Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network
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Abstract
Long-lifetime quantum storages accessible to the telecom photonic infrastructure are essential to long-distance quantum communication. Atomic quantum storages have achieved subsecond storage time corresponding to 1000 km transmission time for a telecom photon through a quantum repeater algorithm. However, the telecom photon cannot be directly interfaced to typical atomic storages. Solid-state quantum frequency conversions fill this wavelength gap. Here we report on the experimental demonstration of a polarization-insensitive solid-state quantum frequency conversion to a telecom photon from a short-wavelength photon entangled with an atomic ensemble. Atom–photon entanglement has been generated with a Rb atomic ensemble and the photon has been translated to telecom range while retaining the entanglement by our nonlinear-crystal-based frequency converter in a Sagnac interferometer. Quantum repeater-based communication requires the ability to interface good quantum memories to telecom photons. Here, the authors report polarization-insensitive frequency conversion to telecom wavelength of a photon entangled with a Rb ensemble, preserving the entanglement in the process.