Photon Coalescence in a Lossy Non-Hermitian Beam Splitter

We investigate photon coalescence in a lossy non-Hermitian system and study a dynamic device modeled by a beam splitter with an extra intrinsic phase term added in the transformation matrix, with which the device is a lossy non-Hermitian linear system. The two-photon interference behavior is altered accordingly since this extra intrinsic phase affects the unitary of transformation and the coalescence of the incoming photons. We calculate the coincidence between two single-photon pulses, considering the interferometric phase between two pulses and the extra intrinsic phase as the tunable parameters. The extra phase turns the famous Hong–Ou–Mandel dip into a bump, with the visibility dependent on both the interferometric phase and the extra phase.