Photon-photon correlations from a pair of strongly coupled two-level emitters

We investigate two-color photon correlations in the light emitted by two strongly driven, interacting two-level emitters. The are interpreted introducing collective dressed states picture, which allows us to describe both bunching and antibunching based on allowed prohibited transitions. At odds from weakly emitters, strong interaction lifts degeneracy of energy differences between different states, leading a temporal breaking symmetry for correlations: photons frequencies may not be any order. Finally, we show that most virtual processes, involve pairs photons, yield nonclassical when sum their energies fits interaction-induced sidebands spectrum. In particular, depending frequency enough violate Bell inequalities can appear.