A Monte Carlo model for the non-equilibrium coherent kinetics of ensembles of two level systems

We describe a model for the time evolution and loss of coherence in an ensemble of two-level systems. Basically we simulate explicitly the ensemble, and associate to any system its internal state using two selected levels as a basis. Collisions are included by the Test Particle Monte Carlo method, which is based on random sampling of collision events. This method gives a description of the relaxation processes more detailed than the one given by the density matrix.