  Recently the possibility of generating nonclassical polariton states by means
of parametric scattering has been demonstrated. Excitonic polaritons propagate
in a complex interacting environment and contain real electronic excitations
subject to scattering events and noise affecting quantum coherence and
entanglement. Here we present a general theoretical framework for the realistic
investigation of polariton quantum correlations in the presence of coherent and
incoherent interaction processes. The proposed theoretical approach is based on
the {\em nonequilibrium quantum Langevin approach for open systems} applied to
interacting-electron complexes described within the dynamics controlled
truncation scheme. It provides an easy recipe to calculate multi-time
correlation functions which are key-quantities in quantum optics. As a first
application, we analyze the build-up of polariton parametric emission in
semiconductor microcavities including the influence of noise originating from
phonon induced scattering.
