-Horne-Zeilinger state coupled to a spin bath.

  13. Time dilation in quantum systems and decoherence

    Science.gov (United States)

    Pikovski, Igor; Zych, Magdalena; Costa, Fabio; Brukner, Časlav

    2017-02-01

    Both quantum mechanics and general relativity are based on principles that defy our daily intuitions, such as time dilation, quantum interference and entanglement. Because the regimes where the two theories are typically tested are widely separated, their foundational principles are rarely jointly studied. Recent works have found that novel phenomena appear for quantum particles with an internal structure in the presence of time dilation, which can take place at low energies and in weak gravitational fields. Here we briefly review the effects of time dilation on quantum interference and generalize the results to a variety of systems. In addition, we provide an extended study of the basic principles of quantum theory and relativity that are of relevance for the effects and also address several questions that have been raised, such as the description in different reference frames, the role of the equivalence principle and the effective irreversibility of the decoherence. The manuscript clarifies some of the counterintuitive aspects arising when quantum phenomena and general relativistic effects are jointly considered.

  14. A Master Equation for Gravitational Decoherence: Probing the Textures of Spacetime

    CERN Document Server

    Anastopoulos, C

    2013-01-01

    We give a first principles derivation of a master equation for the evolution of a quantum matter field in a linearly perturbed Minkowski spacetime, based solely on quantum field theory and general relativity. We make no additional assumptions nor introduce extra ingredients, as is often done in alternative quantum theories. When the quantum matter field is projected to a one-particle state, the master equation for a non-relativistic quantum particle in a weak gravitational field predicts decoherence in the momentum basis, in contrast to most existing theories of gravitational decoherence. We point out the gauge nature of time and space reparameterizations in matter-gravity couplings, and warn that `intrinsic' decoherence or alternative quantum theories invoking stochastic dynamics arising from temporal or spatial fluctuations violate this fundamental symmetry of classical general relativity. Interestingly we find that the decoherence rate depends on extra parameters other than the Planck scale, an important f...

  15. Creation of unstable particles and decoherence in semiclassical cosmology

    CERN Document Server

    Castagnino, M A; Lombardo, F C; Castagnino, Mario; Landau, Susana; Lombardo, Fernando C.

    1999-01-01

    We consider a simple cosmological model in order to show the importance of unstable particle creation for the validity of the semiclassical approximation. Using the mathematical structure of rigged Hilbert spaces we show that particle creation is the seed of decoherence which enables the quantum to classical transition.

  16. Decoherence control in different environments

    CERN Document Server

    Paavola, Janika

    2010-01-01

    We investigate two techniques for controlling decoherence, focusing on the crucial role played by the environmental spectrum. We show how environments with different spectra lead to very different dynamical behaviours. Our study clearly proves that such differences must be taken into account when designing decoherence control schemes. The two techniques we consider are reservoir engineering and quantum-Zeno control. We focus on a quantum harmonic oscillator initially prepared in a nonclassical state and derive analytically its non-Markovian dynamics in presence of different bosonic thermal environments. On the one hand we show how, by modifying the spectrum of the environment, it is possible to prolong or reduce the life of a Schr\\"odinger cat state. On the other hand we study the effect of nonselective energy measurements on the degradation of quantumness of initial Fock states. In this latter case we see that the crossover between Zeno (QZE) and anti-Zeno (AZE) effects, discussed by Maniscalco et al. [Phys....

  17. Quantum simulation with natural decoherence

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, C. H. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Somaroo, S. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Sharf, Y. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Knill, E. [Theoretical Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87455 (United States); Laflamme, R. [Theoretical Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87455 (United States); Havel, T. F. [BCMP Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115 (United States); Cory, D. G. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2000-09-01

    A quantum system may be efficiently simulated by a quantum information processor as suggested by Feynman and developed by Lloyd, Wiesner, and Zalka. Within the limits of the experimental implementation, simulation permits the design and control of the kinematic and dynamic parameters of a quantum system. Extension to the inclusion of the effects of decoherence, if approached from a full quantum-mechanical treatment of the system and the environment, or from a semiclassical fluctuating field treatment (Langevin), requires the difficult access to dynamics on the time scale of the environment correlation time. Alternatively, a quantum-statistical approach may be taken which exploits the natural decoherence of the experimental system, and requires a more modest control of the dynamics. This is illustrated for quantum simulations of a four-level quantum system by a two-spin NMR ensemble quantum information processor. (c) 2000 The American Physical Society.

  18. Decoherence, Control, and Symmetry in Quantum Computers

    CERN Document Server

    Bacon, D J

    2003-01-01

    In this thesis we describe methods for avoiding the detrimental effects of decoherence while at the same time still allowing for computation of the quantum information. The philosophy of the method discussed in the first part of this thesis is to use a symmetry of the decoherence mechanism to find robust encodings of the quantum information. Stability, control, and methods for using decoherence-free information in a quantum computer are presented with a specific emphasis on decoherence due to a collective coupling between the system and its environment. Universal quantum computation on such collective decoherence decoherence-free encodings is demonstrated. Rigorous definitions of control and the use of encoded universality in quantum computers are addressed. Explicit gate constructions for encoded universality on ion trap and exchange based quantum computers are given. In the second part of the thesis we examine physical systems with error correcting properties. We examine systems that can store quantum infor...

  19. Decoherence of the Unruh detector

    CERN Document Server

    Demers, G

    1995-01-01

    As it is well known, the Minkowski vacuum appears thermally populated to a quantum mechanical detector on a uniformly accelerating course. We investigate how this thermal radiation may contribute to the classical nature of the detector's trajectory through the criteria of decoherence. An uncertainty-type relation is obtained for the detector involving the fluctuation in temperature, the time of flight and the coupling to the bath.

  20. Decoherence delays false vacuum decay

    OpenAIRE

    Bachlechner, Thomas C.

    2012-01-01

    We show that gravitational interactions between massless thermal modes and a nucleating Coleman-de Luccia bubble may lead to efficient decoherence and strongly suppress metastable vacuum decay for bubbles that are small compared to the Hubble radius. The vacuum decay rate including gravity and thermal photon interactions has the exponential scaling $\\Gamma\\sim\\Gamma_{CDL}^{2}$, where $\\Gamma_{CDL}$ is the Coleman-de Luccia decay rate neglecting photon interactions. For the lowest metastable i...

  1. First principles model of carbonate compaction creep

    Science.gov (United States)

    Keszthelyi, Daniel; Dysthe, Dag Kristian; Jamtveit, Bjørn

    2016-05-01

    Rocks under compressional stress conditions are subject to long-term creep deformation. From first principles we develop a simple micromechanical model of creep in rocks under compressional stress that combines microscopic fracturing and pressure solution. This model was then upscaled by a statistical mechanical approach to predict strain rate at core and reservoir scale. The model uses no fitting parameter and has few input parameters: effective stress, temperature, water saturation porosity, and material parameters. Material parameters are porosity, pore size distribution, Young's modulus, interfacial energy of wet calcite, the dissolution, and precipitation rates of calcite, and the diffusion rate of calcium carbonate, all of which are independently measurable without performing any type of deformation or creep test. Existing long-term creep experiments were used to test the model which successfully predicts the magnitude of the resulting strain rate under very different effective stress, temperature, and water saturation conditions. The model was used to predict the observed compaction of a producing chalk reservoir.

  2. Insights: Simple Models for Teaching Equilibrium and Le Chatelier's Principle.

    Science.gov (United States)

    Russell, Joan M.

    1988-01-01

    Presents three models that have been effective for teaching chemical equilibrium and Le Chatelier's principle: (1) the liquid transfer model, (2) the fish model, and (3) the teeter-totter model. Explains each model and its relation to Le Chatelier's principle. (MVL)

  3. Safeguards First Principle Initiative (SFPI) Cost Model

    Energy Technology Data Exchange (ETDEWEB)

    Mary Alice Price

    2010-07-11

    The Nevada Test Site (NTS) began operating Material Control and Accountability (MC&A) under the Safeguards First Principle Initiative (SFPI), a risk-based and cost-effective program, in December 2006. The NTS SFPI Comprehensive Assessment of Safeguards Systems (COMPASS) Model is made up of specific elements (MC&A plan, graded safeguards, accounting systems, measurements, containment, surveillance, physical inventories, shipper/receiver differences, assessments/performance tests) and various sub-elements, which are each assigned effectiveness and contribution factors that when weighted and rated reflect the health of the MC&A program. The MC&A Cost Model, using an Excel workbook, calculates budget and/or actual costs using these same elements/sub-elements resulting in total costs and effectiveness costs per element/sub-element. These calculations allow management to identify how costs are distributed for each element/sub-element. The Cost Model, as part of the SFPI program review process, enables management to determine if spending is appropriate for each element/sub-element.

  4. Electron Spin Dephasing and Decoherence by Interaction with Nuclear Spins in Self-Assembled Quantum Dots

    Science.gov (United States)

    Lee, Seungwon; vonAllmen, Paul; Oyafuso, Fabiano; Klimeck, Gerhard; Whale, K. Birgitta

    2004-01-01

    Electron spin dephasing and decoherence by its interaction with nuclear spins in self-assembled quantum dots are investigated in the framework of the empirical tight-binding model. Electron spin dephasing in an ensemble of dots is induced by the inhomogeneous precession frequencies of the electron among dots, while electron spin decoherence in a single dot arises from the inhomogeneous precession frequencies of nuclear spins in the dot. For In(x)Ga(1-x) As self-assembled dots containing 30000 nuclei, the dephasing and decoherence times are predicted to be on the order of 100 ps and 1 (micro)s.

  5. Modelling subset multivariate ARCH model via the AIC principle

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this paper we consider the problem of identifying a parsimonious subset multivariate ARCH model based on the AIC principle. The proposed approach can reduce the number of parameters in the final ARCH specification and allows for non-constant correlations between the components. Some simulation results illustrate the viability of the proposed procedure.

  6. Decoherence due to gravitational time dilation: Analysis of competing decoherence effects

    Energy Technology Data Exchange (ETDEWEB)

    Carlesso, Matteo, E-mail: matteo.carlesso@ts.infn.it [Department of Physics, University of Trieste, Strada Costiera 11, 34151 Trieste (Italy); Istituto Nazionale di Fisica Nucleare, Trieste Section, Via Valerio 2, 34127 Trieste (Italy); Bassi, Angelo, E-mail: bassi@ts.infn.it [Department of Physics, University of Trieste, Strada Costiera 11, 34151 Trieste (Italy); Istituto Nazionale di Fisica Nucleare, Trieste Section, Via Valerio 2, 34127 Trieste (Italy)

    2016-07-15

    Recently, a static gravitational field, such as that of the Earth, was proposed as a new source of decoherence [1]. We study the conditions under which it becomes the dominant decoherence effect in typical interferometric experiments. The following competing sources are considered: spontaneous emission of light, absorption, scattering with the thermal photons and collisions with the residual gas. We quantify all these effects. As we will see, current experiments are off by several orders of magnitude. New ideas are needed in order to achieve the necessary requirements: having as large a system as possible, to increase gravitational decoherence, cool it and isolate well enough to reduce thermal and collisional decoherence, and resolve very small distances. - Highlights: • Debye's heat capacity is used at low temperatures. • Collisional decoherence is taken into account. • Gravitational decoherence is quantified against other competing decoherence effects.

  7. Decoherence and damping in ideal gases

    OpenAIRE

    Polonyi, Janos

    2010-01-01

    The particle and current densities are shown to display damping and undergo decoherence in ideal quantum gases. The damping is read off from the equations of motion reminiscent of the Navier-Stokes equations and shows some formal similarity with Landau damping. The decoherence leads to consistent density and current histories with characteristic length and time scales given by the ideal gas.

  8. Decoherence at constant excitation

    Science.gov (United States)

    Torres, J. M.; Sadurní, E.; Seligman, T. H.

    2012-02-01

    We present a simple exactly solvable extension of the Jaynes-Cummings model by adding dissipation. This is done such that the total number of excitations is conserved. The Liouville operator in the resulting master equation can be reduced to blocks of 4×4 matrices.

  9. Decoherence at constant excitation

    CERN Document Server

    Torres, Juan Mauricio; Seligman, Thomas H

    2011-01-01

    We present a simple exactly solvable extension of of the Jaynes-Cummings model by adding dissipation. This is done such that the total number of excitations is conserved. The Liouville operator in the resulting master equation can be reduced to blocks of $4\\times 4$ matrices.

  10. Probability, Arrow of Time and Decoherence

    CERN Document Server

    Bacciagaluppi, G

    2007-01-01

    This paper relates both to the metaphysics of probability and to the physics of time asymmetry. Using the formalism of decoherent histories, it investigates whether intuitions about intrinsic time directedness that are often associated with probability can be justified in the context of no-collapse approaches to quantum mechanics. The standard (two-vector) approach to time symmetry in the decoherent histories literature is criticised, and an alternative approach is proposed, based on two decoherence conditions ('forwards' and 'backwards') within the one-vector formalism. In turn, considerations of forwards and backwards decoherence and of decoherence and recoherence suggest that a time-directed interpretation of probabilities, if adopted, should be both contingent and perspectival.

  11. Decoherence at absolute zero

    OpenAIRE

    Sinha, Supurna

    2005-01-01

    We present an analytical study of the loss of quantum coherence at absolute zero. Our model consists of a harmonic oscillator coupled to an environment of harmonic oscillators at absolute zero. We find that for an Ohmic bath, the offdiagonal elements of the density matrix in the position representation decay as a power law in time at late times. This slow loss of coherence in the quantum domain is qualitatively different from the exponential decay observed in studies of high temperature envir...

  12. Suppression of decoherence by bath ordering

    Institute of Scientific and Technical Information of China (English)

    Jing Jun; Ma Hong-Ru

    2007-01-01

    The dynamics of two coupled spins-1/2 coupled to a spin-bath is studied as an extended model of the TessieriWilkie Hamiltonian. The pair of spins served as an open subsystem is prepared in one of the Bell states and the bath consisting of some spins-1/2 is in a thermal equilibrium state from the very beginning. It is found that with increasing coupling strength of the bath spins, the bath forms a resonant antiferromagnetic order. The polarization correlation between the two spins of the subsystem and the concurrence of it are recovered to some extent in the isolated subsystem. This suppression of the subsystem decoherence may be used to control the quantum devices in practical applications.

  13. Self-gravitating Interferometry and Intrinsic Decoherence

    CERN Document Server

    Gooding, Cisco

    2014-01-01

    To investigate the possibility that intrinsic gravitational decoherence can be theoretically demonstrated within canonical quantum gravity, we develop a model of a self-gravitating interferometer. We search for evidence in the resulting interference pattern that would indicate coherence is fundamentally limited due to general relativistic effects. To eliminate the occurence of gravitational waves, we work in spherical symmetry, and construct the "beam" of the interferometer out of WKB states for an infinitesimally thin shell of matter. For internal consistency, we encode information about the beam optics within the dynamics of the shell itself, by arranging an ideal fluid on the surface of the shell with an equation of state that enforces beam-splitting and reflections. We then determine sufficient conditions for (interferometric) coherence to be fully present even after general relativistic corrections are introduced, test whether or not they can be satisfied, and remark on the implications of the results.

  14. CPT Violation and Decoherence in Quantum Gravity

    CERN Document Server

    Mavromatos, Nick E

    2009-01-01

    In this brief review I discuss ways and tests of CPT-Violation in the context of quantum gravity theories with space-time foam vacua, which entail quantum decoherence of matter propagating in such backgrounds. I cover a wide variety of sensitive probes, ranging from cosmic neutrinos to meson factories. I pay particular emphasis on associating the latter with specific, probably unique ("smoking-gun"), effects of this type of CPT Violation, related to a modification of Einstein-Podolsky-Rosen (EPR) correlations in the entangled states of the relevant neutral mesons. I also present some semi-microscopic estimates of these latter effects, in the context of a specific string-inspired model of space-time foam ("D-particle foam").

  15. Intrinsic Decoherence on Two-Qubit Heisenberg ⅩⅩ Chain

    Institute of Scientific and Technical Information of China (English)

    HE Zheng-Hong; XIONG Zu-Hong; HU Dong-Mei

    2007-01-01

    Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg ⅩⅩ chain in an external uniform magnetic field as resources in the model of Milburn's intrinsic decoherence. Though intrinsic decoherence on quantum entanglement and quantum teleportation exerts different effects in different initial systems,proper magnetic fields and probabilities of different eigenstates in the initial states can weaken the effects.

  16. Influence of Intrinsic Decoherence on Entanglement in Two-Qubit Quantum Heisenberg XYZ Chain

    Institute of Scientific and Technical Information of China (English)

    SHAO Bin; ZENG Tian-Hai; ZOU Jian

    2005-01-01

    Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.

  17. The decoherence of quantum entanglement and teleportation in Bell-diagonal states

    Institute of Scientific and Technical Information of China (English)

    QIN Meng; LI Yan-Biao; WANG Xiao; BAI Zhong

    2012-01-01

    We study the dynamics of entanglement and teleportation in Bell-diagonal states. Using the concepts of concurrence and fidelity,the analytical expressions of the entanglement,the output entanglement and the average fidelity with decoherence are obtained for this model.We discover a class of initial states in which the output entanglement and the average fidelity are destroyed by decoherence. The quality of teleportation depends on the system parameters and time.

  18. A reservoir for inverse power law decoherence of a qubit

    CERN Document Server

    Giraldi, Filippo

    2010-01-01

    The exact dynamics of a Jaynes-Cummings model for a qubit interacting with a continuous distribution of bosons, characterized by a special form of the spectral density, is evaluated analytically. The special reservoir is designed to induce anomalous decoherence, resulting in an inverse power law relaxation, of power $3/2$, over an evaluated long time scale. If compared to the exponential-like relaxation obtained from the original Jaynes-Cummings model for Lorentzian-type spectral density functions, decoherence is strongly suppressed. The special reservoir exhibits an upper band edge frequency coinciding with the qubit transition frequency. Known theoretical models of photonic band gap media suitable for the realization of the designed reservoir are proposed.

  19. Robust control of decoherence in realistic one-qubit quantum gates

    CERN Document Server

    Protopopescu, V; D'Helon, C; Schmulen, J

    2003-01-01

    We present an open-loop (bang-bang) scheme to control decoherence in a generic one-qubit quantum gate and implement it in a realistic simulation. The system is consistently described within the spin-boson model, with interactions accounting for both adiabatic and thermal decoherence. The external control is included from the beginning in the Hamiltonian as an independent interaction term. After tracing out the environment modes, reduced equations are obtained for the two-level system in which the effects of both decoherence and external control appear explicitly. The controls are determined exactly from the condition to eliminate decoherence, i.e. to restore unitarity. Numerical simulations show excellent performance and robustness of the proposed control scheme.

  20. Decoherence as a way to measure extremely soft collisions with Dark Matter

    CERN Document Server

    Riedel, C Jess

    2016-01-01

    A new frontier in the search for dark matter (DM) is based on the idea of detecting the decoherence caused by DM scattering against a mesoscopic superposition of normal matter. Such superpositions are uniquely sensitive to very small momentum transfers from new particles and forces, especially DM with a mass below 100 MeV. Here we investigate what sorts of dark sectors are inaccessible with existing methods but would induce noticeable decoherence in the next generation of matter interferometers. We show that very soft, but medium range (0.1 nm - 1 {\\mu}m) elastic interactions between matter and DM are particularly suitable. We construct toy models for such interactions, discuss existing constraints, and delineate the expected sensitivity of forthcoming experiments. The first hints of DM in these devices would appear as small variations in the anomalous decoherence rate with a period of one sidereal day. This is a generic signature of interstellar sources of decoherence, clearly distinguishing it from terrestr...

  1. Declarative business process modelling: principles and modelling languages

    Science.gov (United States)

    Goedertier, Stijn; Vanthienen, Jan; Caron, Filip

    2015-02-01

    The business process literature has proposed a multitude of business process modelling approaches or paradigms, each in response to a different business process type with a unique set of requirements. Two polar paradigms, i.e. the imperative and the declarative paradigm, appear to define the extreme positions on the paradigm spectrum. While imperative approaches focus on explicitly defining how an organisational goal should be reached, the declarative approaches focus on the directives, policies and regulations restricting the potential ways to achieve the organisational goal. In between, a variety of hybrid-paradigms can be distinguished, e.g. the advanced and adaptive case management. This article focuses on the less-exposed declarative approach on process modelling. An outline of the declarative process modelling and the modelling approaches is presented, followed by an overview of the observed declarative process modelling principles and an evaluation of the declarative process modelling approaches.

  2. A master equation for gravitational decoherence: probing the textures of spacetime

    Science.gov (United States)

    Anastopoulos, C.; Hu, B. L.

    2013-08-01

    We give a first principles derivation of a master equation for the evolution of a quantum matter field in a linearly perturbed Minkowski spacetime, based solely on quantum field theory and general relativity. We make no additional assumptions nor introduce extra ingredients, as is often done in alternative quantum theories. When the quantum matter field is projected to a one-particle state, the master equation for a non-relativistic quantum particle in a weak gravitational field predicts decoherence in the energy basis, in contrast to most existing theories of gravitational decoherence. We point out the gauge nature of time and space reparameterizations in matter-gravity couplings, and warn that ‘intrinsic’ decoherence or alternative quantum theories invoking stochastic dynamics arising from temporal or spatial fluctuations violate this fundamental symmetry of classical general relativity. Interestingly we find that the decoherence rate depends on extra parameters other than the Planck scale, an important feature of gravitational decoherence. This is similar to the dependence of the decoherence rate of a quantum Brownian particle to the temperature and spectral density of the environment it interacts with. The corresponding features when gravity acts as an environment in decohering quantum objects are what we call the ‘textures’ of spacetime. We point out the marked difference between the case when gravity is represented as a background spacetime versus the case when gravity acts like a thermodynamic bath to quantum particles. This points to the possibility of using gravitational decoherence measurements to discern whether gravity is intrinsically elemental or emergent.

  3. Decoherence can relax cosmic acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Markkanen, Tommi [Department of Physics, King’s College London,Strand, London WC2R 2LS (United Kingdom)

    2016-11-11

    In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.

  4. Decoherence Can Relax Cosmic Acceleration

    CERN Document Server

    Markkanen, Tommi

    2016-01-01

    In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the environment decoheres the system into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.

  5. Decoherence Time of a Microtubule

    CERN Document Server

    Hiramatsu, T; Sakakibara, K; Hiramatsu, Takashi; Matsui, Tetsuo; Sakakibara, Kazuhiko

    2006-01-01

    We formulate and study a quantum field theory of a microtubule, a basic element of living cells. Following the quantum theory of consciousness by Hameroff and Penrose, we let the system to make self-reductions, and measure the decoherence time $\\tau_N$ (the mean interval between two successive reductions) of a cluster consisting of more than $N$ neighboring cells (tubulins). $\\tau_N$ is interpreted as an instance of the stream of consciousness. For a sufficiently small electron hopping amplitude, $\\tau_N$ obeys an exponential law, $\\tau_N \\sim \\exp(c' N)$, and may take realistic values $\\tau_N $ \\raisebox{-0.5ex} {$\\stackrel{>}{\\sim}$} $ 10^{-2}$ sec for $N \\raisebox{-0.5ex} {$\\stackrel{>}{\\sim}$} 1100$.

  6. Decoherence can relax cosmic acceleration

    Science.gov (United States)

    Markkanen, Tommi

    2016-11-01

    In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.

  7. Dynamics and decoherence of a single spin-qubit in a tunable environment

    CERN Document Server

    Ratschbacher, L; Carcagni, L; Silver, J M; Zipkes, C; Köhl, M

    2013-01-01

    We report on the immersion of a spin-qubit encoded in a single trapped ion into a spin-polarized neutral atom environment, which possesses both continuous (motional) and discrete (spin) degrees of freedom. The environment is widely tunable and offers the possibility of a precise microscopic description, both of which allows us to understand dynamics and decoherence from first principles. We observe the spin dynamics of the qubit and measure the decoherence times (T1 and T2), which are determined by the spin-exchange interaction as well as by an unexpectedly strong spin-nonconserving coupling mechanism.

  8. The Real and the Mathematical in Quantum Modeling: From Principles to Models and from Models to Principles

    Directory of Open Access Journals (Sweden)

    Arkady Plotnitsky

    2017-06-01

    Full Text Available The history of mathematical modeling outside physics has been dominated by the use of classical mathematical models, C-models, primarily those of a probabilistic or statistical nature. More recently, however, quantum mathematical models, Q-models, based in the mathematical formalism of quantum theory have become more prominent in psychology, economics, and decision science. The use of Q-models in these fields remains controversial, in part because it is not entirely clear whether Q-models are necessary for dealing with the phenomena in question or whether C-models would still suffice. My aim, however, is not to assess the necessity of Q-models in these fields, but instead to reflect on what the possible applicability of Q-models may tell us about the corresponding phenomena there, vis-à-vis quantum phenomena in physics. In order to do so, I shall first discuss the key reasons for the use of Q-models in physics. In particular, I shall examine the fundamental principles that led to the development of quantum mechanics. Then I shall consider a possible role of similar principles in using Q-models outside physics. Psychology, economics, and decision science borrow already available Q-models from quantum theory, rather than derive them from their own internal principles, while quantum mechanics was derived from such principles, because there was no readily available mathematical model to handle quantum phenomena, although the mathematics ultimately used in quantum did in fact exist then. I shall argue, however, that the principle perspective on mathematical modeling outside physics might help us to understand better the role of Q-models in these fields and possibly to envision new models, conceptually analogous to but mathematically different from those of quantum theory, that may be helpful or even necessary there or in physics itself. I shall, in closing, suggest one possible type of such models, singularized probabilistic models, SP-models, some

  9. Decoherence of superposition states in trapped ions

    CSIR Research Space (South Africa)

    Uys, H

    2010-09-01

    Full Text Available This paper investigates the decoherence of superpositions of hyperfine states of 9Be+ ions due to spontaneous scattering of off-resonant light. It was found that, contrary to conventional wisdom, elastic Raleigh scattering can have major...

  10. Stability of Pairwise Entanglement in Decoherence Environment

    Institute of Scientific and Technical Information of China (English)

    蔡建明

    2004-01-01

    @@ Consider the dynamics of a bipartite entangled system in the decoherence environment, we investigate the stability of pairwise entanglement under decoherence.We find that with the same initial entanglement, the lifetime of entanglement in pure states and some mixed states is the longest.We call these special entangled states as Decoherence Path States (DPS).Besides, we present simple analytic evolution equations of the entanglement in these states.The lifetimes can also be obtained easily.Furthermore, we also study the stability of the nearest neighbor entanglement in the ground state of an antiferromagnetic spin-1/2 ring.Coincidentally, the conclusion is that it is as stable as Decoherence Path States.Thus the nearest neighbor entanglement in the ground state is not maximized but it is the most stable.This interesting result links the energy and entanglement in a spin system from a new point of view.

  11. SCIENTIFIC PRINCIPLES AND MATHEMATICAL MODELS OF PROCESSES OF MINING

    OpenAIRE

    Kriuchkov, Anatolii Ivanovych

    2016-01-01

    The connection between mathematical models of the mining industry with the basic scientific principles. The method of simulation of random non-stationary processes in the form of a set of Hamilton-Jacobi equations and Fokker-Planck-Kolmogorov using the principle of duality movement of mass in space

  12. Gradient-Diffusion Methods for Simulating Decoherence by NMR Spectroscopy

    CERN Document Server

    Havel, T F; Viola, L; Cory, D G; Havel, Timothy F.; Sharf, Yehuda; Viola, Lorenza; Cory, David G.

    2001-01-01

    Theoretical techniques are developed for designing nuclear magnetic resonance (NMR) experiments to simulate a variety of adiabatic decoherence (aka T_2 relaxation) processes, using sequences of pulsed field gradients and diffusion periods. To this end an efficient Hadamard product formalism is introduced and used to derive Lindblad master equations from NMR pulse sequences for both collective and independent phase damping on any number of spins. The Kraus operator sum form is shown to be related to the Hadamard form by diagonalization, and explicit Lindblad and Kraus operators given for arbitrary correlations between two spins. Finally, gradient-diffusion methods are outlined for more complex forms of decoherence, including the three-axis collective model.

  13. Decoherence and loss of entanglement in acoustic black holes.

    Science.gov (United States)

    Lombardo, Fernando C; Turiaci, Gustavo J

    2012-06-29

    We study the process of decoherence in acoustic black holes. We focus on the ion trap model proposed by Horstmann et al. [Phys. Rev. Lett. 104, 250403 (2010)], but the formalism is general to any experimental implementation. For that particular setup, we compute the decoherence time for the experimental parameters that they proposed. We find that a quantum to classical transition occurs during the measurement, and we propose improved parameters to avoid such a feature. We also study the entanglement between the Hawking-pair phonons for an acoustic black hole while in contact with a reservoir, through the quantum correlations, showing that they remain strongly correlated for small enough times and temperatures.

  14. Radar hydrology principles, models, and applications

    CERN Document Server

    Hong, Yang

    2014-01-01

    ""This is the first book on radar hydrology written by hydrologists. Whereas the excellent knowledge of radar technology by the authors permits an adequate coverage of the principles of rainfall rate estimation by radar, their hydrological background allows them to provide a unique message on the benefits (and on the remaining challenges) in exploiting radar techniques in hydrology. … In a clear and concise manner, the book combines topics from different scientific disciplines into a unified approach aiming to guide the reader through the requirements, strengths, and pitfalls of the applica

  15. Exact master equation and quantum decoherence of two coupled harmonic oscillators in a general environment.

    Science.gov (United States)

    Chou, Chung-Hsien; Yu, Ting; Hu, B L

    2008-01-01

    In this paper we derive an exact master equation for two coupled quantum harmonic oscillators interacting via bilinear coupling with a common environment at arbitrary temperature made up of many harmonic oscillators with a general spectral density function. We first show a simple derivation based on the observation that the two harmonic oscillator model can be effectively mapped into that of a single harmonic oscillator in a general environment plus a free harmonic oscillator. Since the exact one harmonic oscillator master equation is available [B. L. Hu, J. P. Paz, and Y. Zhang, Phys. Rev. D 45, 2843 (1992)], the exact master equation with all its coefficients for this two harmonic oscillator model can be easily deduced from the known results of the single harmonic oscillator case. In the second part we give an influence functional treatment of this model and provide explicit expressions for the evolutionary operator of the reduced density matrix which are useful for the study of decoherence and disentanglement issues. We show three applications of this master equation: on the decoherence and disentanglement of two harmonic oscillators due to their interaction with a common environment under Markovian approximation, and a derivation of the uncertainty principle at finite temperature for a composite object, modeled by two interacting harmonic oscillators. The exact master equation for two, and its generalization to N, harmonic oscillators interacting with a general environment are expected to be useful for the analysis of quantum coherence, entanglement, fluctuations, and dissipation of mesoscopic objects toward the construction of a theoretical framework for macroscopic quantum phenomena.

  16. Maximum-entropy principle as Galerkin modelling paradigm

    Science.gov (United States)

    Noack, Bernd R.; Niven, Robert K.; Rowley, Clarence W.

    2012-11-01

    We show how the empirical Galerkin method, leading e.g. to POD models, can be derived from maximum-entropy principles building on Noack & Niven 2012 JFM. In particular, principles are proposed (1) for the Galerkin expansion, (2) for the Galerkin system identification, and (3) for the probability distribution of the attractor. Examples will illustrate the advantages of the entropic modelling paradigm. Partially supported by the ANR Chair of Excellence TUCOROM and an ADFA/UNSW Visiting Fellowship.

  17. Quantum Error Correction Protects Quantum Search Algorithms Against Decoherence.

    Science.gov (United States)

    Botsinis, Panagiotis; Babar, Zunaira; Alanis, Dimitrios; Chandra, Daryus; Nguyen, Hung; Ng, Soon Xin; Hanzo, Lajos

    2016-12-07

    When quantum computing becomes a wide-spread commercial reality, Quantum Search Algorithms (QSA) and especially Grover's QSA will inevitably be one of their main applications, constituting their cornerstone. Most of the literature assumes that the quantum circuits are free from decoherence. Practically, decoherence will remain unavoidable as is the Gaussian noise of classic circuits imposed by the Brownian motion of electrons, hence it may have to be mitigated. In this contribution, we investigate the effect of quantum noise on the performance of QSAs, in terms of their success probability as a function of the database size to be searched, when decoherence is modelled by depolarizing channels' deleterious effects imposed on the quantum gates. Moreover, we employ quantum error correction codes for limiting the effects of quantum noise and for correcting quantum flips. More specifically, we demonstrate that, when we search for a single solution in a database having 4096 entries using Grover's QSA at an aggressive depolarizing probability of 10(-3), the success probability of the search is 0.22 when no quantum coding is used, which is improved to 0.96 when Steane's quantum error correction code is employed. Finally, apart from Steane's code, the employment of Quantum Bose-Chaudhuri-Hocquenghem (QBCH) codes is also considered.

  18. Quantum Error Correction Protects Quantum Search Algorithms Against Decoherence

    Science.gov (United States)

    Botsinis, Panagiotis; Babar, Zunaira; Alanis, Dimitrios; Chandra, Daryus; Nguyen, Hung; Ng, Soon Xin; Hanzo, Lajos

    2016-12-01

    When quantum computing becomes a wide-spread commercial reality, Quantum Search Algorithms (QSA) and especially Grover’s QSA will inevitably be one of their main applications, constituting their cornerstone. Most of the literature assumes that the quantum circuits are free from decoherence. Practically, decoherence will remain unavoidable as is the Gaussian noise of classic circuits imposed by the Brownian motion of electrons, hence it may have to be mitigated. In this contribution, we investigate the effect of quantum noise on the performance of QSAs, in terms of their success probability as a function of the database size to be searched, when decoherence is modelled by depolarizing channels’ deleterious effects imposed on the quantum gates. Moreover, we employ quantum error correction codes for limiting the effects of quantum noise and for correcting quantum flips. More specifically, we demonstrate that, when we search for a single solution in a database having 4096 entries using Grover’s QSA at an aggressive depolarizing probability of 10-3, the success probability of the search is 0.22 when no quantum coding is used, which is improved to 0.96 when Steane’s quantum error correction code is employed. Finally, apart from Steane’s code, the employment of Quantum Bose-Chaudhuri-Hocquenghem (QBCH) codes is also considered.

  19. THERMODYNAMIC MODELING AND FIRST-PRINCIPLES CALCULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P; Abrikosov, I; Burton, B; Fries, S; Grimvall, G; Kaufman, L; Korzhavyi, P; Manga, R; Ohno, M; Pisch, A; Scott, A; Zhang, W

    2005-12-15

    The increased application of quantum mechanical-based methodologies to the study of alloy stability has required a re-assessment of the field. The focus is mainly on inorganic materials in the solid state. In a first part, after a brief overview of the so-called ab initio methods with their approximations, constraints, and limitations, recommendations are made for a good usage of first-principles codes with a set of qualifiers. Examples are given to illustrate the power and the limitations of ab initio codes. However, despite the ''success'' of these methodologies, thermodynamics of complex multi-component alloys, as used in engineering applications, requires a more versatile approach presently afforded within CALPHAD. Hence, in a second part, the links that presently exist between ab initio methodologies, experiments, and CALPHAD approach are examined with illustrations. Finally, the issues of dynamical instability and of the role of lattice vibrations that still constitute the subject of ample discussions within the CALPHAD community are revisited in the light of the current knowledge with a set of recommendations.

  20. Feynman's Entropy and Decoherence Mechanism

    CERN Document Server

    Kim, Y S

    2000-01-01

    If we reduce coherence in a given quantum system, the result is an increase in entropy. Does this necessarily convert this quantum system into a classical system? The answer to this question is No. The decrease of coherence means more uncertainty. This does not seem to make the system closer to classical system where there are no uncertainties. We examine the problem using two coupled harmonic oscillators where we make observations on one of them while the other oscillator is assumed to be unobservable or to be in Feynman's rest of the universe. Our ignorance about the rest of the universe causes an increase in entropy. However, does the system act like a classical system? The answer is again No. When and how does this system appear like a classical system? It is shown that this paradox can be resolved only if measurements are taken along the normal coordinates. It is also shown that Feynman's parton picture is one concrete physical example of this decoherence mechanism.

  1. Mechanisms of relaxation and spin decoherence in nanomagnets

    Science.gov (United States)

    van Tol, Johan

    Relaxation in spin systems is of great interest with respect to various possible applications like quantum information processing and storage, spintronics, and dynamic nuclear polarization (DNP). The implementation of high frequencies and fields is crucial in the study of systems with large zero-field splitting or large interactions, as for example molecular magnets and low dimensional magnetic materials. Here we will focus on the implementation of pulsed Electron Paramagnetic Resonance (ERP) at multiple frequencies of 10, 95, 120, 240, and 336 GHz, and the relaxation and decoherence processes as a function of magnetic field and temperature. Firstly, at higher frequencies the direct single-phonon spin-lattice relaxation (SLR) is considerably enhanced, and will more often than not be the dominant relaxation mechanism at low temperatures, and can be much faster than at lower fields and frequencies. In principle the measurement of the SLR rates as a function of the frequency provides a means to map the phonon density of states. Secondly, the high electron spin polarization at high fields has a strong influence on the spin fluctuations in relatively concentrated spin systems, and the contribution of the electron-electron dipolar interactions to the coherence rate can be partially quenched at low temperatures. This not only allows the study of relatively concentrated spin systems by pulsed EPR (as for example magnetic nanoparticles and molecular magnets), it enables the separation of the contribution of the fluctuations of the electron spin system from other decoherence mechanisms. Besides choice of temperature and field, several strategies in sample design, pulse sequences, or clock transitions can be employed to extend the coherence time in nanomagnets. A review will be given of the decoherence mechanisms with an attempt at a quantitative comparison of experimental rates with theory.

  2. Action principles for extended magnetohydrodynamic models

    Energy Technology Data Exchange (ETDEWEB)

    Keramidas Charidakos, I.; Lingam, M.; Morrison, P. J.; White, R. L. [Institute for Fusion Studies and Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States); Wurm, A. [Department of Physical and Biological Sciences, Western New England University, Springfield, Massachusetts 01119 (United States)

    2014-09-15

    The general, non-dissipative, two-fluid model in plasma physics is Hamiltonian, but this property is sometimes lost or obscured in the process of deriving simplified (or reduced) two-fluid or one-fluid models from the two-fluid equations of motion. To ensure that the reduced models are Hamiltonian, we start with the general two-fluid action functional, and make all the approximations, changes of variables, and expansions directly within the action context. The resulting equations are then mapped to the Eulerian fluid variables using a novel nonlocal Lagrange-Euler map. Using this method, we recover Lüst's general two-fluid model, extended magnetohydrodynamic (MHD), Hall MHD, and electron MHD from a unified framework. The variational formulation allows us to use Noether's theorem to derive conserved quantities for each symmetry of the action.

  3. Multimodal electromechanical model of piezoelectric transformers by Hamilton's principle.

    Science.gov (United States)

    Nadal, Clement; Pigache, Francois

    2009-11-01

    This work deals with a general energetic approach to establish an accurate electromechanical model of a piezoelectric transformer (PT). Hamilton's principle is used to obtain the equations of motion for free vibrations. The modal characteristics (mass, stiffness, primary and secondary electromechanical conversion factors) are also deduced. Then, to illustrate this general electromechanical method, the variational principle is applied to both homogeneous and nonhomogeneous Rosen-type PT models. A comparison of modal parameters, mechanical displacements, and electrical potentials are presented for both models. Finally, the validity of the electrodynamical model of nonhomogeneous Rosen-type PT is confirmed by a numerical comparison based on a finite elements method and an experimental identification.

  4. Review of Decoherence Free Subspaces, Noiseless Subsystems, and Dynamical Decoupling

    CERN Document Server

    Lidar, Daniel A

    2012-01-01

    Quantum information requires protection from the adverse affects of decoherence and noise. This review provides an introduction to the theory of decoherence-free subspaces, noiseless subsystems, and dynamical decoupling. It addresses quantum information preservation as well protected computation.

  5. Principles and practice of structural equation modeling

    CERN Document Server

    Kline, Rex B

    2015-01-01

    Emphasizing concepts and rationale over mathematical minutiae, this is the most widely used, complete, and accessible structural equation modeling (SEM) text. Continuing the tradition of using real data examples from a variety of disciplines, the significantly revised fourth edition incorporates recent developments such as Pearl's graphing theory and the structural causal model (SCM), measurement invariance, and more. Readers gain a comprehensive understanding of all phases of SEM, from data collection and screening to the interpretation and reporting of the results. Learning is enhanced by ex

  6. Decoherence effects in the Stern-Gerlach experiment using matrix Wigner functions

    Science.gov (United States)

    Gomis, P.; Pérez, A.

    2016-07-01

    We analyze the Stern-Gerlach experiment in phase space with the help of the matrix Wigner function, which includes the spin degree of freedom. Such analysis allows for an intuitive visualization of the quantum dynamics of the device. We include the interaction with the environment, as described by the Caldeira-Leggett model. The diagonal terms of the matrix provide us with information about the two components of the state that arise from interaction with the magnetic field gradient. In particular, from the marginals of these components, we obtain an analytical formula for the position and momentum probability distributions in the presence of decoherence that shows a diffusive behavior for large values of the decoherence parameter. These features limit the dynamics of the present model. We also observe the decay of the nondiagonal terms with time and use this fact to quantify the amount of decoherence from the norm of those terms in phase space. From here, we can define a decoherence time scale, which differs from previous results that make use of the same model. We analyze a typical experiment and show that, for that setup, the decoherence time is much smaller than the characteristic time scale for the separation of the two beams, implying that they can be described as an incoherent mixture of atoms traveling in the up and down directions with opposite values of the spin projection. Therefore, entanglement is quickly destroyed in the setup we analyzed.

  7. Chaos can act as a decoherence suppressor

    CERN Document Server

    Zhang, Jing; Zhang, Wei-Min; Wu, Lian-Ao; Wu, Re-Bing; Tarn, Tzyh-Jong

    2011-01-01

    We propose a strategy to suppress decoherence of a solid-state qubit coupled to non-Markovian noises by attaching the qubit to a chaotic setup with the broad power distribution in particular in the high-frequency domain. Different from the existing decoherence control methods such as the usual dynamics decoupling control, high-frequency components of our control are generated by the chaotic setup driven by a low-frequency field, and the generation of complex optimized control pulses is not necessary. We apply the scheme to superconducting quantum circuits and find that various noises in a wide frequency domain, including low-frequency $1/f$, high-frequency Ohmic, sub-Ohmic, and super-Ohmic noises, can be efficiently suppressed by coupling the qubits to a Duffing oscillator as the chaotic setup. Significantly, the decoherence time of the qubit is prolonged approximately $100$ times in magnitude.

  8. Vibrational Quantum Decoherence in Liquid Water.

    Science.gov (United States)

    Joutsuka, Tatsuya; Thompson, Ward H; Laage, Damien

    2016-02-18

    Traditional descriptions of vibrational energy transfer consider a quantum oscillator interacting with a classical environment. However, a major limitation of this simplified description is the neglect of quantum decoherence induced by the different interactions between two distinct quantum states and their environment, which can strongly affect the predicted energy-transfer rate and vibrational spectra. Here, we use quantum-classical molecular dynamics simulations to determine the vibrational quantum decoherence time for an OH stretch vibration in liquid heavy water. We show that coherence is lost on a sub-100 fs time scale due to the different responses of the first shell neighbors to the ground and excited OH vibrational states. This ultrafast decoherence induces a strong homogeneous contribution to the linear infrared spectrum and suggests that resonant vibrational energy transfer in H2O may be more incoherent than previously thought.

  9. Quantum Gravitational Decoherence of Light and Matter

    CERN Document Server

    Oniga, Teodora

    2015-01-01

    Real world quantum systems are open to perpetual influence from the wider environment. Vacuum gravitational fluctuations provide a most fundamental source of the environmental influence through their universal interactions with all forms of energy and matter causing decoherence. This may have subtle implications on precision laboratory experiments and astronomical observations and could limit the ultimate capacities for quantum technologies prone to decoherence. To establish the essential physical mechanism of decoherence under weak spacetime fluctuations, we carry out a sequence of analytical steps utilizing the Dirac constraint quantization and gauge invariant influence functional techniques, resulting in a general master equation of a compact form, that describes an open quantum gravitational system with arbitrary bosonic fields. An initial application of the theory is illustrated by the implied quantum gravitational dissipation of light as well as (non)relativistic massive or massless scalar particles. Re...

  10. Decoherence as a Probe of Coherent Quantum Dynamics

    CERN Document Server

    D'Arcy, M B; Summy, G S; Guarneri, I; Wimberger, S M; Fishman, S; Buchleitner, A; Arcy, Michael B. d'; Godun, Rachel M.; Summy, Gil S.; Guarneri, Italo; Wimberger, Sandro; Fishman, Shmuel; Buchleitner, Andreas

    2004-01-01

    The effect of decoherence, induced by spontaneous emission, on the dynamics of periodically kicked cold atoms at quantum resonance is experimentally and theoretically studied. We clarify the nature of the coherent evolution, and the way in which decoherence disrupts it, thereby resolving the puzzle of the observed enhancement of the atomic mean energy growth by decoherence [Phys. Rev. Lett. 87, 074102 (2001)].

  11. Long-distance quantum communication. Decoherence-avoiding mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Kolb Bernardes, Nadja

    2012-12-17

    Entanglement is the essence of most quantum information processes. For instance, it is used as a resource for quantum teleportation or perfectly secure classical communication. Unfortunately, inevitable noise in the quantum channel will typically affect the distribution of entanglement. Owing to fundamental principles, common procedures used in classical communication, such as amplification, cannot be applied. Therefore, the fidelity and rate of transmission will be limited by the length of the channel. Quantum repeaters were proposed to avoid the exponential decay with the distance and to permit long-distance quantum communication. Long-distance quantum communication constitutes the framework for the results presented in this thesis. The main question addressed in this thesis is how the performance of quantum repeaters are affected by various sources of decoherence. Moreover, what can be done against decoherence to improve the performance of the repeater. We are especially interested in the so-called hybrid quantum repeater; however, many of the results presented here are sufficiently general and may be applied to other systems as well. First, we present a detailed entanglement generation rate analysis for the quantum repeater. In contrast to what is commonly found in the literature, our analysis is general and analytical. Moreover, various sources of errors are considered, such as imperfect local two-qubit operations and imperfect memories, making it possible to determine the requirements for memory decoherence times. More specifically, we apply our formulae in the context of a hybrid quantum repeater and we show that in a possible experimental scenario, our hybrid system can create near-maximally entangled pairs over a distance of 1280 km at rates of the order of 100 Hz. Furthermore, aiming to protect the system against different types of errors, we analyze the hybrid quantum repeater when supplemented by quantum error correction. We propose a scheme for

  12. Principles of the radiative ablation modeling

    Science.gov (United States)

    Saillard, Yves; Arnault, Philippe; Silvert, Virginie

    2010-12-01

    Indirectly driven inertial confinement fusion (ICF) rests on the setting up of a radiation temperature within a laser cavity and on the optimization of the capsule implosion ablated by this radiation. In both circumstances, the ablation of an optically thick medium is at work. The nonlinear radiation conduction equations that describe this phenomenon admit different kinds of solutions called generically Marshak waves. In this paper, a completely analytic model is proposed to describe the ablation in the subsonic regime relevant to ICF experiments. This model approximates the flow by a deflagrationlike structure where Hugoniot relations are used in the stationary part from the ablation front up to the isothermal sonic Chapman-Jouguet point and where the unstationary expansion from the sonic point up to the external boundary is assumed quasi-isothermal. It uses power law matter properties. It can also accommodate arbitrary boundary conditions provided the ablation wave stays very subsonic and the surface temperature does not vary too quickly. These requirements are often met in realistic situations. Interestingly, the ablated mass rate, the ablation pressure, and the absorbed radiative energy depend on the time history of the surface temperature, not only on the instantaneous temperature values. The results compare very well with self-similar solutions and with numerical simulations obtained by hydrodynamic code. This analytic model gives insight into the physical processes involved in the ablation and is helpful for optimization and sensitivity studies in many situations of interest: radiation temperature within a laser cavity, acceleration of finite size medium, and ICF capsule implosion, for instance.

  13. Tsunami Propagation Models Based on First Principles

    Science.gov (United States)

    2012-11-21

    obstacle and strike land in the shadow regions. Since v h according to Eq. (9), the velocity decreases nearer the coast as the depth decreases. The wave...Earth by the two locations is, from spherical trigonometry ,  1cos sin sin cos cos coss d s d d sθ λ λ λ λ φ φ      (37) The linear...speed of propagation, bending of tsunamis around obstacles and depth of the ocean, among others. Two-dimensional models on flat and spherical ocean

  14. Genetic Algorithms Principles Towards Hidden Markov Model

    Directory of Open Access Journals (Sweden)

    Nabil M. Hewahi

    2011-10-01

    Full Text Available In this paper we propose a general approach based on Genetic Algorithms (GAs to evolve Hidden Markov Models (HMM. The problem appears when experts assign probability values for HMM, they use only some limited inputs. The assigned probability values might not be accurate to serve in other cases related to the same domain. We introduce an approach based on GAs to find
    out the suitable probability values for the HMM to be mostly correct in more cases than what have been used to assign the probability values.

  15. Learning Transfer Principles in a Comprehensive Integration Model

    Science.gov (United States)

    Boitel, Craig; Farkas, Kathleen; Fromm, Laurentine; Hokenstad, M. C.

    2009-01-01

    In this article, the authors propose a comprehensive integration model (CIM) based on learning transfer principles that promote integration by systematically and multidimensionally linking coursework with field education. This model improves the integration of classroom and field instruction by specifying how content in each course and in the…

  16. First principles for financial modeling in medicine.

    Science.gov (United States)

    Lexa, Frank James; Berlin, Jonathan W

    2005-03-01

    This article provides an overview of some of the core issues in business for physicians and is intended as an introduction. No prior understanding of business processes, finance, or accounting will be assumed or expected. The impetus for this work is the changing nature of medical practice in the United States in the past 20 years. Organizational changes and financial pressures challenge those of us in medicine as never before. For the vast majority of physicians, these realms are outside the scope of our traditional training and expertise. This article will provide an introduction to understanding these issues, starting with misconceptions about the overlap between medicine and finance. We will then introduce core concepts of cash vs. revenue, risk and uncertainty, and basic financial modeling.

  17. Decoherence, chaos, the quantum and the classical

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, W.H.; Paz, J.P.

    1994-04-01

    The key ideas of the environment-induced decoherence approach are reviewed. Application of decoherence to the transition from quantum to classical in open quantum systems with chaotic classical analogs is described. The arrow of time is, in this context, a result of the information loss to the correlations with the environment. The asymptotic rate of entropy production (which is reached quickly, on the dynamical timescale) is independent of the details of the coupling of the quantum system to the environment, and is set by the Lyapunov exponents. We also briefly outline the existential interpretation of quantum mechanics, justifying the slogan ``No information without representation.``

  18. Controlled decoherence of floating flux qubits

    Institute of Scientific and Technical Information of China (English)

    Ji Ying-Hua; Xu Lin

    2010-01-01

    In Born-Markov approximation, this paper calculates the energy relaxation time T1 and the decoherence time T2 of a floating flux qubit by solving the set of Bloch-Redfield equations. It shows that there are two main factors influencing the floating flux qubits: coupling capacitor in the circuit and the environment resistor. It also discusses how to improvethe quantum coherence time of a qubit. Through shunt connecting/series connecting inductive elements, an inductive environment resistor is obtained and further the reactance component of the environment resistor is improved, which is beneficial to the enhancement of decoherence time of floating flux qubits.

  19. Dynamical Suppression of Decoherence in Two-Qubit Quantum Memory

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In this paper, we have detailedly studied the dynamical suppression of the phase damping for the two-qubit quantum memory of Ising model by the quantum "bang-bang" technique. We find the sequence of periodic radiofrequency pulses repetitively to flip the state of the two-qubit system and quantitatively find that these pulses can be used to effectively suppress the phase damping decoherence of the quantum memory and freeze the system state into its initial state. The general sequence of periodic radio-frequency pulses to suppress the phase damping of multi-qubit of Ising model is also given.

  20. Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths

    Science.gov (United States)

    Yang, Wen; Ma, Wen-Long; Liu, Ren-Bao

    2017-01-01

    Decoherence of electron spins in nanoscale systems is important to quantum technologies such as quantum information processing and magnetometry. It is also an ideal model problem for studying the crossover between quantum and classical phenomena. At low temperatures or in light-element materials where the spin-orbit coupling is weak, the phonon scattering in nanostructures is less important and the fluctuations of nuclear spins become the dominant decoherence mechanism for electron spins. Since the 1950s, semi-classical noise theories have been developed for understanding electron spin decoherence. In spin-based solid-state quantum technologies, the relevant systems are in the nanometer scale and nuclear spin baths are quantum objects which require a quantum description. Recently, quantum pictures have been established to understand the decoherence and quantum many-body theories have been developed to quantitatively describe this phenomenon. Anomalous quantum effects have been predicted and some have been experimentally confirmed. A systematically truncated cluster-correlation expansion theory has been developed to account for the many-body correlations in nanoscale nuclear spin baths that are built up during electron spin decoherence. The theory has successfully predicted and explained a number of experimental results in a wide range of physical systems. In this review, we will cover this recent progress. The limitations of the present quantum many-body theories and possible directions for future development will also be discussed.

  1. Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths.

    Science.gov (United States)

    Yang, Wen; Ma, Wen-Long; Liu, Ren-Bao

    2017-01-01

    Decoherence of electron spins in nanoscale systems is important to quantum technologies such as quantum information processing and magnetometry. It is also an ideal model problem for studying the crossover between quantum and classical phenomena. At low temperatures or in light-element materials where the spin-orbit coupling is weak, the phonon scattering in nanostructures is less important and the fluctuations of nuclear spins become the dominant decoherence mechanism for electron spins. Since the 1950s, semi-classical noise theories have been developed for understanding electron spin decoherence. In spin-based solid-state quantum technologies, the relevant systems are in the nanometer scale and nuclear spin baths are quantum objects which require a quantum description. Recently, quantum pictures have been established to understand the decoherence and quantum many-body theories have been developed to quantitatively describe this phenomenon. Anomalous quantum effects have been predicted and some have been experimentally confirmed. A systematically truncated cluster-correlation expansion theory has been developed to account for the many-body correlations in nanoscale nuclear spin baths that are built up during electron spin decoherence. The theory has successfully predicted and explained a number of experimental results in a wide range of physical systems. In this review, we will cover this recent progress. The limitations of the present quantum many-body theories and possible directions for future development will also be discussed.

  2. Effect of mutual inductance coupling on superconducting flux qubit decoherence

    Institute of Scientific and Technical Information of China (English)

    Yanyan Jiang; Hualan Xu; Yinghua Ji

    2009-01-01

    In the Born-Markov approximation and two-level approximation, and using the Bloch-Redfield equation, the decoherence property of superconducting quantum circuit with a flux qubit is investigated. The influence on decoherence of the mutual inductance coupling between the circuit components is complicated. The mutual inductance coupling between different loops will decrease the decoherence time. However, the mutual inductance coupling of the same loop, in a certain interval, will increase the decoherence time. Therefore, we can control the decoherence time by changing the mutual inductance parameters such as the strength and direction of coupling.

  3. Optimality principles for model-based prediction of human gait.

    Science.gov (United States)

    Ackermann, Marko; van den Bogert, Antonie J

    2010-04-19

    Although humans have a large repertoire of potential movements, gait patterns tend to be stereotypical and appear to be selected according to optimality principles such as minimal energy. When applied to dynamic musculoskeletal models such optimality principles might be used to predict how a patient's gait adapts to mechanical interventions such as prosthetic devices or surgery. In this paper we study the effects of different performance criteria on predicted gait patterns using a 2D musculoskeletal model. The associated optimal control problem for a family of different cost functions was solved utilizing the direct collocation method. It was found that fatigue-like cost functions produced realistic gait, with stance phase knee flexion, as opposed to energy-related cost functions which avoided knee flexion during the stance phase. We conclude that fatigue minimization may be one of the primary optimality principles governing human gait.

  4. Decoherence in the chemical compass: The role of decoherence for avian magnetoreception

    CERN Document Server

    Tiersch, Markus

    2012-01-01

    Contrary to the usual picture that decoherence destroys quantum properties and causes the quantum-to-classical transition, we argue that decoherence can also play a constructive role in driving quantum dynamics and amplifying its results to macroscopic scales. We support this perspective by presenting an example system from spin chemistry, which is also of importance for biological systems, e.g. in avian magnetoreception.

  5. Decoherence of Topological Qubit in Linear Motions: Decoherence Impedance, Anti-Unruh and Information Backflow

    Science.gov (United States)

    Liu, Pei-Hua; Lin, Feng-Li

    2017-08-01

    In this work we study the decoherence of topological qubits in linear motions. The topological qubit is made of two spatially-separated Majorana zero modes which are the edge excitations of Kitaev chain [1]. In a previous work [2], it was shown by one of us and his collaborators that the decoherence of topological qubit is exactly solvable, moreover, topological qubit is robust against decoherence in the super-Ohmic environments. We extend the setup of [2] to consider the effect of motions on the decoherence of the topological qubits. Our results show the thermalization as expected by Unruh effect. Besides, we also find the so-called “anti-Unruh” phenomena which shows the rate of decoherence is anti-correlated with the acceleration in short-time scale. Moreover, we modulate the motion patterns of each Majorana modes and find information backflow and the preservation of coherence even with nonzero accelerations. This is the characteristics of the underlying non-Markovian reduced dynamics. We conclude that he topological qubit is in general more robust against decoherence than the usual qubits, and can be take into serious consideration for realistic implementation to have robust quantum computation and communication. This talk is based on our work in [3].

  6. What classicality? Decoherence and Bohr's classical concepts

    CERN Document Server

    Schlosshauer, Maximilian

    2010-01-01

    Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In the context of the decoherence program, on the other hand, it has become fashionable to talk about the "dynamical emergence of classicality" from the quantum formalism alone. Does this mean that decoherence challenges Bohr's dictum and signifies a break with the Copenhagen interpretation-for example, that classical concepts do not need to be assumed but can be derived? In this paper we'll try to shine some light down the murky waters where formalism and philosophy cohabitate. To begin, we'll clarify the notion of classicality in the decoherence description. We'll then discuss Bohr's and Heisenberg's take on the quantum-classical problem and reflect on different meanings of the terms "classicality" and "classical concepts" in the writings of Bohr and his followers. This analysis will allow us to put forward some tentative suggestions for how we may better understand the relation between decoherence-induced classical...

  7. Multiparticle entanglement under the influence of decoherence

    NARCIS (Netherlands)

    Gühne, O.; Bodoky, F.; Blaauboer, M.

    2008-01-01

    We present a method to determine the decay of multiparticle quantum correlations as quantified by the geometric measure of entanglement under the influence of decoherence. With this, we compare the robustness of entanglement in Greenberger-Horne-Zeilinger (GHZ), cluster, W, and Dicke states of four

  8. Multiparticle entanglement under the influence of decoherence

    NARCIS (Netherlands)

    Gühne, O.; Bodoky, F.; Blaauboer, M.

    2008-01-01

    We present a method to determine the decay of multiparticle quantum correlations as quantified by the geometric measure of entanglement under the influence of decoherence. With this, we compare the robustness of entanglement in Greenberger-Horne-Zeilinger (GHZ), cluster, W, and Dicke states of four

  9. Decoherence of quantum states in QCD vacuum

    Science.gov (United States)

    Kuvshinov, V.; Bagashov, E.

    2017-09-01

    The stochastic vacuum of quantum chromodynamics is used as an environment for quarks considered as color state vectors. It is shown that during interaction with the stochastic vacuum information of the quark color state is lost with time (decoherence of the quark state vector occurs), which effectively means that it is impossible to observe the quark as a free color particle (confinement).

  10. Decoherence of Josephson charge qubit in non-Markovian environment

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Qing-Qian; Zhou, Xing-Fei; Liang, Xian-Ting, E-mail: liangxianting@nbu.edu.cn

    2016-05-15

    In this paper we investigate the decoherence of Josephson charge qubit (JCQ) by using a time-nonlocal (TNL) dynamical method. Three kinds of environmental models, described with Ohmic, super-Ohmic, and sub-Ohmic spectral density functions are considered. It is shown that the TNL method can effectively include the non-Markovian effects in the dynamical solutions. In particular, it is shown that the sub-Ohmic environment has longer correlation time than the Ohmic and super-Ohmic ones. And the Markovian and non-Markovian dynamics are obviously different for the qubit in sub-Ohmic environment.

  11. Decoherence during Inflation: the generation of classical inhomogeneities

    CERN Document Server

    Lombardo, F C; Lombardo, Fernando C.; Nacir, Diana Lopez

    2005-01-01

    We show how the quantum to classical transition of the cosmological fluctuations produced during inflation can be described by means of the influence functional and the master equation. We split the inflaton field into the system-field (long-wavelength modes), and the environment, represented by its own short-wavelength modes. We compute the decoherence times for the system-field modes and compare them with the other time scales of the model. We present the renormalized stochastic Langevin equation for an homogeneous system-field and then we analyze the influence of the environment on the power spectrum for some modes in the system.

  12. Decoherence control: A feedback mechanism based on hamiltonian tracking

    CERN Document Server

    Katz, G; Kosloff, R; Katz, Gil; Ratner, Mark; Kosloff, Ronnie

    2006-01-01

    Enviroment - caused dissipation disrupts the hamiltonian evolution of all quantum systems not fully isolated from any bath. We propose and examine a feedback-control scheme to eliminate such dissipation, by tracking the free hamiltonian evolution. We determine a driving-field that maximizes the projection of the actual molecular system onto the freely propagated one. The evolution of a model two level system in a dephasing bath is followed, and the driving field that overcomes the decoherence is calculated. An implementation of the scheme in the laboratory using feedback control is suggested.

  13. The effect of large decoherence on mixing time in continuous-time quantum walks on long-range interacting cycles

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, S; Radgohar, R, E-mail: shsalimi@uok.ac.i, E-mail: r.radgohar@uok.ac.i [Faculty of Science, Department of Physics, University of Kurdistan, Pasdaran Ave, Sanandaj (Iran, Islamic Republic of)

    2010-01-28

    In this paper, we consider decoherence in continuous-time quantum walks on long-range interacting cycles (LRICs), which are the extensions of the cycle graphs. For this purpose, we use Gurvitz's model and assume that every node is monitored by the corresponding point-contact induced by the decoherence process. Then, we focus on large rates of decoherence and calculate the probability distribution analytically and obtain the lower and upper bounds of the mixing time. Our results prove that the mixing time is proportional to the rate of decoherence and the inverse of the square of the distance parameter (m). This shows that the mixing time decreases with increasing range of interaction. Also, what we obtain for m = 0 is in agreement with Fedichkin, Solenov and Tamon's results [48] for cycle, and we see that the mixing time of CTQWs on cycle improves with adding interacting edges.

  14. First principles modeling of magnetic random access memory devices (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Butler, W.H.; Zhang, X.; Schulthess, T.C.; Nicholson, D.M.; Oparin, A.B. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); MacLaren, J.M. [Department of Physics, Tulane University, New Orleans, Louisiana 70018 (United States)

    1999-04-01

    Giant magnetoresistance (GMR) and spin-dependent tunneling may be used to make magnetic random access memory devices. We have applied first-principles based electronic structure techniques to understand these effects and in the case of GMR to model the transport properties of the devices. {copyright} {ital 1999 American Institute of Physics.}

  15. Towards first principles modeling of electrochemical electrode-electrolyte interfaces

    DEFF Research Database (Denmark)

    Nielsen, Malte; Björketun, Mårten; Hansen, Martin Hangaard;

    2015-01-01

    We present a mini-perspective on the development of first principles modeling of electrochemical interfaces. We show that none of the existing methods deal with all the thermodynamic constraints that the electrochemical environment imposes on the structure of the interface. We present two directi...... directions forward to make the description more realistic and correct. © 2014 Elsevier B.V. All rights reserved....

  16. Riccati equation and the problem of decoherence II: Symmetry and the solution of the Riccati equation

    CERN Document Server

    Gardas, Bartlomiej

    2010-01-01

    The problem of decoherence viewed from a block operator matrix perspective is revisited. We study an algebraic Riccati equation associate with the Hamiltonian modeling the process of decoherence. We proof that if the environment responsible for decoherence process is an invariant under transformation of an antilinear involution, then this operator (a symmetry of the system) is a solution of the Riccati equation in question. We also argue the later solution leads to neither linear not antilinear similarity operator matrix and therefore cause the problem with the standard procedure of solving linear differential equation, like for instance Schrodinger one. Finally, we give an explicit formula for the solution of the Riccati equation in the case when the operators defining the environment commute with each other. We also discuses a connection between our results and the standard Kraus representation approach of the completely positive map. We show that reduced dynamics we obtained dose not posses the Kraus repre...

  17. Application of the Pareto Principle in Rapid Application Development Model

    OpenAIRE

    Vishal Pandey; AvinashBairwa; Sweta Bhattacharya

    2013-01-01

    the Pareto principle or most popularly termed as the 80/20 rule is one of the well-known theories in the field of economics. This rule of thumb was named after the great economist Vilferdo Pareto. The Pareto principle was proposed by a renowned management consultant Joseph M Juran. The rule states that 80% of the required work can be completed in 20% of the time allotted. The idea is to apply this rule of thumb in the Rapid Application Development (RAD) Process model of software engineering. ...

  18. Decoherence and the Appearance of a Classical World in Quantum Theory

    Energy Technology Data Exchange (ETDEWEB)

    Alicki, R [Instytut Fizyki Teoretycznej i Astrofizyki, Uniwersytet Gdanski, ul Wita Stwosza 57, 80-952 Gdansk (Poland)

    2004-02-06

    In the last decade decoherence has become a very popular topic mainly due to the progress in experimental techniques which allow monitoring of the process of decoherence for single microscopic or mesoscopic systems. The other motivation is the rapid development of quantum information and quantum computation theory where decoherence is the main obstacle in the implementation of bold theoretical ideas. All that makes the second improved and extended edition of this book very timely. Despite the enormous efforts of many authors decoherence with its consequences still remains a rather controversial subject. It touches on, namely, the notoriously confusing issues of quantum measurement theory and interpretation of quantum mechanics. The existence of different points of view is reflected by the structure and content of the book. The first three authors (Joos, Zeh and Kiefer) accept the standard formalism of quantum mechanics but seem to reject orthodox Copenhagen interpretation, Giulini and Kupsch stick to both while Stamatescu discusses models which go beyond the standard quantum theory. Fortunately, most of the presented results are independent of the interpretation and the mathematical formalism is common for the (meta)physically different approaches. After a short introduction by Joos followed by a more detailed review of the basic concepts by Zeh, chapter 3 (the longest chapter) by Joos is devoted to the environmental decoherence. Here the author considers mostly rather 'down to earth' and well-motivated mechanisms of decoherence through collisions with atoms or molecules and the processes of emission, absorption and scattering of photons. The issues of decoherence induced superselection rules and localization of objects including the possible explanation of the molecular structure are discussed in details. Many other topics are also reviewed in this chapter, e.g., the so-called Zeno effect, relationships between quantum chaos and decoherence, the role of

  19. BOOK REVIEW: Decoherence and the Appearance of a Classical World in Quantum Theory

    Science.gov (United States)

    Alicki, R.

    2004-02-01

    In the last decade decoherence has become a very popular topic mainly due to the progress in experimental techniques which allow monitoring of the process of decoherence for single microscopic or mesoscopic systems. The other motivation is the rapid development of quantum information and quantum computation theory where decoherence is the main obstacle in the implementation of bold theoretical ideas. All that makes the second improved and extended edition of this book very timely. Despite the enormous efforts of many authors decoherence with its consequences still remains a rather controversial subject. It touches on, namely, the notoriously confusing issues of quantum measurement theory and interpretation of quantum mechanics. The existence of different points of view is reflected by the structure and content of the book. The first three authors (Joos, Zeh and Kiefer) accept the standard formalism of quantum mechanics but seem to reject orthodox Copenhagen interpretation, Giulini and Kupsch stick to both while Stamatescu discusses models which go beyond the standard quantum theory. Fortunately, most of the presented results are independent of the interpretation and the mathematical formalism is common for the (meta)physically different approaches. After a short introduction by Joos followed by a more detailed review of the basic concepts by Zeh, chapter 3 (the longest chapter) by Joos is devoted to the environmental decoherence. Here the author considers mostly rather `down to earth' and well-motivated mechanisms of decoherence through collisions with atoms or molecules and the processes of emission, absorption and scattering of photons. The issues of decoherence induced superselection rules and localization of objects including the possible explanation of the molecular structure are discussed in details. Many other topics are also reviewed in this chapter, e.g., the so-called Zeno effect, relationships between quantum chaos and decoherence, the role of

  20. Onsager reciprocity principle for kinetic models and kinetic schemes

    CERN Document Server

    Mahendra, Ajit Kumar

    2013-01-01

    Boltzmann equation requires some alternative simpler kinetic model like BGK to replace the collision term. Such a kinetic model which replaces the Boltzmann collision integral should preserve the basic properties and characteristics of the Boltzmann equation and comply with the requirements of non equilibrium thermodynamics. Most of the research in development of kinetic theory based methods have focused more on entropy conditions, stability and ignored the crucial aspect of non equilibrium thermodynamics. The paper presents a new kinetic model formulated based on the principles of non equilibrium thermodynamics. The new kinetic model yields correct transport coefficients and satisfies Onsager's reciprocity relationship. The present work also describes a novel kinetic particle method and gas kinetic scheme based on this linkage of non-equilibrium thermodynamics and kinetic theory. The work also presents derivation of kinetic theory based wall boundary condition which complies with the principles of non-equili...

  1. [The bioethical principlism model applied in pain management].

    Science.gov (United States)

    Souza, Layz Alves Ferreira; Pessoa, Ana Paula da Costa; Barbosa, Maria Alves; Pereira, Lilian Varanda

    2013-03-01

    An integrative literature review was developed with the purpose to analyze the scientific production regarding the relationships between pain and the principles of bioethics (autonomy, beneficence, nonmaleficence and justice). Controlled descriptors were used in three international data sources (LILACS, SciELO, MEDLINE), in April of 2012, totaling 14 publications categorized by pain and autonomy, pain and beneficence, pain and nonmaleficence, pain and justice. The adequate relief of pain is a human right and a moral issue directly related with the bioethical principlism standard model (beneficence, non-maleficence, autonomy and justice). However, many professionals overlook the pain of their patients, ignoring their ethical role when facing suffering. It was concluded that principlism has been neglected in the care of patients in pain, showing the need for new practices to change this setting.

  2. First Principles Modeling of Nonlinear Incidence Rates in Seasonal Epidemics

    OpenAIRE

    2011-01-01

    In this paper we used a general stochastic processes framework to derive from first principles the incidence rate function that characterizes epidemic models. We investigate a particular case, the Liu-Hethcote-van den Driessche's (LHD) incidence rate function, which results from modeling the number of successful transmission encounters as a pure birth process. This derivation also takes into account heterogeneity in the population with regard to the per individual transmission probability. We...

  3. Principles of parametric estimation in modeling language competition.

    Science.gov (United States)

    Zhang, Menghan; Gong, Tao

    2013-06-11

    It is generally difficult to define reasonable parameters and interpret their values in mathematical models of social phenomena. Rather than directly fitting abstract parameters against empirical data, we should define some concrete parameters to denote the sociocultural factors relevant for particular phenomena, and compute the values of these parameters based upon the corresponding empirical data. Taking the example of modeling studies of language competition, we propose a language diffusion principle and two language inheritance principles to compute two critical parameters, namely the impacts and inheritance rates of competing languages, in our language competition model derived from the Lotka-Volterra competition model in evolutionary biology. These principles assign explicit sociolinguistic meanings to those parameters and calculate their values from the relevant data of population censuses and language surveys. Using four examples of language competition, we illustrate that our language competition model with thus-estimated parameter values can reliably replicate and predict the dynamics of language competition, and it is especially useful in cases lacking direct competition data.

  4. Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom. Application to 1H NMR reversion experiments in nematic liquid crystals

    CERN Document Server

    Segnorile, H H

    2013-01-01

    An experimental study of NMR spin decoherence in nematic liquid crystals is presented. The outcome of the experiments are analyzed in the framework of a theory that considers the spins as an open quantum system coupled to a quantum molecular environment, presented by the authors recently. Decoherence dynamics can be put in evidence by means of refocusing experiments of the dipolar interactions. The experimental technique used in this work is based on the MREV8 pulse sequence. Non-idealities of the experimental setting, like external field inhomogeneity, pulse misadjustments and the presence of non-reverted spin interaction terms are analysed in detail and their effects on the observed signal decay are estimated. It is found that, though all these non-idealities could in principle affect the evolution of the spin dynamics, their influence can be mitigated and they do not present the characteristic behaviour of the irreversible spin decoherence. As unique characteristic of decoherence, the experimental results ...

  5. A Goldilocks principle for modelling radial velocity noise

    Science.gov (United States)

    Feng, F.; Tuomi, M.; Jones, H. R. A.; Butler, R. P.; Vogt, S.

    2016-09-01

    The Doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial velocity data. To quantify the limitation of various models and methods, we compare different noise models and signal detection criteria for various simulated and real data sets in the Bayesian framework. According to our analyses, the white noise model tend to interpret noise as signal, leading to false positives. On the other hand, the red noise models are likely to interpret signal as noise, resulting in false negatives. We find that the Bayesian information criterion combined with a Bayes factor threshold of 150 can efficiently rule out false positives and confirm true detections. We further propose a Goldilocks principle aimed at modelling radial velocity noise to avoid too many false positives and too many false negatives. We propose that the noise model with RHK-dependent jitter is used in combination with the moving average model to detect planetary signals for M dwarfs. Our work may also shed light on the noise modelling for hotter stars, and provide a valid approach for finding similar principles in other disciplines.

  6. Mosque as a Model of Learning Principles of Sustainable Architecture

    Directory of Open Access Journals (Sweden)

    Swambodo Murdariatmo Adi

    2016-06-01

    Full Text Available The mosque is an integral part of the circuit-worship rituals of Islam. For Muslims in Indonesia, the role of the mosque as a place of worship, examines religion and some other activities occupy a strategic position not only as a religious symbol but more emphasis on the function of the space as a public building. Utilization of space in public buildings as well as space-ritual-social space will have meaning for the people in view of adaptation space used. Awareness of the importance of effective space utilization and management of water resources wisely in support of the ritual apply the principles of sustainable architecture will have a positive impact for the people to give directions as to how the principle of austerity-not wasteful in Islam can be applied. This paper will discuss about the process of continuous learning from the essence of understanding of the mosque as a model in implementing the process of life, taking into account the principles of simplicity, functional and wisdom, especially in the efficiency of utilization of local resources. The method used in this research is qualitative descriptive, which is explained the theory and based on literature and accompanied by case study that have implemented the principles. The output of this application of the principles of sustainable architecture in the planning and use of mosques as a place in the relationship with God and with fellow human relations can be a model for the faithful to deal with wisely challenge natural resource constraints, especially for future generations.

  7. Adherence of Model Molecules to Silica Surfaces: First Principle Calculations

    Science.gov (United States)

    Nuñez, Matías; Prado, Miguel Oscar

    The adherence of "model molecules" methylene blue and eosine Y ("positive" and "negatively" charged respectively) to crystal SiO2 surfaces is studied from first principle calculations at the DFT level. Adsorption energies are calculated which follow the experimental threads obtained elsewhere (Rivera et al., 2013). We study the quantum nature of the electronic charge transfer between the surface and the molecules, showing the localized and delocalized patterns associated to the repulsive and attractive case respectively.

  8. A Goldilocks principle for modeling radial velocity noise

    CERN Document Server

    Feng, Fabo; Jones, H R A; Butler, R P; Vogt, S

    2016-01-01

    The doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial velocity data. To quantify the limitation of various models and methods, we compare different noise models and signal detection criteria for various simulated and real data sets in the Bayesian framework. According to our analyses, the white noise model tend to interpret noise as signal, leading to false positives. On the other hand, the red noise models are likely to interprete signal as noise, resulting in false negatives. We find that the Bayesian information criterion combined with a Bayes factor threshold of 150 can efficiently rule out false positives and confirm true detections. We further propose a Goldilocks principle aimed at modeling radial velocity noise to avoid too many false positives and too many false negatives. We propose that the noise model w...

  9. Quantifying decoherence in continuous variable systems

    Energy Technology Data Exchange (ETDEWEB)

    Serafini, A [Dipartimento di Fisica ' ER Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, Gruppo Collegato Salerno, Via S Allende, 84081 Baronissi, SA (Italy); Paris, M G A [Dipartimento di Fisica and INFM, Universita di Milano, Milan (Italy); Illuminati, F [Dipartimento di Fisica ' ER Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, Gruppo Collegato Salerno, Via S Allende, 84081 Baronissi, SA (Italy); De Siena, S [Dipartimento di Fisica ' ER Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, Gruppo Collegato Salerno, Via S Allende, 84081 Baronissi, SA (Italy)

    2005-04-01

    We present a detailed report on the decoherence of quantum states of continuous variable systems under the action of a quantum optical master equation resulting from the interaction with general Gaussian uncorrelated environments. The rate of decoherence is quantified by relating it to the decay rates of various, complementary measures of the quantum nature of a state, such as the purity, some non-classicality indicators in phase space, and, for two-mode states, entanglement measures and total correlations between the modes. Different sets of physically relevant initial configurations are considered, including one- and two-mode Gaussian states, number states, and coherent superpositions. Our analysis shows that, generally, the use of initially squeezed configurations does not help to preserve the coherence of Gaussian states, whereas it can be effective in protecting coherent superpositions of both number states and Gaussian wavepackets. (review article)

  10. Quantum dynamical entropy and decoherence rate

    Energy Technology Data Exchange (ETDEWEB)

    Alicki, Robert [Institute of Theoretical Physics and Astrophysics, University of Gdansk, ul. Wita Stwosza 57, PL 80-952 Gdansk (Poland); Lozinski, Artur [Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Cracow (Poland); Pakonski, Prot [Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Cracow (Poland); Zyczkowski, Karol [Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow (Poland)

    2004-05-14

    We investigate quantum dynamical systems defined on a finite-dimensional Hilbert space and subjected to an interaction with an environment. The rate of decoherence of initially pure states, measured by the increase of their von Neumann entropy, averaged over an ensemble of random pure states, is proved to be bounded from above by the partial entropy used to define the ALF-dynamical entropy. The rate of decoherence induced by the sequence of the von Neumann projectors measurements is shown to be maximal, if the measurements are performed in a randomly chosen basis. The numerically observed linear increase of entropies is attributed to free independence of the measured observable and the unitary dynamical map.

  11. Quantum dynamical entropy and decoherence rate

    CERN Document Server

    Alicki, R; Pakonski, P; Zyczkowski, K; Alicki, Robert; Lozinski, Artur; Pakonski, Prot; Zyczkowski, Karol

    2004-01-01

    We investigate quantum dynamical systems defined on a finite dimensional Hilbert space and subjected to an interaction with an environment. The rate of decoherence of initially pure states, measured by the increase of their von Neumann entropy, averaged over an ensemble of random pure states, is proved to be bounded from above by the partial entropy used to define the ALF dynamical entropy. The rate of decoherence induced by the sequence of the von Neumann projectors measurements is shown to be maximal, if the measurements are performed in a randomly chosen basis. The numerically observed linear increase of entropies is attributed to free-independence of the measured observable and the unitary dynamical map.

  12. Quantifying decoherence in continuous variable systems

    CERN Document Server

    Serafini, A; Illuminati, F; De Siena, S

    2005-01-01

    We present a detailed report on the decoherence of quantum states of continuous variable systems under the action of a quantum optical master equation resulting from the interaction with general Gaussian uncorrelated environments. The rate of decoherence is quantified by relating it to the decay rates of various, complementary measures of the quantum nature of a state, such as the purity, some nonclassicality indicators in phase space and, for two-mode states, entanglement measures and total correlations between the modes. Different sets of physically relevant initial configurations are considered, including one- and two-mode Gaussian states, number states, and coherent superpositions. Our analysis shows that, generally, the use of initially squeezed configurations does not help to preserve the coherence of Gaussian states, whereas it can be effective in protecting coherent superpositions of both number states and Gaussian wave packets.

  13. Geometric measure of quantum discord under decoherence

    CERN Document Server

    Xiao-Ming, Lu; Sun, Zhe; Wang, Xiaoguang

    2010-01-01

    The dynamics of a geometric measure of the quantum discord (GMQD) under decoherence is investigated. We show that the GMQD of a two-qubit state can be alternatively obtained through the singular values of a 3\\times4 matrix whose elements are the expectation values of Pauli matrices of the two qubits. By using Heisenberg picture, the analytic results of the GMQD is obtained for three typical kinds of the quantum decoherence channels. We compare the dynamics of the GMQD with that of the quantum discord and of entanglement and show that a sudden change in the decay rate of the GMQD does not always imply the sudden change in the decay rate of the quantum discord.

  14. Decoherence and tunneling of an interacting gas

    Science.gov (United States)

    Anglin, James; Rico-Perez, Luis; Wohlfarth, Daniel

    2015-05-01

    In quasi-steady escape of a confined interacting gas by quantum tunneling, collisional decoherence can reduce the escape rate through a many-body version of the Caldeira-Leggett effect. This explains why classical fluids fail to tunnel, even though they are composed of particles small enough to be quantum mechanical. We compute this effect in the Maxwell-Boltzmann regime by deriving a quantum generalization of the Boltzmann equation. We show that decoherence effectively makes tunneling of an interacting gas into an irreversible process: a uniquely quantum mechanical form of throttling. The rate of entropy production in tunneling is related in the semi-classical limit to the imaginary part of the single-particle action.

  15. Quantum Decoherence During Inflation from Gravitational Nonlinearities

    CERN Document Server

    Nelson, Elliot

    2016-01-01

    We study the inflationary quantum-to-classical transition for the adiabatic curvature perturbation $\\zeta$ due to quantum decoherence, focusing on the role played by squeezed-limit mode couplings. We evolve the quantum state $\\Psi$ in the Schr\\"odinger picture, for a generic cubic coupling to additional environment degrees of freedom. Focusing on the case of minimal gravitational interactions, we find the evolution of the reduced density matrix for a given long-wavelength fluctuation by tracing out the other (mostly shorterwavelength) modes of $\\zeta$ as an environment. We show that inflation produces phase oscillations in the wave functional $\\Psi[\\zeta(\\mathbf{x})]$, which suppress off-diagonal components of the reduced density matrix, leaving a diagonal mixture of different classical configurations. Gravitational nonlinearities thus provide a minimal mechanism for generating classical stochastic perturbations from inflation. We identify the time when decoherence occurs, which is delayed after horizon cross...

  16. Application of the Pareto Principle in Rapid Application Development Model

    Directory of Open Access Journals (Sweden)

    Vishal Pandey

    2013-06-01

    Full Text Available the Pareto principle or most popularly termed as the 80/20 rule is one of the well-known theories in the field of economics. This rule of thumb was named after the great economist Vilferdo Pareto. The Pareto principle was proposed by a renowned management consultant Joseph M Juran. The rule states that 80% of the required work can be completed in 20% of the time allotted. The idea is to apply this rule of thumb in the Rapid Application Development (RAD Process model of software engineering. The Rapid application development model integrates end-user in the development using iterative prototyping emphasizing on delivering a series of fully functional prototype to designated user experts. During the application of Pareto Principle the other concepts like the Pareto indifference curve and Pareto efficiency also come into the picture. This enables the development team to invest major amount of time focusing on the major functionalities of the project as per the requirement prioritizationof the customer. The paper involves an extensive study on different unsatisfactory projects in terms of time and financial resources and the reasons of failures are analyzed. Based on the possible reasons offailure, a customized RAD model is proposed integrating the 80/20 rule and advanced software development strategies to develop and deploy excellent quality software product in minimum time duration. The proposed methodology is such that its application will directly affect the quality of the end product for the better.

  17. Modeling Electric Discharges with Entropy Production Rate Principles

    Directory of Open Access Journals (Sweden)

    Thomas Christen

    2009-12-01

    Full Text Available Under which circumstances are variational principles based on entropy production rate useful tools for modeling steady states of electric (gas discharge systems far from equilibrium? It is first shown how various different approaches, as Steenbeck’s minimum voltage and Prigogine’s minimum entropy production rate principles are related to the maximum entropy production rate principle (MEPP. Secondly, three typical examples are discussed, which provide a certain insight in the structure of the models that are candidates for MEPP application. It is then thirdly argued that MEPP, although not being an exact physical law, may provide reasonable model parameter estimates, provided the constraints contain the relevant (nonlinear physical effects and the parameters to be determined are related to disregarded weak constraints that affect mainly global entropy production. Finally, it is additionally conjectured that a further reason for the success of MEPP in certain far from equilibrium systems might be based on a hidden linearity of the underlying kinetic equation(s.

  18. Poincar\\'e Sphere and Decoherence Problems

    CERN Document Server

    Kim, Y S

    2012-01-01

    Henri Poincar\\'e formulated the mathematics of the Lorentz transformations, known as the Poincar\\'e group. He also formulated the Poincar\\'e sphere for polarization optics. It is shown that these two mathematical instruments can be combined into one mathematical device which can address the internal space-time symmetries of elementary particles, decoherence problems in polarization optics, entropy problems, and Feynman's rest of the universe.

  19. Entanglement and decoherence in a quantum dimer

    Institute of Scientific and Technical Information of China (English)

    Hou Xi-Wen; Hui Zi; Ding Rui-Min; Chen Xiao-Yang; Gao Yu

    2006-01-01

    The dynamical properties of quantum entanglement in an integrable quantum dimer are studied in terms of the reduced-density linear entropy with various coupling parameters and total boson numbers. The characteristic time of decoherence process in the early-time evolution of the linear entropy is obtained, indicating that the characteristic time and the corresponding entropy exhibit a maximum near the position of the corresponding classical separatrix energy.

  20. Decoherence in Nearly-Isolated Quantum Dots

    DEFF Research Database (Denmark)

    Folk, J.; M. Marcus, C.; Harris jr, J.

    2000-01-01

    Decoherence in nearly-isolated GaAs quantum dots is investigated using the change in average Coulomb blockade peak height upon breaking time-reversal symmetry. The normalized change in average peak height approaches the predicted universal value of 1/4 at temperatures well below the single......-particle level spacing, but is greatly suppressed for temperature greater than the level spacing, suggesting that inelastic scattering or other dephasing mechanisms dominate in this regime....

  1. The Measurement Problem: Decoherence and Convivial Solipsism

    OpenAIRE

    2015-01-01

    The problem of measurement is often considered as an inconsistency inside the quantum formalism. Many attempts to solve (or to dissolve) it have been made since the inception of quantum mechanics. The form of these attempts depends on the philosophical position that their authors endorse. I will review some of them and analyze their relevance. The phenomenon of decoherence is often presented as a solution lying inside the pure quantum formalism and not demanding any particular philosophical a...

  2. Damping and Decoherence in Neutron Oscillations

    CERN Document Server

    Kerbikov, B O; Kamyshkov, Y A; Varriano, L J

    2015-01-01

    An analysis is made of the role played by the gas environment in neutron-mirror-neutron and neutron-antineutron oscillations. In the first process the interaction with the ambient medium induces a refraction energy shift which plays the role of an extra magnetic field. In the second process antineutron annihilation in practice might lead to strong decoherence, which should be taken into account in experiments with free neutrons looking for the neutron to antineutron transformation.

  3. Damped driven coupled oscillators: entanglement, decoherence and the classical limit

    Energy Technology Data Exchange (ETDEWEB)

    Mancilla, R D Guerrero; Rey-Gonzalez, R R; Fonseca-Romero, K M [Grupo de Optica e Informacion Cuantica, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia)], E-mail: rdguerrerom@unal.edu.co, E-mail: rrreyg@unal.edu.co, E-mail: kmfonsecar@unal.edu.co

    2009-03-13

    We investigate the quantum-classical border, the entanglement and decoherence of an analytically solvable model, comprising a first subsystem (a harmonic oscillator) coupled to a driven and damped second subsystem (another harmonic oscillator). We choose initial states whose dynamics is confined to a couple of two-level systems, and show that the maximum value of entanglement between the two subsystems, as measured by concurrence, depends on the dissipation rate to the coupling-constant ratio and the initial state. While in a related model the entropy of the first subsystem (a two-level system) never grows appreciably (for large dissipation rates), in our model it reaches a maximum before decreasing. Although both models predict small values of entanglement and dissipation, for fixed times of the order of the inverse of the coupling constant and large dissipation rates, these quantities decrease faster, as a function of the ratio of the dissipation rate to the coupling constant, in our model.

  4. Decoherence of matter waves by thermal emission of radiation

    OpenAIRE

    2004-01-01

    Emergent quantum technologies have led to increasing interest in decoherence - the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory has been complemented by experiments using matter waves coupled to external ph...

  5. Multiphysics modeling using COMSOL a first principles approach

    CERN Document Server

    Pryor, Roger W

    2011-01-01

    Multiphysics Modeling Using COMSOL rapidly introduces the senior level undergraduate, graduate or professional scientist or engineer to the art and science of computerized modeling for physical systems and devices. It offers a step-by-step modeling methodology through examples that are linked to the Fundamental Laws of Physics through a First Principles Analysis approach. The text explores a breadth of multiphysics models in coordinate systems that range from 1D to 3D and introduces the readers to the numerical analysis modeling techniques employed in the COMSOL Multiphysics software. After readers have built and run the examples, they will have a much firmer understanding of the concepts, skills, and benefits acquired from the use of computerized modeling techniques to solve their current technological problems and to explore new areas of application for their particular technological areas of interest.

  6. Decoherence, entanglement decay, and equilibration produced by chaotic environments.

    Science.gov (United States)

    Lemos, Gabriela Barreto; Toscano, Fabricio

    2011-07-01

    We investigate decoherence in quantum systems coupled via dephasing-type interactions to an arbitrary environment with chaotic underlying classical dynamics. The coherences of the reduced state of the central system written in the preferential energy eigenbasis are quantum Loschmidt echoes, which in the strong coupling regime are characterized at long time scales by fluctuations around a constant mean value. We show that due to the chaotic dynamics of the environment, the mean value and the width of the Loschmidt-echo fluctuations are inversely proportional to the quantity we define as the effective Hilbert-space dimension of the environment, which in general is smaller than the dimension of the entire available Hilbert space. Nevertheless, in the semiclassical regime this effective Hilbert-space dimension is in general large, in which case even a chaotic environment with few degrees of freedom produces decoherence without revivals. Moreover we show that in this regime the environment leads the central system to equilibrate to the time average of its reduced density matrix, which corresponds to a diagonal state in the preferential energy eigenbasis. For the case of two uncoupled, initially entangled central systems that interact with identical local quantum environments with chaotic underlying classical dynamics, we show that in the semiclassical limit the equilibration state is arbitrarily close to a separable state. We confirm our results with numerical simulations in which the environment is modeled by the quantum kicked rotor in the chaotic regime.

  7. Local decoherence-resistant quantum states of large systems

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Utkarsh; Sen, Aditi; Sen, Ujjwal, E-mail: ujjwal@hri.res.in

    2015-02-06

    We identify an effectively decoherence-free class of quantum states, each of which consists of a “minuscule” and a “large” sector, against local noise. In particular, the content of entanglement and other quantum correlations in the minuscule to large partition is independent of the number of particles in their large sectors, when all the particles suffer passage through local amplitude and phase damping channels. The states of the large sectors are distinct in terms of markedly different amounts of violation of Bell inequality. In case the large sector is macroscopic, such states are akin to the Schrödinger cat. - Highlights: • We identify an effectively decoherence-free class of quantum states of large systems. • We work with local noise models. • Decay of entanglement as well as information-theoretic quantum correlations considered. • The states are of the form of the Schrödinger cats, with minuscule and large sectors. • The states of the large sector are distinguishable by their violation of Bell inequality.

  8. First principles pharmacokinetic modeling: A quantitative study on Cyclosporin

    DEFF Research Database (Denmark)

    Mošat', Andrej; Lueshen, Eric; Heitzig, Martina

    2013-01-01

    renal and hepatic clearances, elimination half-life, and mass transfer coefficients, to establish drug biodistribution dynamics in all organs and tissues. This multi-scale model satisfies first principles and conservation of mass, species and momentum.Prediction of organ drug bioaccumulation...... as a function of cardiac output, physiology, pathology or administration route may be possible with the proposed PBPK framework. Successful application of our model-based drug development method may lead to more efficient preclinical trials, accelerated knowledge gain from animal experiments, and shortened time-to-market...

  9. Principle Generalized Net Model of a Human Stress Reaction

    Directory of Open Access Journals (Sweden)

    Anthony Shannon

    2008-04-01

    Full Text Available The present study was aimed at investigating the mechanism of a human stress reaction by means of Generalized Nets (GNs. A principle GN-model of the main structures, organs and systems of the human body taking part in the acute and chronic reaction of the organism to a stress stimulus is generated. A possible application of the GN-model of the human stress reaction for testing the effect of known or newly synthesized pharmacological products as well as of food supplements is discussed.

  10. Minimal Self-Models and the Free Energy Principle

    Directory of Open Access Journals (Sweden)

    Jakub eLimanowski

    2013-09-01

    Full Text Available The term "minimal phenomenal selfhood" describes the basic, pre-reflective experience of being a self (Blanke & Metzinger, 2009. Theoretical accounts of the minimal self have long recognized the importance and the ambivalence of the body as both part of the physical world, and the enabling condition for being in this world (Gallagher, 2005; Grafton, 2009. A recent account of minimal phenomenal selfhood (MPS, Metzinger, 2004a centers on the consideration that minimal selfhood emerges as the result of basic self-modeling mechanisms, thereby being founded on pre-reflective bodily processes. The free energy principle (FEP, Friston, 2010 is a novel unified theory of cortical function that builds upon the imperative that self-organizing systems entail hierarchical generative models of the causes of their sensory input, which are optimized by minimizing free energy as an approximation of the log-likelihood of the model. The implementation of the FEP via predictive coding mechanisms and in particular the active inference principle emphasizes the role of embodiment for predictive self-modeling, which has been appreciated in recent publications. In this review, we provide an overview of these conceptions and illustrate thereby the potential power of the FEP in explaining the mechanisms underlying minimal selfhood and its key constituents, multisensory integration, interoception, agency, perspective, and the experience of mineness. We conclude that the conceptualization of MPS can be well mapped onto a hierarchical generative model furnished by the free energy principle and may constitute the basis for higher-level, cognitive forms of self-referral, as well as the understanding of other minds.

  11. Using Hydraulic Network Models to Teach Electric Circuit Principles

    Science.gov (United States)

    Jones, Irvin; EERC (Engineering Education Research Center) Collaboration

    2013-11-01

    Unlike other engineering disciplines, teaching electric circuit principles is difficult for some students because there isn't a visual context to rely on. So concepts such as electric potential, current, resistance, capacitance, and inductance have little meaning outside of their definition and the derived mathematical relationships. As a work in progress, we are developing a tool to support teaching, learning, and research of electric circuits. The tool will allow the user to design, build, and operate electric circuits in the form of hydraulic networks. We believe that this system will promote greater learning of electric circuit principles by visually realizing the conceptual and abstract concepts of electric circuits. Furthermore, as a teaching and learning tool, the hydraulic network system can be used to teach and improve comprehension of electrical principles in K through 12 classrooms and in cross-disciplinary environments such as Bioengineering, Mechanical Engineering, Industrial Engineering, and Aeronautical Engineering. As a research tool, the hydraulic network can model and simulate micro/nano bio-electro-chemical systems. Organization within the Swanson School of Engineering at the University of Pittsburgh.

  12. Realtime capable first principle based modelling of tokamak turbulent transport

    Science.gov (United States)

    Citrin, Jonathan; Breton, Sarah; Felici, Federico; Imbeaux, Frederic; Redondo, Juan; Aniel, Thierry; Artaud, Jean-Francois; Baiocchi, Benedetta; Bourdelle, Clarisse; Camenen, Yann; Garcia, Jeronimo

    2015-11-01

    Transport in the tokamak core is dominated by turbulence driven by plasma microinstabilities. When calculating turbulent fluxes, maintaining both a first-principle-based model and computational tractability is a strong constraint. We present a pathway to circumvent this constraint by emulating quasilinear gyrokinetic transport code output through a nonlinear regression using multilayer perceptron neural networks. This recovers the original code output, while accelerating the computing time by five orders of magnitude, allowing realtime applications. A proof-of-principle is presented based on the QuaLiKiz quasilinear transport model, using a training set of five input dimensions, relevant for ITG turbulence. The model is implemented in the RAPTOR real-time capable tokamak simulator, and simulates a 300s ITER discharge in 10s. Progress in generalizing the emulation to include 12 input dimensions is presented. This opens up new possibilities for interpretation of present-day experiments, scenario preparation and open-loop optimization, realtime controller design, realtime discharge supervision, and closed-loop trajectory optimization.

  13. Using continuous time stochastic modelling and nonparametric statistics to improve the quality of first principles models

    DEFF Research Database (Denmark)

    A methodology is presented that combines modelling based on first principles and data based modelling into a modelling cycle that facilitates fast decision-making based on statistical methods. A strong feature of this methodology is that given a first principles model along with process data, the......, the corresponding modelling cycle model of the given system for a given purpose. A computer-aided tool, which integrates the elements of the modelling cycle, is also presented, and an example is given of modelling a fed-batch bioreactor....

  14. Practical use of variational principles for modeling water waves

    CERN Document Server

    Clamond, Didier

    2010-01-01

    This paper describes a method for deriving approximate equations for water waves. The method is based on a `relaxed' variational principle, i.e., on a Lagrangian involving as many variables as possible. This formulation is particularly suitable for the construction of approximate water wave models, since it allows more freedom while preserving the variational structure. The advantages of this relaxed formulation are illustrated with various examples in shallow and deep waters, as well as arbitrary depths. Using subordinate constraints (e.g., irrotationality and free surface impermeability) in various combinations, several model equations are derived, some being well-known, other being new. The models obtained are studied analytically and exact travelling wave solutions are constructed when possible.

  15. Modelling Immune System: Principles, Models,Analysis and Perspectives

    Institute of Scientific and Technical Information of China (English)

    Xiang-hua Li; Zheng-xuan Wang; Tian-yang Lu; Xiang-jiu Che

    2009-01-01

    The biological immune system is a complex adaptive system. There are lots of benefits for building the model of the immune system. For biological researchers, they can test some hypotheses about the infection process or simulate the responses of some drugs. For computer researchers, they can build distributed, robust and fault tolerant networks inspired by the functions of the immune system. This paper provides a comprehensive survey of the literatures on modelling the immune system. From the methodology perspective, the paper compares and analyzes the existing approaches and models, and also demonstrates the focusing research effort on the future immune models in the next few years.

  16. Emergent dark energy via decoherence in quantum interactions

    CERN Document Server

    Altamirano, Natacha; Khosla, Kiran; Mann, Robert B; Milburn, Gerard

    2016-01-01

    Much effort has been devoted into understanding the quantum mechanical properties of gravitational interactions. Here we explore the recent suggestion that gravitational interactions are a fundamental classical channel that is described by continuous quantum measurements and feedforward (CQMF). Specifically, we investigate the possibility that some properties of our universe, modeled using a Friedman-Robertson-Walker metric, can emerge from CQMF by introducing an underlying quantum system for the dynamical variables, avoiding well known difficulties in trying to quantize the spacetime itself. We show that the quantum decoherence necessary in such a measurement model manifests itself as a dark energy fluid that fills the spacetime and whose equation of state asymptotically oscillates around the value $w=-1/3$, regardless of the spatial curvature, which provides the bound between accelerating and decelerating expanding FRW cosmologies.

  17. Functional Approach to Quantum Decoherence and the Classical Final Limit

    CERN Document Server

    Castagnino, M A; Castagnino, Mario; Laura, Roberto

    2000-01-01

    For a wide set of quantum systems it is demonstrated that the quantum regime can be considered as the transient phase while the final classical statistical regime is a permanent state. A basis where exact matrix decoherence appears for these final states is found. The relation with the decoherence of histories formalism is studied. A set of final intrinsically consistent histories is found.

  18. Phase-selective reversible quantum decoherence in cavity QED experiment

    CERN Document Server

    Filip, R

    2001-01-01

    New feasible cavity QED experiment is proposed to analyse reversible quantum decoherence in consequence of quantum complementarity and entanglement. Utilizing the phase selective manipulations with enviroment, it is demonstrated how the complementarity particularly induces a preservation of visibility, whereas quantum decoherence is more progressive due to pronounced entanglement between system and enviroment. This effect can be directly observed using the proposed cavity QED measurements.

  19. Decoherence of number states in phase-sensitive reservoirs

    CERN Document Server

    Serafini, A; Illuminati, F

    2003-01-01

    The non-unitary evolution of initial number states in general Gaussian environments is solved analytically. Decoherence in the channels is quantified by determining explicitly the purity of the state at any time. The influence of the squeezing of the bath on decoherence is discussed. The behavior of coherent superpositions of number states is addressed as well.

  20. Quantum Computing in Decoherence-Free Subspace Constructed by Triangulation

    Directory of Open Access Journals (Sweden)

    Qiao Bi

    2010-01-01

    Full Text Available A formalism for quantum computing in decoherence-free subspaces is presented. The constructed subspaces are partial triangulated to an index related to environment. The quantum states in the subspaces are just projected states which are ruled by a subdynamic kinetic equation. These projected states can be used to perform ideal quantum logical operations without decoherence.

  1. The Measurement Problem: Decoherence and Convivial Solipsism

    Science.gov (United States)

    Zwirn, Hervé

    2016-06-01

    The problem of measurement is often considered an inconsistency inside the quantum formalism. Many attempts to solve (or to dissolve) it have been made since the inception of quantum mechanics. The form of these attempts depends on the philosophical position that their authors endorse. I will review some of them and analyze their relevance. The phenomenon of decoherence is often presented as a solution lying inside the pure quantum formalism and not demanding any particular philosophical assumption. Nevertheless, a widely debated question is to decide between two different interpretations. The first one is to consider that the decoherence process has the effect to actually project a superposed state into one of its classically interpretable component, hence doing the same job as the reduction postulate. For the second one, decoherence is only a way to show why no macroscopic superposed state can be observed, so explaining the classical appearance of the macroscopic world, while the quantum entanglement between the system, the apparatus and the environment never disappears. In this case, explaining why only one single definite outcome is observed remains to do. In this paper, I examine the arguments that have been given for and against both interpretations and defend a new position, the "Convivial Solipsism", according to which the outcome that is observed is relative to the observer, different but in close parallel to the Everett's interpretation and sharing also some similarities with Rovelli's relational interpretation and Quantum Bayesianism. I also show how "Convivial Solipsism" can help getting a new standpoint about the EPR paradox providing a way out of the seemingly unavoidable non-locality of quantum mechanics.

  2. Decoherence due to elastic rayleigh scattering

    CSIR Research Space (South Africa)

    Uys, H

    2010-11-01

    Full Text Available in this manuscript now enables an accurate calculation of Rayleigh decoherence for these low-field trapped ion as well as other coherent-control experiments. We thank W.M. Itano, J. P. Britton, D. Hanneke, and M. J. Holland for useful suggestions.M. J. B.... acknowledges support from Georgia Tech and IARPA. D.M. is supported by NSF. This work was supported by the DARPA OLE program and by IARPA. This manuscript is the contribution of NIST and is not subject to U.S. copyright. *huys@csir.co.za †john...

  3. Decoherence and Spin Echo in Biological Systems

    CERN Document Server

    Nesterov, Alexander I

    2015-01-01

    The spin echo approach is extended to include bio-complexes for which the interaction with dynamical noise is strong. Significant restoration of the free induction decay signal due to homogeneous (decoherence) and inhomogeneous (dephasing) broadening is demonstrated analytically and numerically, for both an individual dimer of interacting chlorophylls and for an ensemble of dimers. This approach is based on an exact and closed system of ordinary differential equations that can be easily solved for a wide range of parameters that are relevant for bio-applications.

  4. Decoherence alias Loschmidt echo of the environment

    CERN Document Server

    Gorin, T; Seligman, T H; Strunz, W T

    2004-01-01

    Entanglement between a quantum system and its environment leads to loss of coherence in the former. In general, the temporal fate of coherences is complicated. Here, we establish the connection between decoherence of a central system and fidelity decay in the environment for a variety of situations, including both, energy conserving and dissipative couplings. We show how properties of unitary time evolution of the environment can be inferred from the non-unitary evolution of coherences in the central system. This opens up promising ways for measuring Loschmidt echoes in a variety of situations.

  5. Decoherent histories approach to the cosmological measure problem

    CERN Document Server

    Lloyd, Seth

    2016-01-01

    The method of decoherent histories allows probabilities to be assigned to sequences of quantum events in systems, such as the universe as a whole, where there is no external observer to make measurements. This paper applies the method of decoherent histories to address cosmological questions. Using a series of simple examples, beginning with the harmonic oscillator, we show that systems in a stationary state such as an energy eigenstate or thermal state can exhibit decoherent histories with non-trivial dynamics. We then examine decoherent histories in a universe that undergoes eternal inflation. Decoherent histories that assign probabilities to sequences of events in the vicinity of a timelike geodesic supply a natural cosmological measure. Under reasonable conditions, such sequences of events do not suffer from the presence of unlikely statistical fluctuations that mimic reality.

  6. Decoherence in optimized quantum random-walk search algorithm

    Science.gov (United States)

    Zhang, Yu-Chao; Bao, Wan-Su; Wang, Xiang; Fu, Xiang-Qun

    2015-08-01

    This paper investigates the effects of decoherence generated by broken-link-type noise in the hypercube on an optimized quantum random-walk search algorithm. When the hypercube occurs with random broken links, the optimized quantum random-walk search algorithm with decoherence is depicted through defining the shift operator which includes the possibility of broken links. For a given database size, we obtain the maximum success rate of the algorithm and the required number of iterations through numerical simulations and analysis when the algorithm is in the presence of decoherence. Then the computational complexity of the algorithm with decoherence is obtained. The results show that the ultimate effect of broken-link-type decoherence on the optimized quantum random-walk search algorithm is negative. Project supported by the National Basic Research Program of China (Grant No. 2013CB338002).

  7. Decoherence in Sub-Systems of an Isolated System and the Disappearance of Quantum Multiverse

    CERN Document Server

    Ishikawa, Takuji

    2016-01-01

    This study was started to know mysterious classicality of nuclei. Using three particles model without external environments, it is found that decisions of respective state of three particles by decoherence are not simultaneous. Furthermore, in this model, wave function of total three body system collapses spontaneously without any external environments. Therefore we may able to insist that a wavefunction of our universe has already collapsed spontaneously without any external observer, because of the same mechanism with this model.

  8. Preclinical models of conduct disorder - principles and pharmacologic perspectives.

    Science.gov (United States)

    Haller, Jozsef

    2016-05-26

    The translational value of preclinical research was recently enhanced by abnormal aggression models, which focus on deviant behaviors induced by the exposure of rodents to etiological factors of aggression-related psychopathologies. Prompted by similar trials in other psychiatric disorders, here we investigate models of abnormal aggression from the perspective of DSM5 criteria. After proposing principles based on which analogies can be established between psychopathology symptoms and rodent behavioral dysfunctions, we show that rodents submitted to abnormal aggression models fulfill basic criteria of aggression-related psychopathologies; moreover, some models can be considered specific to particular disorders e.g. conduct disorder. We also show that abnormal and species-typical aggressions differ in terms of both brain mechanisms and pharmacological responsiveness, which mimics differences observed in psychiatric disorders. We conclude that evaluating abnormal aggression models from a DSM5 perspective is not only possible but also worthwhile, and such models may contribute to the development of novel treatment strategies not only for aggression as a symptom but also for specific aggression-related disorders or multi-symptom clusters at least. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. New strategy for suppressing decoherence in quantum computation

    CERN Document Server

    Dugic, M

    2000-01-01

    Controlable strong interaction of the qubit's bath with an external system (i.e. with the bath's environment) allows for choosing the conditions under which the decoherence of the qubit's states can be substantially decreased (in a certain limit: completely avoided). By "substantially decreased" we mean that the correlations which involve the bath's states prove negligible, while the correlations between the qubit's and the environment's states can be made ineffective during a comparatively long time interval. So, effectively, one may choose the conditions under which, for sufficiently long time interval, the initial state of "qubit + bath" remains unchanged, thus removing any kind of the errors. The method has been successfully employed in the (simplified) model of the solid-state-nuclear quantum computer (proposed by Kane).

  10. Mechanisms of decoherence in electron microscopy.

    Science.gov (United States)

    Howie, A

    2011-06-01

    The understanding and where possible the minimisation of decoherence mechanisms in electron microscopy were first studied in plasmon loss, diffraction contrast images but are of even more acute relevance in high resolution TEM phase contrast imaging and electron holography. With the development of phase retrieval techniques they merit further attention particularly when their effect cannot be eliminated by currently available energy filters. The roles of electronic excitation, thermal diffuse scattering, transition radiation and bremsstrahlung are examined here not only in the specimen but also in the electron optical column. Terahertz-range aloof beam electronic excitation appears to account satisfactorily for recent observations of decoherence in electron holography. An apparent low frequency divergence can emerge for the calculated classical bremsstrahlung event probability but can be ignored for photon wavelengths exceeding the required coherence distance or path lengths in the equipment. Most bremsstrahlung event probabilities are negligibly important except possibly in large-angle bending magnets or mandolin systems. A more reliable procedure for subtracting thermal diffuse scattering from diffraction pattern intensities is proposed. Copyright © 2010 Elsevier B.V. All rights reserved.

  11. Experimental entanglement redistribution under decoherence channels.

    Science.gov (United States)

    Aguilar, G H; Valdés-Hernández, A; Davidovich, L; Walborn, S P; Souto Ribeiro, P H

    2014-12-12

    When an initially entangled pair of qubits undergoes local decoherence processes, there are a number of ways in which the original entanglement can spread throughout the multipartite system consisting of the two qubits and their environments. Here, we report theoretical and experimental results regarding the dynamics of the distribution of entanglement in this system. The experiment employs an all optical setup in which the qubits are encoded in the polarization degrees of freedom of two photons, and each local decoherence channel is implemented with an interferometer that couples the polarization to the path of each photon, which acts as an environment. We monitor the dynamics and distribution of entanglement and observe the transition from bipartite to multipartite entanglement and back, and show how these transitions are intimately related to the sudden death and sudden birth of entanglement. The multipartite entanglement is further analyzed in terms of three- and four-partite entanglement contributions, and genuine four-qubit entanglement is observed at some points of the evolution.

  12. First principles modeling of nonlinear incidence rates in seasonal epidemics.

    Directory of Open Access Journals (Sweden)

    José M Ponciano

    2011-02-01

    Full Text Available In this paper we used a general stochastic processes framework to derive from first principles the incidence rate function that characterizes epidemic models. We investigate a particular case, the Liu-Hethcote-van den Driessche's (LHD incidence rate function, which results from modeling the number of successful transmission encounters as a pure birth process. This derivation also takes into account heterogeneity in the population with regard to the per individual transmission probability. We adjusted a deterministic SIRS model with both the classical and the LHD incidence rate functions to time series of the number of children infected with syncytial respiratory virus in Banjul, Gambia and Turku, Finland. We also adjusted a deterministic SEIR model with both incidence rate functions to the famous measles data sets from the UK cities of London and Birmingham. Two lines of evidence supported our conclusion that the model with the LHD incidence rate may very well be a better description of the seasonal epidemic processes studied here. First, our model was repeatedly selected as best according to two different information criteria and two different likelihood formulations. The second line of evidence is qualitative in nature: contrary to what the SIRS model with classical incidence rate predicts, the solution of the deterministic SIRS model with LHD incidence rate will reach either the disease free equilibrium or the endemic equilibrium depending on the initial conditions. These findings along with computer intensive simulations of the models' Poincaré map with environmental stochasticity contributed to attain a clear separation of the roles of the environmental forcing and the mechanics of the disease transmission in shaping seasonal epidemics dynamics.

  13. First principles modeling of nonlinear incidence rates in seasonal epidemics.

    Science.gov (United States)

    Ponciano, José M; Capistrán, Marcos A

    2011-02-01

    In this paper we used a general stochastic processes framework to derive from first principles the incidence rate function that characterizes epidemic models. We investigate a particular case, the Liu-Hethcote-van den Driessche's (LHD) incidence rate function, which results from modeling the number of successful transmission encounters as a pure birth process. This derivation also takes into account heterogeneity in the population with regard to the per individual transmission probability. We adjusted a deterministic SIRS model with both the classical and the LHD incidence rate functions to time series of the number of children infected with syncytial respiratory virus in Banjul, Gambia and Turku, Finland. We also adjusted a deterministic SEIR model with both incidence rate functions to the famous measles data sets from the UK cities of London and Birmingham. Two lines of evidence supported our conclusion that the model with the LHD incidence rate may very well be a better description of the seasonal epidemic processes studied here. First, our model was repeatedly selected as best according to two different information criteria and two different likelihood formulations. The second line of evidence is qualitative in nature: contrary to what the SIRS model with classical incidence rate predicts, the solution of the deterministic SIRS model with LHD incidence rate will reach either the disease free equilibrium or the endemic equilibrium depending on the initial conditions. These findings along with computer intensive simulations of the models' Poincaré map with environmental stochasticity contributed to attain a clear separation of the roles of the environmental forcing and the mechanics of the disease transmission in shaping seasonal epidemics dynamics.

  14. Eigenmode description of Raman scattering in atomic vapors in the presence of decoherence

    OpenAIRE

    Kolodynski, Jan; Chwedenczuk, Jan; Wasilewski, Wojciech

    2012-01-01

    A theoretical model describing the Raman scattering process in atomic vapors is constructed. The treatment investigates the low-excitation regime suitable for modern experimental applications. Despite the incorporated decoherence effects (possibly mode dependent) it allows for a direct separation of the time evolution from the spatial degrees of freedom. The impact of noise on the temporal properties of the process is examined. The model is applied in two experimentally relevant situations of...

  15. First-principles modeling of magnetic misfit interfaces

    KAUST Repository

    Grytsyuk, Sergiy

    2013-08-16

    We investigate the structural and magnetic properties of interfaces with large lattice mismatch, choosing Pt/Co and Au/Co as prototypes. For our first-principles calculations, we reduce the lattice mismatch to 0.2% by constructing Moiré supercells. Our results show that the roughness and atomic density, and thus the magnetic properties, depend strongly on the substrate and thickness of the Co slab. An increasing thickness leads to the formation of a Co transition layer at the interface, especially for Pt/Co due to strong Pt-Co interaction. A Moiré supercell with a transition layer is found to reproduce the main experimental findings and thus turns out to be the appropriate model for simulating magnetic misfit interfaces.

  16. Principles of the Proposed Czech Postal Sector Price Control Model

    Directory of Open Access Journals (Sweden)

    Libor Švadlenka

    2009-01-01

    Full Text Available The paper deals with the postal sector control. It resultsfrom the control theory and proves the justifiability of control inthe postal sector. Within the price control it results from E U Directive97!67/EC requirements on this control and states individualtypes of price control focusing on ineffective price controlcurrently used in the Czech postal sector (especially withindomestic services and proposes a more effective method ofprice control. The paper also discusses the principles of the proposedmethod of price control of the Czech postal sector. It describesconcrete fulfilment of the price control model resultingfrom the price-cap and tariff formula RP I-X and concentrateson its quantitative expression. The application of the proposedmodel is carried out for a hypothetical period in the past (in orderto compare it with the current control system for letteritems tariff basket.

  17. First Principles Modelling of Shape Memory Alloys Molecular Dynamics Simulations

    CERN Document Server

    Kastner, Oliver

    2012-01-01

    Materials sciences relate the macroscopic properties of materials to their microscopic structure and postulate the need for holistic multiscale research. The investigation of shape memory alloys is a prime example in this regard. This particular class of materials exhibits strong coupling of temperature, strain and stress, determined by solid state phase transformations of their metallic lattices. The present book presents a collection of simulation studies of this behaviour. Employing conceptually simple but comprehensive models, the fundamental material properties of shape memory alloys are qualitatively explained from first principles. Using contemporary methods of molecular dynamics simulation experiments, it is shown how microscale dynamics may produce characteristic macroscopic material properties. The work is rooted in the materials sciences of shape memory alloys and  covers  thermodynamical, micro-mechanical  and crystallographical aspects. It addresses scientists in these research fields and thei...

  18. An electromechanical model of neuronal dynamics using Hamilton's principle

    Science.gov (United States)

    Drapaca, Corina S.

    2015-01-01

    Damage of the brain may be caused by mechanical loads such as penetration, blunt force, shock loading from blast, and by chemical imbalances due to neurological diseases and aging that trigger not only neuronal degeneration but also changes in the mechanical properties of brain tissue. An understanding of the interconnected nature of the electro-chemo-mechanical processes that result in brain damage and ultimately loss of functionality is currently lacking. While modern mathematical models that focus on how to link brain mechanics to its biochemistry are essential in enhancing our understanding of brain science, the lack of experimental data required by these models as well as the complexity of the corresponding computations render these models hard to use in clinical applications. In this paper we propose a unified variational framework for the modeling of neuronal electromechanics. We introduce a constrained Lagrangian formulation that takes into account Newton's law of motion of a linear viscoelastic Kelvin–Voigt solid-state neuron as well as the classic Hodgkin–Huxley equations of the electronic neuron. The system of differential equations describing neuronal electromechanics is obtained by applying Hamilton's principle. Numerical simulations of possible damage dynamics in neurons will be presented. PMID:26236195

  19. An electromechanical model of neuronal dynamics using Hamilton's principle.

    Science.gov (United States)

    Drapaca, Corina S

    2015-01-01

    Damage of the brain may be caused by mechanical loads such as penetration, blunt force, shock loading from blast, and by chemical imbalances due to neurological diseases and aging that trigger not only neuronal degeneration but also changes in the mechanical properties of brain tissue. An understanding of the interconnected nature of the electro-chemo-mechanical processes that result in brain damage and ultimately loss of functionality is currently lacking. While modern mathematical models that focus on how to link brain mechanics to its biochemistry are essential in enhancing our understanding of brain science, the lack of experimental data required by these models as well as the complexity of the corresponding computations render these models hard to use in clinical applications. In this paper we propose a unified variational framework for the modeling of neuronal electromechanics. We introduce a constrained Lagrangian formulation that takes into account Newton's law of motion of a linear viscoelastic Kelvin-Voigt solid-state neuron as well as the classic Hodgkin-Huxley equations of the electronic neuron. The system of differential equations describing neuronal electromechanics is obtained by applying Hamilton's principle. Numerical simulations of possible damage dynamics in neurons will be presented.

  20. An Electromechanical Model of Neuronal Dynamics using Hamilton's Principle

    Directory of Open Access Journals (Sweden)

    Corina Stefania Drapaca

    2015-07-01

    Full Text Available Damage of the brain may be caused by mechanical loads such as penetration, blunt force, shock loading from blast, and by chemical imbalances due to neurological diseases and aging that trigger not only neuronal degeneration but also changes in the mechanical properties of brain tissue. An understanding of the interconnected nature of the electro-chemo-mechanical processes that result in brain damage and ultimately loss of functionality is currently lacking. While modern mathematical models that focus on how to link brain mechanics to its biochemistry are essential in enhancing our understanding of brain science, the lack of experimental data required by these models as well as the complexity of the corresponding computations render these models hard to use in clinical applications. In this paper we propose a unified variational framework for the modeling of neuronal electromechanics. We introduce a constrained Lagrangian formulation that takes into account Newton's law of motion of a linear viscoelastic Kelvin-Voigt solid-state neuron as well as the classic Hodgkin-Huxley equations of the electronic neuron. The system of differential equations describing neuronal electromechanics is obtained by applying Hamilton's principle. Numerical simulations of possible damage dynamics in neurons will be presented.

  1. A structured modeling approach for dynamic hybrid fuzzy-first principles models

    NARCIS (Netherlands)

    Lith, van Pascal F.; Betlem, Ben H.L.; Roffel, Brian

    2002-01-01

    Hybrid fuzzy-first principles models can be attractive if a complete physical model is difficult to derive. These hybrid models consist of a framework of dynamic mass and energy balances, supplemented with fuzzy submodels describing additional equations, such as mass transformation and transfer rate

  2. Electron phase and spin decoherence in the vicinity of the second subband edge in an asymmetrical quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Saveliev, I G [Ioffe Institute, Russian Academy of Sciences, 194021 St Petersburg (Russian Federation); Bykanov, D D [Ioffe Institute, Russian Academy of Sciences, 194021 St Petersburg (Russian Federation); Novikov, S V [Ioffe Institute, Russian Academy of Sciences, 194021 St Petersburg (Russian Federation); Polyanskaya, T A [Ioffe Institute, Russian Academy of Sciences, 194021 St Petersburg (Russian Federation); Ruda, H [University of Toronto, 170 College St, Toronto, ON, M5S 3E3 (Canada)

    2004-02-04

    Weak antilocalization of a two-dimensional electron gas formed at a In{sub 0.53}Ga{sub 0.47}As/InP heterointerface was studied. The Fermi level was varied from below, to above, the energy minimum of the second subband. A model for quantum coherence with two conducting subbands and fast intersubband scattering was used to extract the characteristic phase and spin decoherence rates from experimental magnetoresistance data. Taking into account the spatial inhomogeneity of the energy associated with the subband minimum, the first and second subband decoherence contributions were separated. It was shown that phase decoherence in the second subband is much faster than in the first subband and it decreases with increasing occupation of the second subband. By contrast, spin dephasing due to scattering in the second subband and intersubband scattering does not play a noticeable role.

  3. Simulation Modeling in Plant Breeding: Principles and Applications

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-kang; Wolfgang H Pfeiffer

    2007-01-01

    Conventional plant breeding largely depends on phenotypic selection and breeder's experience, therefore the breeding efficiency is low and the predictions are inaccurate. Along with the fast development in molecular biology and biotechnology, a large amount of biological data is available for genetic studies of important breeding traits in plants,which in turn allows the conduction of genotypic selection in the breeding process. However, gene information has not been effectively used in crop improvement because of the lack of appropriate tools. The simulation approach can utilize the vast and diverse genetic information, predict the cross performance, and compare different selection methods. Thus,the best performing crosses and effective breeding strategies can be identified. QuLine is a computer tool capable of defining a range, from simple to complex genetic models, and simulating breeding processes for developing final advanced lines. On the basis of the results from simulation experiments, breeders can optimize their breeding methodology and greatly improve the breeding efficiency. In this article, the underlying principles of simulation modeling in crop enhancement is initially introduced, following which several applications of QuLine are summarized, by comparing the different selection strategies, the precision parental selection, using known gene information, and the design approach in breeding. Breeding simulation allows the definition of complicated genetic models consisting of multiple alleles, pleiotropy, epistasis, and genes, by environment interaction, and provides a useful tool for breeders, to efficiently use the wide spectrum of genetic data and information available.

  4. Decoherence of two-qubit system in a non-Markovian squeezed reservoir

    Institute of Scientific and Technical Information of China (English)

    Wang Fa-Qiang; Zhang Zhi-Ming; Liang Rui-Sheng

    2009-01-01

    The decoherence of two initially entangled qubits coupled with a squeezed vacuum cavity separately is investigated exactly. The results show that, first, in principle, the disentanglement time decreases with the increase of squeeze parameter r, due to the augmenting of average photon number of every mode in the squeezed vacuum cavity. Second, there appear entanglement revivals after the complete disentanglement for the case of even parity initial Bell state, while there occur the entanglement decrcase and the entanglement revival before the complete disentanglement for the case of odd parity initial Bell state. The results are quite different from those for the case of qubits in a vacuum cavity.

  5. Minimum decoherence cat-like states in Gaussian noisy channels

    Energy Technology Data Exchange (ETDEWEB)

    Serafini, A [Dipartimento di Fisica ' E R Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, G C Salerno, Via S Allende, 84081 Baronissi, SA (Italy); De Siena, S [Dipartimento di Fisica ' E R Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, G C Salerno, Via S Allende, 84081 Baronissi, SA (Italy); Illuminati, F [Dipartimento di Fisica ' E R Caianiello' , Universita di Salerno, INFM UdR Salerno, INFN Sezione Napoli, G C Salerno, Via S Allende, 84081 Baronissi, SA (Italy); Paris, M G A [ISIS ' A Sorbelli' , I-41026 Pavullo nel Frignano, MO (Italy)

    2004-06-01

    We address the evolution of cat-like states in general Gaussian noisy channels, by considering superpositions of coherent and squeezed coherent states coupled to an arbitrarily squeezed bath. The phase space dynamics is solved and decoherence is studied, keeping track of the purity of the evolving state. The influence of the choice of the state and channel parameters on purity is discussed and optimal working regimes that minimize the decoherence rate are determined. In particular, we show that squeezing the bath to protect a non-squeezed cat state against decoherence is equivalent to orthogonally squeezing the initial cat state while letting the bath be phase insensitive.

  6. Minimum decoherence cat-like states in Gaussian noisy channels

    CERN Document Server

    Serafini, A; Illuminati, F; Paris, M G A

    2004-01-01

    We address the evolution of cat-like states in general Gaussian noisy channels, by considering superpositions of coherent and squeezed-coherent states coupled to an arbitrarily squeezed bath. The phase space dynamics is solved and decoherence is studied keeping track of the purity of the evolving state. The influence of the choice of the state and channel parameters on purity is discussed and optimal working regimes that minimize the decoherence rate are determined. In particular, we show that squeezing the bath to protect a non squeezed cat state against decoherence is equivalent to orthogonally squeezing the initial cat state while letting the bath be phase insensitive.

  7. Saving entangled photons from sudden death is a single-mode fiber --- Interplay of Decoherence and dynamical decoupling

    Science.gov (United States)

    Gupta, Manish Kumar; You, Chenglong; Dowling, Jonathan P.; Lee, Hwang

    2016-05-01

    We study the dynamics of decoherence in an optical fiber for the case of entangled photons. Such a study will allow us to increase the physical length of fiber for transmission of entangled photon from the sources such as SPDC. We analytically derive the model for Decoherence of entangled state photons in a single-mode fiber. We also show that entanglement lifetime can be increased for Bell state and Werner state with open loop control technique called Dynamical decoupling. The authors would like to acknowledge support from the Air Force Office of Scientific Research, the Army Research Office, the National Science Foundation and the Northrop Grumman Corporation.

  8. Decoherence of entangled states by colored noise: application to precision measurements

    Science.gov (United States)

    Andre, Axel; Sorensen, Anders; Lukin, Mikhail; van der Wal, Caspar

    2003-05-01

    Controlled manipulation of quantum systems can lead to a number of exciting new applications in quantum information science, from quantum computation to applications in precision measurements. In many such applications, decoherence is a key factor to take into account and ultimately determines the feasibility or usefulness of the proposal. The decoherence of quantum mechanical degrees of freedom is usually modeled through their interaction with a bath consisting of a large number of harmonic oscillators. The separation of energy scales between the energy of the oscillators and the interaction energy leads to separation of time scales so that the decoherence process can be modeled effectively by a markovian process (infinitely short reservoir correlation time). Low-lying state are long-lived and are therefore ideally suited for storage of quantum information and long-lived quantum memory. Due to their long lifetime, these states are sensitive to the low frequency noise of the environment. In particular 1/f noise is dominating at low frequencies and this changes the form of the decoherence. In this case, non-exponential decay is to be expected so that the importance of decoherence depends on the time-scale. We consider the accuracy of frequency measurements using the Ramsey technique when the ensemble of atoms is subject to colored noise during the measurement. It has been shown that the use of entangled states of atomic ensembles (so-called spin squeezed states) may lead to an improvement in the accuracy of frequency measurements when the system is noiseless [1]. To assess the usefulness in a real setup decoherence has to be taken into account. It has been shown that for white noise spectra the net improvement is very small [2], this conclusion is however changed significantly when the system is influenced by colored noise. We study phase noise of the reference oscillator in frequency measurements and show that for non-white noise spectra (e.g. when the noise power

  9. Eigenmode description of Raman scattering in atomic vapors in the presence of decoherence

    CERN Document Server

    Chwedenczuk, Jan; Wasilewski, Wojciech

    2012-01-01

    A theoretical model describing the Raman scattering process in atomic vapors is constructed. Despite the incorporated decoherence effects, it allows for a direct separation of system's time evolution from its spatial degrees of freedom. The impact of noise on the temporal properties of the system is investigated. In particular, it is shown that even in the presence of decoherence, the estimation of the number of spin waves created in the process can reach sensitivity below the projection noise limit. The model is then applied in two experimentally relevant situations of ultra-cold and room-temperature atoms. In both cases, the spatial eigenmodes of the Stokes photon and atomic excitation fields and their coupling parameters are computed.

  10. Multiplayer quantum Minority game with decoherence

    CERN Document Server

    Flitney, A P; Flitney, Adrian P.; Hollenberg, Lloyd C. L.

    2005-01-01

    A quantum version of the Minority game for an arbitrary number of agents is studied. When the number of agents is odd, quantizing the game produces no advantage to the players, however, for an even number of agents new Nash equilibria appear that have no classical analogue. The new Nash equilibria provide far preferable expected payoffs to the players compared to the equivalent classical game. The effect on the Nash equilibrium payoff of reducing the degree of initial entanglement between the players' qubits or of introducing various forms of decoherence is discussed. As the number of players increases the multipartite GHZ state becomes increasingly fragile, as indicated by the smaller error probability required to reduce the Nash equilibrium payoff to the classical level.

  11. Decoherence of mesoscopic states of cavity fields

    CERN Document Server

    Fonseca-Romero, K M; De Faria, J G P; Salgueiro, A N; De Toledo di Piza, A F R

    1998-01-01

    We show that two-atom correlation measurements of the type involved in a recent experimental study of the evolution of a mesoscopic superposition state prepared in a definite mode of a high-Q cavity can be used to determine the eigenvalues of the reduced density matrix of the field, provided the assumed dynamical conditions are actually fulfilled to experimental accuracy. These conditions involve i) a purely dispersive coupling of the field to the Rydberg atoms used to manipulate and to monitor the cavity field, and ii) the effective absence of correlations in the ground state of the system consisting of the cavity coupled to the ``reservoir'' which accounts for the decoherence and damping processes. A microscopic calculation at zero temperature is performed and compared to master equation results.

  12. Reduction of thermal decoherence by optical trapping

    CERN Document Server

    Matsumoto, Nobuyuki; Ito, Sosuke; Michimura, Yuta; Aso, Yoichi

    2016-01-01

    We demonstrate stable control of a massive oscillator's displacement response to an applied force, an important step towards reveling the quantum behavior of massive objects. In this technique, a suspended mirror is optically trapped via a detuned cavity, and its dissipation is controlled by electrical active feedback on an another mirror, which generates damping forces on the target mirror through optical rigidity. We experimentally demonstrate the technique with a 5-mg suspended mirror, which is a part of a triangular optical cavity. The observed enhancement of the pendulum's resonant frequency is from 2.14 Hz to 1.06 kHz, and the lowest temperature achieved is 15 mK. Using this technique we demonstrate reduction of the thermal decoherence rate, i.e. the inverse time of the absorption of a phonon from the thermal environment, of 60-fold from its bare value.

  13. A Simple Model of Entrepreneurship for Principles of Economics Courses

    Science.gov (United States)

    Gunter, Frank R.

    2012-01-01

    The critical roles of entrepreneurs in creating, operating, and destroying markets, as well as their importance in driving long-term economic growth are still generally either absent from principles of economics texts or relegated to later chapters. The primary difficulties in explaining entrepreneurship at the principles level are the lack of a…

  14. Quantum Decoherence Timescales for Ionic Superposition States in Ion Channels

    CERN Document Server

    Salari, V; Fazileh, F; Shahbazi, F

    2014-01-01

    There are many controversial and challenging discussions about quantum effects in microscopic structures in neurons of the human brain. The challenge is mainly because of quick decoherence of quantum states due to hot, wet and noisy environment of the brain which forbids long life coherence for brain processing. Despite these critical discussions, there are only a few number of published papers about numerical aspects of decoherence in neurons. Perhaps the most important issue is offered by Max Tegmark who has calculated decoherence times for the systems of "ions" and "microtubules" in neurons of the brain. In fact, Tegmark did not consider ion channels which are responsible for ions displacement through the membrane and are the building blocks of electrical membrane signals in the nervous system. Here, we would like to re-investigate decoherence times for ionic superposition states by using the data obtained via molecular dynamics simulations. Our main approach is according to what Tegmark has used before. I...

  15. Decoherence of matter waves by thermal emission of radiation

    CERN Document Server

    Hackermüller, L; Brezger, B; Zeilinger, Anton; Arndt, M; Hackermueller, Lucia; Hornberger, Klaus; Brezger, Bjoern; Zeilinger, Anton; Arndt, Markus

    2004-01-01

    Emergent quantum technologies have led to increasing interest in decoherence - the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory has been complemented by experiments using matter waves coupled to external photons or molecules, and by investigations using coherent photon states, trapped ions and electron interferometers. Large molecules are particularly suitable for the investigation of the quantum-classical transition because they can store much energy in numerous internal degrees of freedom; the internal energy can be converted into thermal radiation and thus induce decoherence. Here we report matter wave interferometer experiments in which C70 molecules lose their quantum behaviour by thermal emission of radiation. We find...

  16. How detrimental is decoherence in adiabatic quantum computation?

    CERN Document Server

    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...

  17. Observation of decoherence in a carbon nanotube mechanical resonator.

    Science.gov (United States)

    Schneider, Ben H; Singh, Vibhor; Venstra, Warner J; Meerwaldt, Harold B; Steele, Gary A

    2014-12-19

    In physical systems, decoherence can arise from both dissipative and dephasing processes. In mechanical resonators, the driven frequency response measures a combination of both, whereas time-domain techniques such as ringdown measurements can separate the two. Here we report the first observation of the mechanical ringdown of a carbon nanotube mechanical resonator. Comparing the mechanical quality factor obtained from frequency- and time-domain measurements, we find a spectral quality factor four times smaller than that measured in ringdown, demonstrating dephasing-induced decoherence of the nanomechanical motion. This decoherence is seen to arise at high driving amplitudes, pointing to a nonlinear dephasing mechanism. Our results highlight the importance of time-domain techniques for understanding dissipation in nanomechanical resonators, and the relevance of decoherence mechanisms in nanotube mechanics.

  18. Observation of decoherence in a carbon nanotube mechanical resonator

    Science.gov (United States)

    Schneider, Ben H.; Singh, Vibhor; Venstra, Warner J.; Meerwaldt, Harold B.; Steele, Gary A.

    2014-12-01

    In physical systems, decoherence can arise from both dissipative and dephasing processes. In mechanical resonators, the driven frequency response measures a combination of both, whereas time-domain techniques such as ringdown measurements can separate the two. Here we report the first observation of the mechanical ringdown of a carbon nanotube mechanical resonator. Comparing the mechanical quality factor obtained from frequency- and time-domain measurements, we find a spectral quality factor four times smaller than that measured in ringdown, demonstrating dephasing-induced decoherence of the nanomechanical motion. This decoherence is seen to arise at high driving amplitudes, pointing to a nonlinear dephasing mechanism. Our results highlight the importance of time-domain techniques for understanding dissipation in nanomechanical resonators, and the relevance of decoherence mechanisms in nanotube mechanics.

  19. Modeling of space environment impact on nanostructured materials. General principles

    Science.gov (United States)

    Voronina, Ekaterina; Novikov, Lev

    2016-07-01

    In accordance with the resolution of ISO TC20/SC14 WG4/WG6 joint meeting, Technical Specification (TS) 'Modeling of space environment impact on nanostructured materials. General principles' which describes computer simulation methods of space environment impact on nanostructured materials is being prepared. Nanomaterials surpass traditional materials for space applications in many aspects due to their unique properties associated with nanoscale size of their constituents. This superiority in mechanical, thermal, electrical and optical properties will evidently inspire a wide range of applications in the next generation spacecraft intended for the long-term (~15-20 years) operation in near-Earth orbits and the automatic and manned interplanetary missions. Currently, ISO activity on developing standards concerning different issues of nanomaterials manufacturing and applications is high enough. Most such standards are related to production and characterization of nanostructures, however there is no ISO documents concerning nanomaterials behavior in different environmental conditions, including the space environment. The given TS deals with the peculiarities of the space environment impact on nanostructured materials (i.e. materials with structured objects which size in at least one dimension lies within 1-100 nm). The basic purpose of the document is the general description of the methodology of applying computer simulation methods which relate to different space and time scale to modeling processes occurring in nanostructured materials under the space environment impact. This document will emphasize the necessity of applying multiscale simulation approach and present the recommendations for the choice of the most appropriate methods (or a group of methods) for computer modeling of various processes that can occur in nanostructured materials under the influence of different space environment components. In addition, TS includes the description of possible

  20. Optimal Control of High-Fidelity Quantum Gates in the Presence of Decoherence

    CERN Document Server

    Grace, M; Kosut, R; Lidar, D A; Rabitz, H; Walmsley, I; Brif, Constantin; Grace, Matthew; Kosut, Robert; Lidar, Daniel A.; Rabitz, Herschel; Walmsley, Ian

    2006-01-01

    This work studies the feasibility of optimal control of high-fidelity quantum gates in a model of interacting two-level particles. One set of particles serves as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one- and two-qubit gates in the presence of strong environmentally-induced decoherence and physically motivated restrictions on the control field. The quantum-gate fidelity, expressed in terms of a state-independent distance measure, is maximized with respect to the control field using combined genetic and gradient algorithms. The resulting high-fidelity gates demonstrate the utility of optimal control for precise management of quantum dynamics, especially when the system complexity is exacerbated by environmental coupling.

  1. Parameter Limits for Neutrino Oscillation with Decoherence in KamLAND

    CERN Document Server

    Gomes, G Balieiro; de Holanda, P C; Oliveira, R L N

    2016-01-01

    In the framework of quantum open systems we analyze data from KamLAND by using a model that considers neutrino oscillation in a three-family approximation with the inclusion of the decoherence effect. Using a $\\chi^2$ test we find new limits for the decoherence parameter which we call $\\gamma$, considering the most recent data by KamLAND. Assuming an energy dependence of the type $ \\gamma = \\gamma_0 \\left( E/E_0 \\right) ^n$, in 95 \\% C.L. the limits found are $3.7 \\times 10^{-27} GeV$ for $ n=-1$, $6.8 \\times 10^{-22} GeV$ for $ n=0$, and $1.5 \\times 10^{-16} GeV$ for $ n=1 $ on the energy dependence.

  2. Action scales for decoherence and their relation to structures in phase space

    CERN Document Server

    Alonso, D; Palao, J P; Mayato, R S; Alonso, Daniel; Palao, Jose P.

    2003-01-01

    A characteristic action $\\Delta S$ is defined whose magnitude determines the basic properties of the mean expectation value of a general displacement in phase space. These properties are related to the capability of a given environmental `monitoring' system to induce decoherence in arbitrary quantum systems coupled to it by a broad kind of interactions. We show that according to this quantity the scale for effective decoherence is given by $\\Delta S \\gtrsim\\hbar$. This characteristic action is compared with another previously defined quantity \\cite{zurek2001}, and its connection with the main features of the pattern of structures developed by the different phase space representations of the environmental state is analyzed. The relevance of $\\Delta S$ is illustrated both numerically and by analyzing a set of model quantum systems whose classical analog is chaotic, for which the Berry-Voros conjecture is valid, and where analytical expressions for the mean expectation value of the displacement are obtained expl...

  3. Intrinsic decoherence of entanglement of a single quantized field interacting with a two-level atom

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    How the mean photon number, the probability of excited state and intrinsic decoherence coefficient influence the time evolution of entanglement is unknown, when a single-mode quantized optic field and a two-level atom coupling system is governed by Milburn equation. The Jaynes-Cummings model is considered. A lower bound of concurrence is proposed to calculate the entanglement. Simulation results indicate that the entanglement of system increases following the increasing of intrinsic decoherence coefficient or the decreasing of the mean photon number. Besides that, the entanglement of system decreases, while the probability of exited state increases from 0 to 0.1, and increases, while the probability of exited state increases from 0.1 to 1.

  4. Atom dynamics in optical lattices: Time-dependent simulation and decoherence suppression

    Science.gov (United States)

    de Rinaldis, Sergio; Lidar, Daniel A.

    2004-03-01

    We develop a model to simulate the dynamics of atoms trapped in an optical lattice with gravity in the presence of natural decoherence. The latter, measured by quantum process tomography, is dominated by pure dephasing. The wavefunction is represented on a grid and the time dependent evolution operator is expanded in Chebychev polynomials according to the (t,t') method (*), while a fictitious environment is introduced that simulates the observed dephasing. The control field consists in raising or lowering the potential wells of the atoms and modifying the phase of the laser fields (that results in a translation of the lattice). As an example relevant for quantum information processing, we simulate the effect of bang-bang pulses designed to suppress decoherence. (*) Ref. U.Peskin, R. Kosloff, N. Moiseyev, J. Chem. Phys. 8849 (1994)

  5. Adaptive Coarse Graining, Environment, Strong Decoherence, and Quasiclassical Realms

    CERN Document Server

    Gell-Mann, Murray

    2013-01-01

    Three ideas are introduced that when brought together characterize the realistic quasiclassical realms of our quantum universe as particular kinds of sets of alternative coarse-grained histories defined by quasiclassical variables: (1) Branch dependent adaptive coarse grainings that can be close to maximally refined and can simplify calculation. (2) Narrative coarse grainings that describe how features of the universe change over time and allow the construction of an environment. (3) A notion of strong decoherence that characterizes realistic mechanisms of decoherence.

  6. Decoherence and coherence in gravitational, electric and strong nuclear fields

    CERN Document Server

    Silva, P R

    2010-01-01

    Inspired in the work of Erich Joos which appreciated the role played by matter in making the decoherence of the gravitational field, we developed an alternative way of treating the former problem. Besides this, we used the alternative approach to examine the decoherence of the electric field performed by the conduction electrons in metals. As a counterpoint, we studied the coherence of the electric color field inside nucleons, which renders the strong field a totally quantum character.

  7. Decoherence in quantum systems in a static gravitational field

    CERN Document Server

    Shariati, Ahmad; Loran, Farhang

    2016-01-01

    A small quantum system is studied which is a superposition of states localized in different positions in a static gravitational field. The time evolution of the correlation between different positions is investigated, and it is seen that there are two time scales for such an evolution (decoherence). Both time scales are inversely proportional to the red shift difference between the two points. These time scales correspond to decoherences which are linear and quadratic, respectively, in time.

  8. Decoherence of matter waves by thermal emission of radiation.

    Science.gov (United States)

    Hackermüller, Lucia; Hornberger, Klaus; Brezger, Björn; Zeilinger, Anton; Arndt, Markus

    2004-02-19

    Emergent quantum technologies have led to increasing interest in decoherence--the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory has been complemented by experiments using matter waves coupled to external photons or molecules, and by investigations using coherent photon states, trapped ions and electron interferometers. Large molecules are particularly suitable for the investigation of the quantum-classical transition because they can store much energy in numerous internal degrees of freedom; the internal energy can be converted into thermal radiation and thus induce decoherence. Here we report matter wave interferometer experiments in which C70 molecules lose their quantum behaviour by thermal emission of radiation. We find good quantitative agreement between our experimental observations and microscopic decoherence theory. Decoherence by emission of thermal radiation is a general mechanism that should be relevant to all macroscopic bodies.

  9. Quantum repeaters based on CNOT gate under decoherence

    Institute of Scientific and Technical Information of China (English)

    TONG Zhao-yang; LIAO Ping; KUANG Le-man

    2007-01-01

    In this paper, we study single-qubit and single-user quantum repeaters based on CNOT gates under de, co-herence using the Kraus-operator representations of decoher-ence.We investigate the influence of decoherence on the information-disturbance trade-off of quantum repeaters. It is found that decoherence may lead to the appearance of three subspaces, called as the normal subspace, the anoma-lous subspace, and the decoherence-free subspace (DFS), re-spectively. It is indicated that in the normal subspace deco-herence decreases the transmission and estimation fidelities, in the anomalous subspace decoherence enhances these fideli-ties, and in the DFS these fidelities do not change. The con-cept of the quality factor is introduced to evaluate the quality of the quantum repeater. It is indicated that the quality factor can be efficiently controlled and manipulated by changing the initial state of the probe qubit. It is found that under certain conditions the quantum repeater can be optimal even in the presence of decoherence.

  10. Crucial role of decoherence for electronic transport in molecular wires: Polyaniline as a case study

    Science.gov (United States)

    Cattena, Carlos J.; Bustos-Marún, Raúl A.; Pastawski, Horacio M.

    2010-10-01

    In this work we attempt to elucidate the nature of conductivity in polymers by taking the acid-base doped polyaniline (PAni) polymer. We evaluate the PAni conductance by using realistic ab initio parameters and including decoherent processes within the minimal parametrization model of D’Amato-Pastawski. In contrast to general wisdom, which associates the conducting state with coherent propagation in a periodic polaronic lattice, we show that decoherence can account for high conductance in the strongly disordered bipolaronic lattice. Hence, according to our results, there is no need of considering a mix model of “conducting” polaronic lattice islands separated by “insulating” bipolaronic lattice strands as is usually assumed for PAni. We find that without dephasing events, even very short strands of bipolaronic lattices are not able to sustain electronic transport. We also include a discussion of specific mechanisms that should be involved in decoherence rates of PAni and relate them with Marcus-Hush theory of electron transfer.

  11. First-principles modelling of materials: From polythiophene to phosphorene

    Science.gov (United States)

    Ziletti, Angelo

    As a result of the computing power provided by the current technology, computational methods now play an important role in modeling and designing materials at the nanoscale. The focus of this dissertation is two-fold: first, new computational methods to model nanoscale transport are introduced, then state-of-the-art tools based on density functional theory are employed to explore the properties of phosphorene, a novel low dimensional material with great potential for applications in nanotechnology. A Wannier function description of the electron density is combined with a generalized Slater-Koster interpolation technique, enabling the introduction of a new computational method for constructing first-principles model Hamiltonians for electron and hole transport that maintain the density functional theory accuracy at a fraction of the computational cost. As a proof of concept, this new approach is applied to model polythiophene, a polymer ubiquitous in organic photovoltaic devices. A new low dimensional material, phosphorene - a single layer of black phosphorous - the phosphorous analogue of graphene was first isolated in early 2014 and has attracted considerable attention. It is a semiconductor with a sizable band gap, which makes it a perfect candidate for ultrathin transistors. Multi-layer phosphorene transistors have already achieved the highest hole mobility of any two-dimensional material apart from graphene. Phosphorene is prone to oxidation, which can lead to degradation of electrical properties, and eventually structural breakdown. The calculations reported here are some of the first to explore this oxidation and reveal that different types of oxygen defects are readily introduced in the phosphorene lattice, creating electron traps in some situations. These traps are responsible for the non-ambipolar behavior observed by experimental collaborators in air-exposed few-layer black phosphorus devices. Calculation results predict that air exposure of phosphorene

  12. Decoherence and oscillations of supernova neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    Kersten, Joern [University of Bergen, Institute for Physics and Technology (Norway); Smirnov, Alexei Yu. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); The Abdus Salam ICTP, Trieste (Italy)

    2016-06-15

    Supernova neutrinos have several exceptional features which can lead to interesting physical consequences. At the production point their wave packets have an extremely small size σ{sub x} ∝ 10{sup -11} cm; hence the energy uncertainty can be as large as the energy itself, σ{sub E} ∝ E, and the coherence length is short. On the way to the Earth the wave packets of mass eigenstates spread to macroscopic sizes and separate. Inside the Earth the mass eigenstates split into eigenstates in matter and oscillate again. The coherence length in the Earth is comparable with the radius of the Earth. We explore these features and their consequences. (1) We present new estimates of the wave packet size. (2) We consider the decoherence condition for the case of wave packets with spatial spread and show that it is not modified by the spread. (3) We study the coherence of neutrinos propagating in a multi-layer medium with density jumps at the borders of layers. In this case coherence can be partially restored due to a ''catch-up effect'', increasing the coherence length beyond the usual estimate. This catch-up effect can occur for supernova neutrinos as they cross the shock wave fronts in the exploding star or the core of the Earth. (orig.)

  13. Dynamics of multipartite quantum correlations under decoherence

    CERN Document Server

    Ramzan, M

    2012-01-01

    Quantum discord is an optimal resource for the quantification of classical and non-classical correlations as compared to other related measures. Geometric measure of quantum discord is another measure of quantum correlations. Recently, the geometric quantum discord for multipartite states has been introduced by Jianwei Xu [arxiv:quant/ph.1205.0330]. Motivated from the recent study [Ann. Phys. 327 (2012) 851] for the bipartite systems, I have investigated global quantum discord (QD) and geometric quantum discord (GQD) under the influence of external environments for different multipartite states. Werner-GHZ type three-qubit and six-qubit states are considered in inertial and non-inertial settings. The dynamics of QD and GQD is investigated under amplitude damping, phase damping, depolarizing and flipping channels. It is seen that the quantum discord vanishes for p>0.75 in case of three-qubit GHZ states and for p>0.5 for six qubit GHZ states. This implies that multipartite states are more fragile to decoherence...

  14. Quantum time crystal by decoherence: Proposal with an incommensurate charge density wave ring

    Science.gov (United States)

    Nakatsugawa, K.; Fujii, T.; Tanda, S.

    2017-09-01

    We show that time translation symmetry of a ring system with a macroscopic quantum ground state is broken by decoherence. In particular, we consider a ring-shaped incommensurate charge density wave (ICDW ring) threaded by a fluctuating magnetic flux: the Caldeira-Leggett model is used to model the fluctuating flux as a bath of harmonic oscillators. We show that the charge density expectation value of a quantized ICDW ring coupled to its environment oscillates periodically. The Hamiltonians considered in this model are time independent unlike "Floquet time crystals" considered recently. Our model forms a metastable quantum time crystal with a finite length in space and in time.

  15. Quantum dissipation and decoherence of collective excitations in metallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Weick, G.

    2006-09-22

    The treatment of the surface plasmon as a quantum particle provides a model system for the study of decoherence and quantum dissipation in confined nanoscopic systems, where the role of the electronic correlations is preponderant. Throughout this work we treat the metallic nanoparticle in the jellium approximation where the ionic structure is replaced by a continuous and homogeneous positive charge. The external laser field puts the center of mass into a coherent superposition of its ground and first excited state and thus creates a surface plasmon. The coupling between the center of mass and the relative coordinates causes decoherence and dissipation of this collective excitation. We have developed a theoretical formalism well adapted to the study of this dissipation, which is the reduced-density-matrix formalism. There are mainly two parameters which govern the surface plasmon dynamics: the decay rate of the plasmon, and the resonance frequency. For sizes smaller than 1 nm, presents oscillations as a function of the size. By means of a semiclassical formalism using Gutzwiller's trace formula for the density of states, we have shown that those oscillations are due to the correlations of the density of states of the particles and holes in the nanoparticle. If one considers a noble-metal nanoparticle in an inert matrix, we have shown that a naive application of the Kubo formula for the surface plasmon linewidth fails to reproduce the TDLDA numerical results, which are however consistent with experimental results. We have modified the Kubo theory in order to solve this discrepancy. We have shown, by extending our semiclassical theory to the nonlinear case, that the double plasmon is indeed well defined. We have calculated the lifetime of the double plasmon associated to this second-order effect. In addition to the width, we have also addressed the value of the resonance frequency. The classical electromagnetic Mie theory gives for the resonance frequency of the

  16. First-principles models of equilibrium tellurium isotope fractionation

    Science.gov (United States)

    Haghnegahdar, M. A.; Schauble, E. A.; Fornadel, A. P.; Spry, P. G.

    2013-12-01

    In this study, equilibrium mass-dependent isotopic fractionation among representative Te-bearing species is estimated with first-principles thermodynamic calculations. Tellurium is a group 16 element (along with O, S, and Se) with eight stable isotopes ranging in mass from 120Te to 130Te, and six commonly-occurring oxidation states: -II, -I, 0, +II, +IV, and +VI. In its reduced form, Te(-II), tellurium has a unique crystal-chemical role as a bond partner for gold and silver in epithermal and orogenic gold deposits, which likely form when oxidized Te species (e.g., H2TeO3, TeO32-) or perhaps polytellurides (e.g., Te22-) interact with precious metals in hydrothermal solution. Te(IV) is the most common oxidation state at the Earth's surface, including surface outcrops of telluride ore deposits, where tellurite and tellurate minerals form by oxidation. In the ocean, dissolved tellurium tends to be scavenged by particulate matter. Te(VI) is more abundant than Te(IV) in the ocean water (1), even though it is thought to be less stable thermodynamically. This variety of valence states in natural systems and range of isotopic masses suggest that tellurium could exhibit geochemically useful isotope abundance variations. Tellurium isotope fractionations were determined for representative molecules and crystals of varying complexity and chemistry. Gas-phase calculations are combined with supermolecular cluster models of aqueous and solid species. These in turn are compared with plane-wave density functional theory calculations with periodic boundary conditions. In general, heavyTe/lightTe is predicted to be higher for more oxidized species, and lower for reduced species, with 130Te/125Te fractionations as large as 4‰ at 100οC between coexisting Te(IV) and Te(-II) or Te(0) compounds. This is a much larger fractionation than has been observed in naturally occurring redox pairs (i.e., Te (0) vs. Te(IV) species) so far, suggesting that disequilibrium processes may control

  17. Averaging principle for second-order approximation of heterogeneous models with homogeneous models.

    Science.gov (United States)

    Fibich, Gadi; Gavious, Arieh; Solan, Eilon

    2012-11-27

    Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced by its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of differentiability and symmetry is O(ε(2)) equivalent to the outcome of the corresponding homogeneous model, where ε is the level of heterogeneity. We then use this averaging principle to obtain new results in queuing theory, game theory (auctions), and social networks (marketing).

  18. Another algebraic variational principle for the spectral curve of matrix models

    CERN Document Server

    Eynard, B

    2014-01-01

    We propose an alternative variational principle whose critical point is the algebraic plane curve associated to a matrix model (the spectral curve, i.e. the large $N$ limit of the resolvent). More generally, we consider a variational principle that is equivalent to the problem of finding a plane curve with given asymptotics and given cycle integrals. This variational principle is not given by extremization of the energy, but by the extremization of an "entropy".

  19. First-Principles Modeling of Multiferroic RMn2O5

    Science.gov (United States)

    Cao, Kun; Guo, Guang-Can; Vanderbilt, David; He, Lixin

    2009-12-01

    We investigate the phase diagrams of RMn2O5 via a first-principles effective-Hamiltonian method. We are able to reproduce the most important features of the complicated magnetic and ferroelectric phase transitions. The calculated polarization as a function of temperature agrees very well with experiments. The dielectric-constant step at the commensurate-to-incommensurate magnetic phase transition is well reproduced. The microscopic mechanisms for the phase transitions are discussed.

  20. First-principles modeling of hard and soft matter

    Science.gov (United States)

    Car, Roberto

    2013-03-01

    Electronic and atomistic processes are key to bio-inspired functional materials and nanocatalysts for energy applications. This talk will review recent simulation studies and discuss the challenges that first-principles quantum mechanical approaches face when addressing these issues. Supported by DOE-DE-FG02-06ER-46344, DOE-DE-SC0008626, DOE-DE-SC0005180, and NSF-CHE-0956500.

  1. Quantum energy decays and decoherence in discrete baths

    CERN Document Server

    Galiceanu, M D; Strunz, W

    2011-01-01

    The quantum average energy decay and the purity decay are studied for a system particle as a function of the number of constituents of a discrete bath model. The system particle is subjected to two distinct physical situations: the harmonic oscillator (HO) and the Morse potential. The environment (bath) is composed by a {\\it finite} number N of uncoupled HOs, characterizing the structured bath, which in the limit $N\\to\\infty$ is assumed to have an ohmic, sub-ohmic or super-ohmic spectral density. For very low values of N the mean energy and purity remain constant in time but starts to decay for intermediate values (10decoherence occurs for short times and a non-Markovian dynamics is expected for larger times. When $N$ increases, energy and coherence decay very fast and a Markovian dynamics is expected to occur. Wave packet dynamics is used ...

  2. Semi-Classical field theory as Decoherence Free Subspaces

    CERN Document Server

    Varela, Jaime

    2014-01-01

    We formulate semi-classical field theory as an approximate decoherence-free-subspace of a finite-dimensional quantum-gravity hilbert space. A complementarity construction can be realized as a unitary transformation which changes the decoherence-free-subspace. This can be translated to signify that field theory on a global slice, in certain space-times, is the simultaneous examination of two different superselected sectors of a gauge theory. We posit that a correct course graining procedure of quantum gravity should be WKB states propagating in a curved background in which particles exiting a horizon have imaginary components to their phases. The field theory appears non-unitary, but it is due to the existence of approximate decoherence free sub-spaces. Furthermore, the importance of operator spaces in the course-graining procedure is discussed. We also briefly touch on Firewalls.

  3. Collisional decoherence of tunneling molecules: a consistent histories treatment

    CERN Document Server

    Coles, Patrick J; Griffiths, Robert B

    2012-01-01

    The decoherence of a two-state tunneling molecule, such as a chiral molecule or ammonia, due to collisions with a buffer gas is analyzed in terms of a succession of quantum states of the molecule satisfying the conditions for a consistent family of histories. With $\\hbar \\omega$ the separation in energy of the levels in the isolated molecule and $\\gamma$ a decoherence rate proportional to the rate of collisions, we find for $\\gamma \\gg \\omega$ (strong decoherence) a consistent family in which the molecule flips randomly back and forth between the left- and right-handed chiral states in a stationary Markov process. For $\\gamma \\omega$ and for $\\gamma < \\omega$. In addition we relate the speed with which chiral information is transferred to the environment to the rate of decrease of complementary types of information (e.g., parity information) remaining in the molecule itself.

  4. Decoherence, fluctuations and Wigner function in neutron optics

    CERN Document Server

    Facchi, P; Pascazio, S; Suda, M

    2003-01-01

    We analyze the coherence properties of neutron wave packets, after they have interacted with a phase shifter undergoing different kinds of statistical fluctuations. We give a quantitative (and operational) definition of decoherence and compare it to the standard deviation of the distribution of the phase shifts. We find that in some cases the neutron ensemble is more coherent, even though it has interacted with a wider (i.e. more disordered) distribution of shifts. This feature is independent of the particular definition of decoherence: this is shown by proposing and discussing an alternative definition, based on the Wigner function, that displays a similar behavior. We briefly discuss the notion of entropy of the shifts and find that, in general, it does not correspond to that of decoherence of the neutron.

  5. Decoherence and thermalization dynamics of a quantum oscillator

    CERN Document Server

    Dodonov, V V; De Souza-Silva, A L

    2000-01-01

    We introduce the quantitative measures characterizing the rates of decoherence and thermalization of quantum systems. We study the time evolution of these measures in the case of a quantum harmonic oscillator whose relaxation is described in the framework of the standard master equation, for various initial states (coherent, `cat', squeezed and number). We establish the conditions under which the true decoherence measure can be approximated by the linear entropy $1-{Tr}\\hat\\rho^2$. We show that at low temperatures and for highly excited initial states the decoherence process consists of three distinct stages with quite different time scales. In particular, the `cat' states preserve 50% of the initial coherence for a long time interval which increases logarithmically with increase of the initial energy.

  6. Adaptive coarse graining, environment, strong decoherence, and quasiclassical realms

    Science.gov (United States)

    Gell-Mann, Murray; Hartle, James B.

    2014-05-01

    Three ideas are introduced that when brought together characterize the realistic quasiclassical realms of our quantum universe as particular kinds of sets of alternative coarse-grained histories defined by quasiclassical variables: (i) branch-dependent adaptive coarse grainings that can be close to maximally refined and can simplify calculation, (ii) narrative coarse grainings that describe how features of the universe change over time and allow the construction of an environment, and (iii) a notion of strong decoherence that characterizes realistic mechanisms of decoherence.

  7. Probing possible decoherence effects in atmospheric neutrino oscillations.

    Science.gov (United States)

    Lisi, E; Marrone, A; Montanino, D

    2000-08-01

    It is shown that the results of the Super-Kamiokande atmospheric neutrino experiment, interpreted in terms of nu(mu)nu(tau) flavor transitions, can probe possible decoherence effects induced by new physics (e.g., by quantum gravity) with high sensitivity, supplementing current laboratory tests based on kaon oscillations and on neutron interferometry. By varying the (unknown) energy dependence of such effects, one can either obtain strong limits on their amplitude or use them to find an unconventional solution to the atmospheric nu anomaly based solely on decoherence.

  8. The dynamic behaviors of complementary correlations under decoherence channels

    Science.gov (United States)

    Du, Ming-Ming; Wang, Dong; Ye, Liu

    2017-01-01

    Complementary correlations can reveal the genuine quantum correlations present in a composite quantum system. Here, we explore an effective method to identify the entangled Bell diagonal states by means of Pearson correlation, one of the complementary correlations. Then, we extend this method to expose the dynamic behavior of complementary correlations under various kinds of decoherence channels. The sudden death and revival of entanglement can be explained by the idea of Pearson correlation. The threshold that is used to identify entanglement is proposed. Furthermore, we put forward a new method to expound the underlying physical mechanisms for which classical and quantum correlations suffer a sudden change in the decoherence process.

  9. Non-equilibrium quantum phase transition via entanglement decoherence dynamics

    Science.gov (United States)

    Lin, Yu-Chen; Yang, Pei-Yun; Zhang, Wei-Min

    2016-01-01

    We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained. PMID:27713556

  10. Effects of Collisional Decoherence on Multipartite Entanglement - How would entanglement not be relatively common?

    CERN Document Server

    Low, G H; Yeo, Y; Low, Guang-Hao; Shi, Zhiming; Yeo, Ye

    2006-01-01

    We consider the collision model of Ziman {\\em et al.} and study the robustness of $N$-qubit Greenberger-Horne-Zeilinger (GHZ), W, and linear cluster states. Our results show that $N$-qubit entanglement of GHZ states would be extremely fragile under collisional decoherence, and that of W states could be more robust than of linear cluster states. We indicate that the collision model of Ziman {\\em et al.} could provide a physical mechanism to some known results in this area of investigations. More importantly, we show that it could give a clue as to how $N$-partite distillable entanglement would be relatively rare in our macroscopic classical world.

  11. Multiterminal Conductance and Decoherence Effect of a Three-Terminal Kondo Dot

    Institute of Scientific and Technical Information of China (English)

    FANG Tie-Feng; WANG Shun-Jin

    2006-01-01

    @@ A three-terminal Kondo dot modelled by the Anderson Hamiltonian is investigated. In the strong correlation limit, we calculate the multiterminal conductance and the voltage-induced characteristic splitting of the nonequilibrium Kondo resonance by using the equation of motion approach from viewpoint of the correlation dynamics.A qualitative and reasonable agreement with a recently reported experiment is obtained. We also simulate phenomenologically the decoherence of the Kondo-coherent state formed in the two-terminal setup in the framework of our three-terminal model.

  12. Modeling physiological processes in plankton on enzyme kinetic principles

    Directory of Open Access Journals (Sweden)

    Ted Packard

    2004-04-01

    Full Text Available Many ecologically important chemical transformations in the ocean are controlled by biochemical enzyme reactions in plankton. Nitrogenase regulates the transformation of N2 to ammonium in some cyanobacteria and serves as the entryway for N2 into the ocean biosphere. Nitrate reductase controls the reduction of NO3 to NO2 and hence new production in phytoplankton. The respiratory electron transfer system in all organisms links the carbon oxidation reactions of intermediary metabolism with the reduction of oxygen in respiration. Rubisco controls the fixation of CO2 into organic matter in phytoplankton and thus is the major entry point of carbon into the oceanic biosphere. In addition to these, there are the enzymes that control CO2 production, NH4 excretion and the fluxes of phosphate. Some of these enzymes have been recognized and researched by marine scientists in the last thirty years. However, until recently the kinetic principles of enzyme control have not been exploited to formulate accurate mathematical equations of the controlling physiological expressions. Were such expressions available they would increase our power to predict the rates of chemical transformations in the extracellular environment of microbial populations whether this extracellular environment is culture media or the ocean. Here we formulate from the principles of bisubstrate enzyme kinetics, mathematical expressions for the processes of NO3 reduction, O2 consumption, N2 fixation, total nitrogen uptake.

  13. Decoherence of Topological Qubit in Linear and Circular Motions: Decoherence Impedance, Anti-Unruh and Information Backflow

    CERN Document Server

    Liu, Pei-Hua

    2016-01-01

    In this paper, we consider the decoherence patterns of a topological qubit made of two Majorana zero modes in the generic linear and circular motions in the Minkowski spacetime. We show that the reduced dynamics is exact without Markov approximation. Our results imply that the acceleration will cause thermalization as expected by Unruh effect. However, for the short-time scale, we find the rate of decoherence is anti-correlated with the acceleration, as kind of decoherence impedance. This is in fact related to the "anti-Unruh" phenomenon previously found by studying the transition probability of Unruh-DeWitt detector. We also obtain the information backflow by some time modulations of coupling constant or acceleration, which is a characteristic of the underlying non-Markovian reduced dynamics. Moreover, by exploiting the nonlocal nature of the topological qubit, we find that some incoherent accelerations of the constituent Majorana zero modes can preserve the coherence instead of thermalizing it.

  14. First-principles modeling hydrogenation of bilayered boron nitride

    Science.gov (United States)

    Jing, Wang; Peng, Zhang; Xiang-Mei, Duan

    2016-05-01

    We have investigated the structural and electronic characteristics of hydrogenated boron-nitride bilayer (H-BNBN-H) using first-principles calculations. The results show that hydrogenation can significantly reduce the energy gap of the BN-BN into the visible-light region. Interestingly, the electric field induced by the interface dipoles helps to promote the formation of well-separated electron-hole pairs, as demonstrated by the charge distribution of the VBM and CBM. Moreover, the applied bias voltage on the vertical direction of the bilayer could modulate the band gap, resulting in transition from semiconductor to metal. We conclude that H-BNBN-H could improve the solar energy conversion efficiency, which may provide a new way for tuning the electronic devices to meet different environments and demands. Project supported by the National Natural Science Foundation of China (Grant No. 11574167).

  15. On Process Modelling Using Physical Oriented And Phenomena Based Principles

    Directory of Open Access Journals (Sweden)

    Mihai Culea

    2000-12-01

    Full Text Available This work presents a modelling framework based on phenomena description of the process. The approach is taken to easy understand and construct process model in heterogeneous possible distributed modelling and simulation environments. A simplified case study of a heat exchanger is considered and Modelica modelling language to check the proposed concept. The partial results are promising and the research effort will be extended in a computer aided modelling environment based on phenomena.

  16. Decoherence free subspaces of a quantum Markov semigroup

    Energy Technology Data Exchange (ETDEWEB)

    Agredo, Julián, E-mail: jaagredoe@unal.edu.co [Centro de Análisis Estocástico, Facultad de Ingeniería, Universidad Católica de Chile, Santiago, Chile and Departamento de Matemáticas, Universidad Nacional de Colombia, Manizales (Colombia); Fagnola, Franco, E-mail: franco.fagnola@polimi.it [Dipartimento di Matematica, Politecnico di Milano, Milano (Italy); Rebolledo, Rolando, E-mail: rrebolle@uc.cl [Centro de Análisis Estocástico, Facultad de Ingeniería, Facultad de Matemáticas, Universidad Católica de Chile, Santiago (Chile)

    2014-11-15

    We give a full characterisation of decoherence free subspaces of a given quantum Markov semigroup with generator in a generalised Lindbald form which is valid also for infinite-dimensional systems. Our results, extending those available in the literature concerning finite-dimensional systems, are illustrated by some examples.

  17. Quantum Chaotic Environments, The Butterfly Effect, And Decoherence

    CERN Document Server

    Karkuszewski, Z P; Zurek, W H; Karkuszewski, Zbyszek P.; Jarzynski, Christopher; Zurek, Wojciech H.

    2002-01-01

    We investigate the sensitivity of quantum systems that are chaotic in a classical limit, to small perturbations of their equations of motion. This sensitivity, originally studied in the context of defining quantum chaos, is relevant to decoherence in situations when the environment has a chaotic classical counterpart.

  18. Quantum description of classical apparatus; Zeno effect and decoherence

    CERN Document Server

    Gurvitz, S A

    2003-01-01

    We study the measurement process by treating classical detectors entirely quantum mechanically. Transition to the classical description and the mechanism of decoherence is investigated. We concentrate on influence of continuous measurement on decay of unstable systems (quantum Zeno effect). We discuss the experimental consequences of our results and a role of the projection postulate in a measurement process.

  19. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

    Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.

    2008-01-01

    We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian free-induct

  20. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

    Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.

    2008-01-01

    We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian

  1. Applying the maximum information principle to cell transmission model of tra-ffic flow

    Institute of Scientific and Technical Information of China (English)

    刘喜敏; 卢守峰

    2013-01-01

    This paper integrates the maximum information principle with the Cell Transmission Model (CTM) to formulate the velo-city distribution evolution of vehicle traffic flow. The proposed discrete traffic kinetic model uses the cell transmission model to cal-culate the macroscopic variables of the vehicle transmission, and the maximum information principle to examine the velocity distri-bution in each cell. The velocity distribution based on maximum information principle is solved by the Lagrange multiplier method. The advantage of the proposed model is that it can simultaneously calculate the hydrodynamic variables and velocity distribution at the cell level. An example shows how the proposed model works. The proposed model is a hybrid traffic simulation model, which can be used to understand the self-organization phenomena in traffic flows and predict the traffic evolution.

  2. Intrinsic decoherence in the interaction of two fields with a two-level atom

    Energy Technology Data Exchange (ETDEWEB)

    Juarez-Amaro, R. [Universidad Tecnologica de la Mixteca, Mexico (Mexico); INAOE, Puebla (Mexico); Escudero-Jimenez, J.L. [INAOE, Puebla (Mexico); Moya-Cessa, H.

    2009-06-15

    We study the interaction of a two-level atom and two fields, one of them classical. We obtain an effective Hamiltonian for this system by using a method recently introduced that produces a small rotation to the Hamiltonian that allows to neglect some terms in the rotated Hamiltonian. Then we solve a variation of the Schroedinger equation that models decoherence as the system evolves through intrinsic mechanisms beyond conventional quantum mechanics rather than dissipative interaction with an environment. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  3. Classical states and decoherence by unitary evolution in the thermodynamic limit

    CERN Document Server

    Frasca, M

    2002-01-01

    It is shown how classical states, meant as states representing a classical object, can be produced in the thermodynamic limit, retaining the unitary evolution of quantum mechanics. Besides, using a simple model of a single spin interacting with a spin-bath, it is seen how decoherence, with the off-diagonal terms in the density matrix going to zero, can be obtained when the number of the spins in the bath is taken to go formally to infinity. In this case, indeed, the system appears to flop at a frequency being formally infinity that, from a physical standpoint, can be proved equivalent to a time average.

  4. Single-qubit decoherence under a separable coupling to a random matrix environment

    Science.gov (United States)

    Carrera, M.; Gorin, T.; Seligman, T. H.

    2014-08-01

    This paper describes the dynamics of a quantum two-level system (qubit) under the influence of an environment modeled by an ensemble of random matrices. In distinction to earlier work, we consider here separable couplings and focus on a regime where the decoherence time is of the same order of magnitude as the environmental Heisenberg time. We derive an analytical expression in the linear response approximation, and study its accuracy by comparison with numerical simulations. We discuss a series of unusual properties, such as purity oscillations, strong signatures of spectral correlations (in the environment Hamiltonian), memory effects, and symmetry-breaking equilibrium states.

  5. Transmission coefficients for chemical reactions with multiple states: role of quantum decoherence.

    Science.gov (United States)

    de la Lande, Aurélien; Řezáč, Jan; Lévy, Bernard; Sanders, Barry C; Salahub, Dennis R

    2011-03-23

    Transition-state theory (TST) is a widely accepted paradigm for rationalizing the kinetics of chemical reactions involving one potential energy surface (PES). Multiple PES reaction rate constants can also be estimated within semiclassical approaches provided the hopping probability between the quantum states is taken into account when determining the transmission coefficient. In the Marcus theory of electron transfer, this hopping probability was historically calculated with models such as Landau-Zener theory. Although the hopping probability is intimately related to the question of the transition from the fully quantum to the semiclassical description, this issue is not adequately handled in physicochemical models commonly in use. In particular, quantum nuclear effects such as decoherence or dephasing are not present in the rate constant expressions. Retaining the convenient semiclassical picture, we include these effects through the introduction of a phenomenological quantum decoherence function. A simple modification to the usual TST rate constant expression is proposed: in addition to the electronic coupling, a characteristic decoherence time τ(dec) now also appears as a key parameter of the rate constant. This new parameter captures the idea that molecular systems, although intrinsically obeying quantum mechanical laws, behave semiclassically after a finite but nonzero amount of time (τ(dec)). This new degree of freedom allows a fresh look at the underlying physics of chemical reactions involving more than one quantum state. The ability of the proposed formula to describe the main physical lines of the phenomenon is confirmed by comparison with results obtained from density functional theory molecular dynamics simulations for a triplet to singlet transition within a copper dioxygen adduct relevant to the question of dioxygen activation by copper monooxygenases.

  6. Coherent dynamical recoupling of diffusion-driven decoherence in magnetic resonance

    CERN Document Server

    Alvarez, Gonzalo A; Frydman, Lucio

    2013-01-01

    During recent years, dynamical decoupling (DD) has gained relevance as a tool for manipulating quantum systems and extracting information from them. This is particularly relevant for spins involved in nuclear magnetic resonance (NMR), where DD sequences can be used to prolong quantum coherences, or for selectively couple/decouple the effects imposed by random environmental fluctuations. In this Letter, we show that one can exploit these concepts in order to selectively recouple diffusion processes in restricted spaces. The ensuing method provides a novel tool to measure restriction lengths in confined systems such as capillaries, pores or cells. The principles of this method for selectively recoupling diffusion-driven decoherence, its standing within the context of diffusion NMR, and corroborating experiments, are presented.

  7. Modelling atypical CYP3A4 kinetics: principles and pragmatism.

    Science.gov (United States)

    Houston, J Brian; Galetin, Aleksandra

    2005-01-15

    The Michaelis-Menten model, and the existence of a single active site for the interaction of substrate with drug metabolizing enzyme, adequately describes a substantial number of in vitro metabolite kinetic data sets for both clearance and inhibition determination. However, in an increasing number of cases (involving most notably, but not exclusively, CYP3A4), atypical kinetic features are observed, e.g., auto- and heteroactivation; partial, cooperative, and substrate inhibition; concentration-dependent effector responses (activation/inhibition); limited substrate substitution and inhibitory reciprocity necessitating sub-group classification. The phenomena listed above cannot be readily interpreted using single active site models and the literature indicates that three types of approaches have been adopted. First the 'nai ve' approach of using the Michaelis-Menten model regardless of the kinetic behaviour, second the 'empirical' approach (e.g., employing the Hill or uncompetitive inhibition equations to model homotropic phenomena of sigmoidicity and substrate inhibition, respectively) and finally, the 'mechanistic' approach. The later includes multisite kinetic models derived using the same rapid equilibrium/steady-state assumptions as the single-site model. These models indicate that 2 or 3 binding sites exist for a given CYP3A4 substrate and/or effector. Multisite kinetic models share common features, depending on the substrate kinetics and the nature of the effector response observed in vitro, which allow a generic model to be proposed. Thus although more complex than the other two approaches, they show more utility and can be comprehensively applied in relatively simple versions that can be readily generated from generic model. Multisite kinetic features, observed in isolated hepatocytes as well as in microsomes from hepatic tissue and heterologous expression systems, may be evident in substrate depletion-time profiles as well as in metabolite formation rates

  8. Evaluating Educational Software Authoring Environments Using a Model Based on Software Engineering and Instructional Design Principles.

    Science.gov (United States)

    Collis, Betty A.; Gore, Marilyn

    1987-01-01

    This study suggests a new model for the evaluation of educational software authoring systems and applies this model to a particular authoring system, CSR Trainer 4000. The model used is based on an integrated set of software engineering and instructional design principles. (Author/LRW)

  9. Ferromanganese Furnace Modelling Using Object-Oriented Principles

    Energy Technology Data Exchange (ETDEWEB)

    Wasboe, S.O.

    1996-12-31

    This doctoral thesis defines an object-oriented framework for aiding unit process modelling and applies it to model high-carbon ferromanganese furnaces. A framework is proposed for aiding modelling of the internal topology and the phenomena taking place inside unit processes. Complex unit processes may consist of a number of zones where different phenomena take place. A topology is therefore defined for the unit process itself, which shows the relations between the zones. Inside each zone there is a set of chemical species and phenomena, such as reactions, phase transitions, heat transfer etc. A formalized graphical methodology is developed as a tool for modelling these zones and their interaction. The symbols defined in the graphical framework are associated with objects and classes. The rules for linking the objects are described using OMT (Object Modeling Technique) diagrams and formal language formulations. The basic classes that are defined are implemented using the C++ programming language. The ferromanganese process is a complex unit process. A general description of the process equipment is given, and a detailed discussion of the process itself and a system theoretical overview of it. The object-oriented framework is then used to develop a dynamic model based on mass and energy balances. The model is validated by measurements from an industrial furnace. 101 refs., 119 figs., 20 tabs.

  10. Health Insurance: principles, models and the Nigerian National ...

    African Journals Online (AJOL)

    Open Access DOWNLOAD FULL TEXT ... In addition, they all have different modes of operation. ... Key words: Health insurance, Health insurance models, market failure, Nigerian Health Insurance Scheme, Community Based Health ...

  11. Xanthusbase: adapting wikipedia principles to a model organism database.

    Science.gov (United States)

    Arshinoff, Bradley I; Suen, Garret; Just, Eric M; Merchant, Sohel M; Kibbe, Warren A; Chisholm, Rex L; Welch, Roy D

    2007-01-01

    xanthusBase (http://www.xanthusbase.org) is the official model organism database (MOD) for the social bacterium Myxococcus xanthus. In many respects, M.xanthus represents the pioneer model organism (MO) for studying the genetic, biochemical, and mechanistic basis of prokaryotic multicellularity, a topic that has garnered considerable attention due to the significance of biofilms in both basic and applied microbiology research. To facilitate its utility, the design of xanthusBase incorporates open-source software, leveraging the cumulative experience made available through the Generic Model Organism Database (GMOD) project, MediaWiki (http://www.mediawiki.org), and dictyBase (http://www.dictybase.org), to create a MOD that is both highly useful and easily navigable. In addition, we have incorporated a unique Wikipedia-style curation model which exploits the internet's inherent interactivity, thus enabling M.xanthus and other myxobacterial researchers to contribute directly toward the ongoing genome annotation.

  12. Phase field modelling of interfaces from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Pruessner, G [Mathematics Institute, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Sutton, A P [Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)], E-mail: g.pruessner@imperial.ac.uk, E-mail: a.sutton@imperial.ac.uk

    2008-01-15

    Phase field modelling is a technique in (computational) material science that utilises diffuse interface constructions to simulate the dynamics of microstructural evolution. To date, phase field modelling of crystalline interfaces has been guided mainly by phenomenology and symmetry considerations, rather than microscopic physics. The central equation of motion minimises a free energy with respect to the phase field, which is considered as a space and time dependent, coarse-grained, continuous degree of freedom of the system. However, it is neither clear how to interpret the phase field microscopically, nor how to derive the equation of motion from atomic interactions. Based on the (classical) density functional theory by Haymet and Oxtoby, we derive the phase field model by Allen and Cahn, which is commonly used for modelling crystalline interfaces. In the present article, we summarise the physical implications of the various observables and parameters as well as the underlying approximations.

  13. Energy Convexity as a Consequence of Decoherence and Pair-Extensive Interactions in Many-electron Systems

    Energy Technology Data Exchange (ETDEWEB)

    Gonis, Antonios [ORNL; Zhang, Xiaoguang [ORNL; Nicholson, Don M [ORNL; Stocks, George Malcolm [ORNL

    2014-01-01

    Using the concept of self-entanglement, through which a pure state constructed in an augmented Hilbert space can describe a mixed state and the effects of physical decoherence can be mapped onto systems separated by an infinite distance with the role of environmental states assumed by system states in disjoint Hilbert spaces, we show that expectation values of Hamiltonians subscribing to decoherence and satisfying the condition of extensivity, defined in the text, obey the energy convexity relation. The analysis based on self-entanglement also leads to a surprising interpretation of the failure of the convexity relation for model Hamiltonians such as the Hubbard model: The failure is due to the existence of self-entangled states with lower energies than the ground state so that in such models decoherence, i.e., disentangling from the self-entangled states, would cost energy and disallow the observation of the state through measurement. The Hubbard model is discussed extensively in an appendix where we also discuss and resolve some of the counterarguments to the convexity relation that have been advanced in the literature.

  14. A Mutation Model from First Principles of the Genetic Code.

    Science.gov (United States)

    Thorvaldsen, Steinar

    2016-01-01

    The paper presents a neutral Codons Probability Mutations (CPM) model of molecular evolution and genetic decay of an organism. The CPM model uses a Markov process with a 20-dimensional state space of probability distributions over amino acids. The transition matrix of the Markov process includes the mutation rate and those single point mutations compatible with the genetic code. This is an alternative to the standard Point Accepted Mutation (PAM) and BLOcks of amino acid SUbstitution Matrix (BLOSUM). Genetic decay is quantified as a similarity between the amino acid distribution of proteins from a (group of) species on one hand, and the equilibrium distribution of the Markov chain on the other. Amino acid data for the eukaryote, bacterium, and archaea families are used to illustrate how both the CPM and PAM models predict their genetic decay towards the equilibrium value of 1. A family of bacteria is studied in more detail. It is found that warm environment organisms on average have a higher degree of genetic decay compared to those species that live in cold environments. The paper addresses a new codon-based approach to quantify genetic decay due to single point mutations compatible with the genetic code. The present work may be seen as a first approach to use codon-based Markov models to study how genetic entropy increases with time in an effectively neutral biological regime. Various extensions of the model are also discussed.

  15. Scheme for implementing quantum dense coding with four-particle decoherence-free states in an ion trap

    Institute of Scientific and Technical Information of China (English)

    Zheng Xiao-Juan; Cao Shuai; Fang Mao-Fa; Liao Xiang-Ping

    2008-01-01

    This paper proposes an experimentally feasible scheme for implementing quantum dense coding of trapped-ion system in decoherence-free states.As the phase changes due to time evolution of components with different eigenenergies of quantum superposition are completely frozen,quantum dense coding based on this model would be perfect.The scheme is insensitive to heating of vibrational mode and Bell states can be exactly distinguished via detecting the ionic state.

  16. Variational principles for transversely vibrating multiwalled carbon nanotubes based on nonlocal Euler-Bernoulli beam model.

    Science.gov (United States)

    Adali, Sarp

    2009-05-01

    Variational principles are derived for multiwalled carbon nanotubes undergoing vibrations. Derivations are based on the continuum modeling with the Euler-Bernoulli beam representing the nanotubes and small scale effects taken into account via the nonlocal elastic theory. Hamilton's principle for multiwalled nanotubes is given and Rayleigh's quotient for the frequencies is derived for nanotubes undergoing free vibrations. Natural and geometric boundary conditions are derived which lead to a set of coupled boundary conditions due to nonlocal effects.

  17. Principles of the Concept-Oriented Data Model : technical report

    CERN Document Server

    Savinov, AlexandrInstitute of Mathematics and Computer Science, Academy of Sciences of Moldova

    2004-01-01

    In the paper a new approach to data representation and manipulation is described, which is called the concept-oriented data model (CODM). It is supposed that items represent data units, which are stored in concepts. A concept is a combination of superconcepts, which determine the concept's dimensionality or properties. An item is a combination of superitems taken by one from all the superconcepts. An item stores a combination of references to its superitems. The references implement inclusion relation or attribute-value relation among items. A concept-oriented database is defined by its concept structure called syntax or schema and its item structure called semantics. The model defines formal transformations of syntax and semantics including the canonical semantics where all concepts are merged and the data semantics is represented by one set of items. The concept-oriented data model treats relations as subconcepts where items are instances of the relations. Multi-valued attributes are defined via subconcepts...

  18. Guiding Principles for Language Assessment Reform: A Model for Collaboration

    Science.gov (United States)

    Green, Brent A.; Andrade, Maureen Snow

    2010-01-01

    Traditionally, practitioners interested in language test reform have focused on the qualities within an examination which result in either positive or negative impacts on participants, institutions, and society. Recent views suggest a multifaceted interaction among factors affecting language test reform. We introduce a model for test reform that…

  19. Nine key principles to guide youth mental health: development of service models in New South Wales.

    Science.gov (United States)

    Howe, Deborah; Batchelor, Samantha; Coates, Dominiek; Cashman, Emma

    2014-05-01

    Historically, the Australian health system has failed to meet the needs of young people with mental health problems and mental illness. In 2006, New South Wales (NSW) Health allocated considerable funds to the reform agenda of mental health services in NSW to address this inadequacy. Children and Young People's Mental Health (CYPMH), a service that provides mental health care for young people aged 12-24 years, with moderate to severe mental health problems, was chosen to establish a prototype Youth Mental Health (YMH) Service Model for NSW. This paper describes nine key principles developed by CYPMH to guide the development of YMH Service Models in NSW. A literature review, numerous stakeholder consultations and consideration of clinical best practice were utilized to inform the development of the key principles. Subsequent to their development, the nine key principles were formally endorsed by the Mental Health Program Council to ensure consistency and monitor the progress of YMH services across NSW. As a result, between 2008 and 2012 YMH Services across NSW regularly reported on their activities against each of the nine key principles demonstrating how each principle was addressed within their service. The nine key principles provide mental health services a framework for how to reorient services to accommodate YMH and provide a high-quality model of care. [Corrections added on 29 November 2013, after first online publication: The last two sentences of the Results section have been replaced with "As a result, between 2008 and 2012 YMH Services across NSW regularly reported on their activities against each of the nine key principles demonstrating how each principle was addressed within their service."]. © 2013 Wiley Publishing Asia Pty Ltd.

  20. Noise gates for decoherent quantum circuits

    OpenAIRE

    Bassi, Angelo; Deckert, D. -A.

    2008-01-01

    A major problem in exploiting microscopic systems for developing a new technology based on the principles of Quantum Information is the influence of noise which tends to work against the quantum features of such systems. It becomes then crucial to understand how noise affects the evolution of quantum circuits: several techniques have been proposed among which stochastic differential equations (SDEs) can represent a very convenient tool. We show how SDEs naturally map any Markovian noise into ...

  1. Entanglement of a two-qubit anisotropic Heisenberg XYZ chain in nonuniform magnetic fields with intrinsic decoherence

    Institute of Scientific and Technical Information of China (English)

    Xu Xiao-Bo; Liu Jin-Ming; Yu Peng-Fei

    2008-01-01

    Taking the intrinsic decoherence effect into account,this paper investigates the entanglement of a two-qubit anisotropic Heisenberg XY Z model in the presence of nonuniform external magnetic fields by employing the concurrence as entanglement measure.It is found that both the intrinsic decoherence and the anisotropy of the system give a significant suppression to the entanglement.Moreover it finds that the initial state of the system plays an important role in the time evolution of the entanglement,which means that the entanglement of the system is independent of the nonuniformity and uniformity of the magnetic field when the system is in the initial state |ψ(0)>=|00>and |ψ(0)>=m |01>+n|10>,respectively.

  2. Effect of the time-dependent coupling on a superconducting qubit-field system under decoherence: Entanglement and Wehrl entropy

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Khalek, S., E-mail: sayedquantum@yahoo.co.uk [Mathematics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Miramare-Trieste (Italy); Berrada, K. [The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Miramare-Trieste (Italy); Al Imam Mohammad Ibn Saud Islamic University (IMSIU), College of Science, Department of Physics, Riyadh (Saudi Arabia); Eleuch, H. [Department of Physics, McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada); Department of Physics, Université de Montréal, 2900 boul. douard-Montpetit, Montreal, QC, H3T 1J4 (Canada)

    2015-10-15

    The dynamics of a superconducting (SC) qubit interacting with a field under decoherence with and without time-dependent coupling effect is analyzed. Quantum features like the collapse–revivals for the dynamics of population inversion, sudden birth and sudden death of entanglement, and statistical properties are investigated under the phase damping effect. Analytic results for certain parametric conditions are obtained. We analyze the influence of decoherence on the negativity and Wehrl entropy for different values of the physical parameters. We also explore an interesting relation between the SC-field entanglement and Wehrl entropy behavior during the time evolution. We show that the amount of SC-field entanglement can be enhanced as the field tends to be more classical. The studied model of SC-field system with the time-dependent coupling has high practical importance due to their experimental accessibility which may open new perspectives in different tasks of quantum formation processing.

  3. Modeling & imaging of bioelectrical activity principles and applications

    CERN Document Server

    He, Bin

    2010-01-01

    Over the past several decades, much progress has been made in understanding the mechanisms of electrical activity in biological tissues and systems, and for developing non-invasive functional imaging technologies to aid clinical diagnosis of dysfunction in the human body. The book will provide full basic coverage of the fundamentals of modeling of electrical activity in various human organs, such as heart and brain. It will include details of bioelectromagnetic measurements and source imaging technologies, as well as biomedical applications. The book will review the latest trends in

  4. Material and natural processes as form modelling principles in sculpting

    OpenAIRE

    Smole, Mateja

    2016-01-01

    My final thesis is an analysis of ideas and practical experience, which formed in the process of unfolding various works of art. The underlying questions, which one notices throughout my thesis, are: How does a work of art come to life, what happens with the materials during the modelling process, where will the work of art be displayed and what impact will the environment have on it, and last but not least, what will the interaction between the artist and the public be, where and in what way...

  5. On the Internal Model Principle in the Coordination of Nonlinear Systems

    NARCIS (Netherlands)

    De Persis, C.; Jayawardhana, B.

    2014-01-01

    The role of the internal model principle is investigated in this paper for the coordination of relative-degree-one and relative-degree-two nonlinear systems. For relative-degree-one systems that are incrementally (output-feedback) passive, we propose internal-model-based distributed control laws whi

  6. A Model for Building School-Family-Community Partnerships: Principles and Process

    Science.gov (United States)

    Bryan, Julia; Henry, Lynette

    2012-01-01

    The extant literature documents the importance of school counselors' roles in school-family-community partnerships, yet no model exists to guide school counselors through the process of building partnerships. The authors propose a model to help school counselors navigate the process and principles of partnerships. They define partnerships; discuss…

  7. Comparison of first principles model of beer microfiltration to experiments via systematic parameter identification

    NARCIS (Netherlands)

    Sman, van der R.G.M.; Willigenburg, van G.; Vollebregt, H.M.; Eisner, V.; Mepschen, A.

    2015-01-01

    A first principles microfiltration model based on shear-induced diffusion is compared to experiments performed on the clarification of beer. After performing an identifiability and sensitivity analysis, the model parameters are estimated using global minimization of the sum of least squares. The

  8. On the Internal Model Principle in the Coordination of Nonlinear Systems

    NARCIS (Netherlands)

    De Persis, C.; Jayawardhana, B.

    2014-01-01

    The role of the internal model principle is investigated in this paper for the coordination of relative-degree-one and relative-degree-two nonlinear systems. For relative-degree-one systems that are incrementally (output-feedback) passive, we propose internal-model-based distributed control laws whi

  9. Formulating "Principles of Procedure" for the Foreign Language Classroom: A Framework for Process Model Language Curricula

    Science.gov (United States)

    Villacañas de Castro, Luis S.

    2016-01-01

    This article aims to apply Stenhouse's process model of curriculum to foreign language (FL) education, a model which is characterized by enacting "principles of procedure" which are specific to the discipline which the school subject belongs to. Rather than to replace or dissolve current approaches to FL teaching and curriculum…

  10. Experimental Tests of Quantum Mechanics: Pauli Exclusion Principle and Spontaneous Collapse Models

    CERN Document Server

    Petrascu, Catalina Curceanu; Bragadireanu, Mario; Clozza, Alberto; Guaraldo, Carlo; Iliescu, Mihai; Rizzo, Alessandro; Vidal, Antonio Romero; Scordo, Alessandro; Sirghi, Diana Laura; Sirghi, Florin; Sperandio, Laura; Doce, Oton Vazquez; Bassi, Angelo; Donadi, Sandro; Milotti, Edoardo; Laubenstein, Matthias; Bertolucci, Sergio; Bragadireanu, Mario; Curceanu, Catalina; Pietreanu, Dorel; Ponta, Titus; Cargnelli, Michael; Ishiwatari, Tomoichi; Marton, Johann; Widmann, Eberhard; Zmeskal, Johann; Matteo, Sergio di; Egger, Jean Pierre

    2014-01-01

    The Pauli exclusion principle (PEP), as a consequence or the spin-statistics connection, is one of the basic principles of the modern physics. Being at the very basis of our understanding of matter, it spurs a lively debate on its possible limits, deeply rooted as it is in the very foundations of Quantum Field Theory. The VIP (VIolation of the Pauli exclusion principle) experiment is searching for a possible small violation of the PEP for electrons, using the method of searching for Pauli Exclusion Principle forbidden atomic transitions in copper. We describe the experimental method and the obtained results; we briefly present future plans to go beyond the actual limit by upgrading the experiment using vetoed new spectroscopic fast Silicon Drift Detectors. We also mention the possibility of using a similar experimental technique to search for possible X-rays generated in the spontaneous collapse models of quantum mechanics.

  11. Collective decoherence of cold atoms coupled to a Bose-Einstein condensate

    Energy Technology Data Exchange (ETDEWEB)

    Cirone, M A [Dipartimento di Scienze Fisiche ed Astronomiche, Universita degli Studi di Palermo, via Archirafi 36, I-90123 Palermo (Italy); De Chiara, G [Grup d' Optica, Departament de FIsica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Palma, G M [NEST-CNR-INFM and Dipartimento di Scienze Fisiche ed Astronomiche, Universita degli Studi di Palermo, via Archirafi 36, I-90123 Palermo (Italy); Recati, A [Dipartimento di Fisica, Universita di Trento, CNR-INFM BEC Center, I-38050 Povo, Trento (Italy) and Physik-Department, Technische Universitaet Muenchen, D-85748 Garching (Germany)], E-mail: massimo.palma@fisica.unipa.it

    2009-10-15

    We examine the time evolution of cold atoms (impurities) interacting with an environment consisting of a degenerate bosonic quantum gas. The impurity atoms differ from the environment atoms, being of a different species. This allows one to superimpose two independent trapping potentials, each being effective only on one atomic kind, while transparent to the other. When the environment is homogeneous and the impurities are confined in a potential consisting of a set of double wells, the system can be described in terms of an effective spin-boson model, where the occupation of the left or right well of each site represents the two (pseudo)-spin states. The irreversible dynamics of such system is here studied exactly, i.e. not in terms of a Markovian master equation. The dynamics of one and two impurities is remarkably different in respect of the standard decoherence of the spin-boson system. In particular, we show: (i) the appearance of coherence oscillations, (ii) the presence of super and subdecoherent states that differ from the standard ones of the spin-boson model, and (iii) the persistence of coherence in the system at long times. We show that this behaviour is due to the fact that the pseudospins have an internal spatial structure. We argue that collective decoherence also prompts information about the correlation length of the environment. In a one-dimensional (1D) configuration, one can change even more strongly the qualitative behaviour of the dephasing just by tuning the interaction of the bath.

  12. Impact of Decoherence on Internal State Cooling using Optical Frequency Combs

    CERN Document Server

    Malinovskaya, S A

    2012-01-01

    We discuss femtosecond Raman type techniques to control molecular vibrations, which can be implemented for internal state cooling from Feshbach states with the use of optical frequency combs with and without modulation. The technique makes use of multiple two-photon resonances induced by optical frequencies present in the comb. It provides us with a useful tool to study the details of molecular dynamics at ultracold temperatures. In our theoretical model we take into account decoherence in the form of spontaneous emission and collisional dephasing in order to ascertain an accurate model of the population transfer in the three-level system. We analyze the effects of odd and even chirps of the optical frequency comb in the form of sine and cosine functions on the population transfer. We compare the effects of these chirps to the results attained with the standard optical frequency comb to see if they increase the population transfer to the final deeply bound state in the presence of decoherence. We also analyze...

  13. Cone separation, quadratic control systems and control of spin dynamics in the presence of decoherence.

    Science.gov (United States)

    Khaneja, Navin

    2017-03-06

    In this paper, we study some control problems related to the control of coupled spin dynamics in the presence of relaxation and decoherence in nuclear magnetic resonance spectroscopy. The decoherence is modelled through a master equation. We study some model problems, whereby, through an appropriate choice of state variables, the system is reduced to a control system, where the state enters linearly and controls quadratically. We study this quadratic control system. Study of this system gives us explicit bounds on how close a coupled spin system can be driven to its target state and how much coherence and polarization can be transferred between coupled spins. Optimal control for the quadratic control system can be understood as the separation of closed cones, and we show how the derived results on optimal efficiency can be interpreted in this formulation. Finally, we study some finite-time optimal control problems for the quadratic control system.This article is part of the themed issue 'Horizons of cybernetical physics'.

  14. Cone separation, quadratic control systems and control of spin dynamics in the presence of decoherence

    Science.gov (United States)

    Khaneja, Navin

    2017-03-01

    In this paper, we study some control problems related to the control of coupled spin dynamics in the presence of relaxation and decoherence in nuclear magnetic resonance spectroscopy. The decoherence is modelled through a master equation. We study some model problems, whereby, through an appropriate choice of state variables, the system is reduced to a control system, where the state enters linearly and controls quadratically. We study this quadratic control system. Study of this system gives us explicit bounds on how close a coupled spin system can be driven to its target state and how much coherence and polarization can be transferred between coupled spins. Optimal control for the quadratic control system can be understood as the separation of closed cones, and we show how the derived results on optimal efficiency can be interpreted in this formulation. Finally, we study some finite-time optimal control problems for the quadratic control system. This article is part of the themed issue 'Horizons of cybernetical physics'.

  15. Principles and Ways of Innovation on Organizational Model of Tobacco Production in China

    Institute of Scientific and Technical Information of China (English)

    Liming; LU; Qiang; LEI; Jianxin; HU; Huizhan; GU; Yong; WANG; Jinyou; XIANG; Dingqi; LUO; Xingyou; YANG; Jun; LUO

    2013-01-01

    The innovation of organizational model of tobacco production is the key to realization of sustainable development of tobacco production in China. From the perspective of sustainable development, we analyze the necessity of innovation of organizational model of tobacco production, put forward the principles on innovation of organizational model of tobacco production, and offer corresponding recommendations for the ways of innovation of organizational model of tobacco production.

  16. Application of Steenbeck's minimum principle for three-dimensional modelling of DC arc plasma torches

    CERN Document Server

    Li He Ping; Chen, X

    2003-01-01

    In this paper, physical/mathematical models for the three-dimensional, quasi-steady modelling of the plasma flow and heat transfer inside a non-transferred DC arc plasma torch are described in detail. The Steenbeck's minimum principle (Finkelnburg W and Maecker H 1956 Electric arcs and thermal plasmas Encyclopedia of Physics vol XXII (Berlin: Springer)) is employed to determine the axial position of the anode arc-root at the anode surface. This principle postulates a minimum arc voltage for a given arc current, working gas flow rate, and torch configuration. The modelling results show that the temperature and flow fields inside the DC non-transferred arc plasma torch show significant three-dimensional features. The predicted anode arc-root attachment position and the arc shape by employing Steenbeck's minimum principle are reasonably consistent with experimental observations. The thermal efficiency and the torch power distribution are also calculated in this paper. The results show that the thermal efficiency...

  17. Decoherence of Entangled States Calculated by a Systematic Approximate Method

    Institute of Scientific and Technical Information of China (English)

    LIU Tao; FAN Yun-Xia; HUANG Shu-Weng; WANG Ke-Lin; WANG Yi

    2007-01-01

    In this paper the coherent-state approximation (CA) method is used to deal with the problem of the decoherence of the entangled states of two two-state systems. As the base of the discussion, the dissipation of one two-state system has been investigated at first. The improved results calculated by CA are given in the paper. It is shown that the right approaching behavior and scaling law have been obtained when CA is applied to the problem of dissipation of two two-state systems coupled with environment. The whole evolution process and calculated results of the decoherence of the entangled states show also the scaling law, right approaching behavior, and rich phenomenon.

  18. Interplay between coherence and decoherence in LHCII photosynthetic complex

    CERN Document Server

    Giorda, Paolo; Zanardi, Paolo; Lloyd, Seth

    2011-01-01

    This paper investigates the dynamics of excitonic transport in photocomplex LHCII, the primary component of the photosynthetic apparatus in green plants. The dynamics exhibits a strong interplay between coherent processes mediated by the excitonic Hamiltonian, and incoherent processes due to interactions with the environment. The spreading of the exciton over a single monomer is well described by a proper measure of delocalization that allows one to identify two relevant time scales. An exciton initially localized in one chromophore first spreads coherently to neighboring chromophores. During this initial coherent spreading, quantum effects such as entanglement play a role. As the effects of a decohering environment come into play, coherence and decoherence interact to give rise to efficient and robust excitonic transport, reaching a maximum efficiency at the levels of decoherence found in physiological conditions. We analyze the efficiency for different possible topologies (monomer, dimer, trimer, tetramer) ...

  19. Decoherence, delocalization and irreversibility in quantum chaotic systems

    CERN Document Server

    Shiokawa, K; Shiokawa, K; Hu, B L

    1995-01-01

    Decoherence in quantum systems which are classically chaotic is studied. The Arnold cat map and the quantum kicked rotor are chosen as examples of linear and nonlinear chaotic systems. The Feynman-Vernon influence functional formalism is used to study the effect of the environment on the system. It is well-known that quantum coherence can obliterate many chaotic behavior in the corresponding classical system. But interaction with an environment can under general circumstances quickly diminish quantum coherence and reenact many classical chaotic behavior. How effective decoherence works to sustain chaos, and how the resultant behavior qualitatively differs from the quantum picture depend on the coupling of the system with the environment and the spectral density and temperature of the environment. We show how recurrence in the quantum cat map is lost and classical ergodicity is recovered due to the effect of the environment. Quantum coherence and diffusion suppression are instrumental to dynamical localization...

  20. What is "system" the arguments from the decoherence theory

    CERN Document Server

    Dugic, M

    1999-01-01

    Within the decoherence theory we investigate the physical background of the condition of the separability (diagonalizability in noncorrelated basis) of the interaction Hamiltonian of the composite system, "system plus environment". It proves that the condition of the separability may serve as a criterion for defining "system", but so that "system" cannot be defined unless it is simultaneously defined with its "environment". When extended to a set of the mutually interacting composite systems, this result implies that the separability conditions of the local interactions are mutually tied. The task of defining "system" (and "environment") via investigating the separability of the Hamiltonian is a sort of the inverse task of the decoherence theory. A simple example of doing the task is given.

  1. Jet (decoherence in Pb–Pb collisions at the LHC

    Directory of Open Access Journals (Sweden)

    Yacine Mehtar-Tani

    2015-05-01

    Full Text Available We study the modifications of jets created in heavy-ion collisions at LHC energies. The inherent hierarchy of scales governing the jet evolution allows to distinguish a leading jet structure, which interacts coherently with the medium as a single color charge, from softer sub-structures that will be sensitive to effects of color decoherence. We argue how this separation comes about and show that this picture is consistent with experimental data on reconstructed jets at the LHC, providing a quantitative description simultaneously of the jet nuclear modification factor, the missing energy in di-jet events and the modification of the fragmentation functions. In particular, we demonstrate that effects due to color decoherence are manifest in the excess of soft particles measured in fragmentation functions in Pb–Pb compared to proton–proton collisions.

  2. Universal Fault-Tolerant Computation on Decoherence-Free Subspaces

    CERN Document Server

    Bacon, D J; Lidar, D A; Whaley, K B

    2000-01-01

    A general scheme to perform universal quantum computation fault-tolerantly within decoherence-free subspaces (DFSs) of a system's Hilbert space is derived. This scheme leads to the first fault-tolerant realization of universal quantum computation on DFSs with the properties that (i) only one- and two-qubit interactions are required, and (ii) the system remains within the DFS throughout the entire implementation of a quantum gate. We show explicitly how to perform universal computation on clusters of the four-qubit DFS encoding one logical qubit each under "collective decoherence" (qubit-permutation-invariant system-bath coupling). Our results have immediate relevance to a number of proposed quantum computer implementations, in particular those in which the internal system Hamiltonian is of the Heisenberg type, such as spin-spin coupled quantum dots.

  3. The universe as an eigenstate: spacetime paths and decoherence

    CERN Document Server

    Seidewtz, E

    2006-01-01

    This paper describes how the entire universe might be considered an eigenstate determined by classical limiting conditions within it. This description is in the context of an approach in which the path of each relativistic particle in spacetime represents a fine-grained history for that particle, and a path integral represents a coarse-grained history as a superposition of paths meeting some criteria. Since spacetime paths are parametrized by an invariant parameter, not time, histories based on such paths do not evolve in time but are rather histories of all spacetime. Measurements can then be represented by orthogonal states that correlate with specific points in such coarse-grained histories, causing them to decohere, allowing a consistent probability interpretation. This conception is applied here to the analysis of the two slit experiment, scattering and, ultimately, the universe as a whole. The decoherence of cosmological states of the universe then provides the eigenstates from which our "real" universe...

  4. Extraordinary behaviors in a two-dimensional decoherent alternative quantum walk

    Science.gov (United States)

    Chen, Tian; Zhang, Xiangdong

    2016-07-01

    We reveal the quantum and classical behaviors of the two-dimensional (2D) alternative quantum walk (AQW) in the presence of decoherence. For different kinds of decoherence, the analytic expressions for the moments of position distribution of the AQW are obtained. Taking the broken line noise and coin decoherence as examples of decoherence, we find that when decoherence emerges in only one direction, the anisotropic position distribution pattern appears, and not all the motions of the walker exhibit the transition from quantum to classical behaviors. Considering the effect of decoherence, we reveal the anisotropic correlations between the x (y ) position of the 2D walker and the state of the coin in 2D AQWs.

  5. Real-time capable first principle based modelling of tokamak turbulent transport

    CERN Document Server

    Breton, S; Felici, F; Imbeaux, F; Aniel, T; Artaud, J F; Baiocchi, B; Bourdelle, C; Camenen, Y; Garcia, J

    2015-01-01

    A real-time capable core turbulence tokamak transport model is developed. This model is constructed from the regularized nonlinear regression of quasilinear gyrokinetic transport code output. The regression is performed with a multilayer perceptron neural network. The transport code input for the neural network training set consists of five dimensions, and is limited to adiabatic electrons. The neural network model successfully reproduces transport fluxes predicted by the original quasilinear model, while gaining five orders of magnitude in computation time. The model is implemented in a real-time capable tokamak simulator, and simulates a 300s ITER discharge in 10s. This proof-of-principle for regression based transport models anticipates a significant widening of input space dimensionality and physics realism for future training sets. This aims to provide unprecedented computational speed coupled with first-principle based physics for real-time control and integrated modelling applications.

  6. Quantum decoherence of subcritical bubble in electroweak phase transition

    CERN Document Server

    Shiromizu, T

    1995-01-01

    In a weakly first order phase transition the typical scale of a subcritical bubble calculated in our previous papers turned out to be too small. At this scale quantum fluctuations may dominate and our previous classical result may be altered. So we examine the critical size of a subcritical bubble where quantum-to-classical transition occurs through quantum decoherence. We show that this critical size is almost equal to the typical scale which we previously obtained.

  7. Towards the understanding of Decoherence on Ion Traps

    CERN Document Server

    Terra-Cunha, M O

    2004-01-01

    Two mechanisms of decoherence in ion traps are studied, specially related to the experiment [Kielpinski et al., Science 291 (2001) 1013]. Statistical hypothesis are made about the unknown variables and the expected behaviour of the visibility of the best experimental pattern is calculated for each mechanism. Data from the experiment are analyzed and show to be insufficient to distinguish between them. We suggest improvements which can do this with slight modifications in the present facilities.

  8. Controllable Amplification of Entanglement for Two Qutrits under Decoherence

    Institute of Scientific and Technical Information of China (English)

    ZHENG Qiang; XIE Xiao-Yao; ZHI Qi-Jun; REN Zhong-Zhou

    2011-01-01

    Entanglement dynamics of a two-qutrit Heisenberg spin chain with the external magnetic fields and DM interaction under the intrinsic decoherence is investigated. Depending on whether there is inhomogeneous magnetic field,the entanglement amplification, i.e. the phenomenon that the finally stable entanglement is bigger than that of the initial one, is found for one kind of initial states. The reasons for the controllable entanglement amplification are discussed.

  9. Lindblad theory of dynamical decoherence of quantum-dot excitons

    OpenAIRE

    Eastham, P. R.; Spracklen, A O; Keeling, Jonathan Mark James

    2013-01-01

    We use the Bloch-Redfield-Wangsness theory to calculate the effects of acoustic phonons in coherent control experiments where quantum-dot excitons are driven by shaped laser pulses. This theory yields a generalized Lindblad equation for the density operator of the dot, with time-dependent damping and decoherence due to phonon transitions between the instantaneous dressed states. It captures similar physics to the form recently applied to Rabi oscillation experiments [Ramsay et al., Phys. Rev....

  10. Polarization decoherence differential frequency-modulated continuous-wave gyroscope.

    Science.gov (United States)

    Zheng, Chao; Zheng, Gang; Han, Liwei; Luo, Jianhua; Teng, Fei; Wang, Bing; Song, Ping; Gao, Kun; Hou, Zhiqing

    2014-12-01

    A polarization decoherence differential frequency-modulated continuous-wave (FMCW) gyroscope is presented. The impact of coherent polarization crosstalk noise on the differential FMCW gyro is analyzed. In order to suppress coherent polarization crosstalk noise, a novel method was proposed to produce two incoherent orthogonal polarization narrow band beams from laser diode. In this way, the random drift has been reduced about one order.

  11. Entropy of Operator-valued Random Variables A Variational Principle for Large N Matrix Models

    CERN Document Server

    Akant, L; Rajeev, S G

    2002-01-01

    We show that, in 't Hooft's large N limit, matrix models can be formulated as a classical theory whose equations of motion are the factorized Schwinger--Dyson equations. We discover an action principle for this classical theory. This action contains a universal term describing the entropy of the non-commutative probability distributions. We show that this entropy is a nontrivial 1-cocycle of the non-commutative analogue of the diffeomorphism group and derive an explicit formula for it. The action principle allows us to solve matrix models using novel variational approximation methods; in the simple cases where comparisons with other methods are possible, we get reasonable agreement.

  12. Economic principles and fundamental model of the sustainable utilization of ecological resources

    Institute of Scientific and Technical Information of China (English)

    Du Jinpei; Li Lin

    2006-01-01

    By analyzing the basic rules and measurement principles of the sustainable utilization of ecological resources and constructing its mathematical model, this paper points out that the sustainable utilization of ecological resources is in nature to use the double-period model thousands of times for the dynamic distribution of ecological resources effectively. And it points out that in order to realize the sustainable utilization of ecological resources we must follow the basic principle - non-decreasing ecological capital and put forward corresponding standards, measures, policies and proposals.

  13. First principles based multiparadigm modeling of electronic structures and dynamics

    Science.gov (United States)

    Xiao, Hai

    enabling the tunability of CBO. We predict that Na further improves the CBO through electrostatically elevating the valence levels to decrease the CBO, explaining the observed essential role of Na for high performance. Moreover we find that K leads to a dramatic decrease in the CBO to 0.05 eV, much better than Na. We suggest that the efficiency of CIGS devices might be improved substantially by tuning the ratio of Na to K, with the improved phase stability of Na balancing phase instability from K. All these defects reduce interfacial stability slightly, but not significantly. A number of exotic structures have been formed through high pressure chemistry, but applications have been hindered by difficulties in recovering the high pressure phase to ambient conditions (i.e., one atmosphere and room temperature). Here we use dispersion-corrected DFT (PBE-ulg flavor) to predict that above 60 GPa the most stable form of N2O (the laughing gas in its molecular form) is a 1D polymer with an all-nitrogen backbone analogous to cis-polyacetylene in which alternate N are bonded (ionic covalent) to O. The analogous trans-polymer is only 0.03-0.10 eV/molecular unit less stable. Upon relaxation to ambient conditions both polymers relax below 14 GPa to the same stable non-planar trans-polymer, accompanied by possible electronic structure transitions. The predicted phonon spectrum and dissociation kinetics validate the stability of this trans-poly-NNO at ambient conditions, which has potential applications as a new type of conducting polymer with all-nitrogen chains and as a high-energy oxidizer for rocket propulsion. This work illustrates in silico materials discovery particularly in the realm of extreme conditions. Modeling non-adiabatic electron dynamics has been a long-standing challenge for computational chemistry and materials science, and the eFF method presents a cost-efficient alternative. However, due to the deficiency of FSG representation, eFF is limited to low-Z elements with

  14. Ambient nanoscale sensing with single spins using quantum decoherence

    Science.gov (United States)

    McGuinness, L. P.; Hall, L. T.; Stacey, A.; Simpson, D. A.; Hill, C. D.; Cole, J. H.; Ganesan, K.; Gibson, B. C.; Prawer, S.; Mulvaney, P.; Jelezko, F.; Wrachtrup, J.; Scholten, R. E.; Hollenberg, L. C. L.

    2013-07-01

    Magnetic resonance detection is one of the most important tools used in life-sciences today. However, as the technique detects the magnetization of large ensembles of spins it is fundamentally limited in spatial resolution to mesoscopic scales. Here we detect the natural fluctuations of nanoscale spin ensembles at ambient temperatures by measuring the decoherence rate of a single quantum spin in response to introduced extrinsic target spins. In our experiments 45 nm nanodiamonds with single nitrogen-vacancy (NV) spins were immersed in solution containing spin 5/2 Mn2+ ions and the NV decoherence rate measured though optically detected magnetic resonance. The presence of both freely moving and accreted Mn spins in solution were detected via significant changes in measured NV decoherence rates. Analysis of the data using a quantum cluster expansion treatment of the NV-target system found the measurements to be consistent with the detection of 2500 motionally diffusing Mn spins over an effective volume of (16 nm)3 in 4.2 s, representing a reduction in target ensemble size and acquisition time of several orders of magnitude over conventional, magnetic induction approaches to electron spin resonance detection. These measurements provide the basis for the detection of nanovolume spins in solution, such as in the internal compartments of living cells, and are directly applicable to scanning probe architectures.

  15. Reply to Comment on "Quantum Measurement and Decoherence"

    CERN Document Server

    Ford, G W

    2004-01-01

    While agreeing with our exact expression for the time dependence of the motion of a free particle in an initial superposition state, corresponding to two identical Gaussians separated by a distance $d$, at temperature $T$, Gobert et al., in the preceding Comment [Phys. Rev. A xxx], dispute our conclusions on decoherence time scales. However, the parameters they used to generate their figures are outside the regime of validity of our interpretation of the results and, moreover, are not of physical interest in that they correspond to $T\\approx 0$. The point is that in their figures they have chosen the thermal de Broglie wavelength $\\lambda_{th}=\\hbar \\sqrt{mkT}$ to be equal to slit spacing \\emph{d}, whereas we have clearly stated [in the paragraph preceding Eq. (21) of our paper] that decoherence occurs and that our expression for the decoherence time applies only in the limit where \\emph{d} is large compared not only with the slit width $\\sigma $ but also with the thermal de Broglie wavelength, $d\\gg \\lambda_...

  16. Quantum Decoherence for Multi-Photon Entangled States

    Institute of Scientific and Technical Information of China (English)

    SUN Yan-Hua; ZHU Xia; KUANG Le-Man

    2005-01-01

    @@ We investigate quantum decoherence of the multi-photon entangled state |ψNm> = Nm[cosγ|N- m>1|m>2 +eiθm sinγ|m>1|N - m>2]. When the entangled channel |ψNm> is embedded in an environment, the channel decoheres and becomes a mixed state governed by a master equation. We calculate thelinear entropy and the relative entropy of entanglement, which describe the mixedness and the amount of entanglement for the mixed state, respectively. We show that quantum decoherence weakens the amount of entanglement and enhances the mixedness with the time evolution. It is indicated that the relative entropy of entanglement depends on not only the initial entanglement angle and the decohering parameter, but also the number of photons in each mode. In particular, we find that the decohering speed depends on the number-difference of photons in the two modes. The larger the number-difference of photons is, the higher the decohering speed.

  17. Effects of Intrinsic Decoherence on Information Transport in a Spin Chain

    Institute of Scientific and Technical Information of China (English)

    ZENG Tian-Hai; SHAO Bin; ZOU Jian

    2009-01-01

    Considering Milburn's intrinsic decoherence effect on quantum communication through a spin chain, we show that the transfer quality for quantum state and entanglement will obviously decrease with the increasing intrinsic decoherence rate. Some odd chains are much higher than even ones for the state transfer efficiency. The state transfer of a long chain is very sensitive to the intrinsic decoherence, which turns out to be an obstacle for information transport.

  18. Modelling non-equilibrium thermodynamic systems from the speed-gradient principle

    Science.gov (United States)

    Khantuleva, Tatiana A.; Shalymov, Dmitry S.

    2017-03-01

    The application of the speed-gradient (SG) principle to the non-equilibrium distribution systems far away from thermodynamic equilibrium is investigated. The options for applying the SG principle to describe the non-equilibrium transport processes in real-world environments are discussed. Investigation of a non-equilibrium system's evolution at different scale levels via the SG principle allows for a fresh look at the thermodynamics problems associated with the behaviour of the system entropy. Generalized dynamic equations for finite and infinite number of constraints are proposed. It is shown that the stationary solution to the equations, resulting from the SG principle, entirely coincides with the locally equilibrium distribution function obtained by Zubarev. A new approach to describe time evolution of systems far from equilibrium is proposed based on application of the SG principle at the intermediate scale level of the system's internal structure. The problem of the high-rate shear flow of viscous fluid near the rigid plane plate is discussed. It is shown that the SG principle allows closed mathematical models of non-equilibrium processes to be constructed. This article is part of the themed issue 'Horizons of cybernetical physics'.

  19. Real-time approach to tunnelling in open quantum systems: decoherence and anomalous diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Calzetta, Esteban [Departmento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Verdaguer, Enric [Departament de Fisica Fonamental and CER en AstrofIsica, Fisica de PartIcules i Cosmologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain)

    2006-07-28

    Macroscopic quantum tunnelling is described using the master equation for the reduced Wigner function of an open quantum system at zero temperature. Our model consists of a particle trapped in a cubic potential interacting with an environment characterized by dissipative and normal and anomalous diffusion coefficients. A representation based on the energy eigenfunctions of the isolated system, i.e. the system uncoupled to the environment, is used to write the reduced Wigner function, and the master equation becomes simpler in that representation. The energy eigenfunctions computed in a WKB approximation incorporate the tunnelling effect of the isolated system and the effect of the environment is described by an equation that is in many ways similar to a Fokker-Planck equation. Decoherence is easily identified from the master equation and we find that when the decoherence time is much shorter than the tunnelling time the master equation can be approximated by a Kramers-like equation describing thermal activation due to the zero point fluctuations of the quantum environment. The effect of anomalous diffusion can be dealt with perturbatively and its overall effect is to inhibit tunnelling.

  20. Hybrid quantum-classical hierarchy for mitigation of decoherence and determination of excited states

    Energy Technology Data Exchange (ETDEWEB)

    McClean, Jarrod R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division; Kimchi-Schwartz, Mollie E. [Univ. of California, Berkeley, CA (United States). Quantum Nanoelectronics Lab., Dept. of Physics; Carter, Jonathan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division; de Jong, Wibe A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division

    2017-04-06

    Using quantum devices supported by classical computational resources is a promising approach to quantum-enabled computation. One powerful example of such a hybrid quantum-classical approach optimized for classically intractable eigenvalue problems is the variational quantum eigensolver, built to utilize quantum resources for the solution of eigenvalue problems and optimizations with minimal coherence time requirements by leveraging classical computational resources. These algorithms have been placed as leaders among the candidates for the first to achieve supremacy over classical computation. Here, we provide evidence for the conjecture that variational approaches can automatically suppress even nonsystematic decoherence errors by introducing an exactly solvable channel model of variational state preparation. Moreover, we develop a more general hierarchy of measurement and classical computation that allows one to obtain increasingly accurate solutions by leveraging additional measurements and classical resources. In conclusion, we demonstrate numerically on a sample electronic system that this method both allows for the accurate determination of excited electronic states as well as reduces the impact of decoherence, without using any additional quantum coherence time or formal error-correction codes.

  1. Global coherence of quantum evolutions based on decoherent histories: Theory and application to photosynthetic quantum energy transport

    Science.gov (United States)

    Allegra, Michele; Giorda, Paolo; Lloyd, Seth

    2016-04-01

    Assessing the role of interference in natural and artificial quantum dynamical processes is a crucial task in quantum information theory. To this aim, an appropriate formalism is provided by the decoherent histories framework. While this approach has been deeply explored from different theoretical perspectives, it still lacks of a comprehensive set of tools able to concisely quantify the amount of coherence developed by a given dynamics. In this paper, we introduce and test different measures of the (average) coherence present in dissipative (Markovian) quantum evolutions, at various time scales and for different levels of environmentally induced decoherence. In order to show the effectiveness of the introduced tools, we apply them to a paradigmatic quantum process where the role of coherence is being hotly debated: exciton transport in photosynthetic complexes. To spot out the essential features that may determine the performance of the transport, we focus on a relevant trimeric subunit of the Fenna-Matthews-Olson complex and we use a simplified (Haken-Strobl) model for the system-bath interaction. Our analysis illustrates how the high efficiency of environmentally assisted transport can be traced back to a quantum recoil avoiding effect on the exciton dynamics, that preserves and sustains the benefits of the initial fast quantum delocalization of the exciton over the network. Indeed, for intermediate levels of decoherence, the bath is seen to selectively kill the negative interference between different exciton pathways, while retaining the initial positive one. The concepts and tools here developed show how the decoherent histories approach can be used to quantify the relation between coherence and efficiency in quantum dynamical processes.

  2. Optimal control of quantum gates and suppression of decoherence in a system of interacting two-level particles

    CERN Document Server

    Grace, M; Kosut, R L; Lidar, D A; Rabitz, H; Walmsley, I A; Brif, Constantin; Grace, Matthew; Kosut, Robert L.; Lidar, Daniel A.; Rabitz, Herschel; Walmsley, Ian A.

    2007-01-01

    Methods of optimal control are applied to a model system of interacting two-level particles (e.g., spin-half atomic nuclei or electrons or two-level atoms) to produce high-fidelity quantum gates while simultaneously negating the detrimental effect of decoherence. One set of particles functions as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one- and two-qubit unitary gates in the presence of strong environmentally-induced decoherence and under physically motivated restrictions on the control field. The quantum-gate fidelity, expressed in terms of a novel state-independent distance measure, is maximized with respect to the control field using combined genetic and gradient algorithms. The resulting high-fidelity gates demonstrate the feasibility of precisely guiding the quantum ev...

  3. Mixing and decoherence in continuous-time quantum walks on long-range interacting cycles

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, S; Radgohar, R [Faculty of Science, Department of Physics, University of Kurdistan, Pasdaran Ave., Sanandaj (Iran, Islamic Republic of)], E-mail: shsalimi@uok.ac.ir, E-mail: r.radgohar@uok.ac.ir

    2009-11-27

    We study the effect of small decoherence in continuous-time quantum walks on long-range interacting cycles, which are constructed by connecting all the two nodes of distance m on the cycle graph. In our investigation, each node is continuously monitored by an individual point contact, which induces the decoherence process. We obtain the analytical probability distribution and the mixing time upper bound. Our results show that, for small rates of decoherence, the mixing time upper bound is independent of distance parameter m and is proportional to inverse of decoherence rate.

  4. Quantum Decoherence of a Single Trapped Ion due to Engineered Reservoir

    Institute of Scientific and Technical Information of China (English)

    YI Xue-Xi

    2002-01-01

    Known as an engineered reservoir due to fluctuations in trap parameter,a classical source of quantum decoherence is considered for a single trapped ion theoretically.For simplicity it is assumed that the fluctuations involved are white noise processes,which enables us to give a simple master equation description of this source of decoherence.Our results show that the decoherence rate depends on the vibrational quantum number in different ways corresponding to the vibrational excitation sideband used there.Besides,this source of decoherence also leads to occurrence of dissipation in the ion system.

  5. The Levels of Conceptual Interoperability Model: Applying Systems Engineering Principles to M&S

    CERN Document Server

    WANG, Wenguang; WANG, Weiping

    2009-01-01

    This paper describes the use of the Levels of Conceptual Interoperability Model (LCIM) as a framework for conceptual modeling and its descriptive and prescriptive uses. LCIM is applied to show its potential and shortcomings in the current simulation interoperability approaches, in particular the High Level Architecture (HLA) and Base Object Models (BOM). It emphasizes the need to apply rigorous engineering methods and principles and replace ad-hoc approaches.

  6. Mechanical-Kinetic Modeling of a Molecular Walker from a Modular Design Principle

    Science.gov (United States)

    Hou, Ruizheng; Loh, Iong Ying; Li, Hongrong; Wang, Zhisong

    2017-02-01

    Artificial molecular walkers beyond burnt-bridge designs are complex nanomachines that potentially replicate biological walkers in mechanisms and functionalities. Improving the man-made walkers up to performance for widespread applications remains difficult, largely because their biomimetic design principles involve entangled kinetic and mechanical effects to complicate the link between a walker's construction and ultimate performance. Here, a synergic mechanical-kinetic model is developed for a recently reported DNA bipedal walker, which is based on a modular design principle, potentially enabling many directional walkers driven by a length-switching engine. The model reproduces the experimental data of the walker, and identifies its performance-limiting factors. The model also captures features common to the underlying design principle, including counterintuitive performance-construction relations that are explained by detailed balance, entropy production, and bias cancellation. While indicating a low directional fidelity for the present walker, the model suggests the possibility of improving the fidelity above 90% by a more powerful engine, which may be an improved version of the present engine or an entirely new engine motif, thanks to the flexible design principle. The model is readily adaptable to aid these experimental developments towards high-performance molecular walkers.

  7. Is dark energy an artifact of decoherence?

    CERN Document Server

    Fields, Chris

    2015-01-01

    Within the quantum Darwinist framework introduced by W. H. Zurek ({\\em Nat. Phys.}, 5:181-188, 2009), observers obtain pointer-state information about quantum systems by interacting with the surrounding environment, e.g. the ambient photon field. This framework is applied to the observation of stellar center-of-mass positions, which are assumed to be encoded in a way that is uniformly accessible to all observers regardless of their location. Assuming Landauer's Principle, constructing such environmental encodings requires $\\sim$ kT per bit. For 10$^{25}$ stars and a binary encoding of center-of-mass positions into 10 km$^{3}$ voxels, the free energy required at T = 2.7 K is $\\sim$ 5 $\\cdot$ 10$^{-27}$ kg $\\cdot$ m$^{-3}$, in striking agreement with the observed value of $\\Omega_{\\Lambda} \\rho_{c}$. Decreasing the voxel size to $l_{P}^{3}$ results in a free energy requirement 10$^{117}$ times larger.

  8. Principles of goal-directed spatial robot navigation in biomimetic models.

    Science.gov (United States)

    Milford, Michael; Schulz, Ruth

    2014-11-01

    Mobile robots and animals alike must effectively navigate their environments in order to achieve their goals. For animals goal-directed navigation facilitates finding food, seeking shelter or migration; similarly robots perform goal-directed navigation to find a charging station, get out of the rain or guide a person to a destination. This similarity in tasks extends to the environment as well; increasingly, mobile robots are operating in the same underwater, ground and aerial environments that animals do. Yet despite these similarities, goal-directed navigation research in robotics and biology has proceeded largely in parallel, linked only by a small amount of interdisciplinary research spanning both areas. Most state-of-the-art robotic navigation systems employ a range of sensors, world representations and navigation algorithms that seem far removed from what we know of how animals navigate; their navigation systems are shaped by key principles of navigation in 'real-world' environments including dealing with uncertainty in sensing, landmark observation and world modelling. By contrast, biomimetic animal navigation models produce plausible animal navigation behaviour in a range of laboratory experimental navigation paradigms, typically without addressing many of these robotic navigation principles. In this paper, we attempt to link robotics and biology by reviewing the current state of the art in conventional and biomimetic goal-directed navigation models, focusing on the key principles of goal-oriented robotic navigation and the extent to which these principles have been adapted by biomimetic navigation models and why.

  9. Variational Principle for Non-Equilibrium Steady States of the XX Model

    CERN Document Server

    Matsui, T

    2003-01-01

    We show that non-equilibrium steady states of the one dimensional exactly solved XY model can be characterized by the variational principle of free energy of a long range interaction and that they cannot be a KMS state for any C$^*$-dynamical system.

  10. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution o

  11. Invariance principle and model reduction for the Fokker-Planck equation

    Science.gov (United States)

    Karlin, I. V.

    2016-11-01

    The principle of dynamic invariance is applied to obtain closed moment equations from the Fokker-Planck kinetic equation. The analysis is carried out to explicit formulae for computation of the lowest eigenvalue and of the corresponding eigenfunction for arbitrary potentials. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  12. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution o

  13. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution

  14. Using Pontryagin maximum principle for parametrical identification of ship maneuvering mathematical model

    Directory of Open Access Journals (Sweden)

    Uri UDIN

    2014-06-01

    Full Text Available This article proposes usage of Pontryagin maximum principle for parametrical identification of mathematical vessel’s model. Proposed method has a special perspective for identification in real time mode, when the parameters identified can be used for forecasting of coming maneuvers.

  15. First principles dynamic modeling and multivariable control of a cryogenic distillation process

    NARCIS (Netherlands)

    Roffel, B.; Betlem, B.H.L.; Ruijter, J.A.

    2000-01-01

    In order to investigate the feasibility of constrained multivariable control of a heat-integrated cryogenic distillation process, a rigorous first principles dynamic model was developed and tested against a limited number of experiments. It was found that the process variables showed a large amount

  16. Exact Master Equation and Quantum Decoherence of Two Coupled Harmonic Oscillators in a General Environment

    CERN Document Server

    Chou, C H; Yu, T; Chou, Chung-Hsien; Yu, Ting

    2007-01-01

    In this paper we derive an exact master equation for two coupled quantum harmonic oscillators interacting via bilinear coupling with a common environment made up of many harmonic oscillators at arbitrary temperature for a general spectral density function. We first show a simple derivation based on the observation that the two harmonic oscillator model can be effectively mapped into that of a single harmonic oscillator in a general environment plus a free harmonic oscillator. Since the exact one harmonic oscillator master equation is known [Hu, Paz and Zhang, Phys. Rev. D \\textbf{45}, 2843 (1992)], the exact master equation with all its coefficients for this two harmonic oscillator model can be easily deduced from the known results of the single harmonic oscillator case. In the second part we give an influence functional treatment of this model and provide explicit expressions for the evolution operator of the reduced density matrix which are useful for the study of decoherence and disentanglement issues. We ...

  17. A study of tumour growth based on stoichiometric principles: a continuous model and its discrete analogue.

    Science.gov (United States)

    Saleem, M; Agrawal, Tanuja; Anees, Afzal

    2014-01-01

    In this paper, we consider a continuous mathematically tractable model and its discrete analogue for the tumour growth. The model formulation is based on stoichiometric principles considering tumour-immune cell interactions in potassium (K (+))-limited environment. Our both continuous and discrete models illustrate 'cancer immunoediting' as a dynamic process having all three phases namely elimination, equilibrium and escape. The stoichiometric principles introduced into the model allow us to study its dynamics with the variation in the total potassium in the surrounding of the tumour region. It is found that an increase in the total potassium may help the patient fight the disease for a longer period of time. This result seems to be in line with the protective role of the potassium against the risk of pancreatic cancer as has been reported by Bravi et al. [Dietary intake of selected micronutrients and risk of pancreatic cancer: An Italian case-control study, Ann. Oncol. 22 (2011), pp. 202-206].

  18. Coding conventions and principles for a National Land-Change Modeling Framework

    Science.gov (United States)

    Donato, David I.

    2017-07-14

    This report establishes specific rules for writing computer source code for use with the National Land-Change Modeling Framework (NLCMF). These specific rules consist of conventions and principles for writing code primarily in the C and C++ programming languages. Collectively, these coding conventions and coding principles create an NLCMF programming style. In addition to detailed naming conventions, this report provides general coding conventions and principles intended to facilitate the development of high-performance software implemented with code that is extensible, flexible, and interoperable. Conventions for developing modular code are explained in general terms and also enabled and demonstrated through the appended templates for C++ base source-code and header files. The NLCMF limited-extern approach to module structure, code inclusion, and cross-module access to data is both explained in the text and then illustrated through the module templates. Advice on the use of global variables is provided.

  19. Low-energy electron reflectivity from graphene: First-principles computations and approximate models

    Energy Technology Data Exchange (ETDEWEB)

    Feenstra, R.M., E-mail: feenstra@cmu.edu [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Widom, M. [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

    2013-07-15

    A computational method is developed whereby the reflectivity of low-energy electrons from a surface can be obtained from a first-principles solution of the electronic structure of the system. The method is applied to multilayer graphene. Two bands of reflectivity minima are found, one at 0–8 eV and the other at 14–22 eV above the vacuum level. For a free-standing slab with n layers of graphene, each band contains n−1 zeroes in the reflectivity. Two additional image-potential type states form at the ends of the graphene slab, with energies just below the vacuum level, hence producing a total of 2n states. A tight-binding model is developed, with basis functions localized in the spaces between the graphene planes (and at the ends of the slab). The spectrum of states produced by the tight-binding model is found to be in good agreement with the zeros of reflectivity (i.e. transmission resonances) of the first-principles results. - Highlights: ► Developed method for simulation of low-energy electron reflectivity spectra. ► Reflectivity spectra of graphene are computed by a first-principles method. ► Comparison is made between results from first-principles and from a tight-binding model.

  20. System principles, mathematical models and methods to ensure high reliability of safety systems

    Science.gov (United States)

    Zaslavskyi, V.

    2017-04-01

    Modern safety and security systems are composed of a large number of various components designed for detection, localization, tracking, collecting, and processing of information from the systems of monitoring, telemetry, control, etc. They are required to be highly reliable in a view to correctly perform data aggregation, processing and analysis for subsequent decision making support. On design and construction phases of the manufacturing of such systems a various types of components (elements, devices, and subsystems) are considered and used to ensure high reliability of signals detection, noise isolation, and erroneous commands reduction. When generating design solutions for highly reliable systems a number of restrictions and conditions such as types of components and various constrains on resources should be considered. Various types of components perform identical functions; however, they are implemented using diverse principles, approaches and have distinct technical and economic indicators such as cost or power consumption. The systematic use of different component types increases the probability of tasks performing and eliminates the common cause failure. We consider type-variety principle as an engineering principle of system analysis, mathematical models based on this principle, and algorithms for solving optimization problems of highly reliable safety and security systems design. Mathematical models are formalized in a class of two-level discrete optimization problems of large dimension. The proposed approach, mathematical models, algorithms can be used for problem solving of optimal redundancy on the basis of a variety of methods and control devices for fault and defects detection in technical systems, telecommunication networks, and energy systems.

  1. Presenting the SCL model: adding value to business strategy through UCD principles

    OpenAIRE

    Moreno, M. A.; Lilley, D; Lofthouse, V.

    2014-01-01

    This paper presents the Sustainable Consumption Leveraging (SCL) Model and its toolkit, which was developed to help businesses examine their potential for enabling sustainable consumption whilst identifying areas of opportunity to improve their business model and value proposition. The paper begins by establishing the contribution of business towards sustainable consumption and sets out user-centred design (UCD) principles as a valuable approach to leverage sustainable consumption. The relati...

  2. Two-dimensional models as testing ground for principles and concepts of local quantum physics

    CERN Document Server

    Schrör, B

    2005-01-01

    In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g. chiral models, factorizing models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) and a modular interpretation of the chiral model Diff(S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime. As a special case of the thermal duality, the SL(2,Z) modular Verlinde relation is thus a consequence of the principles of thermal QFT togeth...

  3. Stochasticity, decoherence and an arrow of time from the discretization of time?

    Indian Academy of Sciences (India)

    M C Valsakumar

    2005-04-01

    Certain intriguing consequences of the discreteness of time on the time evolution of dynamical systems are discussed. In the discrete-time classical mechanics proposed here, there is an arrow of time that follows from the fact that the replacement of the time derivative by the backward difference operator alone can preserve the non-negativity of the phase space density. It is seen that, even for free particles, all the degrees of freedom are correlated in principle. The forward evolution of functions of phase space variables by a finite number of time steps, in this discrete-time mechanics, depends on the entire continuous-time history in the interval [0, ∞]. In this sense, discrete time evolution is non-local in time from a continuous-time point of view. A corresponding quantum mechanical treatment is possible via the density matrix approach. The interference between non-degenerate quantum mechanical states decays exponentially. This decoherence is present, in principle, for all systems; however, it is of practical importance only in macroscopic systems, or in processes involving large energy changes.

  4. Riccati equation and the problem of decoherence

    Science.gov (United States)

    Gardas, Bartłomiej

    2010-06-01

    The block operator matrix theory is used to investigate the problem of a single qubit. We establish a connection between the Riccati operator equation and the possibility of obtaining an exact reduced dynamics for the qubit in question. The model of the half spin particle in the rotating magnetic field coupling with the external environment is discussed. We show that the model defined in such a way can be reduced to a time independent problem.

  5. Riccati equation and the problem of decoherence

    CERN Document Server

    Gardas, Bartłomiej

    2010-01-01

    The block operator matrix theory is used to investigate the problem of a single qubit. We will establish a connection between Riccati operator equation and the possibility of obtaining an exact reduced dynamics for the qubit in question. The model of the half spin particle in the rotating magnetic field coupling with the external environment is discussed. We show that the model defined in such a way can be reduced to the time independent problem.

  6. Measurement-induced decoherence and information in double-slit interference

    Science.gov (United States)

    Kincaid, Joshua; McLelland, Kyle; Zwolak, Michael

    2016-07-01

    The double slit experiment provides a classic example of both interference and the effect of observation in quantum physics. When particles are sent individually through a pair of slits, a wave-like interference pattern develops, but no such interference is found when one observes which "path" the particles take. We present a model of interference, dephasing, and measurement-induced decoherence in a one-dimensional version of the double-slit experiment. Using this model, we demonstrate how the loss of interference in the system is correlated with the information gain by the measuring apparatus/observer. In doing so, we give a modern account of measurement in this paradigmatic example of quantum physics that is accessible to students taking quantum mechanics at the graduate or senior undergraduate levels.

  7. Decoherence and disentanglement of qubits detecting scalar fields in an expanded universe

    CERN Document Server

    Li, Yujie; Shi, Yu

    2016-01-01

    We consider Unruh-Wald qubit detector model adopted for the far future region of an exactly solvable 1+1 dimensional scalar field theory in a Robertson-Walker expanding spacetime. It is shown that the expansion of the universe in its history enhances the decoherence of the qubit coupled with a scalar field. Moreover, we consider two entangled qubits, each locally coupled a scalar field. The expansion of the universe in its history degrades the entanglement between the qubits, and can lead to entanglement sudden death if the initial entanglement is small enough. The details depend on the parameters characterizing the expansion of the universe. This work, albeit on a toy model, suggests that the history of the universe might be probed through the coherent and entanglement behavior of future detectors of quantum fields.

  8. Measurement-induced decoherence and information in double-slit interference

    Science.gov (United States)

    Kincaid, Joshua; McLelland, Kyle; Zwolak, Michael

    2016-01-01

    The double slit experiment provides a classic example of both interference and the effect of observation in quantum physics. When particles are sent individually through a pair of slits, a wave-like interference pattern develops, but no such interference is found when one observes which “path” the particles take. We present a model of interference, dephasing, and measurement-induced decoherence in a one-dimensional version of the double-slit experiment. Using this model, we demonstrate how the loss of interference in the system is correlated with the information gain by the measuring apparatus/observer. In doing so, we give a modern account of measurement in this paradigmatic example of quantum physics that is accessible to students taking quantum mechanics at the graduate or senior undergraduate levels. PMID:27807373

  9. Measurement-induced decoherence and information in double-slit interference.

    Science.gov (United States)

    Kincaid, Joshua; McLelland, Kyle; Zwolak, Michael

    2016-07-01

    The double slit experiment provides a classic example of both interference and the effect of observation in quantum physics. When particles are sent individually through a pair of slits, a wave-like interference pattern develops, but no such interference is found when one observes which "path" the particles take. We present a model of interference, dephasing, and measurement-induced decoherence in a one-dimensional version of the double-slit experiment. Using this model, we demonstrate how the loss of interference in the system is correlated with the information gain by the measuring apparatus/observer. In doing so, we give a modern account of measurement in this paradigmatic example of quantum physics that is accessible to students taking quantum mechanics at the graduate or senior undergraduate levels.

  10. Control-Oriented First Principles-Based Model of a Diesel Generator

    DEFF Research Database (Denmark)

    Knudsen, Jesper Viese; Bendtsen, Jan Dimon; Andersen, Palle;

    2016-01-01

    This paper presents the development of a control-oriented tenth-order nonlinear model of a diesel driven generator set, using first principles modeling. The model provides physical system insight, while keeping the complexity at a level where it can be a tool for future design of improved automatic...... generation control (AGC), by including important nonlinearities of the machine. The nonlinearities are, as would be expected for a generator, primarily of bilinear nature. Validation of the model is done with measurements on a 60 kVA/48 kW diesel driven generator set in island operation during steps...

  11. Influence of Decoherence on Interference Between Two Bose-Einstein Condensates

    Institute of Scientific and Technical Information of China (English)

    ZENG Ai-Hua; KUANG Le-Man

    2004-01-01

    The influence of decoherence on interference between two trapped Bose-Einstein condensates with arbitrary initial states is studied. Analytic expressions of the intensity and visibility of the interference pattern are found. It is shown that the decoherence weakens the interference intensity and decreases the visibility of the interference pattern.

  12. Coherence vs. decoherence in (some) problems of condensed matter physics

    Indian Academy of Sciences (India)

    Sushanta Dattagupta

    2002-08-01

    We present an `overview’ of coherence-to-decoherence transition in certain selected problems of condensed matter physics. Our treatment is based on a subsystem-plus-environment approach. All the examples chosen in this paper have one thing in common – the environmental degrees of freedom are taken to be bosonic and their spectral density of excitations is assumed to be `ohmic’. The examples are drawn from a variety of phenomena in condensed matter physics involving, for instance, quantum diffusion of hydrogen in metals, Landau diamagnetism and -axis transport in high c superconductors.

  13. Decoherence induced by a fluctuating Aharonov-Casher phase

    CERN Document Server

    Lombardo, F C; Villar, P I

    2005-01-01

    Dipoles interference is studied when atomic systems are coupled to classical electromagnetic fields. The interaction between the dipoles and the classical fields induces a time-varying Aharonov-Casher phase. Averaging over the phase generates a suppression of fringe visibility in the interference pattern. We show that, for suitable experimental conditions, the loss of contrast for dipoles can be observable and almost as large as the corresponding one for coherent electrons. We analyze different trajectories in order to show the dependence of the decoherence factor with the velocity of the particles.

  14. Gravitational Decoherence, Alternative Quantum Theories and Semiclassical Gravity

    CERN Document Server

    Hu, B L

    2014-01-01

    In this report we discuss three aspects: 1) Semiclassical gravity theory (SCG): 4 levels of theories describing the interaction of quantum matter with classical gravity; 2) Alternative Quantum Theories: Discerning those which are derivable from general relativity (GR) plus quantum field theory (QFT) from those which are not; 3) Gravitational Decoherence: Derivation of a master equation and examination of the assumptions which led to the claims of observational possibilities. We list three sets of corresponding problems worthy of pursuit: a) Newton-Schr\\"odinger Equations in relation to SCG; b) Master equation of gravity-induced effects serving as discriminator of 2); and c) Role of gravity in macroscopic quantum phenomena.

  15. Suppressing decoherence of quantum algorithms by jump codes

    CERN Document Server

    Kern, O; Kern, Oliver; Alber, Gernot

    2005-01-01

    The stabilizing properties of one-error correcting jump codes are explored under realistic non-ideal conditions. For this purpose the quantum algorithm of the tent-map is decomposed into a universal set of Hamiltonian quantum gates which ensure perfect correction of spontaneous decay processes under ideal circumstances even if they occur during a gate operation. An entanglement gate is presented which is capable of entangling any two logical qubits of different one-error correcting code spaces. With the help of this gate simultaneous spontaneous decay processes affecting physical qubits of different code spaces can be corrected and decoherence can be suppressed significantly.

  16. Onset of color decoherence for soft gluon radiation in medium

    CERN Document Server

    Mehtar-Tani, Yacine; Tywoniuk, Konrad

    2011-01-01

    We report on recent studies of the phenomenon of color decoherence in jets in QCD media. The effect is most clearly observed in the radiation pattern of a quark-antiquark antenna, created in the same quantum state, traversing a dense color deconfined plasma. Multiple scattering with the medium color charges gradually destroys the coherence of the antenna. In the limit of opaque media this ultimately leads to independent radiation off the antenna constituents. Accordingly, radiation off the total charge vanishes implying a memory loss effect induced by the medium.

  17. Connection between decoherence and fidelity decay in echo dynamics

    Science.gov (United States)

    Gorin, T.; Prosen, T.; Seligman, T. H.; Strunz, W. T.

    2004-10-01

    Entanglement between a quantum system and its environment leads to loss of coherence in the former. In general, the temporal fate of coherences is complicated. Here, we establish the connection between decoherence of a central system and fidelity decay in the environment for a variety of situations, including both energy conserving and dissipative couplings. We show how properties of unitary time evolution of the environment can be inferred from the nonunitary evolution of coherences in the central system. This opens up promising ways for measuring Loschmidt echoes in a variety of situations.

  18. Reservoir-induced decoherence of resonantly excited confined polaritons

    Science.gov (United States)

    Ouellet-Plamondon, C.; Sallen, G.; Morier-Genoud, F.; Oberli, D. Y.; Portella-Oberli, M. T.; Deveaud, B.

    2017-02-01

    We report on the effect of decoherence on polariton bistability. The polariton hysteresis loop is shown to collapse in a similar way when increasing the temperature or under nonresonant excitation power. The hysteresis upward threshold is pulled to lower excitation power, whereas the downward threshold remains almost constant. This effect is explained by the population of an incoherent reservoir that induces dephasing and repulsive interaction that saturates at large densities. All experimental findings are accurately simulated with the excitonic Bloch equations and indicate that reservoir-induced dephasing can be dominant over the reservoir-induced energy blueshift.

  19. First-Principles Models for Biological Light-Harvesting: Phycobiliprotein Complexes from Cryptophyte Algae.

    Science.gov (United States)

    Lee, Mi Kyung; Bravaya, Ksenia B; Coker, David F

    2017-06-14

    There have been numerous efforts, both experimental and theoretical, that have attempted to parametrize model Hamiltonians to describe excited state energy transfer in photosynthetic light harvesting systems. The Frenkel exciton model, with its set of electronically coupled two level chromophores that are each linearly coupled to dissipative baths of harmonic oscillators, has become the workhorse of this field. The challenges to parametrizing such Hamiltonians have been their uniqueness, and physical interpretation. Here we present a computational approach that uses accurate first-principles electronic structure methods to compute unique model parameters for a collection of local minima that are sampled with molecular dynamics and QM geometry optimization enabling the construction of an ensemble of local models that captures fluctuations as these systems move between local basins of inherent structure. The accuracy, robustness, and reliability of the approach is demonstrated in an application to the phycobiliprotein light harvesting complexes from cryptophyte algae. Our computed Hamiltonian ensemble provides a first-principles description of inhomogeneous broadening processes, and a standard approximate non-Markovian reduced density matrix dynamics description is used to estimate lifetime broadening contributions to the spectral line shape arising from electronic-vibrational coupling. Despite the overbroadening arising from this approximate line shape theory, we demonstrate that our model Hamiltonian ensemble approach is able to provide a reliable fully first-principles method for computation of spectra and can distinguish the influence of different chromophore protonation states in experimental results. A key feature in the dynamics of these systems is the excitation of intrachromophore vibrations upon electronic excitation and energy transfer. We demonstrate that the Hamiltonian ensemble approach provides a reliable first-principles description of these

  20. First-principles modeling of electromagnetic scattering by discrete and discretely heterogeneous random media

    CERN Document Server

    Mishchenko, Michael I; Yurkin, Maxim A; Bi, Lei; Cairns, Brian; Liu, Li; Panetta, R Lee; Travis, Larry D; Yang, Ping; Zakharova, Nadezhda T

    2016-01-01

    The main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell-Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell-Lorentz equations, we trace the development of the first-principles formalism enabling accurate calculations of monochromatic and quasi-monochromatic scattering by static and randomly varying multiparticle groups. We illustrate how this general framework can be coupled with state-of-the-art computer solvers of the Maxwell equations and applied to direct modeling of electromagnetic scattering by representative random multi-particle groups with arbitrary packing densities. This first-principles modeling yields general physical insights unavailable with phenomenological approaches. We discuss how the first-order-scattering approximation, the radiative transfer theory, and the theory of weak localization of electromagnetic waves ...

  1. Decoherence in Optically Excited Semiconductors: a perspective from non-equilibrium Green functions

    Science.gov (United States)

    Virk, Kuljit Singh

    Decoherence is central to our understanding of the transition from the quantum to the classical world. It is also a way of probing the dynamics of interacting many-body systems. Photoexcited semiconductors are such systems in which the transient dynamics can be studied in considerable detail experimentally. Recent advances in spectroscopy of semiconductors provide powerful tools to explore many-body physics in new regimes. An appropriate theoretical framework is necessary to describe new physical effects now accessible for observation. We present a possible approach in this thesis, and discuss results of its application to an experimentally relevant scenario. The major portion of this thesis is devoted to a formalism for the multi-dimensional Fourier spectroscopy of semiconductors. A perturbative treatment of the electromagnetic field is used to derive a closed set of differential equations for the multi-particle correlation functions, which take into account the many-body effects up to third order in the field. A diagrammatic method is developed, in which we retain all features of the double-sided Feynman diagrams for bookkeeping the excitation scenario, and complement them by allowing for the description of interactions. We apply the formalism to study decoherence between the states of optically excited excitons embedded in an electron gas, and compare it with the decoherence between these states and the ground state. We derive a dynamical equation for the two-time correlation functions of excitons, and compare it with the corresponding equation for the interband polarization. It is argued, and verified by numerical calculation, that the decay of Raman coherence depends sensitively on how differently the superimposed exciton states interact with the electron gas, and that it can be much slower than the decay of interband polarization. We also present a new numerical approach based on the length gauge for modeling the time-dependent laser-semiconductor interaction

  2. Limits of I-models Principles Application on Czech SMEs'’ Internationalization Process

    Directory of Open Access Journals (Sweden)

    Lea Kubíčková

    2014-01-01

    Full Text Available Internationalization process of small and medium sized enterprises is examined often in an effort to get detailed description of particular stages of this process. There are many authors who deal with the internationalization process theories. The most popular theory is so-called Uppsala Model (Johanson, Vahlne, 1977. Very popular is also a group of models based on theory of innovations, called I-models (Bilkey, Tesar, 1977. These models are based on the idea that the process of internationalization is gradual, sequential process built on innovative decisions relating to new company’s needs, possibilities or new resources. The aim of this paper is to apply I-models principles on the internationalization process of Czech SMEs. There were processed data from the survey conducted in 2009-2012. The data were obtained from 385 Czech SMEs operating in the field of engineering, constructing, wood processing industry, food industry and viticulture. To apply the basic principles of the I-models to internationalization process of Czech SMEs it was necessary to determine if there are so-called Born Globals which deny the I-model’s internationalization theories. It was necessary to examine motives of internationalization of Czech SMEs, to prove dependency between the number of years on the market and proactivity/reactivity of the motives for entering foreign markets. Processing obtained data did not enable to unequivocally confirm that the basic principles forming a keystone of the I-models are functional in the internationalization process of Czech SMEs.

  3. Quantum Optics Including Noise Reduction, Trapped Ions, Quantum Trajectories, and Decoherence

    CERN Document Server

    Orszag, Miguel

    2008-01-01

    Quantum Optics gives a very broad coverage of basic laser-related phenomena that allow scientist and engineers to carry out research in quantum optics and laser physics. It covers quantization of the electromagnetic field, quantum theory of coherence, atom-field interaction models, resonance fluorescence, quantum theory of damping, laser theory using both the master equation and the Langevin theory, the correlated emission laser, input-output theory with applications to non-linear optics, quantum trajectories, quantum non-demolition measurements and generation of non-classical vibrational states of ions in a Paul trap. In this second edition, there is an enlarged chapter on decoherence, as well as additional material dealing with elements of quantum computation, entanglement of pure and mixed states as well as a chapter on quantum copying and processors. These topics are presented in a unified and didactic manner. The presentation of the book is clear and pedagogical; it balances the theoretical aspect of qua...

  4. Hybrid Quantum-Classical Hierarchy for Mitigation of Decoherence and Determination of Excited States

    CERN Document Server

    McClean, Jarrod R; Carter, Jonathan; de Jong, Wibe A

    2016-01-01

    Using quantum devices supported by classical computational resources is a promising approach to quantum-enabled computation. One example of such a hybrid quantum-classical approach is the variational quantum eigensolver (VQE) built to utilize quantum resources for the solution of eigenvalue problems and optimizations with minimal coherence time requirements by leveraging classical computational resources. These algorithms have been placed among the candidates for first to achieve supremacy over classical computation. Here, we provide evidence for the conjecture that variational approaches can automatically suppress even non-systematic decoherence errors by introducing an exactly solvable channel model of variational state preparation. Moreover, we show how variational quantum-classical approaches fit in a more general hierarchy of measurement and classical computation that allows one to obtain increasingly accurate solutions with additional classical resources. We demonstrate numerically on a sample electroni...

  5. Decoherence induced by a chaotic environment: A quantum walker with a complex coin

    CERN Document Server

    Ermann, L; Saraceno, M; Ermann, Leonardo; Paz, Juan Pablo; Saraceno, Marcos

    2005-01-01

    We study the differences between the process of decoherence induced by chaotic and regular environments. For this we analyze a family of simple models wich contain both regular and chaotic environments. In all cases the system of interest is a "quantum walker", i.e. a quantum particle that can move on a lattice with a finite number of sites. The walker interacts with an environment wich has a D dimensional Hilbert space. The results we obtain suggest that regular and chaotic environments are not distinguishable from each other in a (short) timescale t*, wich scales with the dimensionality of the environment as t*~log(D). Howeber, chaotic environments continue to be effective over exponentially longer timescales while regular environments tend to reach saturation much sooner. We present both numerical and analytical results supporting this conclusion. The family of chaotic evolutions we consider includes the so-called quantum multi-baker-map as a particular case.

  6. Prediction and real-time compensation of qubit decoherence via machine-learning

    CERN Document Server

    Mavadia, Sandeep; Sastrawan, Jarrah; Dona, Stephen; Biercuk, Michael J

    2016-01-01

    Control engineering techniques are emerging as a promising approach to realize the stabilisation of quantum systems, and a powerful complement to attempts to design-in passive robustness. However, applications to date have largely been limited by the challenge that projective measurement of quantum devices causes the collapse of quantum superposition states. As a result significant tradeoffs have been mandated in applying the concept of feedback, and experiments have relied on open-loop control, weak measurements, access to ancilla states, or largely sacrificing quantum coherence in the controlled system. In this work we use techniques from control theory and machine learning to enable the real-time feedback suppression of semiclassical decoherence in a qubit when access to measurements is limited. Using a time-series of measurements of a qubit's phase we are able to predict future stochastic evolution without requiring a deterministic model of qubit evolution. We demonstrate this capability by preemptively s...

  7. Various methods of optimizing control pulses for quantum systems with decoherence

    Science.gov (United States)

    Pawela, Łukasz; Sadowski, Przemysław

    2016-05-01

    We design control setting that allows the implementation of an approximation of an unitary operation of a quantum system under decoherence using various quantum system layouts and numerical algorithms. We focus our attention on the possibility of adding ancillary qubits which help to achieve a desired quantum map on the initial system. Furthermore, we use three methods of optimizing the control pulses: genetic optimization, approximate evolution method and approximate gradient method. To model the noise in the system we use the Lindblad equation. We obtain results showing that applying the control pulses to the ancilla allows one to successfully implement unitary operation on a target system in the presence of noise, which is not possible which control field applied to the system qubits.

  8. Development of a model to assess environmental performance, concerning HSE-MS principles.

    Science.gov (United States)

    Abbaspour, M; Hosseinzadeh Lotfi, F; Karbassi, A R; Roayaei, E; Nikoomaram, H

    2010-06-01

    The main objective of the present study was to develop a valid and appropriate model to evaluate companies' efficiency and environmental performance, concerning health, safety, and environmental management system principles. The proposed model overcomes the shortcomings of the previous models developed in this area. This model has been designed on the basis of a mathematical method known as Data Envelopment Analysis (DEA). In order to differentiate high-performing companies from weak ones, one of DEA nonradial models named as enhanced Russell graph efficiency measure has been applied. Since some of the environmental performance indicators cannot be controlled by companies' managers, it was necessary to develop the model in a way that it could be applied when discretionary and/or nondiscretionary factors were involved. The model, then, has been modified on a real case that comprised 12 oil and gas general contractors. The results showed the relative efficiency, inefficiency sources, and the rank of contractors.

  9. Exact Description of Decoherence in Optical Cavities

    CERN Document Server

    Romero, K M F

    2002-01-01

    The exact reduced dynamics for the independent oscillator model in the RWA approximation at zero and finite temperatures is derived. It is shown that the information about the interaction and the environment is encapsulated into three time dependent coefficients of the master equation, one of which vanishes in the zero temperature case. In currently used optical cavities all the information about the field dynamics is contained into {\\it two} (or three) experimentally accesible and physically meaningful real functions of time. From the phenomenological point of view it suffices then to carefully measure two ({\\it three}) adequate observables in order to map the evolution of any initial condition, as shown with several examples: (generalized) coherent states, Fock states, Schr\\"odinger cat states, and squeezed states.

  10. From Principles to Details: Integrated Framework for Architecture Modelling of Large Scale Software Systems

    Directory of Open Access Journals (Sweden)

    Andrzej Zalewski

    2013-06-01

    Full Text Available There exist numerous models of software architecture (box models, ADL’s, UML, architectural decisions, architecture modelling frameworks (views, enterprise architecture frameworks and even standards recommending practice for the architectural description. We show in this paper, that there is still a gap between these rather abstract frameworks/standards and existing architecture models. Frameworks and standards define what should be modelled rather than which models should be used and how these models are related to each other. We intend to prove that a less abstract modelling framework is needed for the effective modelling of large scale software intensive systems. It should provide a more precise guidance kinds of models to be employed and how they should relate to each other. The paper defines principles that can serve as base for an integrated model. Finally, structure of such a model has been proposed. It comprises three layers: the upper one – architectural policy – reflects corporate policy and strategies in architectural terms, the middle one –system organisation pattern – represents the core structural concepts and their rationale at a given level of scope, the lower one contains detailed architecture models. Architectural decisions play an important role here: they model the core architectural concepts explaining detailed models as well as organise the entire integrated model and the relations between its submodels.

  11. Macroscopic superposition states and decoherence by quantum telegraph noise

    Energy Technology Data Exchange (ETDEWEB)

    Abel, Benjamin Simon

    2008-12-19

    In the first part of the present thesis we address the question about the size of superpositions of macroscopically distinct quantum states. We propose a measure for the ''size'' of a Schroedinger cat state, i.e. a quantum superposition of two many-body states with (supposedly) macroscopically distinct properties, by counting how many single-particle operations are needed to map one state onto the other. We apply our measure to a superconducting three-junction flux qubit put into a superposition of clockwise and counterclockwise circulating supercurrent states and find this Schroedinger cat to be surprisingly small. The unavoidable coupling of any quantum system to many environmental degrees of freedom leads to an irreversible loss of information about an initially prepared superposition of quantum states. This phenomenon, commonly referred to as decoherence or dephasing, is the subject of the second part of the thesis. We have studied the time evolution of the reduced density matrix of a two-level system (qubit) subject to quantum telegraph noise which is the major source of decoherence in Josephson charge qubits. We are able to derive an exact expression for the time evolution of the reduced density matrix. (orig.)

  12. Multiphoton catalysis with coherent state input: nonclassicality and decoherence

    Science.gov (United States)

    Hu, Li-Yun; Wu, Jia-Ni; Liao, Zeyang; Zubairy, M. Suhail

    2016-09-01

    We propose a scheme to generate a new kind of non-Gaussian state—the Laguerre polynomial excited coherent state (LPECS)—by using multiphoton catalysis with coherent state input. The nonclassical properties of the LPECS are studied in terms of nonclassical depth, Mandel’s parameter, second-order correlation, quadrature squeezing, and the negativity of the Wigner function (WF). It is found that the LPECS is highly nonclassical and its nonclassicality depends on the amplitude of the coherent state, the catalysis photon number, and the parameters of the unbalanced beam splitter (BS). In particular, the maximum degree of squeezing can be enhanced by increasing the catalysis photon number. In addition, we examine the effect of decoherence using the WF, which shows that the negative region, the characteristic time of decoherence, and the structure of the WF are affected by catalysis photon number and the parameters of the unbalanced BS. Our work provides general analysis on how to prepare polynomial quantum states, which may be useful in the fields of quantum information and quantum computation.

  13. Energy loss and (de)coherence effects beyond eikonal approximation

    Energy Technology Data Exchange (ETDEWEB)

    Apolinário, Liliana, E-mail: lilianamarisa.cunha@usc.es [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia (Spain); CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Armesto, Néstor [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia (Spain); Milhano, Guilherme [CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Physics Department, Theory Unit, CERN, CH-1211 Genéve 23 (Switzerland); Salgado, Carlos A. [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia (Spain)

    2014-11-15

    The parton branching process is known to be modified in the presence of a medium. Colour decoherence processes are known to determine the process of energy loss when the density of the medium is large enough to break the correlations between partons emitted from the same parent. In order to improve existing calculations that consider eikonal trajectories for both the emitter and the hardest emitted parton, we provide in this work the calculation of all finite energy corrections for the gluon radiation off a quark in a QCD medium that exist in the small angle approximation and for static scattering centres. Using the path integral formalism, all particles are allowed to undergo Brownian motion in the transverse plane and the offspring is allowed to carry an arbitrary fraction of the initial energy. The result is a general expression that contains both coherence and decoherence regimes that are controlled by the density of the medium and by the amount of broadening that each parton acquires independently.

  14. Energy loss and (de)coherence effects beyond eikonal approximation

    CERN Document Server

    Apolinário, Liliana; Milhano, Guilherme; Salgado, Carlos A.

    2014-01-01

    The parton branching process is known to be modified in the presence of a medium. Colour decoherence processes are known to determine the process of energy loss when the density of the medium is large enough to break the correlations between partons emitted from the same parent. In order to improve existing calculations that consider eikonal trajectories for both the emitter and the hardest emitted parton, we provide in this work, the calculation of all finite energy corrections for the gluon radiation off a quark in a QCD medium that exist in the small angle approximation and for static scattering centres. Using the path integral formalism, all particles are allowed to undergo Brownian motion in the transverse plane and the offspring allowed to carry an arbitrary fraction of the initial energy. The result is a general expression that contains both coherence and decoherence regimes that are controlled by the density of the medium and by the amount of broadening that each parton acquires independently.

  15. Energy loss and (de)coherence effects beyond eikonal approximation

    Science.gov (United States)

    Apolinário, Liliana; Armesto, Néstor; Milhano, Guilherme; Salgado, Carlos A.

    2014-11-01

    The parton branching process is known to be modified in the presence of a medium. Colour decoherence processes are known to determine the process of energy loss when the density of the medium is large enough to break the correlations between partons emitted from the same parent. In order to improve existing calculations that consider eikonal trajectories for both the emitter and the hardest emitted parton, we provide in this work the calculation of all finite energy corrections for the gluon radiation off a quark in a QCD medium that exist in the small angle approximation and for static scattering centres. Using the path integral formalism, all particles are allowed to undergo Brownian motion in the transverse plane and the offspring is allowed to carry an arbitrary fraction of the initial energy. The result is a general expression that contains both coherence and decoherence regimes that are controlled by the density of the medium and by the amount of broadening that each parton acquires independently.

  16. Extending the Extreme Physical Information to Universal Cognitive Models via a Confident Information First Principle

    Directory of Open Access Journals (Sweden)

    Xiaozhao Zhao

    2014-07-01

    Full Text Available The principle of extreme physical information (EPI can be used to derive many known laws and distributions in theoretical physics by extremizing the physical information loss K, i.e., the difference between the observed Fisher information I and the intrinsic information bound J of the physical phenomenon being measured. However, for complex cognitive systems of high dimensionality (e.g., human language processing and image recognition, the information bound J could be excessively larger than I (J ≫ I, due to insufficient observation, which would lead to serious over-fitting problems in the derivation of cognitive models. Moreover, there is a lack of an established exact invariance principle that gives rise to the bound information in universal cognitive systems. This limits the direct application of EPI. To narrow down the gap between I and J, in this paper, we propose a confident-information-first (CIF principle to lower the information bound J by preserving confident parameters and ruling out unreliable or noisy parameters in the probability density function being measured. The confidence of each parameter can be assessed by its contribution to the expected Fisher information distance between the physical phenomenon and its observations. In addition, given a specific parametric representation, this contribution can often be directly assessed by the Fisher information, which establishes a connection with the inverse variance of any unbiased estimate for the parameter via the Cramér–Rao bound. We then consider the dimensionality reduction in the parameter spaces of binary multivariate distributions. We show that the single-layer Boltzmann machine without hidden units (SBM can be derived using the CIF principle. An illustrative experiment is conducted to show how the CIF principle improves the density estimation performance.

  17. The Assesment of Inclusiveness Principle of Malaysian New Economic Model: Maqashid Syar’iyyah Perspective

    Directory of Open Access Journals (Sweden)

    M. Sabri Haron

    2015-03-01

    Full Text Available Objective of this article is to assess how far the principles of inclusiveness in the Economic New Model in Malaysia can fulfil the needs of maqasid syar’iyyah. The assessment is conducted through the key concepts and strategic measures of the principles of inclusiveness. This study is a qualitative which descriptive and analytical approach is used for assessing  the  principles  of  inclusiveness  in  the  Economic  New  Model  based  on maqasid  syar’iyyah  perspective.  The  method  of  this  study  is  using  the  literature review  with  references  from  secondary  data.  This  study  is  expected  to  provide recommendations about the important role of maqasid syar’iyyah for maintaining the welfare of society and developing of a country, in this context for developing the Malaysian economy, in line with the vision 2020, Malaysia on par with developed countries.DOI:10.15408/aiq.v7i1.1362

  18. First-principles approach to heat and mass transfer effects in model catalyst studies

    OpenAIRE

    Matera, S.; Reuter, K.

    2009-01-01

    We assess heat and mass transfer limitations in in situ studies of model catalysts with a first-principles based multiscale modeling approach that integrates a detailed description of the surface reaction chemistry and the macro-scale flow structures. Using the CO oxidation at RuO2(110) as a prototypical example we demonstrate that factors like a suppressed heat conduction at the backside of the thin single-crystal, and the build-up of a product boundary layer above the flat-faced surface pla...

  19. Global Analysis of New Malaria Intrahost Models with a Competitive Exclusion Principle

    CERN Document Server

    Iggidr, Abderrahman; Sallet, Gauthier; Tewa, Jean-Jules; 10.1137/050643271

    2011-01-01

    In this paper we propose a malaria within-host model with k classes of age for the parasitized red blood cells and n strains for the parasite. We provide a global analysis for this model. A competitive exclusion principle holds. If R0, the basic reproduction number, satisfies R0 1, then generically there is a unique endemic equilibrium which corresponds to the endemic stabilization of the most virulent parasite strain and to the extinction of all the other parasites strains. We prove that this equilibrium is globally asymptotically stable on the positive orthant if a mild sufficient condition is satisfied.

  20. An 18 Moments Model for Dense Gases: Entropy and Galilean Relativity Principles without Expansions

    Directory of Open Access Journals (Sweden)

    M. Cristina Carrisi

    2015-01-01

    Full Text Available The 14 moments model for dense gases, introduced in the last few years by Arima, Taniguchi, Ruggeri and Sugiyama, is here extended up to 18 moments. They have found the closure of the balance equations up to a finite order with respect to equilibrium; it is also possible to impose for that model the entropy and Galilean relativity principles up to whatever order with respect to equilibrium, but by using Taylor’s expansion. Here, the exact solution is found, without expansions, but a bigger number of moments has to be considered and reasons will be shown suggesting that this number is at least 18.

  1. Ammonia synthesis and decomposition on a Ru-based catalyst modeled by first-principles

    DEFF Research Database (Denmark)

    Hellman, A.; Honkala, Johanna Karoliina; Remediakis, Ioannis

    2009-01-01

    A recently published first-principles model for the ammonia synthesis on an unpromoted Ru-based catalyst is extended to also describe ammonia decomposition. In addition, further analysis concerning trends in ammonia productivity, surface conditions during the reaction, and macro......-properties, such as apparent activation energies and reaction orders are provided. All observed trends in activity are captured by the model and the absolute value of ammonia synthesis/decomposition productivity is predicted to within a factor of 1-100 depending on the experimental conditions. Moreover it is shown: (i...

  2. Model-driven engineering of information systems principles, techniques, and practice

    CERN Document Server

    Cretu, Liviu Gabriel

    2015-01-01

    Model-driven engineering (MDE) is the automatic production of software from simplified models of structure and functionality. It mainly involves the automation of the routine and technologically complex programming tasks, thus allowing developers to focus on the true value-adding functionality that the system needs to deliver. This book serves an overview of some of the core topics in MDE. The volume is broken into two sections offering a selection of papers that helps the reader not only understand the MDE principles and techniques, but also learn from practical examples. Also covered are the

  3. Survival analysis of stochastic competitive models in a polluted environment and stochastic competitive exclusion principle.

    Science.gov (United States)

    Liu, Meng; Wang, Ke; Wu, Qiong

    2011-09-01

    Stochastic competitive models with pollution and without pollution are proposed and studied. For the first system with pollution, sufficient criteria for extinction, nonpersistence in the mean, weak persistence in the mean, strong persistence in the mean, and stochastic permanence are established. The threshold between weak persistence in the mean and extinction for each population is obtained. It is found that stochastic disturbance is favorable for the survival of one species and is unfavorable for the survival of the other species. For the second system with pollution, sufficient conditions for extinction and weak persistence are obtained. For the model without pollution, a partial stochastic competitive exclusion principle is derived.

  4. Quantum decoherence and quasi-equilibrium in open quantum systems with few degrees of freedom: application to 1H NMR of nematic liquid crystals.

    Science.gov (United States)

    Segnorile, Héctor H; Zamar, Ricardo C

    2011-12-28

    the coupling with an infinite quantum environment. The reversible part can be represented by a semiclassical model, similar to standard line-shape adiabatic models. By exploiting the separation existing between the time scales of the spin coherences and the irreversible decoherence, we present a novel technique to obtain the orientational molecular distribution function for a nematic liquid crystal. The procedure is based on the comparison of the observed coherence time evolution and numerical calculation under the adiabatic quantum decoherence approach. As an example, it is used the experimental free induction decay from a nematic PAA(d6) sample to extract such an orientational distribution. This is the first theoretical description of the experimental liquid crystal NMR signal in the time domain. On the contrary, the irreversible decoherence is intrinsically full-quantum mechanical, as it is governed by the commutation properties of the environment and the spin-lattice Hamiltonians. Consistently, it depends on the molecular correlation in a decisive way, since it vanishes under a mean-field model for the molecular dynamics. The results of this work can contribute to the understanding of the open question of the applicability of the spin-temperature concept in spin systems with few degrees of freedom.

  5. Conservation principles suspended solids distribution modeling to support ATS introduction on a recirculating WWTP

    DEFF Research Database (Denmark)

    Gernaey, Krist Victor Bernard; Nielsen, M.K.; Thornberg, D.

    2004-01-01

    A model for the description of the SS distribution in a full-scale recirculating activated sludge WWTP was developed. The model, based on conservation principles, uses on-line plant data as model inputs, and provides a prediction of the SS load in the inlet to the secondary clarifiers and the SS...... distribution in the WWTP as outputs. The calibrated model produces excellent predictions of the SS load to the secondary clarifiers, an essential variable for the operation of the aeration tank settling (ATS) process. A case study illustrated how the calibrated SS distribution model can be used to evaluate...... the potential benefit of ATS implementation on a full-scale recirculating WWTP. A reduction of the maximum SS peak load to the secondary clarifiers with 24.9% was obtained with ATS, whereas the cumulative SS load to the clarifiers is foreseen to be reduced with 22.5% for short rain events (4 hours duration...

  6. Understanding the Principles of Recursive Neural networks: A Generative Approach to Tackle Model Complexity

    CERN Document Server

    Chinea, Alejandro

    2009-01-01

    Recursive Neural Networks are non-linear adaptive models that are able to learn deep structured information. However, these models have not yet been broadly accepted. This fact is mainly due to its inherent complexity. In particular, not only for being extremely complex information processing models, but also because of a computational expensive learning phase. The most popular training method for these models is back-propagation through the structure. This algorithm has been revealed not to be the most appropriate for structured processing due to problems of convergence, while more sophisticated training methods enhance the speed of convergence at the expense of increasing significantly the computational cost. In this paper, we firstly perform an analysis of the underlying principles behind these models aimed at understanding their computational power. Secondly, we propose an approximate second order stochastic learning algorithm. The proposed algorithm dynamically adapts the learning rate throughout the tra...

  7. Multiple-point principle with a scalar singlet extension of the standard model

    Science.gov (United States)

    Haba, Naoyuki; Ishida, Hiroyuki; Okada, Nobuchika; Yamaguchi, Yuya

    2017-01-01

    We suggest a scalar singlet extension of the standard model, in which the multiple-point principle (MPP) condition of a vanishing Higgs potential at the Planck scale is realized. Although there have been lots of attempts to realize the MPP at the Planck scale, a realization maintaining naturalness is quite difficult. Our model can easily achieve the MPP at the Planck scale without large Higgs mass corrections. It is worth noting that the electroweak symmetry can be radiatively broken in our model. In the naturalness point of view, the singlet scalar mass should be of calligraphy">O(1) TeV or less. We also consider a right-handed neutrino extension of the model for neutrino mass generation. The model does not affect the MPP scenario, and might keep the naturalness with the new particle mass scale beyond TeV, thanks to accidental cancellation of Higgs mass corrections.

  8. Multiple-point principle with a scalar singlet extension of the Standard Model

    CERN Document Server

    Haba, Naoyuki; Okada, Nobuchika; Yamaguchi, Yuya

    2016-01-01

    We suggest a scalar singlet extension of the standard model, in which the multiple-point principle (MPP) condition of a vanishing Higgs potential at the Planck scale is realized. Although there have been lots of attempts to realize the MPP at the Planck scale, the realization with keeping naturalness is quite difficult. Our model can easily achieve the MPP at the Planck scale without large Higgs mass corrections. It is worth noting that the electroweak symmetry can be radiatively broken in our model. In the naturalness point of view, the singlet scalar mass should be of ${\\cal O}(1)\\,{\\rm TeV}$ or less. We also consider right-handed neutrino extension of the model for neutrino mass generation. The model does not affect the MPP scenario, and might keep the naturalness with the new particle mass scale beyond TeV, thanks to accidental cancellation of Higgs mass corrections.

  9. First-principles model of time-dependent variations in transmission through a fluctuating scattering environment.

    Science.gov (United States)

    Yeh, Jen-Hao; Antonsen, Thomas M; Ott, Edward; Anlage, Steven M

    2012-01-01

    Fading is the time-dependent variation in transmitted signal strength through a complex medium due to interference or temporally evolving multipath scattering. In this paper we use random matrix theory (RMT) to establish a first-principles model for fading, including both universal and nonuniversal effects. This model provides a more general understanding of the most common statistical models (Rayleigh fading and Rice fading) and provides a detailed physical basis for their parameters. We also report experimental tests on two ray-chaotic microwave cavities. The results show that our RMT model agrees with the Rayleigh and Rice models in the high-loss regime, but there are strong deviations in low-loss systems where the RMT approach describes the data well.

  10. Efficient systematic scheme to construct second-principles lattice dynamical models

    Science.gov (United States)

    Escorihuela-Sayalero, Carlos; Wojdeł, Jacek C.; Íñiguez, Jorge

    2017-03-01

    We start from the polynomial interatomic potentials introduced by Wojdeł et al. [J. Phys.: Condens. Matter 25, 305401 (2013), 10.1088/0953-8984/25/30/305401] and take advantage of one of their key features—namely, the linear dependence of the energy on the potential's adjustable parameters—to devise a scheme for the construction of first-principles-based (second-principles) models for large-scale lattice-dynamical simulations. Our method presents the following convenient features. The parameters of the model are computed in a very fast and efficient way, as it is possible to recast the fit to a training set of first-principles data into a simple matrix diagonalization problem. Our method selects automatically the interactions that are most relevant to reproduce the training-set data, by choosing from a pool that includes virtually all possible coupling terms, and produces a family of models of increasing complexity and accuracy. We work with practical and convenient cross-validation criteria linked to the physical properties that will be relevant in future simulations based on the new model, and which greatly facilitate the task of identifying a potential that is simultaneously simple (thus computationally light), very accurate, and predictive. We also discuss practical ways to guarantee that our energy models are bounded from below, with a minimal impact on their accuracy. Finally, we demonstrate our scheme with an application to ferroelastic perovskite SrTiO3, which features many nontrivial lattice-dynamical features (e.g., a phase transition driven by soft phonons, competing structural instabilities, highly anharmonic dynamics) and provides a very demanding test.

  11. Experimental bounds on collapse models from gravitational wave detectors

    Science.gov (United States)

    Carlesso, Matteo; Bassi, Angelo; Falferi, Paolo; Vinante, Andrea

    2016-12-01

    Wave function collapse models postulate a fundamental breakdown of the quantum superposition principle at the macroscale. Therefore, experimental tests of collapse models are also fundamental tests of quantum mechanics. Here, we compute the upper bounds on the collapse parameters, which can be inferred by the gravitational wave detectors LIGO, LISA Pathfinder, and AURIGA. We consider the most widely used collapse model, the continuous spontaneous localization (CSL) model. We show that these experiments exclude a huge portion of the CSL parameter space, the strongest bound being set by the recently launched space mission LISA Pathfinder. We also rule out a proposal for quantum-gravity-induced decoherence.

  12. Decoherence-Free Quantum Information Processing with Four-Photon Entangled States

    CERN Document Server

    Bourennane, M; Gaertner, S; Kurtsiefer, C; Cabello, A; Weinfurter, H; Bourennane, Mohamed; Eibl, Manfred; Gaertner, Sascha; Kurtsiefer, Christian; Cabello, Adan; Weinfurter, Harald

    2004-01-01

    Decoherence-free states protect quantum information from collective noise, the predominant cause of decoherence in current implementations of quantum communication and computation. Here we demonstrate that spontaneous parametric down-conversion can be used to generate four-photon states which enable the encoding of one qubit in a decoherence-free subspace. The immunity against noise is verified by quantum state tomography of the encoded qubit. We show that particular states of the encoded qubit can be distinguished by local measurements on the four photons only.

  13. Human-on-a-chip design strategies and principles for physiologically based pharmacokinetics/pharmacodynamics modeling.

    Science.gov (United States)

    Abaci, Hasan Erbil; Shuler, Michael L

    2015-04-01

    Advances in maintaining multiple human tissues on microfluidic platforms has led to a growing interest in the development of microphysiological systems for drug development studies. Determination of the proper design principles and scaling rules for body-on-a-chip systems is critical for their strategic incorporation into physiologically based pharmacokinetic (PBPK)/pharmacodynamic (PD) model-aided drug development. While the need for a functional design considering organ-organ interactions has been considered, robust design criteria and steps to build such systems have not yet been defined mathematically. In this paper, we first discuss strategies for incorporating body-on-a-chip technology into the current PBPK modeling-based drug discovery to provide a conceptual model. We propose two types of platforms that can be involved in the different stages of PBPK modeling and drug development; these are μOrgans-on-a-chip and μHuman-on-a-chip. Then we establish the design principles for both types of systems and develop parametric design equations that can be used to determine dimensions and operating conditions. In addition, we discuss the availability of the critical parameters required to satisfy the design criteria, consider possible limitations for estimating such parameter values and propose strategies to address such limitations. This paper is intended to be a useful guide to the researchers focused on the design of microphysiological platforms for PBPK/PD based drug discovery.

  14. Coarse graining approach to First principles modeling of radiation cascade in large Fe super-cells

    Science.gov (United States)

    Odbadrakh, Khorgolkhuu; Nicholson, Don; Rusanu, Aurelian; Wang, Yang; Stoller, Roger; Zhang, Xiaoguang; Stocks, George

    2012-02-01

    First principles techniques employed to understand systems at an atomistic level are not practical for large systems consisting of millions of atoms. We present an efficient coarse graining approach to bridge the first principles calculations of local electronic properties to classical Molecular Dynamics (MD) simulations of large structures. Local atomic magnetic moments in crystalline Fe are perturbed by radiation generated defects. The effects are most pronounced near the defect core and decay with distance. We develop a coarse grained technique based on the Locally Self-consistent Multiple Scattering (LSMS) method that exploits the near-sightedness of the electron Green function. The atomic positions were determined by MD with an embedded atom force field. The local moments in the neighborhood of the defect cores are calculated with first-principles based on full local structure information. Atoms in the rest of the system are modeled by representative atoms with approximated properties. This work was supported by the Center for Defect Physics, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  15. Two-dimensional models as testing ground for principles and concepts of local quantum physics

    Science.gov (United States)

    Schroer, Bert

    2006-02-01

    In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g., chiral models, factorizing models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work, I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff( S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL (2, Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular "Euclideanization" is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J.A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an "Encyclopedia of Mathematical Physics" contribution hep-th/0502125.

  16. Two-dimensional models as testing ground for principles and concepts of local quantum physics

    Energy Technology Data Exchange (ETDEWEB)

    Schroer, Bert [FU Berlin (Germany). Institut fuer Theoretische Physik

    2005-04-15

    In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g. chiral models, factoring models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff(S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL(2,Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular 'Euclideanization' is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J. A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an 'Encyclopedia of Mathematical Physics' contribution hep-th/0502125. (author)

  17. Quasi-Hamiltonian Method for Computation of Decoherence Rates

    CERN Document Server

    Joynt, Robert; Wang, Qiang-Hua

    2009-01-01

    We present a general formalism for the dissipative dynamics of an arbitrary quantum system in the presence of a classical stochastic process. It is applicable to a wide range of physical situations, and in particular it can be used for qubit arrays in the presence of classical two-level systems (TLS). In this formalism, all decoherence rates appear as eigenvalues of an evolution matrix. Thus the method is linear, and the close analogy to Hamiltonian systems opens up a toolbox of well-developed methods such as perturbation theory and mean-field theory. We apply the method to the problem of a single qubit in the presence of TLS that give rise to pure dephasing 1/f noise and solve this problem exactly. The exact solution gives an experimentally observable improvement over the popular Gaussian approximation.

  18. Universal quantum computation in waveguide QED using decoherence free subspaces

    Science.gov (United States)

    Paulisch, V.; Kimble, H. J.; González-Tudela, A.

    2016-04-01

    The interaction of quantum emitters with one-dimensional photon-like reservoirs induces strong and long-range dissipative couplings that give rise to the emergence of the so-called decoherence free subspaces (DFSs) which are decoupled from dissipation. When introducing weak perturbations on the emitters, e.g., driving, the strong collective dissipation enforces an effective coherent evolution within the DFS. In this work, we show explicitly how by introducing single-site resolved drivings, we can use the effective dynamics within the DFS to design a universal set of one and two-qubit gates within the DFS of an ensemble of two-level atom-like systems. Using Liouvillian perturbation theory we calculate the scaling with the relevant figures of merit of the systems, such as the Purcell factor and imperfect control of the drivings. Finally, we compare our results with previous proposals using atomic Λ systems in leaky cavities.

  19. Implementation of Universal Control on a Decoherence-Free Qubit

    CERN Document Server

    Fortunato, E M; Hodges, J; Teklemariam, G; Cory, D G; Fortunato, Evan M.; Viola, Lorenza; Hodges, Jonathan; Teklemariam, Grum; Cory, David G.

    2001-01-01

    We demonstrate storage and manipulation of one qubit encoded into a decoherence-free subspace (DFS) of two nuclear spins using liquid state nuclear magnetic resonance (NMR) techniques. The DFS is spanned by states that are unaffected by arbitrary collective phase noise. Encoding and decoding procedures reversibly map an arbitrary qubit state from a single data spin to the DFS and back. The implementation demonstrates the robustness of the DFS memory against engineered dephasing with arbitrary strength as well as a substantial increase in the amount of quantum information retained, relative to an un-encoded qubit, under both engineered and natural noise processes. In addition, a universal set of logical manipulations over the encoded qubit is also realized. Although intrinsic limitations prevent maintaining full noise tolerance during quantum gates, we show how the use of dynamical control methods at the encoded level can ensure that computation is protected with finite distance. We demonstrate noise-tolerant ...

  20. Preserving entanglement under decoherence and sandwiching all separable states

    CERN Document Server

    Lockhart, R B; Lockhart, Robert; Steiner, Michael

    2000-01-01

    Every entangled state can be perturbed, for instance by decoherence, and stay entangled. For a large class of pure entangled states, we show how large the perturbation can be. Our class includes all pure bipartite and all maximally entangled states. For an entangled state, E, the constucted neighborhood of entangled states is the region outside two parallel hyperplanes, which sandwich the set of all separable states. The states for which these neighborhoods are largest are the maximally entangled ones. As the number of particles, or the dimensions of the Hilbert spaces for two of the particles increases, the distance between two of the hyperplanes which sandwich the separable states goes to zero. It is easy to decide if a state Q is in the neighborhood of entangled states we construct for an entangled state E. One merely has to check if the trace of EQ is greater than a constant which depends upon E and which we determine.

  1. Decoherence control in quantum computing with simple chirped pulses

    Indian Academy of Sciences (India)

    Debabrata Goswami

    2002-08-01

    We show how the use of optimally shaped pulses to guide the time evolution of a system (‘coherent control’) can be an effective approach towards quantum computation logic. We demonstrate this with selective control of decoherence for a multilevel system with a simple linearly chirped pulse. We use a multiphoton density-matrix approach to explore the effects of ultrafast shaped pulses for two-level systems that do not have a single photon resonance, and show that many multiphoton results are surprisingly similar to the single-photon results. Finally, we choose two specific chirped pulses: one that always generates inversion and the other that always generates self-induced transparency to demonstrate an ensemble CNOT gate.

  2. Simple Solution to Loss and Decoherence in Optical Fibers

    CERN Document Server

    Wu, L A; Lidar, D A; Wu, Lian-Ao; Lo, Hoi-Kwong; Lidar, Daniel A.

    2003-01-01

    Attenuation and dispersion losses in optical Telecom fibers are important limitations on both classical (conventional) and quantum communication. We propose a method to reduce such losses, as well as decoherence. Our proposal is to insert phase-shifters at fixed distance intervals. This can be viewed as a spatial analog of the ``bang-bang'' decoupling method of time-dependent quantum control. We analyze in detail the case of qubits encoded into polarization states of low-intensity light, which is of central importance to various quantum information tasks, such as quantum cryptography and communication. We discuss the experimental feasibility of our scheme and the generality of our method in dealing with other types of noises in both quantum and classical information processing.

  3. Amplification, Decoherence, and the Acquisition of Information by Spin Environments

    Science.gov (United States)

    Zwolak, Michael; Riedel, C. Jess; Zurek, Wojciech H.

    2016-05-01

    Quantum Darwinism recognizes the role of the environment as a communication channel: Decoherence can selectively amplify information about the pointer states of a system of interest (preventing access to complementary information about their superpositions) and can make records of this information accessible to many observers. This redundancy explains the emergence of objective, classical reality in our quantum Universe. Here, we demonstrate that the amplification of information in realistic spin environments can be quantified by the quantum Chernoff information, which characterizes the distinguishability of partial records in individual environment subsystems. We show that, except for a set of initial states of measure zero, the environment always acquires redundant information. Moreover, the Chernoff information captures the rich behavior of amplification in both finite and infinite spin environments, from quadratic growth of the redundancy to oscillatory behavior. These results will considerably simplify experimental testing of quantum Darwinism, e.g., using nitrogen vacancies in diamond.

  4. Decoherence in Superconducting Qubits from Surface Magnetic States

    Science.gov (United States)

    Hover, David; Sendelbach, Steven; Kittel, Achim; Mueck, Michael; McDermott, Robert

    2008-03-01

    Unpaired spins in amorphous surface oxides can act as a source of decoherence in superconducting and other solid-state qubits. A density of surface spins can give rise to low-frequency magnetic flux noise, which in turn leads to dephasing of the qubit state. In addition, magnetic surface states can couple to high-frequency resonant magnetic fields, and thereby contribute to energy relaxation of the qubit. We present the results of low-frequency measurements of the nonlinear and imaginary spin susceptibility of surface magnetic states in superconducting devices at millikelvin temperatures. In addition, we describe high-frequency magnetic resonance measurements that directly probe the surface spin density of states. We present calculations that connect the measurement results to qubit energy relaxation and dephasing times.

  5. Effects of decoherence on entanglement in a correlated emission laser

    Energy Technology Data Exchange (ETDEWEB)

    Tesfa, Sintayehu [Physics Department, Addis Ababa University, PO Box 1176, Addis Ababa (Ethiopia)

    2007-06-28

    We present the analysis of the effects of decoherence on quantum features of the cavity radiation of the two-photon-correlated emission laser, employing the stochastic differential equations associated with the normal ordering. We study how a thermal noise entering the cavity affects the squeezing, entanglement amplification, mean number of photon pairs and intensity difference in the cavity radiation. It turns out that the generated light exhibits a two-mode squeezing and entanglement when initially there are more atoms at the lower level, even when the cavity is coupled to a thermal reservoir. It is also found that though the thermal noise entering the cavity degrades the squeezing and entanglement, it significantly increases the mean number of photon pairs of the superimposed radiation.

  6. Studies on coherence and decoherence in Fast Atom Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, J.; Lienemann, J. [Institut für Physik der Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin (Germany); Schüller, A. [Physikalisch-Technische Bundesanstalt (PTB), AG 6.21, Bundesallee 100, D-38116 Braunschweig (Germany); Winter, H., E-mail: winter@physik.hu-berlin.de [Institut für Physik der Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin (Germany)

    2015-05-01

    A few years ago, quantum effects were observed for the scattering of fast atoms from surfaces under a grazing angle of incidence. We discuss basic features of Fast Atom Diffraction (FAD) which adds a further powerful method to the established tools in ion beam analysis and surface science. Attractive features of FAD in studies on the structure of surfaces comprise negligible radiation damage, cost effective operation of the complete setup, no charging effects in studies with insulators, and an extreme sensitivity to the topmost layer of surface atoms. The observation of diffraction patterns is based on the quantum coherence which is preserved during the scattering process with the target surface. We will discuss basic features of the coherence phenomena and its role for the observation of quantum effects in the angular distributions for grazingly scattered atoms. In a comparison of data obtained for H and He atoms we demonstrate that two different mechanisms for decoherence are important.

  7. First-principles theory, coarse-grained models, and simulations of ferroelectrics.

    Science.gov (United States)

    Waghmare, Umesh V

    2014-11-18

    CONSPECTUS: A ferroelectric crystal exhibits macroscopic electric dipole or polarization arising from spontaneous ordering of its atomic-scale dipoles that breaks inversion symmetry. Changes in applied pressure or electric field generate changes in electric polarization in a ferroelectric, defining its piezoelectric and dielectric properties, respectively, which make it useful as an electromechanical sensor and actuator in a number of applications. In addition, a characteristic of a ferroelectric is the presence of domains or states with different symmetry equivalent orientations of spontaneous polarization that are switchable with large enough applied electric field, a nonlinear property that makes it useful for applications in nonvolatile memory devices. Central to these properties of a ferroelectric are the phase transitions it undergoes as a function of temperature that involve lowering of the symmetry of its high temperature centrosymmetric paraelectric phase. Ferroelectricity arises from a delicate balance between short and long-range interatomic interactions, and hence the resulting properties are quite sensitive to chemistry, strains, and electric charges associated with its interface with substrate and electrodes. First-principles density functional theoretical (DFT) calculations have been very effective in capturing this and predicting material and environment specific properties of ferroelectrics, leading to fundamental insights into origins of ferroelectricity in oxides and chalcogenides uncovering a precise picture of electronic hybridization, topology, and mechanisms. However, use of DFT in molecular dynamics for detailed prediction of ferroelectric phase transitions and associated temperature dependent properties has been limited due to large length and time scales of the processes involved. To this end, it is quite appealing to start with input from DFT calculations and construct material-specific models that are realistic yet simple for use in

  8. Ultra-fast fiber lasers principles and applications with Matlab models

    CERN Document Server

    Binh, Le Nguyen

    2010-01-01

    Ultrashort pulses in mode-locked lasers are receiving focused attention from researchers looking to apply them in a variety of fields, from optical clock technology to measurements of the fundamental constants of nature and ultrahigh-speed optical communications. Ultrashort pulses are especially important for the next generation of ultrahigh-speed optical systems and networks operating at 100 Gbps per carrier. Ultra Fast Fiber Lasers: Principles and Applications with MATLAB(R) Models is a self-contained reference for engineers and others in the fields of applied photonics and optical communica

  9. A Novel Model of IDS Based on Fuzzy Cluster and Immune Principle

    Institute of Scientific and Technical Information of China (English)

    TAO Xin-min; LIU Fu-rong

    2005-01-01

    This paper presents a novel intrusion detection model based on fuzzy cluster and immune principle. The original rival penalized competitive learning (RPCL) algorithm is modified in order to address the problem of different variability of variables and correlation between variables, the sensitivity to initial number of clusters is also solved. Especially, we use the extended RPCL algorithm to determine the initial number of clusters in the fuzzy cluster algorithm. The genetic algorithm is used to optimize the radius deviation for the determination of characteristic function of abnormal subspace.

  10. Decoherence and Multipartite Entanglement of Non-Inertial Observers

    Institute of Scientific and Technical Information of China (English)

    M. Ramzan

    2012-01-01

    The decoherence effect on multipartite entanglement in non-inertial frames is investigated.The GHZ state is considered to be shared between partners with one partner in the inertial frame whereas the other two are in accelerated frames.One-tangle and π-tangles are used to quantify the entanglement of the multipartite system influenced by phase damping and phase flip channels.It is seen that for the phase damping channel,entanglement sudden death (ESD) occurs for p > 0.5 in the infinite acceleration limit.On the other hand,in the case of the phase flip channel,ESD behavior occurs at p =0.5.It is also seen that entanglement sudden birth (ESB) occurs in the case of phase flip channel just after ESD,i.e.p > 0.5.Furthermore,it is seen that the effect of the environment on multipartite entanglement is much stronger than that of the acceleration of non-inertial frames.%The decoherence effect on multipartite entanglement in non-inertial frames is investigated. The GHZ state is considered to be shared between partners with one partner in the inertial frame whereas the other two are in accelerated frames. One-tangle and w-tangles are used to quantify the entanglement of the multipartite system influenced by phase damping and phase Hip channels. It is seen that for the phase damping channel, entanglement sudden death (ESD) occurs for p > 0.5 in the inSnite acceleration limit. On the other hand, in the case of the phase Hip channel, ESD behavior occurs at p = 0.5. It is also seen that entanglement sudden birth (ESB) occurs in the case of phase flip channel just after ESD, I.e. p > 0.5. Furthermore, it is seen that the effect of the environment on multipartite entanglement is much stronger than that of the acceleration of non-inertial frames.

  11. First-principles calculations, experimental study, and thermodynamic modeling of the Al-Co-Cr system.

    Directory of Open Access Journals (Sweden)

    Xuan L Liu

    Full Text Available The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT and phase-equilibria experiments that led to X-ray diffraction (XRD and electron probe micro-analysis (EPMA measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS calculations predict a large bcc-A2 (disordered/B2 (ordered miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.

  12. Cogging force rejection method of linear motor based on internal model principle

    Science.gov (United States)

    Liu, Yang; Chen, Zhenyu; Yang, Tianbo

    2015-02-01

    The cogging force disturbance of linear motor is one of the main factors affecting the positioning accuracy of ultraprecision moving platform. And this drawback could not be completely overcome by improving the design of motor body, such as location modification of permanent magnet array, or optimization design of the shape of teeth-slot. So the active compensation algorithms become prevalent in cogging force rejection area. This paper proposed a control structure based on internal mode principle to attenuate the cogging force of linear motor which deteriorated the accuracy of position, and this structure could make tracking and anti-disturbing performance of close-loop designed respectively. In the first place, the cogging force was seen as the intrinsic property of linear motor and its model constituting controlled object with motor ontology model was obtained by data driven recursive identification method. Then, a control structure was designed to accommodate tracking and anti-interference ability separately by using internal model principle. Finally, the proposed method was verified in a long stroke moving platform driven by linear motor. The experiment results show that, by employing this control strategy, the positioning error caused by cogging force was decreased by 70%.

  13. Robotic and mathematical modeling reveal general principles of appendage control and coordination in terrestrial locomotion

    Science.gov (United States)

    McInroe, Benjamin; Astley, Henry; Gong, Chaohui; Kawano, Sandy; Schiebel, Perrin; Choset, Howie; Goldman, Daniel I.

    The transition from aquatic to terrestrial life presented new challenges to early walkers, necessitating robust locomotion on complex, flowable substrates (e.g. sand, mud). Locomotion on such substrates is sensitive to limb morphology and kinematics. Although early walker morphologies are known, principles of appendage control remain elusive. To reveal limb control strategies that facilitated the invasion of land, we study both robotic and mathematical models. Robot experiments show that an active tail is critical for robust locomotion on granular media, enabling locomotion even with poor foot placement and limited ability to lift the body. Using a granular resistive force theory model, we construct connection vector fields that reveal how appendage coordination and terrain inclination impact locomotor performance. This model replicates experimental results, showing that moving limbs/tail in phase is most effective (suggesting a locomotor template). Varying limb trajectories and contacts, we find gaits for which tail use can be neutral or harmful, suggesting limb-tail coordination to be a nontrivial aspect of locomotion. Our findings show that robot experiments coupled with geometric mechanics provide a general framework to reveal principles of robust terrestrial locomotion. This work was supported by NSF PoLS.

  14. First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems

    Energy Technology Data Exchange (ETDEWEB)

    J. Karl Johnson

    2011-05-20

    The objective of this project is to complement experimental efforts of MHoCE partners by using state-of-the-art theory and modeling to study the structure, thermodynamics, and kinetics of hydrogen storage materials. Specific goals include prediction of the heats of formation and other thermodynamic properties of alloys from first principles methods, identification of new alloys that can be tested experimentally, calculation of surface and energetic properties of nanoparticles, and calculation of kinetics involved with hydrogenation and dehydrogenation processes. Discovery of new metal hydrides with enhanced properties compared with existing materials is a critical need for the Metal Hydride Center of Excellence. New materials discovery can be aided by the use of first principles (ab initio) computational modeling in two ways: (1) The properties, including mechanisms, of existing materials can be better elucidated through a combined modeling/experimental approach. (2) The thermodynamic properties of novel materials that have not been made can, in many cases, be quickly screened with ab initio methods. We have used state-of-the-art computational techniques to explore millions of possible reaction conditions consisting of different element spaces, compositions, and temperatures. We have identified potentially promising single- and multi-step reactions that can be explored experimentally.

  15. A generalized variational principle and theoretical model for magnetoelastic interaction of ferromagnetic bodies

    Institute of Scientific and Technical Information of China (English)

    周又和; 郑晓静

    1999-01-01

    The quantitative analysis shows that no theoretical model for 3-d magnetoelastic bodies, in literatures to date, can commonly simulate two kinds of distinct experimental phenomena on magnetoelastic interaction of ferromagnetic structures. This makes it difficult to effectively discribe the magnetoelastic mechanical behavior of structures with complex geometry, such as shells. Therefore, it is a key step for simulating magnetoelastic mechanical characteristics of structures with complex geometry to establish a 3-d model which also can commonly characterize the two distinct experimental phenomena. A theoretical model for three dimension magnetizable elastic bodies, which is commonly suitable for the two kinds of experimental phenomena on magnetoelastic interaction of ferromagnetic plates, is presented by the variational principle for the total energy functional of the coupling system of the 3-d ferromagnetic bodies. It is found that for the case of linear isotropic magnetic materials, the magnetic forces

  16. Cancer control through principles of systems science, complexity, and chaos theory: a model.

    Science.gov (United States)

    Janecka, Ivo P

    2007-06-05

    Cancer is a significant medical and societal problem. This reality arises from the fact that an exponential and an unrestricted cellular growth destabilizes human body as a system. From this perspective, cancer is a manifestation of a system-in-failing.A model of normal and abnormal cell cycle oscillations has been developed incorporating systems science, complexity, and chaos theories. Using this model, cancer expresses a failing subsystem and is characterized by a positive exponential growth taking place in the outer edge of chaos. The overall survival of human body as a system is threatened. This model suggests, however, that cancer's exponential cellular growth and disorganized complexity could be controlled through the process of induction of differentiation of cancer stem cells into cells of low and basic functionality. This concept would imply reorientation of current treatment principles from cellular killing (cyto-toxic therapies) to cellular retraining (cyto-education).

  17. Mach's Principle and Model for a Broken Symmetric Theory of Gravity

    CERN Document Server

    Bisabr, Y

    2003-01-01

    We investigate spontaneous symmetry breaking in a conformally invariant gravitational model. In particular, we use a conformally invariant scalar tensor theory as the vacuum sector of a gravitational model to examine the idea that gravitational coupling may be the result of a spontanous symmetry breaking. In this model matter is taken to be coupled with a metric which is different but conformally related to the metric appearing explicitly in the vacuum sector. We show that after the spontanous symmetry breaking the resulting theory is consistent with Mach's principle in the sense that inertial masses of particles have variable configurations in a cosmological context. Moreover, our analysis allows to construct a mechanism in which the resulting large vacuum energy density relaxes during evolution of the universe.

  18. Tundish Open Eye Formation in Inert Gas-Shrouded Tundishes: A Macroscopic Model from First Principles

    Science.gov (United States)

    Chatterjee, Saikat; Chattopadhyay, Kinnor

    2016-10-01

    Open eye formation in tundishes can result in reoxidation of liquid steel leading to the formation of harmful inclusions. Moreover, it is also a site for heat loss, gas absorption, and slag emulsification. All these factors make it necessary to understand the fundamentals of open eye formation, which in turn will allow us to prevent or control its harmful effects. In the present study, the bubble plume regions in a ladle and tundish were compared, and it was observed that there are significant differences between the two. Moreover, a simplistic model for predicting the open eye area in tundishes for `thin slag' practices was derived using the principles of conservation of mass and momentum. The proposed model was able to predict open eye areas in tundish reasonably well and was compared with other models, and experimental results.

  19. The bond graph model of planar flexible multibody mechanical systems and its dynamic principle

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to increase the efficiency and reliability of the dynamic analysis for flexible planar linkage containing the coupling of multi-energy domains, a method based on bond graph is introduced. From the viewpoint of power conservation, the peculiar property of bond graph multiport element MTF is discussed. The procedure of modeling planar flexible multibody mechanical systems by bond graphs and its dynamic principle are described. To overcome the algebraic difficulty brought by differential causality and nonlinear junction structure, the constraint forces at joints can be considered as unknown effort sources and added to the corresponding O-junctions of system bond graph model. As a result, the automatic modeling on a computer is realized. The validity of the procedure is illustrated by a practical example.

  20. An Intrusion Detection System Model Based on Immune Principle and Performance Analysis

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhi-xian; WANG Ru-chuan; WANG Shao-di; SUN Zhi-xin

    2005-01-01

    The study of security in computer networks is a key issue,which is a rapidly growing area of interest because of its importance.Main network security problems are analyzed in this paper above all,which currently are confronted with network systems and existing works in intrusion detection.And then an intrusion detection system model based on Immune Principle(IPIDS)is presented.Meanwhile,it expatiates detailed implementation of the methods how to reduce the high false positive and negative alarms of the traditional Intrusion Detection System(IDS).At last a simple simulation is performed on this model just using string match algorithm as binding mechanism.The simulation results indicate that the model can detect malicious activity effectively,and consequently the security and steadiness of the whole network system are improved also.

  1. Many-body decoherence dynamics and optimised operation of a single-photon switch

    CERN Document Server

    Murray, Callum R; Pohl, Thomas

    2016-01-01

    We develop a theoretical framework to characterize the decoherence dynamics due to multi-photon scattering in an all-optical switch based on Rydberg atom induced nonlinearities. By incorporating the knowledge of this decoherence process into optimal photon storage and retrieval strategies, we establish optimised switching protocols for experimentally relevant conditions, and evaluate the corresponding limits in the achievable fidelities. Based on these results we work out a simplified description that reproduces recent experiments [arXiv:1511.09445] and provides a new interpretation in terms of many-body decoherence involving multiple incident photons and multiple gate excitations forming the switch. Aside from offering insights into the operational capacity of realistic photon switching capabilities, our work provides a complete description of spin wave decoherence in a Rydberg quantum optics setting, and has immediate relevance to a number of further applications employing photon storage in Rydberg media.

  2. Many-body decoherence dynamics and optimized operation of a single-photon switch

    Science.gov (United States)

    Murray, C. R.; Gorshkov, A. V.; Pohl, T.

    2016-09-01

    We develop a theoretical framework to characterize the decoherence dynamics due to multi-photon scattering in an all-optical switch based on Rydberg atom induced nonlinearities. By incorporating the knowledge of this decoherence process into optimal photon storage and retrieval strategies, we establish optimized switching protocols for experimentally relevant conditions, and evaluate the corresponding limits in the achievable fidelities. Based on these results we work out a simplified description that reproduces recent experiments (Nat. Commun. 7 12480) and provides a new interpretation in terms of many-body decoherence involving multiple incident photons and multiple gate excitations forming the switch. Aside from offering insights into the operational capacity of realistic photon switching capabilities, our work provides a complete description of spin wave decoherence in a Rydberg quantum optics setting, and has immediate relevance to a number of further applications employing photon storage in Rydberg media.

  3. Geometrical dependence of quantum decoherence in circular arenas with side-wires

    Science.gov (United States)

    Xie, Yuantao; Le Priol, Clément; Heremans, Jean J.

    2016-12-01

    Low-temperature quantum phase coherence lengths were experimentally measured in mesoscopic circular arenas fabricated on InGaAs quantum wells. The arenas are connected to wide sample regions by short side-wires, to investigate the effects of geometry in comparison to intrinsic materials properties on quantum decoherence. Universal conductance fluctuations were used to quantify the phase coherence lengths as a function of temperature and geometry. The experimental data show a dependence of phase coherence lengths on side-wire length and width-to-length ratio, which is accounted for by the competing effects of decoherence by coupling to the classical environment and Nyquist decoherence in ergodic wires. The observed decay of phase coherence lengths with the increasing temperature is consistent with expectations. The work demonstrates that geometrical effects influence the measured mesoscopic quantum decoherence.

  4. Nonadiabatic geometric quantum computation in decoherence-free subspaces based on unconventional geometric phases

    Science.gov (United States)

    Zhao, P. Z.; Xu, G. F.; Tong, D. M.

    2016-12-01

    Nonadiabatic geometric quantum computation in decoherence-free subspaces has received increasing attention due to the merits of its high-speed implementation and robustness against both control errors and decoherence. However, all the previous schemes in this direction have been based on the conventional geometric phases, of which the dynamical phases need to be removed. In this paper, we put forward a scheme of nonadiabatic geometric quantum computation in decoherence-free subspaces based on unconventional geometric phases, of which the dynamical phases do not need to be removed. Specifically, by using three physical qubits undergoing collective dephasing to encode one logical qubit, we realize a universal set of geometric gates nonadiabatically and unconventionally. Our scheme not only maintains all the merits of nonadiabatic geometric quantum computation in decoherence-free subspaces, but also avoids the additional operations required in the conventional schemes to cancel the dynamical phases.

  5. Solvable Quantum Macroscopic Motions and Decoherence Mechanisms in Quantum Mechanics on Nonstandard Space

    Science.gov (United States)

    Kobayashi, Tsunehiro

    1996-01-01

    Quantum macroscopic motions are investigated in the scheme consisting of N-number of harmonic oscillators in terms of ultra-power representations of nonstandard analysis. Decoherence is derived from the large internal degrees of freedom of macroscopic matters.

  6. Modelling and Simulation of Seasonal Rainfall Using the Principle of Maximum Entropy

    Directory of Open Access Journals (Sweden)

    Jonathan Borwein

    2014-02-01

    Full Text Available We use the principle of maximum entropy to propose a parsimonious model for the generation of simulated rainfall during the wettest three-month season at a typical location on the east coast of Australia. The model uses a checkerboard copula of maximum entropy to model the joint probability distribution for total seasonal rainfall and a set of two-parameter gamma distributions to model each of the marginal monthly rainfall totals. The model allows us to match the grade correlation coefficients for the checkerboard copula to the observed Spearman rank correlation coefficients for the monthly rainfalls and, hence, provides a model that correctly describes the mean and variance for each of the monthly totals and also for the overall seasonal total. Thus, we avoid the need for a posteriori adjustment of simulated monthly totals in order to correctly simulate the observed seasonal statistics. Detailed results are presented for the modelling and simulation of seasonal rainfall in the town of Kempsey on the mid-north coast of New South Wales. Empirical evidence from extensive simulations is used to validate this application of the model. A similar analysis for Sydney is also described.

  7. Structure of naturally hydrated ferrihydrite revealed through neutron diffraction and first-principles modeling

    Science.gov (United States)

    Chappell, Helen F.; Thom, William; Bowron, Daniel T.; Faria, Nuno; Hasnip, Philip J.; Powell, Jonathan J.

    2017-08-01

    Ferrihydrite, with a ``two-line'' x-ray diffraction pattern (2L-Fh), is the most amorphous of the iron oxides and is ubiquitous in both terrestrial and aquatic environments. It also plays a central role in the regulation and metabolism of iron in bacteria, algae, higher plants, and animals, including humans. In this study, we present a single-phase model for ferrihydrite that unifies existing analytical data while adhering to fundamental chemical principles. The primary particle is small (20-50 Å) and has a dynamic and variably hydrated surface, which negates long-range order; collectively, these features have hampered complete characterization and frustrated our understanding of the mineral's reactivity and chemical/biochemical function. Near and intermediate range neutron diffraction (NIMROD) and first-principles density functional theory (DFT) were employed in this study to generate and interpret high-resolution data of naturally hydrated, synthetic 2L-Fh at standard temperature. The structural optimization overcomes transgressions of coordination chemistry inherent within previously proposed structures, to produce a robust and unambiguous single-phase model.

  8. VARIATIONAL PRINCIPLES FOR NONLOCAL CONTINUUM MODEL OF ORTHOTROPIC GRAPHENE SHEETS EMBEDDED IN AN ELASTIC MEDIUM

    Institute of Scientific and Technical Information of China (English)

    Sarp Adali

    2012-01-01

    Equations governing the vibrations and buckling of multilayered orthotropic graphene sheets can be expressed as a system of n partial differential equations where n refers to the number of sheets.This description is based on the continuum model of the graphene sheets which can also take the small scale effects into account by employing a nonlocal theory.In the present article a variational principle is derived for the nonlocal elastic theory of rectangular graphene sheets embedded in an elastic medium and undergoing transverse vibrations.Moreover the graphene sheets are subject to biaxial compression.Rayleigh quotients are obtained for the frequencies of freely vibrating graphene sheets and for the buckling load. The influence of small scale effects on the frequencies and the buckling load can be observed qualiatively from the expressions of the Rayleigh quotients.Elastic medium is modeled as a combination of Winkler and Pasternak foundations acting on the top and bottom layers of the mutilayered nano-structure.Natural boundary conditions of the problem are derived using the variational principle formulated in the study.It is observed that free boundaries lead to coupled boundary conditions due to nonlocal theory used in the continuum formulation while the local (classical) elasticity theory leads to uncoupled boundary conditions.The mathematical methods used in the study involve calculus of variations and the semi-inverse method for deriving the variational integrals.

  9. Control of Decoherence and Relaxation by Frequency Modulation of Heat Bath

    CERN Document Server

    Agarwal, G S

    2000-01-01

    We demonstrate in a very general fashion, considerable slowing down of decoherence and relaxation by fast frequency modulation of the system heat bath coupling. The slowing occurs as the decoherence rates are now determined by the spectral components of bath correlations which are shifted due to fast modulation. We present several examples including the slowing down of the heating of a trapped ion, where the system - bath interaction is not necessarily Markovian.

  10. The Impact of Decoherence and Dissipation on Cosmological Systems and on the Generation of Entanglement

    OpenAIRE

    2010-01-01

    The physics of open quantum systems, and therefore the phenomenon of decoherence, has become important in many branches of research. Within this thesis, we investigate the system--environment interaction in the context of different problems. The influence of decoherence is ubiquitous and, due to the scale independence of quantum theory, not limited to microscopic systems. One of the great open problems in theoretical physics is the appearance of a cosmological constant which differs by many o...

  11. An Alternative to Decoherence by Environment and the Appearance of a Classical World

    OpenAIRE

    2010-01-01

    We provide an alternative approach to the decoherence-by-environment paradigm in the field of the quantum measurement process and the appearance of a classical world. In contrast to the decoherence approach we argue that the transition from pure states to mixtures and the appearance of macro objects (and macroscopic properties) can be understood without invoking the measurement-like influence of the environment on the pointer-states of the measuring instrument. We show that every generic many...

  12. Spin Pumping from a Quantum Dot in the Presence of Decoherence

    Institute of Scientific and Technical Information of China (English)

    XIONG Yong-Jian; GE Sen-Quan

    2008-01-01

    We study the pumped spin current of an interacting quantum dot tunnel coupled to a single lead in the presence Using the nonequilibrium Green's function technique,we show that ESR-induced spin flip can generate finite spin current with no charge transport.Both the Coulomb interaction and spin decoherence decrease the amplitude of spin current.The dependence of pumped spin current on the intensity and frequency of ESR field,and the spin decoherence is discussed.

  13. Quantum computing in decoherence-free subspaces with superconducting charge qubits

    Energy Technology Data Exchange (ETDEWEB)

    Feng Zhibo [National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093 (China); Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China); Zhang Xinding [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: xdzhang2000@gmail.com

    2007-12-10

    Taking into account the main noises in superconducting charge qubits (SCQs), we propose a feasible scheme to realize quantum computing (QC) in a specially-designed decoherence-free subspace (DFS). In our scheme two physical qubits are connected with a common inductance to form a strong coupling subsystem, which acts as a logical qubit. Benefiting from the well-designed DFS, our scheme is helpful to suppress certain decoherence effects.

  14. Decoherence free in subspace using Na at C{sub 60} as quantum qubit

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Xianghua; Bi Qiao; Guo Guangcan; Ruda, H.E

    2003-06-23

    An approach of quantum computing based on endohedral metallofullerenes has been discussed, which includes the construction of c{sup n}-Not logic gates and decoherence-free in the projected subspace to protect against the decoherence from the interaction with environment. As the special structure of Na at C{sub 60}, symmetrically alignment of n Na at C{sub 60} along z direction, we can construct the multiqubits under the control of the STM setups.

  15. Measurement of the decoherence of a mesoscopic superposition of motional states of a trapped ion

    Institute of Scientific and Technical Information of China (English)

    Zheng Shi-Biao

    2004-01-01

    We propose a scheme to observe the decoherence of a mesoscopic superposition of two coherent states in the motion of a trapped ion. In the scheme the ion is excited by two perpendicular lasers tuned to the ion transition. The decoherence is revealed by the decrease of the correlation between two successive measurements of the internal state of the ion after relevant laser-ion interaction.

  16. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier.

    Science.gov (United States)

    Zhou, C; Li, J H; Duan, J A; Deng, G L

    2015-01-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted.

  17. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier

    Science.gov (United States)

    Zhou, C.; Li, J. H.; Duan, J. A.; Deng, G. L.

    2015-12-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted.

  18. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier

    Science.gov (United States)

    Zhou, C.; Li, J.H.; Duan, J.A.; Deng, G.L.

    2015-01-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted. PMID:26670008

  19. A unified electrostatic and cavitation model for first-principles molecular dynamics in solution

    Energy Technology Data Exchange (ETDEWEB)

    Scherlis, D A; Fattebert, J; Gygi, F; Cococcioni, M; Marzari, N

    2005-11-14

    The electrostatic continuum solvent model developed by Fattebert and Gygi is combined with a first-principles formulation of the cavitation energy based on a natural quantum-mechanical definition for the surface of a solute. Despite its simplicity, the cavitation contribution calculated by this approach is found to be in remarkable agreement with that obtained by more complex algorithms relying on a large set of parameters. The model allows for very efficient Car-Parrinello simulations of finite or extended systems in solution, and demonstrates a level of accuracy as good as that of established quantum-chemistry continuum solvent methods. They apply this approach to the study of tetracyanoethylene dimers in dichloromethane, providing valuable structural and dynamical insights on the dimerization phenomenon.

  20. Using Model Building in Structural Engineering to Enhance Understanding of Construction Principles and Methods

    Directory of Open Access Journals (Sweden)

    Niall Holmes

    2013-05-01

    Full Text Available This paper presents a new model building exercise in a second year module in the Department of Civil & Structural Engineering in the Dublin Institute of Technology (DIT. The activity aimed to improve students’ understanding of structural engineering, construction principles and methods. It allowed students to practically apply lecture material and construct a scaled model giving them an opportunity to study and visualise a real structure and generate their own ideas on how it should be assembled within a constructivist active learning environment. As a result, lectures were found to be more interactive and students more engaged in the discussions and provided a pathway to bridge the gap between theory (presented in lectures and the reality of their professions, which can aid them in their graduate careers. It is hoped that this type of active learning can be used in other engineering programmes to improve student understanding and as an opportunity to better apply lecture material to the real world.