Hidden quantum correlations in cavity-based quantum optics

TL;DR

This paper investigates hidden quantum correlations in multimode Gaussian states within cavity-based quantum optics, revealing conditions where correlations are inaccessible to standard detection, and provides criteria for their identification and exploitation.

Contribution

It introduces a systematic framework and explicit criteria to identify experimental setups with hidden quantum correlations due to non-real spectral covariance matrices.

Findings

Certain quantum correlations remain inaccessible to standard detection methods.

Explicit criteria can identify configurations with hidden correlations.

Framework aids in engineering and exploiting CV quantum resources.

Abstract

In multimode optical systems, the spectral covariance matrix encodes all the information about quantum correlations between the quadratures of Gaussian states. Recent research has revealed that, in scenarios that are more common than previously thought, part of these correlations remain inaccessible to standard homodyne detection scheme. Formally, this effect can be attributed to a non-real spectral covariance matrix. In this work, we provide a systematic framework and explicit criteria for identifying experimental configurations leading to such a behavior. This study will facilitate the proper exploitation and optimal engineering of CV quantum resources.