Experimental characterization of Gaussian quantum discord generated by four-wave mixing

TL;DR

This paper experimentally investigates the quantum discord in two-mode squeezed vacuum generated by four-wave mixing in rubidium vapor, analyzing its spectral properties, effects of attenuation, and spatial mode dependence.

Contribution

It provides the first detailed experimental characterization of Gaussian quantum discord in four-wave mixing generated states, including effects of attenuation and spatial mode considerations.

Findings

Quantum discord varies with frequency spectra and mutual information.

Attenuation affects quantum and classical correlations differently.

Quantum discord can be sub- or superadditive depending on spatial channels.

Abstract

We experimentally determine the quantum discord present in two-mode squeezed vacuum generated by a four-wave mixing process in hot rubidium vapor. The frequency spectra of the discord, as well as the quantum and classical mutual information are also measured. In addition, the effects of symmetric attenuation introduced into both modes of the squeezed vacuum on the discord, the quantum mutual information and the classical correlations are examined experimentally. Finally, we show that due to the multi-spatial-mode nature of the four-wave mixing process, the quantum discord may exhibit sub- or superadditivity depending on which spatial channels are selected.