Showing papers on "Quantum error correction published in 1973"
TL;DR: It is shown that the optimal receiver measures the photon annihilation operator, which corresponds to optical heterodyning, demonstrating the possible optimality of nonselfadjoint operators and clearly indicates the importance of considering more general quantum measurements in quantum signal detection.
Abstract: A quantum mechanical form of the Cramer-Rao inequality and a minimum-mcan-square-error quantum estimator for multiple parameters are derived, allowing all possible quantum measurements of the received field. The role of nonselfadjoint operators is emphasized in the formulation. Relations of our results to previous work on quantum estimation are discussed. For the estimation of complex mode amplitudes of coherent signals in Gaussian noise, it is shown that the optimal receiver measures the photon annihilation operator, which corresponds to optical heterodyning. This demonstrates the possible optimality of nonselfadjoint operators and clearly indicates the importance of considering more general quantum measurements in quantum signal detection.
248 citations
14 citations
TL;DR: In this article, a facial version of superposition principle is introduced in algebraic quantum theory; similar to the quantum logic approach it exhibits characteristic features of quantum theory, and it is shown that any pair of primary states satisfy the superposition principles if and only if they are quasiequivalent.
Abstract: A facial version of superposition principle is introduced in algebraic quantum theory; similar to the quantum logic approach it exhibits characteristic features of quantum theory. It is shown that any pair of primary states satisfy the superposition principle if and only if they are quasiequivalent. A coherent sector is then defined as a quasi‐equivalent class of primary states, which holds for both pure states in quantum theory and pure thermodynamic phases in quantum statistical mechanics.
7 citations
01 Jan 1973
TL;DR: The purpose of the present article is to draw attention to the fact that at least some of these difficulties occur in a much more general theory, which admits conventional Hilbert space quantum mechanics as a particular case.
Abstract: The attempts at interpreting elementary quantum mechanics in terms of statements bearing on the physical systems themselves meet with several difficulties which have been known for a long time. The purpose of the present article is to draw attention to the fact that at least some of these difficulties occur in a much more general theory, which admits conventional Hilbert space quantum mechanics as a particular case.
6 citations