Satellite-Relayed Intercontinental Quantum Network

TLDR

The satellite establishes secure keys with multiple ground stations, enabling inter‑satellite key distribution. The study aims to demonstrate an efficient solution for an ultralong‑distance global quantum network, paving the way toward a future quantum internet. The authors perform decoy‑state quantum key distribution between a low‑Earth‑orbit satellite and several ground stations, then use the satellite as a trusted relay that XORs the two keys and forwards the result to a ground station. The intercontinental secret key produced 7600‑km quantum communication, allowing one‑time‑pad image transmission and a videoconference between Austria and China.

Abstract

We perform decoy-state quantum key distribution between a low-Earth-orbit satellite and multiple ground stations located in Xinglong, Nanshan, and Graz, which establish satellite-to-ground secure keys with ~kHz rate per passage of the satellite Micius over a ground station. The satellite thus establishes a secure key between itself and, say, Xinglong, and another key between itself and, say, Graz. Then, upon request from the ground command, Micius acts as a trusted relay. It performs bitwise exclusive OR operations between the two keys and relays the result to one of the ground stations. That way, a secret key is created between China and Europe at locations separated by 7600 km on Earth. These keys are then used for intercontinental quantum-secured communication. This was on the one hand the transmission of images in a one-time pad configuration from China to Austria as well as from Austria to China. Also, a videoconference was performed between the Austrian Academy of Sciences and the Chinese Academy of Sciences, which also included a 280 km optical ground connection between Xinglong and Beijing. Our work points towards an efficient solution for an ultralong-distance global quantum network, laying the groundwork for a future quantum internet.