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Author: Alessandra Colla Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Abstract: We investigate the dynamics of open quantum systems which are initially correlated with their environment. The strategy of our approach is to analyze how given, fixed initial correlations modify the evolution of the open system with respect to the corresponding uncorrelated dynamical behavior with the same fixed initial environmental state, described by a completely positive dynamical map. We show that, for any predetermined initial correlations, one can introduce a linear dynamical map on the space of operators of the open system which acts like the proper dynamical map on the set of physical states and represents its unique linear extension. Furthermore, we demonstrate that this construction leads to a linear, time-local quantum master equation with generalized Lindblad structure involving time-dependent, possibly negative transition rates. Thus, the general non-Markovian dynamics of an open quantum system can be described by means of a time-local master equation even in the case of arbitrary, fixed initial system-environment correlations. We present some illustrative examples and explain the relation of our approach to several other approaches proposed in the literature
Author: Alessandra Colla Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Abstract: We investigate the dynamics of open quantum systems which are initially correlated with their environment. The strategy of our approach is to analyze how given, fixed initial correlations modify the evolution of the open system with respect to the corresponding uncorrelated dynamical behavior with the same fixed initial environmental state, described by a completely positive dynamical map. We show that, for any predetermined initial correlations, one can introduce a linear dynamical map on the space of operators of the open system which acts like the proper dynamical map on the set of physical states and represents its unique linear extension. Furthermore, we demonstrate that this construction leads to a linear, time-local quantum master equation with generalized Lindblad structure involving time-dependent, possibly negative transition rates. Thus, the general non-Markovian dynamics of an open quantum system can be described by means of a time-local master equation even in the case of arbitrary, fixed initial system-environment correlations. We present some illustrative examples and explain the relation of our approach to several other approaches proposed in the literature
Author: Niklas Felix Neubrand Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Abstract: Quantum thermodynamics is a relatively young scientific field that tries to extend the phenomenological theory of thermodynamics to the quantum regime. Many dynamical approaches are based on the theory of open quantum systems and assume factorizing initial conditions. In this work we relax this requirement and study an open system which is initially correlated with a thermal environment. For a predetermined environmental state and correlation operator the reduced evolution can be described by affine equations of motion. We prove that these maps can be linearized uniquely from the set of trace-one operators to the set of all bounded operators. Hence, we introduce a linearized dynamical map which acts identical to the affine map on the set of physical system states. Likewise, we obtain a linear time-local master equation with a generalized Lindblad form involving an time-dependent effective Hamiltonian and a time-dependent dissipator with possibly negative coefficients. By applying a principle of minimal dissipation, we prove that the effective Hamiltonian is identical to its uncorrelated version. Then, we generalize the formalism of Colla and Breuer [1] for exact non-equilibrium thermodynamics. We identify the effective Hamiltonian with the internal energy observable and define a first law of thermodynamics. Here, the effects of the initial correlations appear as additional terms in the work, heat and internal energy rates. Similarly, we generalize the entropy production rate. As the expression is non-linear in the system state, the influence of the initial correlations is harder to analyze. Also meaningful conditions for positive entropy production rates, i.e. the second law, have still to be found for correlated initial states. To illustrate our results, we finally consider the application to the Jaynes-Cummings model, where we explicitly compare the thermodynamic quantities for the correlated and uncorrelated cases. [1] A. Colla and H.-P. Breuer, Phys Rev A 105, 052216 (2022)
Author: Russell R. Ceballos Publisher: ISBN: Category : Quantum maps Languages : en Pages : 174
Book Description
A quantum system which evolves in time while interacting with an external environment is said to be an open quantum system (OQS), and the influence of the environment on the unperturbed unitary evolution of the system generally leads to non-unitary dynamics. This kind of open system dynamical evolution has been typically modeled by a Standard Prescription (SP) which assumes that the state of the OQS is initially uncorrelated with the environment state. It is here shown that when a minimal set of physically motivated assumptions are adopted, not only does there exist constraints on the reduced dynamics of an OQS such that this SP does not always accurately describe the possible initial correlations existing between the OQS and environment, but such initial correlations, and even entanglement, can be witnessed when observing a particular class of reduced state transformations termed purity extractions are observed. Furthermore, as part of a more fundamental investigation to better understand the minimal set of assumptions required to formulate well defined reduced dynamical quantum maps, it is demonstrated that there exists a one-to-one correspondence between the set of initial reduced states and the set of admissible initial system-environment composite states when G-consistency is enforced. Given the discussions surrounding the requirement of complete positivity and the reliance on the SP, the results presented here may well be found valuable for determining the ba- sic properties of reduced dynamical maps, and when restrictions on the OQS dynamics naturally emerge.
Author: Heinz-Peter Breuer Publisher: Oxford University Press, USA ISBN: 9780198520634 Category : Mathematics Languages : en Pages : 648
Book Description
This book treats the central physical concepts and mathematical techniques used to investigate the dynamics of open quantum systems. To provide a self-contained presentation the text begins with a survey of classical probability theory and with an introduction into the foundations of quantum mechanics with particular emphasis on its statistical interpretation. The fundamentals of density matrix theory, quantum Markov processes and dynamical semigroups are developed. The most important master equations used in quantum optics and in the theory of quantum Brownian motion are applied to the study of many examples. Special attention is paid to the theory of environment induced decoherence, its role in the dynamical description of the measurement process and to the experimental observation of decohering Schrodinger cat states. The book includes the modern formulation of open quantum systems in terms of stochastic processes in Hilbert space. Stochastic wave function methods and Monte Carlo algorithms are designed and applied to important examples from quantum optics and atomic physics, such as Levy statistics in the laser cooling of atoms, and the damped Jaynes-Cummings model. The basic features of the non-Markovian quantum behaviour of open systems are examined on the basis of projection operator techniques. In addition, the book expounds the relativistic theory of quantum measurements and discusses several examples from a unified perspective, e.g. non-local measurements and quantum teleportation. Influence functional and super-operator techniques are employed to study the density matrix theory in quantum electrodynamics and applications to the destruction of quantum coherence are presented. The text addresses graduate students and lecturers in physics and applied mathematics, as well as researchers with interests in fundamental questions in quantum mechanics and its applications. Many analytical methods and computer simulation techniques are developed and illustrated with the help of numerous specific examples. Only a basic understanding of quantum mechanics and of elementary concepts of probability theory is assumed.
Author: Fabio Benatti Publisher: Springer ISBN: 3540448748 Category : Science Languages : en Pages : 362
Book Description
The idea of editing the present volume in the Lecture Notes in Physics series arosewhileorganizingthe“ConferenceonIrreversibleQuantumDynamics”that took place at The Abdus Salam International Center for Theoretical Physics, Trieste, Italy, from July 29 to August 2, 2002. The aim of the Conference was to bring together di?erent groups of - searcherswhoseinterestsandpursuitsinvolveirreversibilityandtimeasymmetry in quantum mechanics. The Conference promoted open and in-depth exchanges of di?erent points of view, concerning both the content and character of qu- tum irreversibility and the methodologies used to study it. The following main themes were addressed: • Theoretical Aspects of Quantum Irreversible Dynamics • Open Quantum Systems and Applications • Foundational Aspects of Irreversible Quantum Dynamics • Asymmetric Time Evolution and Resonances Eachthemewasreviewedbyanexpertinthe?eld,accompaniedbymorespeci?c, research-like shorter talks. The whole topic of quantum irreversibility in all its manifold aspects has always raised a lot of interest, starting with the description of unstable systems in quantum mechanics and the issue of quantum measurement. Further, in - cent years a boost of activity concerning noise, dissipation and open systems has been prompted by the fast developing ?eld of quantum communication and information theory. These considerations motivated the editors to put together a volume that tries to summarize the present day status of the research in the ?eld, with the aim of providing the reader with an accessible and exhaustive introduction to it.
Author: Russell R. Ceballos Publisher: ISBN: Category : Languages : en Pages : 106
Book Description
The title may be a bit misleading. Perhaps, "On the Complete Positivity of Reduced Quantum Dynamics," would be a more fitting title. Determining whether or not completely positive (CP) maps are required to describe open system quantum dynamics is an extremely important issue concerning the fundamental mathematical foundations of QM, as well as many other areas of physics. it had been typically believed that only CP maps actually describe the dynamical evolution of open quantum systems, however there has been speculation as to whether this is a strict constraint on the mathematical and physical structure of stochastic quantum dynamical maps. The objective of this thesis is to demonstrate that given a particular unitary operator, an initial system state, a final system state, and the dimension of the environment state, there exists no CP map with a composite system-environment, product initial state that is compatible with the given constraints on the reduced quantum dynamics of the system under investigation.
Author: Anjala Mullaparambil Babu Publisher: ISBN: Category : Correlation (Statistics) Languages : en Pages : 86
Book Description
In this thesis, we discuss correlations arising between a system and its environment that lead to errors in an open quantum system. Detecting those correlations would be valuable for avoiding and/or correcting those errors. It was studied previously that we can detect correlations by only measuring the system itself if we know the cause of interaction between the two, for example in the case of a dipole-dipole interaction for a spin 1/2-spin 1/2 interaction Hamiltonian. We investigate the unitary, U which is associated with the exchange Hamiltonian and examine the ability to detect initial correlations between a system and its environment for a spin-1/2(qubit) system interacting with a larger higher dimensional environment. We provide bounds for when we can state with certainty that there are initial system-environment correlations given experimental data.
Author: Gernot Schaller Publisher: Springer ISBN: 9783319038766 Category : Science Languages : en Pages : 0
Book Description
This monograph provides graduate students and also professional researchers aiming to understand the dynamics of open quantum systems with a valuable and self-contained toolbox. Special focus is laid on the link between microscopic models and the resulting open-system dynamics. This includes how to derive the celebrated Lindblad master equation without applying the rotating wave approximation. As typical representatives for non-equilibrium configurations it treats systems coupled to multiple reservoirs (including the description of quantum transport), driven systems and feedback-controlled quantum systems. Each method is illustrated with easy-to-follow examples from recent research. Exercises and short summaries at the end of every chapter enable the reader to approach the frontiers of current research quickly and make the book useful for quick reference.
Author: Christopher James Wood Publisher: ISBN: Category : Interferometry, Neutron Languages : en Pages : 273
Book Description
In this thesis we address three topics of open quantum systems theory. The first concerns the operational characterization of an open quantum system. We develop a graphical calculus for open quantum systems and use it to review the operational representation and characterization of noisy evolution using completely-positive maps, or quantum channels. These graphical techniques facilitate an intuitive unification of the various representations of CP-maps, and the transformations between these representations. We generalize the channel formalism by introducing quantum superchannels -- effective quantum channels which take another channel as input. Superchannels may be constructed using graphical techniques to rearrange the tensor network for a sequence of channels, and these constructions allow for the description of a strictly greater set of dynamics than is possible with the standard formalism. We demonstrate this by providing a method for the complete characterization of an open system initially correlated with its environment. In doing so we introduce and develop several novel quantitative measures for characterizing the strength and presence of initial correlations in a quantum system. These techniques may be implemented using measurement of the system alone, and do not require any access or prior knowledge about the environment. The second topic we discuss is the parallel initialization of an ensemble quantum system into a high purity state. We describe a dissipative state engineering technique where an ensemble of identical spins may be prepared in its ground state by coupling the spins to the resolved sidebands of a high-Q resonator. This allows for parallel removal of entropy from a large number of quantum systems, enabling an ensemble to achieve a polarization greater than thermal equilibrium, and in principle on a time scale much shorter than thermal relaxation processes. This is achieved by the collective enhancement in coupling strength of the coupled angular momentum subspaces which behave as larger effective spins. Cavity cooling is shown to cool each of these subspaces to their respective ground state, however by including a local $T_2$ dephasing dissipator on each spin we show how one may use this to break the identical spin degeneracy and couple the subspaces to enable cooling to the full ground state of the joint system. The third topic concerns quantum correlations between the momentum and spin subsystems of a neutron in a neutron interferometer. We explore the robustness of these correlations in the presence of dephasing noise due to randomized phase differences between interferometer paths. We demonstrate that even in the presence of strong noise quantum correlations persist and can be detected by introducing post-selected spin measurements at the output of the interferometer. We relate these post-selected experiments to which-way measurements and a quantum eraser.
Author: Alessandra Colla
Author: Alessandra Colla
Author: Niklas Felix Neubrand
Author: Russell R. Ceballos
Author: Heinz-Peter Breuer
Author: Fabio Benatti
Author: Russell R. Ceballos
Author: Anjala Mullaparambil Babu
Author: Gernot Schaller
Author: Christopher James Wood
Author: St Phane Attal