Quantumness of Gaussian Discord: Experimental Evidence and Role of System-Environment Correlations

TL;DR

This paper experimentally demonstrates quantum features in classically classified bipartite states with non-zero Gaussian discord, revealing the role of system-environment correlations and counterintuitive effects of local loss.

Contribution

It provides experimental evidence of quantum properties in Gaussian states with zero P-function and explores the influence of environment-induced correlations on quantum discord.

Findings

Quantum features detected in classically classified states.

Discord can increase under local loss, linked to environment entanglement.

Entanglement can be recovered through system-environment correlations.

Abstract

We provide experimental evidence of quantum features in bi-partite states classified as entirely classical according to a conventional criterion based on the Glauber P-function but possessing non-zero Gaussian quantum discord. Their quantum nature is experimentally revealed by acting locally on one part of the discordant state. Adding an environmental system purifying the state, we unveil the flow of quantum correlations within a global pure system using the Koashi-Winter inequality. We experimentally verify and investigate the counterintuitive effect of discord increase under the action of local loss and link it to the entanglement with the environment. For a discordant state generated by splitting a state in which the initial squeezing is destroyed by random displacements, we demonstrate the recovery of entanglement highlighting the role of system-environment correlations.