Two-step procedure to discriminate discordant from classical correlated or factorized states

TL;DR

This paper presents an experimental two-step method to detect and differentiate quantum discord, classical correlations, and factorized states in a bipartite system using polarization and spatial degrees of freedom.

Contribution

The work introduces a novel experimental scheme based on trace distance and state tomography to distinguish various types of correlations in a quantum system.

Findings

Successfully discriminated quantum discord from classical correlations.

Identified factorized states in a system-environment setting.

Validated the method through experimental implementation.

Abstract

We devise and experimentally realize a procedure capable of detecting and distinguishing quantum discord and classical correlations as well the presence of factorized states in a joint system-environment setting. Our scheme builds on recent theoretical results showing how the distinguishability between two reduced states of a quantum system in a bipartite setting can convey important information about the correlations present in the bipartite state and the interaction between the subsystems. The two addressed subsystems are the polarization and spatial degrees of freedom of the signal beam generated by parametric down-conversion, which are suitably prepared by the idler beam. Different global and local operations allow for the detection of different correlations by studying via state tomography the trace distance behavior between suitable polarization subsystem states.