Title: Spatially distributed multipartite entanglement enables Einstein-Podolsky-Rosen steering of atomic clouds,
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.