Displaced photon-number entanglement tests

TL;DR

This paper introduces new entanglement criteria based on displaced photon-number correlations, capable of verifying non-Gaussian entanglement in complex light states even under high losses, using experimentally accessible measurements.

Contribution

It develops a novel method for detecting non-Gaussian entanglement with loss tolerance, employing optimized witnesses and correlation schemes for complex multipartite states.

Findings

Verified entanglement persists despite high losses

Constructed witnesses for various two-mode states

Demonstrated entanglement in a four-mode non-Gaussian state

Abstract

Based on correlations of coherently displaced photon-numbers, we derive entanglement criteria for the purpose to verify non-Gaussian entanglement. Our construction method enables us to verify bipartite and multipartite entanglement of complex states of light. An important advantage of our technique is that the certified entanglement even persists in the presence of arbitrarily high, constant losses. We exploit experimental correlation schemes for the two-mode and multimode scenarios, which allow us to directly measure the desired observables. To detect entanglement of a given state, a genetic algorithm is applied to optimize over the infinite set of our constructed witnesses. In particular, we provide suitable witnesses for several distinct two-mode states. Moreover, a mixed non-Gaussian four-mode state is shown to be entangled in all possible non-trivial partitions.