Extended Data Fig. 3: Hardware of follow-up optics at the Xinglong ground station.
From: An integrated space-to-ground quantum communication network over 4,600 kilometres
a, The upgraded receiving optics at the Xinglong ground station. b, c, The two major changes were the beam expander (b) and the BB84 module (c). A beam expander with lower magnification is used to increase the field of view. The BB84 module is modified to match the larger size of the incident light beam. A beam splitter with a bias of 10:90 (50:50) for the X–Z basis in the BB84 module is used in Nanshan (Xionglong).
