Satellites promise global-scale quantum networks

TL;DR

Satellite-based quantum communication offers a promising solution for long-distance quantum networks, overcoming the exponential photon loss faced by ground-based channels and enabling intercontinental quantum links.

Contribution

This paper reviews recent advancements and prospects of satellite quantum communication, highlighting its advantages over ground-based methods and potential architectures for global quantum networks.

Findings

Single satellite achieved entanglement distribution over 1,200 km

Satellite links face minimal exponential loss compared to fiber channels

Satellite quantum communication is poised for intercontinental deployment

Abstract

Academia, governments, and industry around the world are on a quest to build long-distance quantum communication networks for a future quantum internet. Using air and fiber channels, quantum communication quickly faced the daunting challenge of exponential photon loss with distance. Quantum repeaters were invented to solve the loss problem by probabilistically establishing entanglement over short distances and using quantum memories to synchronize the teleportation of such entanglement to long distances. However, due to imperfections and complexities of quantum memories, ground-based proof-of-concept repeater demonstrations have been restricted to metropolitan-scale distances. In contrast, direct photon transmission from satellites through empty space faces almost no exponential absorption loss and only quadratic beam divergence loss. A single satellite successfully distributed entanglement over more than 1,200 km. It is becoming increasingly clear that quantum communication over large intercontinental distances (e.g. 4,000-20,000 km) will likely employ a satellite-based architecture. This could involve quantum memories and repeater protocols in satellites, or memory-less satellite-chains through which photons are simply reflected, or some combination thereof. Rapid advancements in the space launch and classical satellite communications industry provide a strong tailwind for satellite quantum communication, promising economical and easier deployment of quantum communication satellites.