Accidental Coincidence Counts Observed in Mandel Dip Measurement Using Independently Produced Photon Pairs at 1550 nm

摘要

Mandel dip measurement was performed at 1550nm using photon pairs created via spontaneous parametric down conversion in two separately located periodically poled lithium niobate waveguides. A visibility of 77.6% was obtained in fourfold coincidence counting. We experimentally clarified that the simultaneous generation of three pairs (one pair created in one waveguide and two pairs created in another waveguide) is the main source of accidental coincidence counts. Propagation loss before mixing two photons at a beamsplitter for observing photon bunching plays an important role in the determination of visibility. A large loss improves visibility, but also reduces the number of fourfold coincidence counts.