We experimentally demonstrated the Hong-Ou-Mandel (HOM) interference between two photons after visible-to-telecommunication wavelength conversion. In the experiment, we prepared a heralded single photon by using spontaneous parametric down-conversion and the other photon from a weak laser source at 780 nm. We converted the wavelength of both photons to the telecommunication wavelength of 1522 nm by using difference-frequency generation in a periodically-poled lithium niobate, and then observed the HOM interference between the photons. The observed visibility is 0.76±0.12 which clearly shows the non-classical interference of the two photons. The high-visibility interference is an important step for fiber-based quantum communications of photons generated from visible photon emitters.
@article{arxiv.1304.0304,
title = {Non-classical two-photon interference between independent telecom light pulses converted by difference-frequency generation},
author = {Rikizo Ikuta and Toshiki Kobayashi and Hiroshi Kato and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},
journal= {arXiv preprint arXiv:1304.0304},
year = {2013}
}