Satellite-relayed intercontinental quantum network

TL;DR

This paper demonstrates a satellite-based quantum key distribution system enabling secure intercontinental communication between China and Europe, establishing a foundational step towards a global quantum internet.

Contribution

It introduces a satellite-relayed quantum network that performs intercontinental secure key exchange and relays, advancing the development of global quantum communication infrastructure.

Findings

Successful satellite-to-ground quantum key distribution at ~kHz rate.

Secure intercontinental keys established between China and Europe.

Demonstrated quantum-secured image transmission and videoconferencing.

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.