Tradeoffs for number-squeezing in collisions of Bose-Einstein condensates

TL;DR

This paper examines how factors like non-monochromaticity and density affect number squeezing in Bose-Einstein condensate collisions, providing models to optimize entangled atomic pair sources.

Contribution

It introduces a simple model linking density correlations to number squeezing and analyzes the impact of multi-mode scattering and Bose enhancement on squeezing robustness.

Findings

Non-monochromaticity limits number squeezing.

Squeezing is less robust at higher pair densities.

Optimal squeezing occurs with atoms scattered into two separated regions.

Abstract

We investigate the factors that influence the usefulness of supersonic collisions of Bose-Einstein condensates as a potential source of entangled atomic pairs by analyzing the reduction of the number difference fluctuations between regions of opposite momenta. We show that non-monochromaticity of the mother clouds is typically the leading limitation on number squeezing, and that the squeezing becomes less robust to this effect as the density of pairs grows. We develop a simple model that explains the relationship between density correlations and the number squeezing, allows one to estimate the squeezing from properties of the correlation peaks, and shows how the multi-mode nature of the scattering must be taken into account to understand the behavior of the pairing. We analyze the impact of the Bose enhancement on the number squeezing, by introducing a simplified low-gain model. We conclude that as far as squeezing is concerned the preferable configuration occurs when atoms are scattered not uniformly but rather into two well separated regions.