  We develop a framework for solving the action of a three-channel passive
optical interferometer on single-photon pulse inputs to each channel using
SU(3) group-theoretic methods, which can be readily generalized to higher-order
photon-coincidence experiments. We show that features of the coincidence plots
vs relative time delays of photons yield information about permanents,
immanants, and determinants of the interferometer SU(3) matrix.
