We report a coherence-preserving photon frequency down-conversion experiment based on difference-frequency generation in a periodically poled Lithium niobate waveguide, at the single-photon level. The coherence of the process has been demonstrated by measuring the phase coherence of pseudo single-photon time-bin qubits after frequency conversion with an interference visibility of > 96 %. This interface could be of interest for quantum repeater based hybrid networks.
@article{arxiv.1006.4585,
title = {Coherent frequency-down-conversion interface for quantum repeaters},
author = {Noé Curtz and Rob Thew and Christoph Simon and Nicolas Gisin and Hugo Zbinden},
journal= {arXiv preprint arXiv:1006.4585},
year = {2015}
}