Quantum Experiments at Space Scale

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.{{Cite journal |last1=Ren |first1=Ji-Gang |last2=Xu |first2=Ping |last3=Yong |first3=Hai-Lin |last4=Zhang |first4=Liang |last5=Liao |first5=Sheng-Kai |last6=Yin |first6=Juan |last7=Liu |first7=Wei-Yue |last8=Cai |first8=Wen-Qi |last9=Yang |first9=Meng |last10=Li |first10=Li |last11=Yang |first11=Kui-Xing |date=2017-08-09 |title=Ground-to-satellite quantum teleportation |journal=Nature |language=en |volume=549 |issue=7670 |pages=70–73 |doi=10.1038/nature23675 |pmid=28825708 |issn=1476-4687 |arxiv=1707.00934 |bibcode=2017Natur.549...70R |s2cid=4468803}}{{cite journal |title=Satellite-based entanglement distribution over 1200 kilometers |author1=Juan Yin |author2=Yuan Cao |author3=Yu-Huai Li |author4=Sheng-Kai Liao |author5=Liang Zhang |author6=Ji-Gang Ren |author7=Wen-Qi Cai |author8=Wei-Yue Liu |author9=Bo Li |author10=Hui Dai |author11=Guang-Bing Li |author12=Qi-Ming Lu |author13=Yun-Hong Gong |author14=Yu Xu |author15=Shuang-Lin Li |author16=Feng-Zhi Li |author17=Ya-Yun Yin |author18=Zi-Qing Jiang |author19=Ming Li |author20=Jian-Jun Jia |author21=Ge Ren |author22=Dong He |author23=Yi-Lin Zhou |author24=Xiao-Xiang Zhang |author25=Na Wang |author26=Xiang Chang |author27=Zhen-Cai Zhu |author28=Nai-Le Liu |author29=Yu-Ao Chen |author30=Chao-Yang Lu |author31=Rong Shu |author32=Cheng-Zhi Peng |author33=Jian-Yu Wang |author34=Jian-Wei Pan |journal=Quantum Optics |year=2017 |volume=356 |issue=6343 |pages=1140–1144 |doi=10.1126/science.aan3211 |pmid=28619937 |arxiv=1707.01339 |s2cid=5206894}}{{cite web |title=China Shatters "Spooky Action at a Distance" Record, Preps for Quantum Internet |first=Lee |last=Billings |website=Scientific American |date=23 April 2020 |url=https://www.scientificamerican.com/article/china-shatters-ldquo-spooky-action-at-a-distance-rdquo-record-preps-for-quantum-internet/}}{{cite web |url=https://www.science.org/content/article/china-s-quantum-satellite-achieves-spooky-action-record-distance |title=China's quantum satellite achieves 'spooky action' at record distance |first1=Gabriel |last1=Popkin |date=15 June 2017 |website=Science - AAAS}}{{cite web |last1=Wall |first1=Mike |title=China Launches Pioneering 'Hack-Proof' Quantum-Communications Satellite |url=http://www.space.com/33760-china-launches-quantum-communications-satellite.html |website=Space.com |publisher=Purch |access-date=17 August 2016 |date=16 August 2016}} 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.{{cite news |url=https://physicsworld.com/a/china-launches-worlds-first-quantum-science-satellite/|title=China launches world's first quantum science satellite|author=Lin Xing |newspaper=Physics World|publisher=Institute of Physics |date=16 August 2016 |access-date=22 November 2020}} QUESS itself has limited communication capabilities: it needs line-of-sight, and can only operate when not in sunlight.{{cite news |url=http://news.xinhuanet.com/english/2016-08/16/c_135604287.htm |access-date=17 August 2016 |archive-url=https://web.archive.org/web/20160817155904/http://news.xinhuanet.com/english/2016-08/16/c_135604287.htm |url-status=dead |archive-date=August 17, 2016 |title=China Focus: China's space satellites make quantum leap |author=huaxia|date=16 August 2016 |publisher=Xinhua}}

Further Micius satellites were planned, including a global network by 2030.{{cite news |url=http://www.popsci.com/chinas-quantum-satellite-could-change-cryptography-forever|title=China's Quantum Satellite Could Change Cryptography Forever|author1=Jeffrey Lin |author2=P.W. Singer |author3=John Costello |date=3 March 2016|access-date=17 August 2016 |newspaper=Popular Science}}

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

{{Location map+ |Asia| float =

| caption = Ground stations

| places =

{{Location map~ |Asia

| label = Xinglong

| position = top

| marksize = 10

| link = Beijing Astronomical Observatory#Xinglong

| lat_deg = 40.39457

| lon_deg = 117.577048

}}

{{Location map~ |Asia

| label = Ürümqi

| position = top

| marksize = 10

| link = Xinjiang Astronomical Observatory

| lat_deg = 43.47

| lon_deg = 87.18

}}

{{Location map~ |Asia

| label = Ali

| position = top

| marksize = 10

| link = Shiquanhe#Shiquanhe Observatory

| lat_deg = 32.316667

| lon_deg = 80.016667

}}

{{Location map~ |Asia

| label = Vienna

| position = top

| marksize = 10

| link = Institute for Quantum Optics and Quantum Information

| lat_deg = 48.22 | lon_deg = 16.35

}}

}}

The initial experiment demonstrated quantum key distribution (QKD) between Xinjiang Astronomical Observatory near Ürümqi and Xinglong Observatory near Beijing – a great-circle distance of approximately {{convert|2500|km|mi}}. In addition, QUESS tested Bell's inequality at a distance of {{convert|1200|km|mi|abbr=on}} – further than any experiment to date – and teleported a photon state between Shiquanhe Observatory in Ali, Tibet Autonomous Region, and the satellite. This requires very accurate orbital maneuvering and satellite tracking so the base stations can keep line-of-sight with the craft.{{cite news |url = http://bigstory.ap.org/article/533a4f56ef664f8081a4bbb4aed00f79/chinas-launch-quantum-satellite-major-step-space-race |title = China's launch of quantum satellite major step in space race |date = 16 August 2016 |access-date = 17 August 2016 |publisher = Associated Press |archive-date = 27 October 2016 |archive-url = https://web.archive.org/web/20161027000232/http://bigstory.ap.org/article/533a4f56ef664f8081a4bbb4aed00f79/chinas-launch-quantum-satellite-major-step-space-race |url-status = dead }} In 2021 full quantum state teleportation was demonstrated over {{convert|1200|km|mi|abbr=on}} at ground, based on entanglement distributed by the satellite.{{Cite journal |last1=Li |first1=Bo |last2=Cao |first2=Yuan |last3=Li |first3=Yu-Huai |last4=Cai |first4=Wen-Qi |last5=Liu |first5=Wei-Yue |last6=Ren |first6=Ji-Gang |last7=Liao |first7=Sheng-Kai |last8=Wu |first8=Hui-Nan |last9=Li |first9=Shuang-Lin |last10=Li |first10=Li |last11=Liu |first11=Nai-Le |date=2022-04-26 |title=Quantum State Transfer over 1200 km Assisted by Prior Distributed Entanglement |url=https://link.aps.org/doi/10.1103/PhysRevLett.128.170501 |journal=Physical Review Letters |language=en |volume=128 |issue=17 |pages=170501 |doi=10.1103/PhysRevLett.128.170501 |pmid=35570417 |bibcode=2022PhRvL.128q0501L |s2cid=248812124 |issn=0031-9007|url-access=subscription }}

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 {{convert|7500|km|mi|abbr=on}}, enabling the first intercontinental secure quantum video call in 2016.

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.{{cite news |url=http://www.spaceflightinsider.com/space-flight-news/china-launches-world-first-quantum-communications-satellite/ |title=China launches world's first quantum communications satellite into space |date=16 August 2016 |access-date=17 August 2016 |author=Tomasz Nowakowski |publisher=Spaceflight Insider}} 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).

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 flying a novel GNSS Reflectometer (GNSS-R) payload for Earth observation. Its mass is 7.1 kg.

{{main|Quantum key distribution}}

The main instrument on board QUESS is a "Sagnac effect" interferometer. 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 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, 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. Bell's theorem 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 over {{convert|1200|km|mi|abbr=on}}.

The quantum key distribution experiment won American Association for the Advancement of Science (AAAS)'s Newcomb Cleveland Prize in 2018 for its contribution to laying the foundation for ultra-secure communication networks of the future.{{cite web|url=https://www.aaas.org/news/advancement-quantum-entanglement-earns-2018-aaas-newcomb-cleveland-prize |title=Advancement in Quantum Entanglement Earns 2018 AAAS Newcomb Cleveland Prize |date=31 January 2019 |website=American Association for the Advancement of Science |first=Adam |last=D. Cohen }}

QUESS lead scientist Pan Jianwei told Reuters that the project has "enormous prospects" in the defence sphere.{{cite news |url=http://uk.reuters.com/article/uk-china-space-satellite-idUKKCN10R073 |archive-url=https://web.archive.org/web/20160817010454/http://uk.reuters.com/article/uk-china-space-satellite-idUKKCN10R073 |url-status=dead |archive-date=August 17, 2016 |title=China launches 'hack-proof' communications satellite |work=Reuters |date=2016-08-16 |access-date=2016-08-18 }} The satellite will provide secure communications between Beijing and Ürümqi, capital of Xinjiang, the remote western region of China. The US Department of Defense believes China is aiming to achieve the capability to counter the use of enemy space technology. Chinese Communist Party general secretary Xi Jinping has prioritised China's space program, which has included anti-satellite missile tests, and the New York Times noted that quantum technology was a focus of the thirteenth five-year plan, which the China government set out earlier that year.{{cite news|url=https://www.nytimes.com/2016/08/17/world/asia/china-quantum-satellite-mozi.html?_r=0|title=China Launches Quantum Satellite in Bid to Pioneer Secure Communications|author=Edward Wong|date=16 August 2016|access-date=19 August 2016|newspaper=New York Times}} The Wall Street Journal said that the launch put China ahead of rivals, and brought them closer to "hack-proof communications".{{cite news|url=https://www.wsj.com/articles/chinas-latest-leap-forward-isnt-just-greatits-quantum-1471269555?mod=rss_Technology|title=China's Latest Leap Forward Isn't Just Great—It's Quantum|author=Josh Chin|date=16 August 2016|access-date=19 August 2016|newspaper=Wall Street Journal}} Several outlets identified Edward Snowden's leak of US surveillance documents as an impetus for the development of QUESS, with Popular Science calling it "a satellite for the post-Snowden age".{{cite news|url=http://www.popsci.com/china-launches-quantum-satellite-in-search-for-unhackable-communications|title=China Launches Quantum Satellite In Search Of Unhackable Communications|author1=Jeffrey Lin |author2=P.W. Singer|date=17 August 2016|access-date=19 August 2016}}{{cite news|url=http://www.ft.com/cms/s/0/f333dbea-6371-11e6-a08a-c7ac04ef00aa.html#axzz4Hm0TcdSW|title=China launches quantum satellite in battle against hackers|author=Lucy Hornby, Clive Cookson|date=16 August 2016|access-date=19 August 2016}}

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.{{cite journal|title=Chinese satellite is one giant step for the quantum internet|date=27 July 2016|pages=478–479|doi=10.1038/535478a|journal=Nature|author=Elizabeth Gibney|volume=535|issue=7613|pmid=27466107|bibcode=2016Natur.535..478G|doi-access=free}} While not generating fully entangled photons, correlated pairs of photons have been produced in space using a cubesat by the National University of Singapore and the University of Strathclyde. A German consortium has performed quantum measurements of optical signals from the geostationary Alphasat Laser Communication Terminal.{{Cite journal |arxiv=1608.03511|last1=Günthner|first1=Kevin|title=Quantum-limited measurements of optical signals from a geostationary satellite|last2=Khan|first2=Imran|last3=Elser|first3=Dominique|last4=Stiller|first4=Birgit|last5=Bayraktar|first5=Ömer|last6=Müller|first6=Christian R|last7=Saucke|first7=Karen|last8=Tröndle|first8=Daniel|last9=Heine|first9=Frank|last10=Seel|first10=Stefan|last11=Greulich|first11=Peter|last12=Zech|first12=Herwig|last13=Gütlich|first13=Björn|last14=Philipp-May|first14=Sabine|last15=Marquardt|first15=Christoph|last16=Leuchs|first16=Gerd|journal=Optica|year=2017|volume=4|issue=6|pages=611–616|doi=10.1364/OPTICA.4.000611|bibcode=2017Optic...4..611G|s2cid=15100033}} 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).{{cite web |url=https://www.esa.int/Applications/Connectivity_and_Secure_Communications/Eagle-1 |title=ESA - Eagle-1 |publisher=ESA |date=5 March 2025}}

{{Portal|Spaceflight}}

• Chinese space program
• Quantum information science
• Quantum information
• Quantum cryptography
• Quantum computing
• Quantum key distribution
• Quantum teleportation

{{Reflist|30em}}

• [http://www.chinaspaceflight.com/satellite/Space-Science/QUESS/QUESS-launch.html QUESS Launching] {{Webarchive|url=https://web.archive.org/web/20171106155940/http://www.chinaspaceflight.com/satellite/Space-Science/QUESS/QUESS-launch.html |date=2017-11-06 }}(Chinese)
• [http://nanosatlab.upc.edu/en/missions-and-projects/3cat-2 3Cat-2 Satellite web site] at Polytechnic University of Catalonia

{{Orbital launches in 2016}}

Category:Communications satellites

Category:Satellites of China

Category:Satellites of Austria

Category:2016 in China

Category:Quantum information science

Category:Spacecraft launched in 2016

Category:Communications satellites in low Earth orbit

Category:2016 in Austria