Atomic four-wave mixing via condensate collisions

We perform a theoretical analysis of atomic four-wave mixing via a collision of two Bose-Einstein condensates of metastable helium atoms. The analysis is based on first-principles quantum simulations using the positive P-representation method and is aimed at modeling recent experiments at Orsay [2]. Using the actual experimental parameters, we calculate atom-atom pair correlations within the s-wave scattering halo produced spontaneously during the collision (see Fig. 1). Our results for the strength and the width of the correlation signal are consistent with the experimental observations. We also analyze relative atom number squeezing and the violation of the classical Causchy-Schwartz inequality.