Sub-Poissonian atom-number fluctuations using light-assisted collisions
Résumé
We investigate experimentally the number statistics of a mesoscopic ensemble of cold atoms in a microscopic
dipole trap loaded from a magneto-optical trap and find that the atom-number fluctuations are reduced with respect
to a Poisson distribution due to light-assisted two-body collisions. For numbers of atoms N 2, we measure a
reduction factor (Fano factor) of 0.72 ± 0.07, which differs from 1 by more than four standard deviations. We
analyze this fact by a general stochastic model describing the competition between the loading of the trap from a
reservoir of cold atoms and multiatom losses, leading to a master equation. Applied to our experimental regime,
this model indicates an asymptotic value of 3/4 for the Fano factor at large N and in the steady state. We thus
show that we have reached the ultimate level of reduction in number fluctuations in our system.
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PRA85p035403a2012.pdf (200.37 Ko)
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1111.5203.pdf (189.39 Ko)
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