Kinetics of quantum fluctuations in polariton Bose Einstein condensation

We develop a model of the collective excitation kinetics in the non-equilibrium polariton condensation. The model accounts for mutual interaction and for energy relaxation processes and predicts the effect of quantum fluctuations. In realistic situations with incoherent optical excitation, we find a significant depletion of the condensate caused by long-wavelength fluctuations. As a consequence, the spatial correlation function displays a partially suppressed long-range order.