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It is verified experimentally that the transmissivity of a Michelson interferometer for pairs of coherent photons is the square of the single-photon transmissivity. This behaviour is connected with an enhancement of interferometer finesse and resolution and can be understood as a consequence of quantum-mechanical interference between the multiple ways the photon pair can traverse the interferometer. A modification of the experiment is suggested which allows to study different types of two-photon multiple-beam interferences.
Möhler et al. (Wed,) studied this question.