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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.
Modern quantum measurement for graduate students and researchers in quantum information, quantum metrology, quantum control and related fields.
This detailed, accessible introduction to the field of quantum decoherence reviews the basics and then explains the essential consequences of the phenomenon for our understanding of the world. The discussion includes, among other things: How the classical world of our experience can emerge from quantum mechanics; the implications of decoherence for various interpretations of quantum mechanics; recent experiments confirming the puzzling consequences of the quantum superposition principle and making decoherence processes directly observable.
Semiconductor nanostructures are attracting a great deal of interest as the most promising device with which to implement quantum information processing and quantum computing. This book surveys the present status of nanofabrication techniques, near field spectroscopy and microscopy to assist the fabricated nanostructures. It will be essential reading for academic and industrial researchers in pure and applied physics, optics, semiconductors and microelectronics. - The first up-to-date review articles on various aspects on quantum coherence, correlation and decoherence in semiconductor nanostructures
Decoherence, a concept known only to few physicists when the first edition appeared in 1996, has since become firmly established experimentally and understood theoretically, as well as widely reported in the literature. The major consequences of decoherence are the emergence of "classicality" in general, superselection rules, the border line between microscopic and macroscopic behavior in molecules and field theory, the emergence of classical spacetime, and the appearance of quantum jumps. The most important new developments in this rapidly evolving field are included in the second edition of this book, which has become a standard reference on the subject. All chapters have been thoroughly revised and updated. New fields of application now addressed span chaos theory, quantum information, neuroscience, primordial fluctuations in cosmology, black holes and string theory, experimental tests, and interpretational issues. While the major part of the book is concerned with environmental decoherence derived from a universal Schrödinger equation, later chapters address related or competing methods, such as consistent histories, open system dynamics, algebraic approaches, and collapse models.
The Quantum Measurement Problem (QMP) is a single resource for information on the QMP and it establishes a basis for research on what is arguably the most well-known and still-unresolved scientific problem: how does our observed world relate to the quantum? The book is suitable for both undergraduate level study on a selective basis as well as graduate level study and for use as a resource for research scientists interested in aspects of the QMP. There are many sections that can even be profitably read by the general public to appreciate the history and future importance of the QMP. Although many books are now available that adequately address Quantum Information, this is the first book offering a comparable treatment for the QMP. The QMP has a companion website, https: //theqmp.com, with video presentations and other resources. There are some in the physics community that view the QMP only as a problem that requires an interpretation while others view its solution as essential to complete our physical description of the world and enhance our ability to design experimental probes of its physical elements in terms of quantum physics. This book critically examines these two viewpoints and resolves this dichotomy in favor of the latter viewpoint. The problem is precisely defined in terms of experimental operations and the scientific requirements that a resolution would have to meet. It explains why the QMP is a physical problem that requires more than an interpretation for its resolution and why a solution could have profound implications for physics as well as other fields. In particular, it uses quantum information methods for a constructive demonstration that unitary Schrödinger processes can be experimentally distinguished from measurement processes using well-established techniques such as Bell measurements, which would establish that measurement is a non-unitary process. Neither Schrödinger's equation nor the measurement postulate is found to be sufficient to explain measurement. For the first time, The QMP offers a single resource that thoroughly assesses the strengths and weaknesses of the major approaches to the QMP. . The exposition in The QMP contains eight chapters, including problem sets, with dual tracks throughout the book that allow both those with a technical background in quantum physics or quantum information as well as less-technical readers to come up to speed on the QMP, depending on their interests and background. . Chapters 1 and 2 are an introductory-level presentation of wave-particle duality and unitary Schrödinger processes. Chapter 3 is a key chapter that uses quantum information methods for a constructive demonstration that unitary Schrödinger processes can be experimentally distinguished from measurement processes using well-established techniques such as Bell measurements, which would establish that measurement is a non-unitary process. Chapter 4 presents a detailed definition of the QMP in terms of experimental observations and uses the results of Chapter 3 to systematically evaluate the strength and weaknesses of all the major approaches to the QMP in the literature and determine which constitute physical theories as opposed to philosophical interpretations. Chapter 5 gives an uncensored historical perspective leading to the development of quantum physics from the viewpoint of those physical aspects which will ultimately form the elements of the QMP. Chapter 6 presents a unique discussion of the Scientific Method and how the use of scientific deduction within the approach of radical conservatism can most proficiently address problems of quantum foundations. Chapter 7 presents concepts and mathematical tools useful for further research developments of both closed and open system approaches to the QMP. Chapter 8 presents conclusions and the status of the QMP for moving forward.
This volume is devoted to Quantum Decoherence with lectures from the Séminaire Poincaré, held in November 2005 at the Institute Henri Poincaré 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 contains contributions based on the lectures delivered and posters presented at the Fifth International Conference on Quantum Communication, Measurement and Computing (QCM&C-Y2K). This Conference is the fifth of a successful series hosted this time in Italy, was held in Capri, 3-7 July, 2000. The conference was attended by more than 200 participants from all over the world. There was also a high level of participation from graduate students, who greatly benefited from the opportunity to attend world-class conferences. The Conference Hall was hosted in La Residenza Hotel in Capri, where part of p- ticipants where housed, while others where housed in various cozy nearby - tels. All enjoyed the pleasant atmosphere offered by the island of Capri. There were 59 invited lectures given as oral presentations of 30 minutes and 94 poster papers. The major topics covered at the Conference where new experimental and theoretical results in quantum information. They were divided in five parts; i) Quantum Information and Communication, ii) Quantum Measurement, - coherence, and Tomography, iii) Quantum Computing, iv) Cryptography, v) Entanglement and Teleportation. We were lucky in that almost all major - perimental groups in the world working in this area were represented, as were the major theoreticians. There was very active audience participation. A n- ber of graduate students and post-docs were able to present their contributions in four after dinner poster sessions.
Recent experimental advances in the control of quantum superconducting circuits, nano-mechanical resonators and photonic crystals has meant that quantum measurement theory is now an indispensable part of the modelling and design of experimental technologies. This book, aimed at graduate students and researchers in physics, gives a thorough introduction to the basic theory of quantum measurement and many of its important modern applications. Measurement and control is explicitly treated in superconducting circuits and optical and opto-mechanical systems, and methods for deriving the Hamiltonians of superconducting circuits are introduced in detail. Further applications covered include feedback control, metrology, open systems and thermal environments, Maxwell's demon, and the quantum-to-classical transition.