Experimental implementation of quantum entanglement and hyperentanglement with a fiber-based two-photon source

We describe the generation of entangled and hyperentlangled photon pairs using a, microstructure-fiber Sagnac interferometer, which is formed by a polarizing beam splitter and a highly nonlinear microstructure fiber twisted by 90 degrees from end to end. This interferometer allows two identical four-wave mixing processes to occur on the same fiber principal axis, ensuring perfect spatial and temporal mode matching of the two four-wave mixing outputs on the polarizing beam splitter to create entanglement over the entire four-wave mixing phase-matching spectral range. with an average pump power of 220 mu W, we measure a two-photon coincidence rate of 1 kHz with AA 0.9 nm. Two-photon interference visibilities exceed 91% for polarization-entangled photon pairs generated from this source, and are > 84% for both time-bin and polarization degrees of freedom for hyperentangled photons, all without subtracting accidental coincidences.