Quantification of Quantum Correlations in Two-Beam Gaussian States Using Photon-Number Measurements

TL;DR

This paper presents a method to quantify quantum correlations in two-beam Gaussian states using only intensity moments up to the fourth order, enabling practical analysis of quantum properties in experiments.

Contribution

The authors develop and demonstrate a general approach to quantify quantum correlations from experimental intensity moments, applicable to various Gaussian states.

Findings

Successfully applied to twin beams with increasing intensity

Determined principal squeezing variances from intensity moments

Provides bounds for negativity and measures of nonseparability

Abstract

Identification, and subsequent quantification of quantum correlations, is critical for understanding, controlling, and engineering quantum devices and processes. We derive and implement a general method to quantify various forms of quantum correlations using solely the experimental intensity moments up to the fourth order. This is possible as these moments allow for an exact determination of the global and marginal impurities of two-beam Gaussian fields. This leads to the determination of steering, tight lower and upper bounds for the negativity, and the Kullback-Leibler divergence used as a quantifier of state nonseparability. The principal squeezing variances are determined as well using the intensity moments. The approach is demonstrated on the experimental twin beams with increasing intensity and the squeezed super-Gaussian beams composed of photon pairs. Our method is readily applicable to multibeam Gaussian fields to characterize their quantum correlations.