  Two-photon interference is an interesting quantum phenomenon that is usually
captured in two distinct types of experiments, namely the Hanbury-Brown- Twiss
(HBT) experiment and the Hong-Ou-Mandel (HOM) experiment. While the HBT
experiment was carried out much earlier in 1956, with classical light, the
demonstration of the HOM effect came much later in 1987. Unlike the former, the
latter has been argued to be a purely quantum effect. A generalized formulation
of two-particle interference is presented here. The HOM and the HBT effects
emerge as special cases in the general analysis. A realizable two-particle
interference experiment, which is intermediate between the two effects, is
proposed and analyzed. Thus two-particle interference is shown to be a single
phenomenon with various possible implementations, including the HBT and HOM
setups.
