Testing for Multipartite Quantum Nonlocality Using Functional Bell Inequalities

TL;DR

This paper introduces optimized functional Bell inequalities for continuous variables, enabling more robust tests of quantum nonlocality that are resistant to noise and decoherence, potentially facilitating loophole-free Bell experiments.

Contribution

It develops a method to optimize functional Bell inequalities for continuous variables, enhancing robustness against noise and decoherence compared to previous approaches.

Findings

Optimized functional inequalities show stronger violations of local causality.

The inequalities are resistant to standard decoherence effects.

Potential for loophole-free Bell tests with efficient detection methods.

Abstract

We show that arbitrary functions of continuous variables, e.g. position and momentum, can be used to generate tests that distinguish quantum theory from local hidden variable theories. By optimising these functions, we obtain more robust violations of local causality than obtained previously. We analytically calculate the optimal function and include the effect of nonideal detectors and noise, revealing that optimized functional inequalities are resistant to standard forms of decoherence. These inequalities could allow a loophole-free Bell test with efficient homodyne detection.