Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Tracking challenges of QKD over relay satellite

: Sharma, S.; Perlot, N.; Rödiger, J.; Freund, R.

Fulltext ()

Sodnik, Z. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
International Conference on Space Optics, ICSO 2018 : Chania, Greece, 9-12 October 2018
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 11180)
ISBN: 978-1-5106-3077-2
Paper 1118062, 9 pp.
International Conference on Space Optics (ICSO) <12, 2018, Chania>
Conference Paper, Electronic Publication
Fraunhofer HHI ()

We investigate a quantum key distribution (QKD) system with relay satellite for communication between two distant Earth-based parties, Alice and Bob. The satellite acts as a relay station which simply redirects the QKD signal. It has several advantages that can be decisive. The optical relay provides a high transparency to protocols and wavelengths. The relay node does not have to be trusted. Like entanglement-based or measurement-device-independent satellite QKD, relayassisted QKD suffers from a higher propagation loss than trusted-node scenarios. Challenges are expected when pointing the relay mirror precisely between Alice and Bob and dealing with significant point-ahead angles that result from the satellite velocity. We start our analysis by evaluating the point ahead angles (PAA) of Alice and Bob for scenarios of interest. The difference between the two PAA vectors tells us whether the relay mirror will be able to maintain a bidirectional transmission with beams sent from the ground. Considering a satellite altitude of 500 km and an Alice-Bob separation of 1000 km, observation of large PAA vector difference enjoins us to place additional beacon sources on the satellite. A conceptual design of the relay-tracking system is drafted. Onboard measurements of the beacons from Alice and Bob provide feedback to the relay-mirror positioning control loop. With a typical relay-mirror size of 0.2 m, propagation losses are calculated for different ground antennas. We conclude on the attractiveness and feasibility of satellite relay QKD.