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

• Published in: Nature communications Vol. 9; no. 1; pp. 1997 - 8
• Main Authors: Ikuta, Rikizo, Kobayashi, Toshiki, Kawakami, Tetsuo, Miki, Shigehito, Yabuno, Masahiro, Yamashita, Taro, Terai, Hirotaka, Koashi, Masato, Mukai, Tetsuya, Yamamoto, Takashi, Imoto, Nobuyuki
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 21.05.2018; Nature Publishing Group UK; Nature Portfolio
• Subjects: Atoms & subatomic particles; Conversion; Entanglement; Frequency converters; Lasers; Light; Photonics; Polarization; Solid state; Telecommunications; Wavelength
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-04338-x

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.