Towards spontaneous parametric down-conversion at low temperatures Dmitrii Akatiev, Kirill Boldyrev, Nikolai Kuzmin, Ilnur Latypov, Marina Popova, Andrey Shkalikov and Alexey Kalachev EPJ Web Conf., 161 (2017) 02002 Published online: 31 October 2017 DOI: 10.1051/epjconf/201716102002