Einstein-Podolsky-Rosen steering in a Bose-Einstein condensate and novel fiber-lasers system for rubidium cold atoms experiments.

Simone Pengue, Matteo Fadel, Tilman Zibold, Boris Décamps, and Philipp Treutlein
Department of Physics, University of Basel, Switzerland

We investigate the spatial entanglement in a spin squeezed Bose-Einstein condensate of rubidium atoms. By letting the atomic cloud expand and using high resolution absorption imaging we are able to access the spatial spin distribution of the many-body state. The observed spin correlations between different regions go beyond classical correlations and reveal spatial non-separability. Furthermore they allow for EPR steering of a subregion of the atomic spin. By inferring measurement outcomes of non-commuting observables in one region based on measurements in a separate region we are able to seemingly beat the Heisenberg uncertainty relation, realizing the EPR paradox with an atomic system.

We also present the current technical advances to improve our experimental setup. Specifically, we characterize a commercial laser system which would replace large part of our current optical setup. The device consists of several fiber-lasers at telecom wavelength (1560 nm) which are frequency stabilized to each other. The system integrates both frequency and intensity control of the lasers and the doubled outputs can be readily used as resonant sources for a cold atom experiment of 87Rb.