Spatial entanglement patterns and Einstein-Podolsky-Rosen steering in a Bose-Einstein condensate

TL;DR

This paper demonstrates direct measurement of spatial entanglement and EPR steering in a Bose-Einstein condensate, revealing strong quantum correlations useful for advanced quantum technologies.

Contribution

It provides the first direct measurement of spatially separated entanglement and EPR steering in a BEC using high-resolution imaging, confirming nonclassical correlations beyond collective measurements.

Findings

Observed entanglement strong enough for EPR steering

Measured spin correlations between separated regions

Potential applications in quantum imaging and information

Abstract

Many-particle entanglement is a fundamental concept of quantum physics that still presents conceptual challenges. While spin-squeezed and other nonclassical states of atomic ensembles were used to enhance measurement precision in quantum metrology, the notion of entanglement in these systems remained controversial because the correlations between the indistinguishable atoms were witnessed by collective measurements only. Here we use highresolution imaging to directly measure the spin correlations between spatially separated parts of a spin-squeezed Bose-Einstein condensate. We observe entanglement that is strong enough for Einstein-Podolsky-Rosen steering: we can predict measurement outcomes for non-commuting observables in one spatial region based on a corresponding measurement in another region with an inferred uncertainty product below the Heisenberg relation. This could be exploited for entanglement-enhanced imaging of electromagnetic field distributions and quantum information tasks beyond metrology.