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

Abstract

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.

Efficient collisional blockade loading of a single atom into a tight microtrap

“…) being the probability that there is one (zero) atoms in the microtrap as a function of time 5 . The long time steady state probabilities for detecting one (the maximal efficiency of the method) [15,16] and the numerical prediction that p 1 1 = when p 0 2 0 = → and R γ ≫ [20]. We see that in order to obtain a high probability for the microtrap to be occupied by one atom, we must have R γ ≫ and p 2 0 → must be small.…”

In-trap fluorescence detection of atoms in a microscopic dipole trap

“…A similar approach using standard red-detuned cooling light was recently demonstrated for up to ∼ 20 atoms in a larger volume dipole trap [5]. We model the atom loss during imaging with a master equation, in which the time evolution of the probability p N to obtain N atoms in the microtrap is given by [35,36] …”

Inelastic Atom–Atom Collisions in an External Electromagnetic Field: Cooling of Dense Atomic Gases

“…For making quantitative predictions, one has to make certain assumptions about the properties of the potential V inel (q). For simplicity, we consider that V eff in the formula (12) does not depend on q. Then, we can write…”

“…Nevertheless, the problem of obtaining new methods of cooling is still relevant. Though, usually the density of the cold atoms in the current traps is rather low, even in this case, the atom-atom collisions can play an important role [6][7][8][9][10][11][12][13][14]. Within this context, the effects occurring in dense systems of cold atoms exposed to an applied electromagnetic field are particularly interesting.…”