Correlations in a BEC collision: First-principles quantum dynamics with 150 000 atoms

TL;DR

This paper presents a first-principles quantum simulation of a large Bose-Einstein condensate collision, revealing detailed two-body correlations and phase grain growth, advancing understanding of quantum dynamics in cold atom systems.

Contribution

It introduces a stochastic positive-P method for simulating large-scale BEC collisions from the Hamiltonian, capturing correlations and phase dynamics.

Findings

Two-body correlations between scattered atoms are observed.

Thermal-like correlations for copropagating atoms are identified.

Growth of phase grains correlates with stimulated scattering onset.

Abstract

The quantum dynamics of colliding Bose-Einstein condensates with 150 000 atoms are simulated directly from the Hamiltonian using the stochastic positive-P method. Two-body correlations between the scattered atoms and their velocity distribution are found for experimentally accessible parameters. Hanbury Brown-Twiss or thermal-like correlations are seen for copropagating atoms, while number correlations for counterpropagating atoms are even stronger than thermal correlations at short times. The coherent phase grains grow in size as the collision progresses with the onset of growth coinciding with the beginning of stimulated scattering. The method is versatile and usable for a range of cold atom systems.