19 Mar 2025

A quantum microsatellite distributes real-time keys to portable ground stations, linking Beijing and Stellenbosch

Quantum technologiesSpace and aerospace
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

What was demonstrated

Li, Cai, Ren, Pan, Peng, Liao and colleagues at the University of Science and Technology of China report a quantum microsatellite performing space-to-ground QKD in real time with several portable ground stations. Bidirectional optical communication is multiplexed with the quantum channel, so keys can be distilled and used for encrypted communication in real time. The satellite acted as a trusted relay for key sharing between Beijing and Stellenbosch, South Africa, about 12,900 km apart. The 2024 preprint gives a payload of about 23 kg and a portable ground station of about 100 kg. The CAS press release reports up to 1 Mbit of secure key per satellite pass.

Why it matters

The preprint abstract says scaling quantum satellite constellations would need lighter satellites and cheaper, portable ground hardware. A real-time demonstration with a light satellite and portable ground terminals is consistent with that aim.

Caveats

  • The satellite is a trusted relay. Keys are established with the satellite in the middle, so users must trust the satellite. This is not end-to-end quantum security between the two cities.
  • The 12,900 km figure is the separation between the two cities, not the length of any single optical link.
  • The key amount differs between sources. The CAS press release reports up to 1 Mbit per pass, while the 2024 arXiv preprint gives 0.59 million bits per pass. The published figure should be checked against the Nature paper before reuse.
  • The Nature article redirects to a sign-in page, so the payload and ground station masses are taken from the preprint and the key amount from the press release. The preprint presents this as a step towards constellations, not an operating network.

Technology profiles

Sources

  1. peer reviewed paper
    Microsatellite-based real-time quantum key distribution
    Yang Li, Wen-Qi Cai, Ji-Gang Ren et al.. Nature, 19 Mar 2025. DOI: 10.1038/s41586-025-08739-z.
  2. other
    USTC Demonstrates Successful Satellite-Enabled Quantum Key Distribution
    Chinese Academy of Sciences, 24 Mar 2025.
  3. preprint
    Microsatellite-based real-time quantum key distribution (preprint)
    Yang Li, Wen-Qi Cai, Ji-Gang Ren et al.. arXiv, 20 Aug 2024.

Last reviewed 21 Oct 2026.