Sub-Poissonian atom-number fluctuations using light-assisted collisions

Yvan R. P. Sortais (1) , A. Fuhrmanek (1) , R. Bourgain (1) , Antoine Browaeys (1)

1 Laboratoire Charles Fabry / Optique Quantique

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.

Domaines: Gaz Quantiques [cond-mat.quant-gas]; Physique Atomique [physics.atom-ph]; Physique Quantique [quant-ph]

Yvan R. P. Sortais, A. Fuhrmanek, R. Bourgain, Antoine Browaeys. Sub-Poissonian atom-number fluctuations using light-assisted collisions. Physical Review Online Archive (PROLA), 2012, 85, pp.035406. ⟨10.1103/PhysRevA.85.035403⟩. ⟨hal-00685861⟩