Hidden quantum correlations in cavity-based quantum optics
Phys. Rev. A 112, 023705 – Published 11 August, 2025
DOI: https://doi.org/10.1103/8sjn-rb9b
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 remains inaccessible to standard homodyne detection schemes. Formally, this effect can be attributed to a nonreal 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 continuous-variable quantum resources.
