  Two-photon intensity correlation of the Hong-Ou-Mandel (HOM) effect has been
intensively studied over the last several decades for one of the most
interesting quantum features. According to the particle nature of quantum
mechanics, indistinguishable photon characteristics interacting on a beam
splitter are the prerequisite of the photon bunching phenomenon. Here, a
coherence approach based on the wave nature of a photon is used to interpret
HOM effect based on entangled photon pairs. As a result, a complete solution of
the HOM effect is derived from the coherence approach for the indistinguishable
photon characteristics in a deterministic way without violation of quantum
mechanics. Thus, HOM effect is now perfectly understood as a relative phase
relation between paired photons in an interferometric system, where the HOM dip
with no interference fringe is due to ensemble decoherence of all interacting
photon pairs.
