R. L. Stratonovich | Searcharxiv

arXiv2005

On the Dynamical Interpretation for the Quantum-Measurement Projection Postulate

An apparatus model with discrete momentum space suitable for the exact solution of the problem is considered. The special Hamiltonian of its interaction with the object system under consideration is chosen. In this simple case it is easy to illustrate how difficulties in constructing the dynamical interpretation of selective collapse could be overcomed without any limiting procedure. For this purpose one can apply either averaging with respect to a non-quantum parameter or reducing the algebra of the joint system operators (i. e. passing to the quantum system subalgebra). The latter procedure effectively implies averaging with respect to apparatus quantum variables not belonging to the system.

quant-ph↗

arXiv2005

Optimization of Quantum Information Processing Maximizing Mutual Information

A model of quantum noisy channel with input encoding by a classical random vector is described. An equation of optimality is derived to determine a complete set of wave functions describing quantum decodings based on quasi-measurements maximizing the classical amount of transmitted information. A solution of this equation is found for the Gaussian multimode case with input Gaussian distribution. It is described by the overcomplete family of coherent vectors describing an optimal quasimeasurement of the canonical annihilation amplitudes in the output Hilbert space. It is found that the optimal decoding in this case realizes the maximum amount I=Spln[1+S/(N+1)] of the classical information as transmitted via the classical Gaussian channel with the effective noise covariance matrix N+I. A physical realization of optimal quasi-measurement based on an indirect (heterodyne) observation of the canonical operators is suggested.

quant-ph↗