China launches world’s first quantum communications satellite

QUESS (Credit: Xinhua News)

A CZ-2D (Long March 2D) launch vehicle has delivered the world’s first quantum communications experiment satellite into orbit. The launcher rocket, carrying the experimental satellite named Quantum Experiments at Space Scale (QUESS), or Mozi after the famous ancient Chinese philospher, lifted off from Pad 603 (SLS2) at the Jiuquan Satellite Launch Centre (JSLC) at 01:40 CST on 16 August 2016 (17:40 UTC on 15 August). After nearly 10 minutes of flight, the satellite was placed into a 500 km polar orbit (97.37° inclination).

QUESS Mozi launch Jiuquan CZ-2D 3

CZ-2D carrying QUESS/Mozi lifting off from Jiuquan (Credit: Xinhua News)


In 2011, the Chinese government initiated the Strategic Priority Programme on Space Science (空间科学战略性先导科技专项), the country’s first space exploration programme intended purely for scientific research rather than economic benefit. The programme includes a series of satellite missions, planned to be launched between 2015 and 2030, to look at black holes, dark matter, and cosmic background radiation. The QUESS is the third mission of the programme, following the Dark Mater Particle Explorer (DAMPE) in December 2015 and the Shijian 10 mission in April 2016.

Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks. The best known example of quantum cryptography is quantum key distribution which offers a theoretically secure solution to the key exchange problem in cryptography. Quantum encryption takes advantage of quantum entanglement, using it to detect would-be eavesdroppers, whose presence causes quantum states to collapse and reveal their spying to legitimate parties. Additionally, the complexity of quantum mechanics makes it virtually impossible to reverse engineer the quantum key generated through quantum entanglement.

The QUESS mission seeks to turn this theory into reality. The satellite is designed to test the secure transmission of data by establishing a strong quantum communication between space and Earth. Data sent between the two cannot be copied, stolen or spied on. It is expected to augment China’s 2,000 km (1,242 mile) quantum computer network, which is currently under construction. This computer network, which connects Beijing and Shanghai, could become fully operational by the end of 2016 to serve Chinese government and financial institutions.

The QUESS programme is sponsored and managed by the China Academy of Sciences (CAS). The satellite was designed and built by the CAS’s Shanghai Engineering Centre for Microsatellites (SECM). The mission payload was developed jointly by the CAS’s Shanghai Institute of Technical Physics (SITP) and the University of Science and Technology of China (USTC). The ground section of the QUESS satellite includes four quantum communication ground stations (Xinglong, Urumqi, Delingha, and Lijiang) and a quantum transmission test ground station.


The QUESS satellite weights 640 kg, and operates in a 500 km Low Earth Orbit (LEO) inclined at 97.37°.

The satellite carries four pieces of mission payload, including a quantum key distributor, a quantum entanglement transmitter, a quantum entanglement generator, and a quantum test control processor. It has two separate antennas to simultaneously establish quantum communications with two ground stations on Earth.

The communications data from the QUESS satellite is received by three ground receiving stations located at Miyun (Beijing), Sanya (Hainan), and Kashgar (Xinjiang), and processed by the National Space Science Centre (NSSC) of the China Academy of Sciences (CAS) in Beijing.


The QUESS mission’s launch campaign began with the arrival of the spacecraft and its CZ-2D (Y-32) launch vehicle to the launch site on 8 July 2016. The launch took place at 01:40 CST on 16 August 2016. The first data transmission from the satellite was received by the Miyun Ground Receiving Station at 17:11 CST on 18 August. It took 7 minutes for the 202 MB data to be transmitted.

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