Fig. 2: Strategies for utilizing three satellites.
From: Simulating quantum repeater strategies for multiple satellites
a Illustration of the considered scenarios. Satellites SA and SB are equipped with entangled pair sources (EPS) and send qubits to the other satellite and the ground stations (dashed lines). In Scenario 1 only the central satellite SC has quantum memories and two repeater links are established. In Scenario 2 all of the satellites have quantum memories and a protocol with four repeater links are used. b Scenario 1: Choosing an appropriate cutoff time tcut—a maximum time a qubit is kept in a quantum memory—can be very beneficial to the key rate. The optimal value for tcut is distance-dependent and it is possible to choose a value that is too low. A dashed line indicates a BBM92 protocol with only one satellite and a clock rate of 20MHz with the same loss model. This plot is for a divergence of θd = 6 μrad as the effect is more pronounced in situations with high loss.
