Bell inequalities for nonlocality depth

TL;DR

This paper classifies Bell inequalities for multi-particle systems to detect nonlocality depth and entanglement, providing device-independent witnesses and generalizations of Svetlichny inequalities using cone-projection techniques.

Contribution

It offers an exhaustive classification of Bell inequalities for hybrid models in multi-particle systems and introduces new inequalities for detecting nonlocality depth.

Findings

Classified Bell inequalities for four- and five-particle systems.

Constructed inequalities for nonlocality depth of (n-1) in n-particle systems.

Generalized Svetlichny inequalities for hybrid models.

Abstract

When three or more particles are considered, quantum correlations can be stronger than the correlations generated by so-called hybrid local hidden variable models, where some of the particles are considered as a single block inside which communication and signaling is allowed. We provide an exhaustive classification of Bell inequalities to characterize various hybrid scenarios in four- and five-particle systems. In quantum mechanics, these inequalities provide device-independent witnesses for the entanglement depth. In addition, we construct a family of inequalities to detect a non-locality depth of (n-1) in n-particle systems. Moreover, we present two generalizations of the original Svetlichny inequality, which was the first Bell inequality designed for hybrid models. Our results are based on the cone-projection technique, which can be used to completely characterize Bell inequalities under affine constraints; even for many parties, measurements, and outcomes.