Quantum Experiments at Space Scale (QUESS; Chinese: 量子科学实验卫星; pinyin: Liàngzǐ kēxué shíyàn wèixīng; lit. 'Quantum Science Experiment Satellite'), is a Chinese research project in the field of quantum physics.

Tiangong-2 is China's second Space Laboratory module which was launched on 15 Sep 2016. Tiangong-2 carries a total of 14 mission and experiment packages, including Space-Earth quantum key distribution (Chinese: 量子密钥分发) and laser communications experiment to facilitate space-to-ground quantum communication.

A satellite, nicknamed Micius or Mozi (Chinese: 墨子) after the ancient Chinese philosopher and scientist, is operated by the Chinese Academy of Sciences, as well as ground stations in China. The University of Vienna and the Austrian Academy of Sciences are running the satellite's European receiving stations.

QUESS is a proof-of-concept mission designed to facilitate quantum optics experiments over long distances to allow the development of quantum encryption and quantum teleportation technology. Quantum encryption uses the principle of entanglement to facilitate communication that can absolutely detect whether a third party has intercepted a message in transit thus denying undetected decryption. By producing pairs of entangled photons, QUESS will allow ground stations separated by many thousands of kilometres to establish secure quantum channels. QUESS itself has limited communication capabilities: it needs line-of-sight, and can only operate when not in sunlight.

Further Micius satellites were planned, including a global network by 2030.

The mission cost was around US$100 million in total.

 

Note:   The above text is excerpted from the Wikipedia article Quantum Experiments at Space Scale, which has been released under the GNU Free Documentation License.