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

While the GP equation or perturbation theory (e.g. Bogoliubov excitations) can often used to describe the dynamics of macroscopic quantum gases of bosons, experimental situations where these are inaccurate are now common. BEC collisions are an example of this---the scattered atoms can build up sufficient phase-space density (one or more particles per mode) to stimulate coherent scattering out of the condensate into localised 'phase-grains' while remaining dephased from the main condensate and other phase-grains.