Few photon scattering on Bose-Hubbard lattices

We theoretically investigate the scattering of few photon light on Bose-Hubbard lattices using diagrammatic scattering theory. We explicitly derive general analytical expressions for the lowest order photonic correlation functions, which we apply numerically to several different lattices. We focus specifically on non-linear effects visible in the intensity-intensity correlation function and explain bunching and anti-bunching effects in dimers, chains, rings and planes. The numerical implementation can be applied to arbitrary Bose-Hubbard graphs, and we provide it as an attachment to this publication.