Large violation of Bell inequalities using both particle and wave measurements

TL;DR

This paper demonstrates a straightforward method to achieve large violations of Bell inequalities using both particle and wave measurements, overcoming previous experimental challenges and enabling nonlocality tests with feasible states.

Contribution

It introduces a simple scheme combining photon counting and homodyne detection to generate significant Bell violations with practical states and measurements.

Findings

Achieves large Bell inequality violations with feasible states.

Uses both photon counting and homodyne measurements effectively.

Enables nonlocality tests with Gaussian states like two-mode squeezed states.

Abstract

When separated measurements on entangled quantum systems are performed, the theory predicts correlations that cannot be explained by any classical mechanism: communication is excluded because the signal should travel faster than light; pre-established agreement is excluded because Bell inequalities are violated. All optical demonstrations of such violations have involved discrete degrees of freedom and are plagued by the detection-efficiency loophole. A promising alternative is to use continuous variables combined with highly efficient homodyne measurements. However, all the schemes proposed so far use states or measurements that are extremely difficult to achieve, or produce very weak violations. We present a simple method to generate large violations for feasible states using both photon counting and homodyne detections. The present scheme can also be used to obtain nonlocality from easy-to-prepare Gaussian states (e.g. two-mode squeezed state).