Photoluminescence asymmetry with quantum state preparation

We show that the number of photons in a strongly coupled exciton-photon system is asymmetric with the detuning of the modes when, in the spontaneous emission regime, the two modes are entangled. As changing the detuning is easy in semiconductor microcavities-where on the other hand the nature of the strong-coupling in terms of single-particle effects is not yet resolved-we propose this effect as a test of the quantum character of microcavity polaritons.