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The Poincaré Seminar is held twice a year at the Institute Henri Poincaré in Paris. The goal of this seminar is to provide up-to-date information about general topics of great interest in physics. Both the theoretical and experimental results are covered, with some historical background. Particular care is devoted to the pedagogical nature of the presentation. This volume is devoted to Quantum Decoherence. A broad perspective on the subject is provided by the contributions of W. H. Zurek, H. D. Zeh and E. Joos, together with clean up-to-date presentations of the actual experiments on decoherence both in the mesoscopic systems of atomic physics, by J.M. Raimond and S. Haroche, and in the "quantronic" or condensed matter context, by D. Esteve et al. Further, the question of quantum codes and error corrections is discussed in the contribution of J. Kempe.

The Poincaré Seminar is held twice a year at the Institute Henri Poincaré in Paris. The goal of this seminar is to provide up-to-date information about general topics of great interest in physics. Both the theoretical and experimental results are covered, with some historical background. Particular care is devoted to the pedagogical nature of the presentation. This volume is devoted to Quantum Decoherence. A broad perspective on the subject is provided by the contributions of W. H. Zurek, H. D. Zeh and E. Joos, together with clean up-to-date presentations of the actual experiments on decoherence both in the mesoscopic systems of atomic physics, by J.M. Raimond and S. Haroche, and in the "quantronic" or condensed matter context, by D. Esteve et al. Further, the question of quantum codes and error corrections is discussed in the contribution of J. Kempe.

Over the course of the past decade, decoherence has become a ubiquitous scienti?c term popular in all kinds of research, from fundamental theories of quantum physics to applications in nanoengineering. Decoherence has been hailed as the solution to long-standing foundational problems dating back to the beginnings of quantum mechanics. It has been cursed as the key obstacle to next-generation technologies, such as quantum computers (another se- ingly omnipresent ?eld of research). And while decoherence has been directly observed in various experiments, its scope and meaning have often been m- understood and misrepresented. Decoherence makes a fantastic subject of research, as it touches upon many di?erent facets of physics, from phi- sophically inclined questions of interpretation all the way to down-to-earth problems in experimental settings and engineering applications. This book will introduce the reader, in an accessible and self-contained manner, to these various fascinating aspects of decoherence. It will focus in particularontherelationofdecoherencetotheso-calledquantum-to-classical transition, i. e. , the question of how decoherence may explain the emergence of the classical appearance of the macroscopic world around us from the underlying quantum substrate. Thescopeofthisbookisrelativelybroadinordertofamiliarizethereader withthemanyfacetsofdecoherence,inboththetheoreticalandexperimental domains. Throughout the book, I have sought to maintain a healthy balance betweentheconceptualideasassociatedwiththedecoherenceprogramonthe one hand and the formal and mathematical details on the other hand. This book will establish a proper understanding of decoherence as a pure quantum phenomenon and will emphasize the importance of the correct interpretation of theconsequences and achievements of decoherence.

Over the course of the past decade, decoherence has become a ubiquitous scienti?c term popular in all kinds of research, from fundamental theories of quantum physics to applications in nanoengineering. Decoherence has been hailed as the solution to long-standing foundational problems dating back to the beginnings of quantum mechanics. It has been cursed as the key obstacle to next-generation technologies, such as quantum computers (another se- ingly omnipresent ?eld of research). And while decoherence has been directly observed in various experiments, its scope and meaning have often been m- understood and misrepresented. Decoherence makes a fantastic subject of research, as it touches upon many di?erent facets of physics, from phi- sophically inclined questions of interpretation all the way to down-to-earth problems in experimental settings and engineering applications. This book will introduce the reader, in an accessible and self-contained manner, to these various fascinating aspects of decoherence. It will focus in particularontherelationofdecoherencetotheso-calledquantum-to-classical transition, i. e. , the question of how decoherence may explain the emergence of the classical appearance of the macroscopic world around us from the underlying quantum substrate. Thescopeofthisbookisrelativelybroadinordertofamiliarizethereader withthemanyfacetsofdecoherence,inboththetheoreticalandexperimental domains. Throughout the book, I have sought to maintain a healthy balance betweentheconceptualideasassociatedwiththedecoherenceprogramonthe one hand and the formal and mathematical details on the other hand. This book will establish a proper understanding of decoherence as a pure quantum phenomenon and will emphasize the importance of the correct interpretation of theconsequences and achievements of decoherence.

Quantum measurement (Le., a measurement which is sufficiently precise for quantum effects to be essential) was always one of the most impor­ tant points in quantum mechanics because it most evidently revealed the difference between quantum and classical physics. Now quantum measure­ ment is again under active investigation, first of all because of the practical necessity of dealing with highly precise and complicated measurements. The nature of quantum measurement has become understood much bet­ ter during this new period of activity, the understanding being expressed by the concept of decoherence. This term means a physical process lead­ ing from a pure quantum state (wave function) of the system prior to the measurement to its state after the measurement which includes classical elements. More concretely, decoherence occurs as a result of the entangle­ ment of the measured system with its environment and results in the loss of phase relations between components of the wave function of the measured system. Decoherence is essentially nothing else than quantum measurement, but considered from the point of view of its physical mechanism and resolved in time. The present book is devoted to the two concepts of quantum measure­ ment and decoherence and to their interrelation, especially in the context of continuous quantum measurement.

Quantum measurement (Le., a measurement which is sufficiently precise for quantum effects to be essential) was always one of the most impor­ tant points in quantum mechanics because it most evidently revealed the difference between quantum and classical physics. Now quantum measure­ ment is again under active investigation, first of all because of the practical necessity of dealing with highly precise and complicated measurements. The nature of quantum measurement has become understood much bet­ ter during this new period of activity, the understanding being expressed by the concept of decoherence. This term means a physical process lead­ ing from a pure quantum state (wave function) of the system prior to the measurement to its state after the measurement which includes classical elements. More concretely, decoherence occurs as a result of the entangle­ ment of the measured system with its environment and results in the loss of phase relations between components of the wave function of the measured system. Decoherence is essentially nothing else than quantum measurement, but considered from the point of view of its physical mechanism and resolved in time. The present book is devoted to the two concepts of quantum measure­ ment and decoherence and to their interrelation, especially in the context of continuous quantum measurement.

The contributions to this volume are based on selected lectures from the first international workshop on decoherence, information, complexity and entropy (DICE). The aim of this volume is to reflect the growing importance ot common concepts behind seemingly different fields such as quantum mechanics, general relativity and statistical physics in a form accessible to nonspecialist researchers. Many presentations include original results which are published here for the first time.

The contributions to this volume are based on selected lectures from the first international workshop on decoherence, information, complexity and entropy (DICE). The aim of this volume is to reflect the growing importance ot common concepts behind seemingly different fields such as quantum mechanics, general relativity and statistical physics in a form accessible to nonspecialist researchers. Many presentations include original results which are published here for the first time.

Dissipative Quantum Chaos and Decoherence provides an overview of the state of the art of research in this exciting field. The main emphasis is on the development of a semiclassical formalism that allows one to incorporate the effect of dissipation and decoherence in a precise, yet tractable way into the quantum mechanics of classically chaotic systems. The formalism is employed to reveal how the spectrum of the quantum mechanical propagator of a density matrix is determined by the spectrum of the corresponding classical propagator of phase space density. Simple quantum--classical hybrid formulae for experimentally relevant correlation functions and time-dependent expectation values of observables are derived. The problem of decoherence is treated in detail, and highly unexpected cases of very slow decoherence are revealed, with important consequences for the long-debated realizability of Schrödinger cat states as well as for the construction of quantum computers.

Dissipative Quantum Chaos and Decoherence provides an overview of the state of the art of research in this exciting field. The main emphasis is on the development of a semiclassical formalism that allows one to incorporate the effect of dissipation and decoherence in a precise, yet tractable way into the quantum mechanics of classically chaotic systems. The formalism is employed to reveal how the spectrum of the quantum mechanical propagator of a density matrix is determined by the spectrum of the corresponding classical propagator of phase space density. Simple quantum--classical hybrid formulae for experimentally relevant correlation functions and time-dependent expectation values of observables are derived. The problem of decoherence is treated in detail, and highly unexpected cases of very slow decoherence are revealed, with important consequences for the long-debated realizability of Schrödinger cat states as well as for the construction of quantum computers.

Cherry Red Records Incoherence - Vinyl Edition (Peter Hammill) (52543456)

The ?eld that encompasses the term “quantum interference” combines a number of separate concepts, and has a variety of manifestations in d- ferent areas of physics. In the sense considered here, quantum interference is concerned with coherence and correlation phenomena in radiation ?elds and between their sources. It is intimately connected with the phenomenon of non-separability (or entanglement) in quantum mechanics. On account of this, it is obvious that quantum interference may be regarded as a com- nent of quantum information theory, which investigates the ability of the electromagnetic ?eld to transfer information between correlated (entangled) systems. Since it is important to transfer information with the minimum of corruption, the theory of quantum interference is naturally related to the theory of quantum ?uctuations and decoherence. Since the early days of quantum mechanics, interference has been - scribed as the real quantum mystery. Feynman, in his famous introduction to the lectures on the single particle superposition principle, referred in the following way to the phenomenon of interference: “it has in it the heart of quantum mechanics”, and it is really ‘the only mystery’ of quantum mech- ics. With the development of experimental techniques, it has been possible to carry out many of the early Gedanken experiments that played an important role in developing our understanding of the fundamentals of quantum int- ference and entanglement. Despite its long history, quantum interference still challenges our understanding, and continues to excite our imagination.

The ?eld that encompasses the term “quantum interference” combines a number of separate concepts, and has a variety of manifestations in d- ferent areas of physics. In the sense considered here, quantum interference is concerned with coherence and correlation phenomena in radiation ?elds and between their sources. It is intimately connected with the phenomenon of non-separability (or entanglement) in quantum mechanics. On account of this, it is obvious that quantum interference may be regarded as a com- nent of quantum information theory, which investigates the ability of the electromagnetic ?eld to transfer information between correlated (entangled) systems. Since it is important to transfer information with the minimum of corruption, the theory of quantum interference is naturally related to the theory of quantum ?uctuations and decoherence. Since the early days of quantum mechanics, interference has been - scribed as the real quantum mystery. Feynman, in his famous introduction to the lectures on the single particle superposition principle, referred in the following way to the phenomenon of interference: “it has in it the heart of quantum mechanics”, and it is really ‘the only mystery’ of quantum mech- ics. With the development of experimental techniques, it has been possible to carry out many of the early Gedanken experiments that played an important role in developing our understanding of the fundamentals of quantum int- ference and entanglement. Despite its long history, quantum interference still challenges our understanding, and continues to excite our imagination.

The ?eld that encompasses the term “quantum interference” combines a number of separate concepts, and has a variety of manifestations in d- ferent areas of physics. In the sense considered here, quantum interference is concerned with coherence and correlation phenomena in radiation ?elds and between their sources. It is intimately connected with the phenomenon of non-separability (or entanglement) in quantum mechanics. On account of this, it is obvious that quantum interference may be regarded as a com- nent of quantum information theory, which investigates the ability of the electromagnetic ?eld to transfer information between correlated (entangled) systems. Since it is important to transfer information with the minimum of corruption, the theory of quantum interference is naturally related to the theory of quantum ?uctuations and decoherence. Since the early days of quantum mechanics, interference has been - scribed as the real quantum mystery. Feynman, in his famous introduction to the lectures on the single particle superposition principle, referred in the following way to the phenomenon of interference: “it has in it the heart of quantum mechanics”, and it is really ‘the only mystery’ of quantum mech- ics. With the development of experimental techniques, it has been possible to carry out many of the early Gedanken experiments that played an important role in developing our understanding of the fundamentals of quantum int- ference and entanglement. Despite its long history, quantum interference still challenges our understanding, and continues to excite our imagination.

When we were preparing the first edition of this book, the concept of de­ coherence was known only to a minority of physicists. In the meantime, a wealth of contributions has appeared in the literature - important ones as well as serious misunderstandings. The phenomenon itself is now experimen­ tally clearly established and theoretically well understood in principle. New fields of application, discussed in the revised book, are chaos theory, informa­ tion theory, quantum computers, neuroscience, primordial cosmology, some aspects of black holes and strings, and others. While the first edition arose from regular discussions between the authors, thus leading to a clear" entanglement" of their otherwise quite different chap­ ters, the latter have thereafter evolved more or less independently. While this may broaden the book's scope as far as applications and methods are con­ cerned, it may also appear confusing to the reader wherever basic assumptions and intentions differ (as they do). For this reason we have rearranged the or­ der of the authors: they now appear in the same order as the chapters, such that those most closely related to the "early" and most ambitious concept of decoherence are listed first. The first three authors (Joos, Zeh, Kiefer) agree with one another that decoherence (in contradistinction to the Copen­ hagen interpretation) allows one to eliminate primary classical concepts, thus neither relying on an axiomatic concept of observables nor on a probability interpretation of the wave function in terms of classical concepts.

The development of a consistent picture for the processes of decoherence and quantum measurement requires a treatment which is compatible with the theory of relativity. This volume reviews some of the approaches suggested to solve or circumvent the arising difficulties. Starting from an analysis of the level of compatibility of the measurement problem with the special theory of relativity, the role of non-locality and entanglement are discussed. The subject is also addressed from the point of view of quantum optics and quantum information theory, as well as on the basis of group theoretic and algebraic methods. The emergence of decoherence in quantum electrodynamics is discussed from an open systems perspective.

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The Seventh Rochester Conference on Coherence and Quantum Optics was held on the campus of the University of Rochester during the four-day period June 7 - 10, 1996. More than 280 scientists from 33 countries participated. This book contains the Proceedings of the meeting. This Conference differed from the previous six in the series in having only a limited number of oral presentations, in order to avoid too many parallel sessions. Another new feature was the introduction of tutorial lectures. Most contributed papers were presented in poster sessions. The Conference was sponsored by the American Physical Society, by the Optical Society of America, by the International Union of Pure and Applied Physics and by the University of Rochester. We wish to express our appreciation to these organizations for their support and we especially extend our thanks to the International Union of Pure and Applied Physics for providing financial assistance to a number of speakers from Third World countries, to enable them to take part in the meeting.

The Eighth Rochester Conference on Coherence and Quantum Optics was held on the campus of the University of Rochester during the period June 13-16,2001. This volume contains the proceedings of the meeting. The meeting was preceded by an affiliated conference, the International Conference on Quantum Information, with some overlapping sessions on June 13. The proceedings of the affiliated conference will be published separately by the Optical Society of America. A few papers that were presented in common plenary sessions of the two conferences will be published in both proceedings volumes. More than 268 scientists from 28 countries participated in the week long discussions and presentations. This Conference differed from the previous seven in the CQO series in several ways, the most important of which was the absence of Leonard Mandel. Professor Mandel died a few months before the conference. A special memorial symposium in his honor was held at the end of the conference. The presentations from that symposium are included in this proceedings volume. An innovation, that we believe made an important contribution to the conference, was the inclusion of a series of invited lectures chaired by CQO founder Emil Wolf, reviewing the history of the fields of coherence and quantum optics before about 1970. These were given by three prominent participants in the development of the field, C. Cohen-Tannoudji, 1. F. Clauser, and R. I. Glauber.