Bell's experiment with intra- and inter-pair entanglement: Single-particle mode entanglement as a case study

TL;DR

This paper explores Bell-inequality experiments involving entangled pairs from many-body systems with intra- and inter-pair entanglement, revealing probabilistic violations that differ from traditional independent-pair scenarios.

Contribution

It introduces a theoretical framework for Bell tests with entangled pairs from many-body systems, highlighting novel probabilistic violation phenomena.

Findings

Bell violations can be probabilistic rather than deterministic.

Finite fractions of runs show violation even when averages do not.

Intra- and inter-pair entanglement affect Bell test outcomes.

Abstract

Theoretical considerations of Bell-inequality experiments usually assume identically prepared and independent pairs of particles. Here we consider pairs that exhibit both intra- and inter-pair entanglement. The pairs are taken from a large many-body system where all the pairs are generally entangled with each other. Using an explicit example based on single mode entanglement and an ancillary Bose-Einstein condensate, we show that the Bell-inequality violation in such systems can display statistical properties that are remarkably different from those obtained using identically prepared, independent pairs. In particular, one can have probabilistic violation of Bell's inequalities in which a finite fraction of all the runs result in violation, even though there could be no violation when averaging over all the runs. Whether or not a particular run of results will end up being local realistically explainable is "decided" by a sequence of quantum (random) outcomes.