High-performance source of indistinguishable polarization-entangled photons with a local oscillator reference for quantum networking

Optical quantum networking protocols impose stringent requirements on the states produced by sources of entanglement. We demonstrate a free-space, compact, source of indistinguishable pairs of polarization entangled photons, with an integrated local oscillator reference as a significant step towards this goal. This source achieves (99.11 ± 0.01)% polarization entanglement visibility, (96.3±0.6)% successive-photon Hong-Ou-Mandel interference visibility, (68.0±0.1) % heralded efficiency as detected, and (88.6 ± 0.2)% interference visibility with a local oscillator. This simultaneous achievement of state-of-the-art metrics demonstrates an adaptable platform for quantum networking.