High-fidelity conversion of photonic quantum information to telecommunication wavelength with superconducting single-photon detectors

Abstract

We experimentally demonstrate a high-fidelity visible-to-telecommunication wavelength conversion of a photon by using a solid-state-based difference frequency generation. In the experiment, one half of a picosecond visible entangled photon pair at 780 nm is converted to a 1522-nm photon, resulting in the entangled photon pair between 780 and 1522 nm. Using superconducting single-photon detectors with low dark count rates and small timing jitters, we selectively observed well-defined temporal modes containing the two photons. We achieved a fidelity of $0.93\ifmmode\pm\else\textpm\fi{}0.04$ after the wavelength conversion, indicating that our solid-state-based scheme can be used for faithful frequency down conversion of visible photons emitted from quantum memories composed of various media.