Robust nonlocality tests with displacement-based measurements

TL;DR

This paper introduces a robust Bell test scheme using displacement-based measurements with linear optics, demonstrating high loss tolerance and scalability to multiple observers, suitable for current experimental setups.

Contribution

It presents a novel Bell test approach with displacement measurements that is highly tolerant to loss and extendable to multipartite scenarios, advancing practical nonlocality demonstrations.

Findings

Thresholds compatible with current detector efficiencies for entangled squeezed states

Scheme scalable to any number of observers for multipartite nonlocality

Loss thresholds can be lowered with atom-photon entanglement and local filters

Abstract

Lately, much interest has been directed towards designing setups that achieve decisive tests of local realism. Here we present Bell tests with measurements based on linear optical displacements and single-photon detection. The scheme displays good tolerance to loss. In particular, for entangled squeezed states, we find thresholds compatible with current efficiencies of detectors and sources. Furthermore, the scheme is easily extendible to any number of observers, allowing observation of multipartite nonlocality for a single photon shared among multiple modes. We also consider the case of atom-photon entanglement, where the loss threshold can be lowered further, as well as local filters compensating transmission and coupling inefficiencies at the source.