Resolution of the mystery of counter-intuitive photon correlations in far off-resonance emission from a quantum dot-cavity system

Cavity quantum-electrodynamics experiments using an atom coupled to a single radiation-field mode have played a central role in testing foundations of quantum mechanics, thus motivating solid-state implementations using single quantum dots coupled to monolithic nano-cavities. In stark contrast to their atom based counterparts, the latter experiments revealed strong cavity emission, even when the quantum dot is far off resonance. Here we present experimental and theoretical results demonstrating that this effect arises from the mesoscopic nature of quantum dot confinement, ensuring the presence of a quasi-continuum of transitions between excited quantum dot states that are enhanced by the cavity mode. Our model fully explains photon correlation measurements demonstrating that photons emitted at the cavity frequency are essentially uncorrelated with each other even though they are generated by a single quantum dot.