Entanglement Witnesses and Measures for Bright Squeezed Vacuum

TL;DR

This paper develops practical entanglement witnesses and measures for bright squeezed vacuum states, enabling macroscopic quantum correlation detection through polarization measurements and photodetection, with results indicating entanglement scales quadratically with photon number.

Contribution

It introduces feasible entanglement witnesses and measures specifically for bright squeezed vacuum states, enhancing macroscopic entanglement detection methods.

Findings

Entanglement scales as the mean photon number squared.

Efficient detection involves polarization triplet Bell states and Stokes operator variances.

Operational Schmidt number analog is applicable to these states.

Abstract

Quantum entanglement is a fascinating phenomenon, especially if it is observed at the macroscopic scale. Importantly, macroscopic quantum correlations can be revealed only by accurate measurement outcomes and strategies. Here, we formulate feasible entanglement witnesses for bright squeezed vacuum in the form of the macroscopically populated polarization triplet Bell states. Their testing involves efficient photodetection and the measurement of the Stokes operators variances. We also calculate the measures of entanglement for these states such as the Schmidt number and the logarithmic negativity. Our results show that the bright squeezed vacuum degree of polarization entanglement scales as the mean photon number squared. We analyze the applicability of an operational analog of the Schmidt number.