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.
@article{arxiv.1710.09150,
title = {Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network},
author = {Rikizo Ikuta and Toshiki Kobayashi and Tetsuo Kawakami and Shigehito Miki and Masahiro Yabuno and Taro Yamashita and Hirotaka Terai and Masato Koashi and Tetsuya Mukai and Takashi Yamamoto and Nobuyuki Imoto},
journal= {arXiv preprint arXiv:1710.09150},
year = {2018}
}