Spatially distributed multipartite entanglement enables Einstein-Podolsky-Rosen steering of atomic clouds

TL;DR

This paper demonstrates how spin mixing in a Bose-Einstein condensate can generate local entanglement that is then spatially distributed, enabling Einstein-Podolsky-Rosen steering and multipartite entanglement detection in atomic clouds.

Contribution

It introduces a method to generate and detect spatially distributed entanglement and EPR steering in ultracold atomic systems, advancing quantum communication capabilities.

Findings

Successfully generated local entanglement via spin mixing.

Distributed entanglement through cloud expansion.

Detected genuine five-partite entanglement.

Abstract

A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. Yet, the robust generation and detection of nonlocal entanglement between spatially separated regions of an ultracold atomic system remains a challenge. Here, we use spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this local entanglement can be spatially distributed by self-similar expansion of the atomic cloud. Spatially resolved spin read-out is used to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen steering between distinct parts of the expanded cloud. Based on the strength of Einstein-Podolsky-Rosen steering we construct a witness, which testifies up to genuine five-partite entanglement.