Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network

TL;DR

This paper demonstrates a polarization-insensitive solid-state quantum frequency converter that translates entangled photons from atomic ensembles to telecom wavelengths, enabling long-distance quantum communication.

Contribution

It introduces a novel polarization-insensitive frequency conversion technique that preserves atom-photon entanglement during wavelength translation.

Findings

Successful telecom-range photon conversion from atomic entanglement

Retention of entanglement after frequency conversion

Implementation of a nonlinear crystal-based Sagnac interferometer

Abstract

Quantum network with a current telecom photonic infrastructure is deficient in quantum storages that keep arbitrary quantum state in sufficient time duration for a long-distance quantum communication with quantum repeater algorithms. 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 is not directly accessible to typical atomic storages. Solid state quantum frequency conversions fill this wavelength gap and add more abilities, for example, a frequency multiplex. 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.