Generalized Two-Particle Interference

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. First, a duality relation, between the particle distinguishability and the visibility of two-particle interference, is derived. The distinguishability of the two particles, arising from some internal degree of freedom, puts a bound on the sharpness of the two-particle interference they can produce, in a HOM or HBT kind of experiment. This points to a common origin of both the experiments which are generally considered distinct. Then a generalized formulation of two-particle interference is presented. The HOM and the HBT effects emerge as special cases in the general analysis. A 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.