Advantages of the frequency-conversion technique in quantum interference

Abstract

Hong-Ou-Mandel (HOM) interference is a key phenomenon for understanding quantum interference and a basic tool for quantum information and metrological applications. By introducing the nonlinear frequency-conversion (NFC) technique into HOM interferometers, more phenomena could be found and more functions could be developed. Here, tunable quantum spatial beating is observed in a HOM interferometer based on the postfilter scheme, where two NFC modules function as tunable band-pass filters. Degenerate IR photon pairs at 1079.00 nm are generated based on the noncritical phase-matching spontaneous parametric down-conversion process and are up-converted to the visible band around 633.40 nm by the NFC modules before the detectors. We show that in addition to the filtering effect, the NFC can also improve the photon detection efficiency based on silicon avalanched detector, increasing the coherence length, and therefore improving the heralding efficiency and visibility. Our results demonstrate the advantages of the NFC technique in HOM interference, which could also be generalized to other quantum interference.