Abstract
We present two-photon interference experiments with polarization-entangled photon pairs in a polarization-based Franson-type interferometer. Although the two photons do not meet at a common beamsplitter, a phase-insensitive Hong-Ou-Mandel type two-photon interference peak and dip fringes are observed, resulting from the two-photon interference effect between two indistinguishable two-photon probability amplitudes leading to a coincidence detection. A spatial quantum beating fringe is also measured for nondegenerate photon pairs in the same interferometer, although the two-photon states have no frequency entanglement. When unentangled polarization-correlated photons are used as an input state, the polarization entanglement is successfully recovered through the interferometer via delayed compensation.
Highlights
The Hong-Ou-Mandel (HOM) interference[1] is a very important two-photon quantum interference phenomenon in modern quantum mechanics and experimental quantum optics[2, 3]
We employ polarization-entangled photon pairs generated via spontaneous parametric down-conversion (SPDC) using type-II noncollinear quasi-phase matching (QPM) in a periodically poled KTiOPO4 (PPKTP) crystal[23]
The HOM fringes are observed through delayed compensation at the Franson-type interferometer despite the fact that two-photon states of which polarization entanglement was degraded are injected into the interferometer
Summary
The Hong-Ou-Mandel (HOM) interference[1] is a very important two-photon quantum interference phenomenon in modern quantum mechanics and experimental quantum optics[2, 3]. Feynman-like path diagrams for the two possible processes at the BS have been used to explain two-photon interference effects, especially for HOM-type experiments[18, 19] This approach can be applied to explicate various quantum interference experiments employing correlated photons and using Mach-Zehnder and Michelson interferometers[20, 21]. HOM-type two-photon interference fringes have only been observed when the two input photons are mixed at a common BS, regardless of whether the two photons meet simultaneously at the BS1, 18, 21. Note that observation of the HOM interference fringe without mixing two photons via a common BS is very important as regards consistent understanding of the various kinds of quantum interference phenomena involving correlated multiphoton states. The HOM fringes are observed through delayed compensation at the Franson-type interferometer despite the fact that two-photon states of which polarization entanglement was degraded are injected into the interferometer
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