Intensity correlations from linear interactions

We address the generation of intensity correlations arising from the interference between two optical states interacting through a beam splitter. We consider both phase insensitive and sensitive states and write the intensity correlations as functions of the mean number of photons and field quadratures of the input states. In particular we consider Fock number states and squeezed states as a paradigm of non-classical states and mixture of coherent states, which can be experimentally accessible. We show that, under certain conditions on the input states, intensity correlations may vanish or turn into anti-correlations.