Enhanced and Reduced Atom Number Fluctuations in a BEC Splitter

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K. Maussang, G. E. Marti, T. Schneider, P. Treutlein, Yun Li, A. Sinatra, R. Long, J. Esteve, and J. Reichel
Phys. Rev. Lett. 105, 080403 (2010)

We measure atom number statistics after splitting a gas of ultracold 87Rb atoms in a purely magnetic double-well potential created on an atom chip. Well below the critical temperature for Bose-Einstein condensation Tc, we observe reduced fluctuations down to -4.9  dB below the atom shot noise level. Fluctuations rise to more than +3.8  dB close to Tc, before reaching the shot noise level for higher temperatures. We use two-mode and classical field simulations to model these results. This allows us to confirm that the supershot noise fluctuations directly originate from quantum statistics.