Reliable Entanglement Detection Under Coarse--Grained Measurements

TL;DR

This paper develops entanglement witnesses that are reliable under coarse-grained measurements in continuous variable systems, outperforming variance-based methods and ensuring no false positives, with practical applications to photon pair experiments.

Contribution

It introduces entanglement witnesses based on Shannon entropy that are robust against measurement coarse graining, improving reliability over traditional variance-based methods.

Findings

Entropy-based witnesses outperform variance-based ones in coarse measurements

Witnesses guarantee no false positives for entanglement detection

Application demonstrated in spatial entanglement of photon pairs

Abstract

We derive reliable entanglement witnesses for coarse--grained measurements on continuous variable systems. These witnesses never return a "false positive" for identification of entanglement, under any degree of coarse graining. We show that, even in the case of Gaussian states, entanglement witnesses based on the Shannon entropy can outperform those based on variances. We apply our results to experimental identification of spatial entanglement of photon pairs.