Квантовые измерения и декогеренция: Модели и феноменология

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.

This book is devoted to the theory of quantum measurements, an area that recently has attracted much attention because of its new applications for quantum information technology. The phenomenon of decoherence of a measured system is investigated and simple techniques for the description of a wide class of measurements are developed. An individual continuously measured (decohering) system is presented by an effective complex Hamiltonian which supplies a phenomenological theory of gradual decoherence.
The work, which features a clear presentation of physical processes leading to quantum measurement (decoherence) and simple mathematical formalisms, concentrates on the physical nature of quantum measurements and the behaviour of measured (open) quantum systems, but conceptual problems are also treated. The analysis of interrelations between different approaches to quantum measurement is given. The methods developed in this volume are applicable for the description of individual continuously measured (decohering) systems, not only to a whole set of such systems.
Audience: This work will be of interest to both researchers and graduate students in the fields of quantum mechanics, metaphysics, probability theory, stochastic processes, the mathematics of physics and computational physics.

"This book is devoted to the theory of quantum measurements, an area which recently has attracted much attention because of its new applications for quantum information technology. The phenomenon of decoherence of a measured system is investigated and simple techniques for the description of a wide class of measurements are developed. An individual continuously measured (decohering) system is presented by an effective complex Hamiltonian which supplies a phenomenological theory of gradual decoherence." Before starting a detailed exposition of the material we shall give in this chapter a sort of general survey of the book's content.1