For advanced quantum information technology, sources of photon pairs in quantum mechanically factorable states are of great importance for realizing high-fidelity photon-photon quantum gate operations. Here we experimentally demonstrate a technique to produce spectrally factorable photon pairs utilizing multi-order quasi-phase-matching (QPM) conditions in spontaneous parametric downconversion (SPDC). In our scheme, a spatial nonlinearity profile of a nonlinear optical crystal is shaped with current standard poling techniques, and the associated phase-matching function can be approximated to a Gaussian form. By the measurement of a phase-matching function and the second-order autocorrelation function, we demonstrate that telecom-band photon pairs produced by our custom-poled crystal are highly factorable with > 95% single-photon purity.
@article{arxiv.2111.10981,
title = {Generation of spectrally factorable photon pairs via multi-order quasi-phase-matched spontaneous parametric downconversion},
author = {Fumihiro Kaneda and Jo Oikawa and Masahiro Yabuno and Fumihiro China and Shigehito Miki and Hirotaka Terai and Yasuyoshi Mitsumori and Keiichi Edamatsu},
journal= {arXiv preprint arXiv:2111.10981},
year = {2021}
}