Accessible information of a general quantum Gaussian ensemble

TL;DR

This paper calculates the accessible information for general quantum Gaussian ensembles, showing that Gaussian measurements optimize information retrieval, extending previous results to broader cases including single bosonic modes.

Contribution

It generalizes the calculation of accessible information for quantum Gaussian ensembles and proves Gaussian measurements are optimal, broadening prior gauge-invariant findings.

Findings

Gaussian measurements are optimal for accessible information.

Extension of results to general quantum Gaussian ensembles.

Applicable to single bosonic modes under certain conditions.

Abstract

Accessible information, which is a basic quantity in quantum information theory, is computed for a general quantum Gaussian ensemble under certain "threshold condition". It is shown that the maximizing measurement is Gaussian, constituting a far-reaching generalization of the optical heterodyning. This substantially extends the previous result concerning the gauge-invariant case, even for a single bosonic mode.