[USTC Alumni Foundation (ID: USTCIF), the most active USTC alumni organization in the world, publishes USTC news and alumni information in real time] Pan Jianwei’s team at USTC published a review of space quantum experiments in "Modern Physics Review", and Cao Yuan also Recently,

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USTC Pan Jianwei team published in " Modern Physics Review " A review of space quantum experiments, Cao Yuan also participated

Recently, University of Science and Technology of China Pan Jianwei and his colleagues Peng Chengzhi, Lu Chaoyang, and Cao Yuan were invited to give a review in the authoritative international physics review journal "Review of Modern Physics" of Modern Physics) published a long review paper entitled "Micius quantum experiments in space based on the 'Micius' satellite". Interestingly: Dr. Cao Yuan also participated in this work . But this is not Cao Yuan, a grade 10 alumnus of HKUST Junior College and MIT graphene prodigy. There is an introduction to Cao Yuan at the end of the article, so don’t get confused.

This paper starts from the basic concepts of quantum information theory, early quantum communication and quantum information related principle experiments, ground large space scale verification experiments for satellite , and the "Micius" satellite from project establishment, development, on-orbit After running to the end, it was the first in the world to complete a series of satellite-to-ground quantum science experiments, and systematically elaborated and summarized them. At the same time, this review paper also reviews the research progress of international space quantum science. The success of the "Mozi" inspired an upsurge in international space quantum science research. The United States, the European Union, Japan and other international forces subsequently began to explore their own paths to wide-area quantum communication, proposing or accelerating a series of Space quantum science layout. At the end of the paper, a forward-looking outlook is given on the further construction of a global quantum communication network and basic research on quantum physics based on space platforms, indicating that the "Mozi" series of experiments have opened up the use of space platforms to carry out quantum information and quantum physics. A vast world of cutting-edge research.

Figure 1: "Modern Physics Review" paper page

Quantum communication is based on the basic principles of quantum physics and overcomes the inherent security risks of classical encryption technology. It is the only communication method that has been strictly proven to be unconditionally secure so far. It can be obtained from Fundamentally solve information security problems in fields such as national defense, finance, government affairs, and commerce. Quantum communication usually uses single photons as the physical carrier, and the most direct transmission method is optical fiber or near-ground free space channel. However, the losses of both channels increase exponentially with distance, and the near-Earth atmospheric channel is also affected by the curvature of the earth. Due to the principle of quantum unclonability, quantum communication signals cannot be amplified like classical communication, which made the previous world record of quantum communication only in the order of 100 kilometers. Therefore, how to achieve secure, long-distance, and practical quantum communication is the biggest challenge in this field and a common goal that the international academic community has been striving for for decades.

Since outer space is almost a vacuum, the absorption loss of optical signals is almost zero, so the quantum communication distance can be greatly expanded with the assistance of satellites. Since the beginning of this century, this direction has become the focus of fierce competition in the international academic community. Pan Jianwei's team has carried out a series of pioneering experimental research to realize star-to-ground quantum communication . In 2003, the team proposed a plan to use satellites to achieve quantum communication between satellites and ground and build a global quantum secure communication network. Then in 2004, it was the first in the world to achieve a two-way free space with a horizontal distance of 13 kilometers (larger than the vertical thickness of the atmosphere). Quantum entanglement distribution verifies the feasibility of quantum communication through the atmosphere. At the end of 2011, the "Quantum Science Experiment Satellite", a strategic leading science and technology project of the Chinese Academy of Sciences, was officially established. In 2012, a joint research team of the Chinese Academy of Sciences led by Pan Jianwei achieved the first 100-kilometer two-way quantum entanglement distribution and quantum teleportation in Qinghai Lake, fully verifying the feasibility of using satellites to achieve quantum communication.In 2013, the joint research team of the Chinese Academy of Sciences implemented a quantum key distribution experiment in Qinghai Lake that simulated the relative motion of the satellite and the ground and the large loss of the satellite-ground link, fully verifying the feasibility of quantum key distribution from satellite to the ground. Subsequently, the team worked hard and overcame various difficulties, and finally successfully developed the "Mozi" quantum science experimental satellite . The "Mozi" satellite was launched from the Jiuquan Satellite Launch Center on August 16, 2016. After four months of on-orbit testing, it was officially delivered on January 18, 2017 for scientific experiments.

Figure 2: Hundred-kilometer quantum entanglement distribution completed in Qinghai Lake

Pan Jianwei’s team used the "Mozi" quantum satellite to take the lead in the world in completing a series of groundbreaking satellite-to-ground quantum science experiments: Completed the satellite-to-ground quantum key Distribution [Nature549, 43–47 (2017)], intercontinental quantum key distribution from Beijing to Vienna [PRL20, 030501 (2018)], entanglement-based quantum key distribution without trusted relay [Nature582, 501-505 (2020); PRL19, 200502 (2017)], and further successfully achieved docking between the quantum secure communication Beijing-Shanghai trunk line and the "Mozi" quantum satellite [Nature589, 214-219 (2021)], verified The feasibility of satellite-to-ground wide-area quantum communication; the satellite-to-ground two-way quantum entanglement distribution experiment was realized, and the violation of Bell's inequality that strictly satisfies Einstein's locality condition at a distance of thousands of kilometers between the satellite and the ground was observed, verifying the space The existence of scale quantum entanglement and the correctness of the basic principles of quantum mechanics [Science356, 1140-1144 (2017)]; the completion of the first earth-to-satellite quantum teleportation and the star-to-earth quantum state remote transmission, proving The transmission of qubits can be completed at a distance of thousands of kilometers from the earth to the satellite, laying the foundation for the global quantum information processing network [Nature549, 70–73 (2017); PRL28, 170501 (2022)]; after completing the wide-area quantum After setting the scientific goal of testing basic issues in communication and quantum mechanics, we have also launched exploratory work in other directions of space quantum science experiments, using uplink quantum channels to conduct experiments on a type of theoretical model that predicts that gravitational field will cause quantum decoherence. The test has taken the first step to explore the experimental test of the integration of quantum mechanics and general relativity [Science366, 132 (2019)]; combining quantum communication technology with quantum precision measurement technology, it has achieved satellite-ground safe time-frequency The transmission experiment verified the feasibility of conducting wide-area optical frequency standard research at the spatial scale [Nature Physics6, 848-852 (2020)]. These space quantum science experimental results have brought our country to the forefront of the world in the field of space science research for the first time, firmly occupying the dominant and leading position in the field of space quantum science research.

Figure 3 "Mozi" satellite transits Xinglong Ground Station

The successful implementation of the "Mozi" quantum satellite project has further stimulated the global competition for space quantum experiments. In 2017, NASA (NASA) released a white paper on the future development of space quantum physics, with a view to re-establishing "US leadership" ("re-establishing US leadership") in a new round of space quantum science development. At the same time, the European Space Agency (ESA) also released a white paper on space quantum technology. After the successful launch of "Mozi", the world's major powers have begun the research and development of their own quantum satellites, launching plans and timetables based on low-orbit miniaturized quantum satellites. In June 2021, the United States, the United Kingdom, Japan, Canada, Italy, Belgium and Austria 7 countries reached cooperation at the G7 Summit, and for the first time planned to jointly develop a satellite-based quantum encryption network-"Federal Quantum System" (FQS), leveraging breakthroughs in quantum technology to protect against increasingly sophisticated cyberattacks, and more.

The review paper concludes with an outlook on the main development direction of space quantum science in the future, proposing that space quantum scientific research will leap from low orbit platforms to medium and high orbit platforms, and even deep space platforms. On this basis, taking advantage of the advantages of medium and high orbit satellite platforms such as wide coverage, long experimental time, and good microgravity environment, space quantum communication technology will be applied simultaneously to long-distance high-precision time-frequency transmission and space ultra-cold atomic physics. field, and obtain richer scientific output in basic scientific issues such as quantum precision measurement, the integration of quantum physics and general relativity.

Figure 4 Future quantum constellation blueprint

Due to a series of groundbreaking work in long-distance quantum communications, especially the "Mozi" quantum satellite, Pan Jianwei and others were invited to write this article for "Modern Physics Review" The 46-page review paper comprehensively introduces the achievements of international space quantum science research in the past two decades, focusing on the key technological breakthroughs of the "Mozi" quantum science experimental satellite from the early stage, including six major areas including satellite systems and scientific application systems. The construction and development of systematic quantum science experimental satellites and the systematic scientific research results achieved after the satellites are in orbit have provided valuable information to the international academic community.

"Reviews of Modern Physics" is the most authoritative review journal in the international physics community, publishing only about forty academic papers every year. The journal generally does not accept free submissions. It mainly invites physicists who have made outstanding achievements in various fields to write. It aims to provide historical summary, principle explanation, current situation analysis and trend prediction on the major hot issues in today's physics research. This paper is the work of Pan Jianwei's team in this journal following the 2012 "Multiphoton entanglement and interferometry" and the 2020 "Secure quantum key distribution with realistic devices" (Secure quantum key distribution with realistic devices). devices), the third review paper.

Paper link: https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.94.035001

Cao Yuan, male, associate researcher at University of Science and Technology of China, doctoral supervisor. Obtained a Doctorate of Science from the University of Science and Technology of China in 2012. The research field is free space quantum communication and experimental research on basic issues in quantum physics. Recent research directions of major interest include: new quantum entanglement sources, quantum light interference at large spatial scales and their exploration of the integration of quantum theory and general relativity. Applications, single photon three-dimensional imaging, etc. Relevant research results have been selected into China's top ten scientific and technological advances for many times. The work related to realizing counterfactual direct quantum communication based on the quantum Zeno effect completed as the first author was selected into the 2017 "Physics World" website of the British Physical Society . The world's top ten physics breakthroughs of the year. He once served as the deputy chief designer of the quantum entanglement source subsystem of the Mozi quantum science experimental satellite; he was awarded the title of Outstanding Postdoctoral Fellow of the Quantum Information and Quantum Science and Technology Frontier Collaborative Innovation Center Mozi (2015); Chinese Academy of Sciences Youth Member of of Innovation Promotion Association (2018); Member of Quantum Information Branch of China Electronics Society.

Article source : Shanghai Research Institute

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