Dynamical simulation of quantum repeater satellite constellations

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. Here, we analyze scenarios where these approaches are combined: satellites are used as quantum repeater nodes and are employed to distribute entangled photon pairs to far-away optical ground stations. The satellites have to mount optical communication terminals in order to allow the exchange of photonic states over free space, as well as quantum memories and optical Bell-state measurement setups to perform entanglement swapping. Here we report on the development of a full end-to-end simulator of quantum repeater satellite constellations, including detailed orbit dynamics, optical link quality evaluation, calculations of the downstream entanglement generation rate, latency and fidelity. Using only three satellites enables the distribution of entangled states at intercontinental distances; the small number of links in the repeater chain allows us to forgo entanglement purification altogether, resulting in a favorable entanglement swapping rate and state fidelity. We perform numerical simulations of time-varying satellite positions and compare the results to analytical estimates of the entanglement distribution rate based on the average values of the link parameters. The goal is to maximize performance through optimization of the orbits and other system parameters.