Quantum frequency down-conversion of single photons at 1552 nm from single InAs quantum dot

Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single InAs quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate (PPLN) waveguide and a 1.95 μm pump laser, and the frequency conversion efficiency is~40%. The single-photon purity of quantum dot emission is preserved during the down-conversion process, i.e., g⁽²⁾(0), only 0.22 at 1552 nm. This present technique advances the Ⅲ-V semiconductor quantum dots as a promising platform for long-distance quantum communication.