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Quantum Experiments at Space Scale (QUESS; ), is a Chinese research project in the field of quantum physics. QUESS was launched on 15 August 2016. The project consists of the satellite Micius, or
Mozi Mozi, personal name Mo Di, was a Chinese philosopher, logician, and founder of the Mohist school of thought, making him one of the most important figures of the Warring States period (221 BCE). Alongside Confucianism, Mohism became the ...
(), after the ancient Chinese philosopher, operated by the
Chinese Academy of Sciences The Chinese Academy of Sciences (CAS; ) is the national academy for natural sciences and the highest consultancy for science and technology of the People's Republic of China. It is the world's largest research organization, with 106 research i ...
, as well as ground stations in China. The
University of Vienna The University of Vienna (, ) is a public university, public research university in Vienna, Austria. Founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365, it is the oldest university in the German-speaking world and among the largest ...
and the
Austrian Academy of Sciences The Austrian Academy of Sciences (; ÖAW) is a legal entity under the special protection of the Republic of Austria. According to the statutes of the Academy its mission is to promote the sciences and humanities in every respect and in every fi ...
are running the satellite's European receiving stations. The satellite conducted Space-Earth
quantum key distribution Quantum key distribution (QKD) is a secure communication method that implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which then can b ...
() experiments, facilitated by laser communications experiment carried on Tiangong-2 space laboratory module.


Design and development

QUESS is a proof-of-concept mission designed to facilitate
quantum optics Quantum optics is a branch of atomic, molecular, and optical physics and quantum chemistry that studies the behavior of photons (individual quanta of light). It includes the study of the particle-like properties of photons and their interaction ...
experiments over long distances to allow the development of quantum encryption and
quantum teleportation Quantum teleportation is a technique for transferring quantum information from a sender at one location to a receiver some distance away. While teleportation is commonly portrayed in science fiction as a means to transfer physical objects from on ...
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 In cryptography, encryption (more specifically, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the information, known as plai ...
. By producing pairs of entangled
photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that ...
, 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.


Mission

The initial experiment demonstrated
quantum key distribution Quantum key distribution (QKD) is a secure communication method that implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which then can b ...
(QKD) between Xinjiang Astronomical Observatory near
Ürümqi Ürümqi, , is the capital of the Xinjiang, Xinjiang Uyghur Autonomous Region in Northwestern China. With a census population of 4 million in 2020, Ürümqi is the second-largest city in China's northwestern interior after Xi'an, also the ...
and Xinglong Observatory near
Beijing Beijing, Chinese postal romanization, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's List of national capitals by population, most populous national capital city as well as ...
– a
great-circle distance The great-circle distance, orthodromic distance, or spherical distance is the distance between two points on a sphere, measured along the great-circle arc between them. This arc is the shortest path between the two points on the surface of the ...
of approximately . In addition, QUESS tested Bell's inequality at a distance of – further than any experiment to date – and teleported a photon state between Shiquanhe Observatory in Ali,
Tibet Autonomous Region The Tibet Autonomous Region (TAR), often shortened to Tibet in English or Xizang in Pinyin, Hanyu Pinyin, is an Autonomous regions of China, autonomous region of the China, People's Republic of China. It was established in 1965 to replace the ...
, and the satellite. This requires very accurate
orbital maneuver In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth, an orbital maneuver is called a ''deep-space maneuver (DSM)''. When a spacec ...
ing and satellite tracking so the base stations can keep line-of-sight with the craft. In 2021 full quantum state teleportation was demonstrated over at ground, based on entanglement distributed by the satellite. Once experiments within China concluded, QUESS created an international QKD channel between China and the Institute for Quantum Optics and Quantum Information, Vienna, Austria − a ground distance of , enabling the first intercontinental secure quantum video call in 2016.


Launch

The launch was initially scheduled for July 2016, but was rescheduled to August, with notification of the launch being sent just a few days in advance. The spacecraft was launched by a Long March 2D rocket from Jiuquan Launch Pad 603, Launch Area 4 on 17 August 2016, at 17:40 UTC (01:40 local time).


Multi-payload mission

The launch was a multi-payload mission shared with QUESS, LiXing-1 research satellite, and ³Cat-2 Spanish science satellite. * LiXing-1: LiXing-1 is a Chinese satellite designed to measure upper atmospheric density by lowering its orbit to 100–150 km. Its mass is 110 kg. On 19 August 2016, the satellite reentered into the atmosphere, so the mission is closed. * ³Cat-2: The 3Cat-2 (spelled "cube-cat-two") is the second satellite in the 3Cat series and the second satellite developed in Catalonia at Polytechnic University of Catalonia’s NanoSat Lab. It is a 6-Unit
CubeSat A CubeSat is a class of small satellite with a form factor of cubes. CubeSats have a mass of no more than per unit,, url=https://static1.squarespace.com/static/5418c831e4b0fa4ecac1bacd/t/5f24997b6deea10cc52bb016/1596234122437/CDS+REV14+2020-07-3 ...
flying a novel GNSS Reflectometer (GNSS-R) payload for Earth observation. Its mass is 7.1 kg.


Secure key distribution

The main instrument on board QUESS is a " Sagnac effect"
interferometer Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...
. This is a device that generates pairs of entangled photons, allowing one of each to be transmitted to the ground. This will allow QUESS to perform Quantum key distribution (QKD) – the transmission of a secure
cryptographic key A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm In mathematics and computer science, an algorithm () is a finite sequenc ...
that can be used to encrypt and decrypt messages – to two ground stations. QKD theoretically offers truly secure communication. In QKD, two parties who want to communicate share a random secret key transmitted using pairs of entangled photons sent with random polarization, with each party receiving one-half of the pair. This secret key can then be used as a
one-time pad The one-time pad (OTP) is an encryption technique that cannot be Cryptanalysis, cracked in cryptography. It requires the use of a single-use pre-shared key that is larger than or equal to the size of the message being sent. In this technique, ...
, allowing the two parties to communicate securely through normal channels. Any attempt to eavesdrop on the key will disturb the entangled state in a detectable way. QKD has been attempted on Earth, both with direct line-of-sight between two observatories, and using fibre optic cables to transmit the photons. However, fiber optics and the atmosphere both cause scattering, which destroys the entangled state, and this limits the distance over which QKD can be carried out. Sending the keys from an orbiting satellite results in less scattering, which allows QKD to be performed over much greater distances. In addition, QUESS could test some of the basic foundations of
quantum mechanics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
.
Bell's theorem Bell's theorem is a term encompassing a number of closely related results in physics, all of which determine that quantum mechanics is incompatible with local hidden-variable theories, given some basic assumptions about the nature of measuremen ...
says that no local hidden-variable theory can ever reproduce the predictions of quantum physics, and QUESS was able to test the
principle of locality In physics, the principle of locality states that an object is influenced directly only by its immediate surroundings. A theory that includes the principle of locality is said to be a "local theory". This is an alternative to the concept of ins ...
over . The quantum key distribution experiment won
American Association for the Advancement of Science The American Association for the Advancement of Science (AAAS) is a United States–based international nonprofit with the stated mission of promoting cooperation among scientists, defending scientific freedom, encouraging scientific responsib ...
(AAAS)'s
Newcomb Cleveland Prize The Newcomb Cleveland Prize of the American Association for the Advancement of Science (AAAS) is annually awarded to author(s) of outstanding scientific paper published in the Research Articles or Reports sections of ''Science Science is a ...
in 2018 for its contribution to laying the foundation for ultra-secure communication networks of the future.


Analysis

QUESS lead scientist
Pan Jianwei Pan Jianwei (; born 11 March 1970) is a Chinese academic administrator and quantum physicist. He is a university administrator and professor of physics at the University of Science and Technology of China. Pan is known for his work in the field ...
told ''
Reuters Reuters ( ) is a news agency owned by Thomson Reuters. It employs around 2,500 journalists and 600 photojournalists in about 200 locations worldwide writing in 16 languages. Reuters is one of the largest news agencies in the world. The agency ...
'' that the project has "enormous prospects" in the defence sphere. The satellite will provide secure communications between Beijing and Ürümqi, capital of
Xinjiang Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...
, the remote western region of China. The
US Department of Defense The United States Department of Defense (DoD, USDOD, or DOD) is an executive department of the U.S. federal government charged with coordinating and supervising the six U.S. armed services: the Army, Navy, Marines, Air Force, Space Force, ...
believes China is aiming to achieve the capability to counter the use of enemy space technology.
Chinese Communist Party The Communist Party of China (CPC), also translated into English as Chinese Communist Party (CCP), is the founding and One-party state, sole ruling party of the People's Republic of China (PRC). Founded in 1921, the CCP emerged victorious in the ...
general secretary Secretary is a title often used in organizations to indicate a person having a certain amount of authority, Power (social and political), power, or importance in the organization. Secretaries announce important events and communicate to the org ...
Xi Jinping Xi Jinping, pronounced (born 15 June 1953) is a Chinese politician who has been the general secretary of the Chinese Communist Party (CCP) and Chairman of the Central Military Commission (China), chairman of the Central Military Commission ...
has prioritised China's space program, which has included anti-satellite missile tests, and the ''
New York Times ''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...
'' noted that quantum technology was a focus of the thirteenth five-year plan, which the China government set out earlier that year. The ''Wall Street Journal'' said that the launch put China ahead of rivals, and brought them closer to "hack-proof communications". Several outlets identified
Edward Snowden Edward Joseph Snowden (born June 21, 1983) is a former National Security Agency (NSA) intelligence contractor and whistleblower who leaked classified documents revealing the existence of global surveillance programs. Born in 1983 in Elizabeth ...
's leak of US surveillance documents as an impetus for the development of QUESS, with ''
Popular Science Popular science (also called pop-science or popsci) is an interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is more broad ranging. It may be written ...
'' calling it "a satellite for the post-Snowden age".


Similar projects

QUESS is the first spacecraft launched capable of generating entangled photons in space, although transmission of single photons via satellites has previously been demonstrated by reflecting photons generated at ground-based stations off orbiting satellites. While not generating fully entangled photons,
correlated In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistic ...
pairs of photons have been produced in space using a
cubesat A CubeSat is a class of small satellite with a form factor of cubes. CubeSats have a mass of no more than per unit,, url=https://static1.squarespace.com/static/5418c831e4b0fa4ecac1bacd/t/5f24997b6deea10cc52bb016/1596234122437/CDS+REV14+2020-07-3 ...
by the
National University of Singapore The National University of Singapore (NUS) is a national university, national Public university, public research university in Singapore. It was officially established in 1980 by the merging of the University of Singapore and Nanyang University ...
and the University of Strathclyde. A German consortium has performed quantum measurements of optical signals from the geostationary Alphasat Laser Communication Terminal. The US Defense Advanced Research Projects Agency (DARPA) launched the Quiness macroscopic quantum communications project to catalyze the development of an end-to-end global quantum internet in 2012. In the late 2025 to early 2026, ESA intends to launch the Eagle-1 quantum key distribution satellite, with a goal similar to that of the Chinese QUESS. It will be part of the development and deployment of the European Quantum Communication Infrastructure (EuroQCI).


See also

*
Chinese space program The space program of the People's Republic of China is about the activities in outer space conducted and directed by the China, People's Republic of China. The roots of the Chinese space program trace back to the 1950s, when, with the help ...
*
Quantum information science Quantum information science is a field that combines the principles of quantum mechanics with information theory to study the processing, analysis, and transmission of information. It covers both theoretical and experimental aspects of quantum phys ...
*
Quantum information Quantum information is the information of the state of a quantum system. It is the basic entity of study in quantum information theory, and can be manipulated using quantum information processing techniques. Quantum information refers to both t ...
**
Quantum cryptography 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 an information-theoretically secure soluti ...
**
Quantum computing A quantum computer is a computer that exploits quantum mechanical phenomena. On small scales, physical matter exhibits properties of wave-particle duality, both particles and waves, and quantum computing takes advantage of this behavior using s ...
**
Quantum key distribution Quantum key distribution (QKD) is a secure communication method that implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which then can b ...
**
Quantum teleportation Quantum teleportation is a technique for transferring quantum information from a sender at one location to a receiver some distance away. While teleportation is commonly portrayed in science fiction as a means to transfer physical objects from on ...


References


External links


QUESS Launching
(Chinese)
3Cat-2 Satellite web site
at Polytechnic University of Catalonia {{Orbital launches in 2016 Communications satellites Satellites of China Satellites of Austria 2016 in China Quantum information science Spacecraft launched in 2016 Communications satellites in low Earth orbit 2016 in Austria