Coherence measurements with the two-photon Michelson interferometer

The interference of entangled photon pairs permits the study of the fundamental properties of quantum mechanics. The process is also finding practical applications in optical imaging. The Michelson interferometer provides an elegant means for characterizing the degree of two-photon entanglement, but the technique has not yet been described and analyzed in detail. Here we provide a full description of the interference of collinear down-converted photons in a Michelson interferometer. We explain the basic elements that characterize the interference pattern and complement the theory with experimental measurements. The two-photon Michelson interferometer can be used in quantumoptical coherence tomography for dispersion-free imaging and localization.