Philipp Treutlein

Non-locality in a Bose-Einstein condensate   

Roman Schmied¹, Jean-Daniel Bancal², Baptiste Allard¹, Matteo Fadel¹, Philipp Treutlein¹, and Nicolas Sangouard¹

¹ Department of Physics, University of Basel, Switzerland,
² Centre for Quantum Technologies, National University of Singapore   

The results of measurements performed on several quantum systems can exhibit correlations with no classical explanation. These so-called non-local correlations are revealed through the violation of a Bell inequality and form a resource for quantum communication and certified quantum randomness generation. While non-locality has been demonstrated in few-particle systems, the role of non-locality in many-body quantum systems is much less understood. It has recently been proposed that in a many-body system, non-locality can be revealed by single- and two-particle correlations only [1]. Based on this, we present a technique for detecting non-locality in spin-squeezed states of a two-component Bose-Einstein condensate [2]. Measurements of first and second moments of the collective atomic spin along several axes allow us to determine a witness criterion for non-locality in this many-body system. We report on the status of an experiment to detect non-locality using this technique.

[1] J. Tura, R. Augusiak, A.B. Sainz, T. Vértesi, M. Lewenstein, A. Acín, Science 344, 1256 (2014)
[2] M.F. Riedel, P. Böhi, Y. Li, T.W. Hänsch, A. Sinatra, P. Treutlein, Nature 464, 1170 (2010)