Preparation of single-photon states via cavity-assisted spontaneous parametric down-conversion for quantum memory based on Y7LiF4:Nd3+ crystalDmitrii Akatiev, Ilnur Latypov, Andrey Shkalikov and Alexey KalachevEPJ Web Conf., 161 (2017) 02026DOI: https://doi.org/10.1051/epjconf/201716102026