Abstract
High-fidelity polarization-entangled photons are a powerful resource for quantum communication, distributing entanglement and quantum teleportation. Sagnac sources offer intrinsic phase stability, compact footprint and high collection efficiency as no generated photons are discarded. To-date, however, Sagnac sources have failed to reach the Bell-CHSH S parameter values measured with traditional cone sources. Here, we present a Sagnac polarization-entangled source with , over an order of magnitude closer to the Tsirelson bound than previously reported. Our source records 0.995 ± 0.001 concurrence, 0.9974 ± 0.0007 fidelity to an ideal Bell state and is around two orders of magnitude brighter than the highest S parameter cone source. By studying errors in Sagnac sources, we identify that multi-pair generation and the nonlinear crystal position have the greatest impact on the S parameter in our experiment. We provide a clear pathway of improving Sagnac sources that could enable the highest S parameters measured to-date.
© 2020 The Author(s)
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