Non-equilibrium quantum dynamics with collisional correlations

We present a fully quantum mechanical treatment of collisional correlations beyond mean-field dynamics. Correlations are handled by an ensemble of mean-field states emerging from a stochastic propagation scheme. This is done by first propagating two-body correlations in time-dependent perturbation theory for a certain time span, reducing the coherently correlated state into an incoherent sum of two-particle-two-hole states, and then sampling this state into an ensemble of mean-field states according to the jump probability obtained from perturbation theory. The scheme is applied to a simple 1D test case calibrated to typical scales of molecules and clusters. Even for the small system size and low dimension, the scheme produces robust results. Occupation numbers and entropy show steady relaxation towards thermal equilibrium.