Refined Tsirelson Bounds on Multipartite Bell Inequalities

TL;DR

This paper derives refined quantum bounds for multipartite Bell inequalities, specifically Svetlichny and Mermin-Klyshko inequalities, which depend on subsystem correlations and are tighter than previous bounds, aiding in quantum correlation characterization.

Contribution

The work introduces new Tsirelson bounds for multipartite Bell inequalities that depend on subsystem correlations, providing tighter constraints than existing bounds.

Findings

Refined Tsirelson bounds depend on local and bipartite correlations.

Bounds are strictly tighter than known bounds in specific examples.

Analysis enhances understanding of multipartite quantum correlations.

Abstract

Despite their importance, there is an on-going challenge characterizing multipartite quantum correlations. The Svetlichny and Mermin-Klyshko (MK) inequalities present constraints on correlations in multipartite systems, a violation of which allows to classify the correlations by using the non-separability property. In this work we present refined Tsirelson (quantum) bounds on these inequalities, derived from inequalities stemming from a fundamental constraint, tightly akin to quantum uncertainty. Unlike the original, known inequalities, our bounds do not consist of a single constant point but rather depend on correlations in specific subsystems (being local correlations for our bounds on the Svetlichny operators and bipartite correlations for our bounds on the MK operators). We analyze concrete examples in which our bounds are strictly tighter than the known bounds.