Multiboson correlation interferometry with multimode thermal sources

We develop a general description of multiboson interferometry based on correlated measurements in arbitrary passive linear interferometers for multimode thermal sources with arbitrary spectral distributions. The multiorder correlation functions describing the multiboson detection probability rates can be expressed in terms of permanents of positive semidefinite matrices, depending on the interferometer evolution, the spectral distribution of the sources, and the times when the correlated measurements occur. The permanent structure of these multiorder probability rates is a manifestation of the underlying physics of multiboson interference and yields an interesting connection with the so-called boson sampling problem.