Two-photon interference in optical fiber multiports

Abstract

We report the measurement of nonclassical photon statistics at the outputs of 2\ifmmode\times\else\texttimes\fi{}2 and 3\ifmmode\times\else\texttimes\fi{}3 fiber couplers resulting from quantum-mechanical second-order interference of entangled photon pairs from a parametric down-conversion source. This is a demonstration of the bunching of bosons at the outputs of fiber multiports. Single-mode fibers provide precise wavelength selection from the down-conversion source spectrum, thus yielding very long coherence times and good collection efficiency without the need of interference filters. Two-photon interference visibilities close to the theoretical maximum were achieved in the experiments. \textcopyright{} 1996 The American Physical Society.