Coupling of a quantum memory and telecommunication wavelength photons for high-rate entanglement distribution in quantum repeaters

    Kyoko Mannami, Takeshi Kondo, Tomoki Tsuno, Takuto Miyashita, Daisuke Yoshida, Ko Ito, Kazuya Niizeki, Ippei Nakamura, Feng-Lei Hong, and Tomoyuki Horikiri

    Optics Express, 29, 41522-41533 (2021).

    • Memory

    • Interface

    Quantum repeaters are indispensable tools for long-distance quantum communication. However, frequency matching between entangled photon sources and remote quantum memories (QMs) is difficult, which is an obstacle to the implementation of quantum repeaters. In this paper, we demonstrate a method to achieve the coupling of a Pr:YSO as a fixed-time QM with a single telecommunication-wavelength photon through frequency stabilization using an optical frequency comb over all applied laser wavelengths. The demonstrated method can lead to the implementation of a quantum repeater scheme enabling an improvement of the entanglement generation rate, paving the way for long-distance quantum communication.

    Offset-locking-based frequency stabilization of external cavity diode lasers for long-distance quantum communication

    Takuto Miyashita, Takeshi Kondo, Kohei Ikeda, Kazumichi Yoshii, Feng-Lei Hong and Tomoyuki Horikiri

    Japanese Journal of Applied Physics, 60, 122001 (2021).

    • Interface

    Quantum repeaters are required for long-distance quantum communication. For efficient coupling of quantum entangled photon sources with narrow-linewidth quantum memories, we performed the frequency stabilization of two lasers at 1514 and 1010 nm. The 1514 nm pump laser of the entangled photon source exhibited a frequency stability of  3.6 × 10–12(τ = 1 s).The 1010 nm pump laser of the wavelength conversion system exhibited a frequency stability of 3.4 × 10–12(τ = 1 s).The stabilities of both lasers were approximately two orders of magnitude smaller than the frequency width of 4 MHz of the Pr:YSO quantum memory. Such frequency-stabilized lasers can realize the remote coupling of a quantum memory and an entangled photon source in quantum repeaters.