  The Micius satellite is the pioneering initiative to demonstrate quantum
teleportation, entanglement distribution, quantum key distribution (QKD), and
quantum-secured communications experiments at the global scale. In this work,
we report on the results of the 600-mm-aperture ground station design which has
enabled the establishment of a quantum-secured link between the Zvenigorod and
Nanshan ground stations using the Micius satellite. As a result of a quantum
communications session, an overall sifted key of 2.5 Mbits and a total final
key length of 310 kbits have been obtained. We present an extension of the
security analysis of the realization of satellite-based QKD decoy-state
protocol by taking into account the effect of the detection-efficiency mismatch
for four detectors. We also simulate the QKD protocol for the satellite passage
and by that validate our semi-empirical model for a realistic receiver, which
is in good agreement with the experimental data. Our results pave the way to
the considerations of realistic imperfection of the QKD systems, which are
important in the context of their practical security.
