Showing papers on "Quantum channel published in 1987"
TL;DR: In this article, the relation between the quantum and the classical correlation matrices is expressed] in terms of Grothendieck's known constant and it is shown that extremal quantum correlations characterize the Clifford algebra (i.e., canonical anticommutative relations).
Abstract: One Investigates inequalities for the probabilities and mathematical expectations which follow from the postulates of the local quantum theory. It turns out that the relation between the quantum and the classical correlation matrices is expressed] in terms of Grothendieck's known constant. It is also shown that the extremal quantum correlations characterize the Clifford algebra (i.e., canonical anticommutative relations).
335 citations
TL;DR: The intracavity density operator becomes diagonal in the basis which diagonalizes the measured quantity, a quadrature phase amplitude of the field, the ‘‘pointer basis,’’ and this result is the continuous-measurement equivalent of state reduction.
Abstract: An analysis is presented of optical heterodyne detection of an intracavity field within the context of quantum measurement theory. We find the intracavity density operator becomes diagonal in the basis which diagonalizes the measured quantity, a quadrature phase amplitude of the field. This representation is the ‘‘pointer basis,’’ and this result is the continuous-measurement equivalent of state reduction. The model illustrates a general feature of continuous measurement; one parameter given by the product of the system and measuring device coupling bandwidth and the fluctuations in the measuring device completely characterizes the measurement. This constant determines both the rate of diagonalization of the density operator and the rate of growth of fluctuations in the system quantity conjugate to the measured observable.
29 citations
01 Jan 1987
TL;DR: In this article, the entropy defect and Shannon's measure of information are introduced and formulated for both quasiclassical and consistently quantum description of a physical system, and the physical meaning of both quantities is analyzed in connection with Gibbs paradox and the maximum work obtainable from a nonequilibrium system.
Abstract: Basic concepts and results of physical information theory are presented. The entropy defect and Shannon’s measure of information are introduced and the entropy defect principle is formulated for both quasiclassical and consistently quantum description of a physical system. Results related to ideal physical information channels are discussed. The entropy defect and the amount of information coincide in the quasiclassical case, but the latter quantity is, in general, smaller than the former in quantum case due to the quantum-mechanical irreversibility of measurement. The physical meaning of both quantities is analyzed in connection with Gibbs paradox and the maximum work obtainable from a non-equilibrium system. Indirect (generalized) vs. direct (von Neumann’s) quantum measurements are considered. It is shown that in any separable infinite-dimensional Hilbert space direct and indirect quantum measurements yield equal maximum information.
21 citations
TL;DR: In this paper, it is claimed that distinguishability can account for classical as well as quantum statistics, and that the resulting non-local correlations are a manifestation of a fluctuating stochastic metric which has been shown to produce the quantum potential.
11 citations
TL;DR: The correspondence between classical and quantum theories is considered in this article, where the set of linear quantisations of classical Hamiltonians written in various canonical variables is investigated and the inverse problem of defining the classical limit of a quantum theory is also studied.
Abstract: The correspondence between classical and quantum theories is considered. The authors investigate the set of linear quantisations of classical Hamiltonians written in various canonical variables. The inverse problem of defining the classical limit of a quantum theory is also studied.
2 citations