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Mozi: Setting the benchmark for quantum communication in China

Recently, the American Association for the Advancement of Science announced that the scientific research team of the “Micius” quantum science experiment satellite was awarded the 2018 Cleveland Award in recognition of the team’s efforts to promote large-scale quantum communication experimental research by achieving two-way quantum entanglement distribution between thousands of kilometers. outstanding contribution. This is the first time in the more than 90 years since the award was established that Chinese scientists have won this important honor for their scientific research achievements in their own country. A few months ago, on December 17, 2018, the research results of intercontinental quantum key distribution completed by the “Micius” quantum science experimental satellite were also included in the ten major advances in the field of international physics by the American Physical Society in 2018 .

Successful realization of three scientific goals

“The ‘Mozi’ quantum satellite has successfully achieved all the three predetermined scientific goals, laying a solid scientific and technological foundation for my country to continue to lead the world’s quantum communication technology development in the future and to test frontier research on basic problems in space-scale quantum physics.” China Professor Pan Jianwei from the University of Science and Technology told the Science and Technology Daily reporter.

Due to the principle of quantum non-cloning, the signal of quantum communication cannot be amplified like classical communication, and the distance of quantum communication is greatly limited due to the inherent attenuation of fiber channel. Taking advantage of the fact that outer space is almost vacuum and thus the optical signal loss is very small, the quantum communication distance can be greatly extended through satellite assistance. Pan Jianwei’s team has carried out a series of pioneering experimental researches for the realization of satellite-to-earth quantum communication. The “Mozi” quantum science experimental satellite was successfully launched at the Jiuquan Satellite Launch Center on August 16, 2016, and scientific experiments were officially launched on January 18, 2017.

High-speed quantum key distribution between satellite and earth is one of the scientific goals of the “Micius” quantum satellite. The “Mozi” quantum satellite has established an optical link with the Hebei Xinglong Ground Optical Station. At a communication distance of 1,200 kilometers, the transmission efficiency of the satellite-to-ground quantum key is 20 orders of magnitude (trillion times) higher than that of the ground fiber channel at the same distance. .

Achieving terrestrial quantum teleportation is another scientific goal of the “Micius” quantum satellite. Quantum teleportation uses quantum entanglement to precisely transport an unknown quantum state of a particle to a distant location without transporting the particle itself. The “Mozi” quantum teleportation experiment adopts the method of transmitting entangled photons on the ground and receiving them in the sky. When the satellite transits, it establishes an optical link with the Ali ground station in Tibet at an altitude of 5,100 meters. The ground light source generates 8,000 quantum teleportation events per second, and transmits entangled photons to the “Mozi” quantum satellite. The experimental communication distance is from 500 kilometers to 1,400 kilometers. km, all 6 to-be-transmitted states exceed the classical limit with greater than 99.7% confidence.

Quantum entanglement, which Einstein called “spooky action at a distance”, is one of the most amazing phenomena of quantum mechanics. Because quantum entanglement is very fragile, previous quantum entanglement distribution experiments only stayed at a distance of 100 kilometers. Does this “spooky action at a distance” still exist at greater distances? Will it be affected by other factors such as gravity? As one of the three major scientific experimental missions of the satellite, the “Micius” quantum satellite has carried out the quantum entanglement distribution experiment on the spatial scale for the first time in the world.

The entanglement source payload on the “Micius” satellite generates 8 million entangled photon pairs per second, which can establish quantum entanglement between two stations over 1,200 kilometers on the ground at a speed of 1 pair per second. The transmission attenuation of quantum entanglement is only One trillionth of terrestrial fiber.

Open the era of global quantum communication

The series of scientific experimental results obtained by the “Mozi” quantum science experimental satellite have won international acclaim and praise, and also opened the door to the era of global quantum communication.

The realization of satellite-to-earth quantum key distribution has laid a reliable technical foundation for the construction of a quantum secure communication network covering the world. On this basis, using satellites as trusted relays can realize key sharing between any two points on the earth, and expand the scope of quantum key distribution to cover the whole world. In addition, by interconnecting the quantum communication ground station with the intercity optical fiber quantum secure communication network, it is possible to build a global-covering space-earth integrated secure communication network.

The distribution of satellite-to-earth quantum entanglement and the realization of earth-to-star quantum teleportation enable people to use the quantum channel established by quantum entanglement to build the basic unit of quantum information processing network, and also to develop large-scale quantum network and quantum communication for the future. The experimental research and the experimental testing of the basic principles of physics such as general relativity in outer space and quantum gravity have laid a solid technical foundation.

After the completion of the three scheduled scientific experimental tasks of the “Mozi”, in early 2018, through the international cooperation with the Austrian Academy of Sciences, the “Mozi” quantum satellite achieved the first intercontinental quantum secrecy between Beijing and Vienna, which is about 7,600 kilometers away. communication. This achievement was also selected by the American Physical Society as one of the top ten advances in international physics in 2018.

In 2018, the “Wolf Prize in Physics”, known as the wind vane of the Nobel Prize, specifically mentioned in the introduction of the winners: “Quantum key distribution has been successfully commercialized, and it has been able to reach hundreds of kilometers in optical fibers. , you can do thousands of kilometers with satellites.” And these two records are created by Pan Jianwei’s team. One is the safest distance of 404 kilometers for optical fiber quantum key distribution, and the other is the 1,200 kilometers from the star to earth achieved by “Mozi”. This is the contribution of Chinese scientists. It is also a symbol of China’s quantum communication leading the world.

“Quantum communication uses the principles of quantum mechanics to manipulate quantum states, and can accomplish tasks that classical communication cannot.” Pan Jianwei said that quantum key distribution can achieve unconditionally secure key distribution, even if the eavesdropper has the strongest computer in the universe , even a quantum computer cannot crack the encrypted information. The use of quantum key distribution technology can help realize the unconditional security of confidentiality, authenticity and non-repudiation in communication security, that is, to ensure that the communication encryption cannot be deciphered, the identity of the other party is authentic and reliable, and the information cannot be tampered with.

Standardization is the cornerstone of mature industry development

In 2013, my country launched the construction of the Beijing-Shanghai trunk line of quantum secure communication. At present, in addition to the financial users that are connected as planned, power system and big data Internet companies are also accessing. The central bank has already formulated relevant standards for access and use in the financial sector.

Almost at the same time, the world’s major developed countries have or are stepping up the implementation of long-distance quantum communication trunk projects. The users of the Italian quantum communication backbone network include many research institutions and companies such as the Italian National Metrology Institute and the European Nonlinear Spectroscopy Laboratory; the UK is building the UK National Quantum Communication Test Network; the Russian Quantum Center has built a dedicated network for transmitting real financial data. Practical quantum communication line; South Korea’s first phase of quantum secure communication network around Seoul, in addition to serving the fields of public administration, police and postal services, is expanding to the fields of national defense and finance…

“The Beijing-Shanghai trunk line will drive the development of the entire industry chain, especially in the localization of core components and the formulation of relevant standards.” Pan Jianwei said that the quantum secure communication technology (or quantum key distribution, QKD), which is currently the first practical technology, is being developed. It has developed vigorously and has made great progress, but there are still many challenges to further realize the application of QKD from practical to Industrial scale. Among them, standardization is a key step and the cornerstone of the mature development of the future industry.

At present, my country is making every effort to promote the standardization of QKD. In June 2017, the China Communications Standards Association (CCSA) of the Ministry of Industry and Information Technology established an ad hoc group on quantum communication and information technology, with 44 member units, focusing on the terminology, application scenarios, network architecture, technical requirements, and testing of the quantum secure communication standard system. Methods, application interfaces and other content to compile relevant national standards and industry standards. In addition, Chinese experts launched the world’s first international standard project of QKD at the ISO/IEC International Organization for Standardization, officially opening the international standardization process of QKD.

“Like the development of any new technology, the application and development of quantum communication technology also requires experiments and application demonstrations.” Pan Jianwei has always adhered to this point of view for engineering and practical application. Active deployment is necessary, because there are applications that lead to progress and the future. (Reporter Wu Changfeng)

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