Storage and Reemission of Heralded Telecommunication-Wavelength Photons Using a Crystal Waveguide

Telecom-wavelength single photons are the leading carriers of quantum information for practical photonic quantum technologies, and there has been significant progress in developing compatible components like detectors and single-photon sources. However, an on-chip, broadband quantum memory for storage and reemission of single telecom photons---indispensable for future quantum repeaters---has been lacking. The authors demonstrate a light-matter interface for quantum storage of 1532-nm photons: a cryogenically cooled lithium niobate crystal waveguide. The memory hinges on a broadband atomic frequency comb created by persistent spectral hole burning through long-lived superhyperfine levels.