Hannover 2016 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 33: Quantum Effects: Entanglement and Decoherence I
Q 33.5: Talk
Wednesday, March 2, 2016, 12:00–12:15, f442
Detection of Bell correlations in a spin-squeezed Bose-Einstein condensate — •Matteo Fadel1, Roman Schmied1, Jean-Daniel Bancal1, Baptiste Allard1, Valerio Scarani2, Philipp Treutlein1, and Nicolas Sangouard1 — 1University of Basel, Switzerland — 2National University of Singapore, Singapore
The results of measurements by different observers can show correlations that are stronger than any classical theory allows. These Bell correlations can be confirmed by violating a Bell inequality, for which quantum entanglement is not sufficient.
A family of Bell inequalities has recently been proposed that requires only single- and two-particle measurements even for many-body systems [1]. Based on this work, we present the first experimental observation of Bell correlations in squeezed states of a two-mode Bose-Einstein condensate (BEC).
The system consists of a two-component 87Rb BEC of a few hundred atoms created on an atom-chip [2]. A state-selective potential gives rise to nonlinear one-axis twisting dynamics, which we use to prepare spin-squeezed states of the condensate, with up to 7dB of squeezing according to the Wineland criterion.
We measure the first and second moments of the collective spin operator along several axes. These measurement results demonstrate the presence of Bell correlations in our system by more than three standard deviations [3].
[1]J. Tura, et. al. Science 344, 1256 (2014) [2]M.F. Riedel, et. al. Nature 464, 1170 (2010) [3]R. Schmied, et. al. submitted (2015)