Simulation of satellite and optical link dynamics in a quantum repeater constellation

Abstract

Quantum repeaters and satellite-based free-space optical links are complementary technological approaches slated to overcome the exponential photon loss occurring in optical fibers and thus allow quantum communication at global scales. We analyze architectures where these approaches are combined and satellites are used as quantum repeater nodes to distribute entanglement to far-away optical ground stations. Here, we simulate dynamical, three-dimensional satellite-ground-station passes, going beyond previous investigations which typically consider static satellite links. Therefore, we numerically solve the equations of motion of the dynamic system consisting of three, low-Earth-orbit satellites separated in the along-track direction. The optical link model includes atmospheric attenuation, single mode fiber coupling, beam wandering and broadening, as well as adaptive optics effects. Analytical expressions for the Bell state measurement and associated error rates are derived for quantum memory assisted communications, accounting for exponentially decreasing retrieval efficiency and state coherence. We consider uplink and downlink architectures for continental and inter-continental connections and assess the influence of varying orbital elements on the expected entanglement distribution rate. Our simulation model enables us to draw conclusions on how the general satellite-ground-station pass geometry impacts the quantum communication link and to analyze the performance for several consecutive passes under realistic conditions.