Bell correlations in a Bose-Einstein condensate

Roman Schmied; Jean-Daniel Bancal; Baptiste Allard; Matteo Fadel; Valerio Scarani; Philipp Treutlein; Nicolas Sangouard

doi:10.1126/science.aad8665

Bell correlations in a Bose-Einstein condensate

Science. 2016 Apr 22;352(6284):441-4. doi: 10.1126/science.aad8665.

Authors

Roman Schmied¹, Jean-Daniel Bancal², Baptiste Allard¹, Matteo Fadel¹, Valerio Scarani³, Philipp Treutlein⁴, Nicolas Sangouard⁵

Affiliations

¹ Quantum Atom Optics Laboratory, Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
² Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543. Quantum Optics Theory Group, Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
³ Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543. Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542.
⁴ Quantum Atom Optics Laboratory, Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland. philipp.treutlein@unibas.ch nicolas.sangouard@unibas.ch.
⁵ Quantum Optics Theory Group, Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland. philipp.treutlein@unibas.ch nicolas.sangouard@unibas.ch.

PMID: 27102479
DOI: 10.1126/science.aad8665

Abstract

Characterizing many-body systems through the quantum correlations between their constituent particles is a major goal of quantum physics. Although entanglement is routinely observed in many systems, we report here the detection of stronger correlations--Bell correlations--between the spins of about 480 atoms in a Bose-Einstein condensate. We derive a Bell correlation witness from a many-particle Bell inequality involving only one- and two-body correlation functions. Our measurement on a spin-squeezed state exceeds the threshold for Bell correlations by 3.8 standard deviations. Our work shows that the strongest possible nonclassical correlations are experimentally accessible in many-body systems and that they can be revealed by collective measurements.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.