Chinese scientists realize the world's first quantum satellite "thousand kilometers" two-way communication
Electronic enthusiasts eight o'clock in the morning: From the world's first quantum science experimental satellite "Mozi" launched, there will be a full six years, and on August 10, the chief scientist of this satellite, China The joint research team of the Chinese Academy of Sciences led by Academician Pan Jianwei of the University of Science and Technology has thrown a major achievement to the outside world - "Mozi No." successfully achieved the "thousand kilometers" of two-dimensional quantum communication in the world for the first time.
Carl Zimlers, editor of the journal Physical Science of Nature, said, "This is very exciTIng stuff" and gives an evaluation: "In the past, people would say that the limits of quantum technology are on the horizon. However, this statement is actually somewhat conservative." In these experiments by Pan Jianwei, quantum technology has broken through the "gone beyond the sky" and upgraded the research on applied quantum communication technology to such an "astronomical height." (astronomical height)".
More than a month ago, Pan Jianwei team took the lead in the international realization of the "thousand-kilometer-level" two-way quantum entanglement distribution, and published the results in the "Science" magazine on June 16, which completed the "Mozi" The scientific task is “two-way quantum entanglement distributionâ€; today, two other tasks are completed: high-speed satellite quantum key distribution and geostationary quantum teleportation, and related results have been published online on August 10th. Nature magazine.
So far, the "Mozi" quantum satellite belonging to China has completed the three scientific goals set in advance. At the media meeting on August 4th, the Chinese Academy of Sciences Dean Bai Chunli said to the media including China Youth Daily, Zhongqing Online, etc., "(The 'Mozi' quantum satellite) series of achievements won a great international reputation, marking China's research in the field of quantum communication has reached the dominant position of 'all-round leadership' internationally."
(1) Star-studded quantum key experiment: transmission efficiency is increased by tens of billions of times compared with traditional technologyUnlike classic communication, quantum key distribution is transmitted through quantum states. Users in remote locations can share unconditionally secure keys, and use this key to encrypt information once and for all. This is the only one that is currently human. Known unconditional and unbreakable unconditional and secure communication methods.
One of the important research contents is quantum key distribution.
The so-called key distribution experiment should be based on the establishment of some "principles" of quantum mechanics. For example, "quantum non-cloning theorem, quantum indivisibility" makes "the existence of eavesdropping must be discovered", and the quantum "one time, one secret, completely random", and "encrypted content can not be deciphered" become a reality.
Carl Zimlers also mentioned that quantum key is the key to ensuring the high confidentiality of communications. He said, "In the absence of a key, you can't read these communications. If someone else has eavesdropped on your key, the principle of quantum mechanics guarantees that you will know, and the security of your communication is up again." One floor."
Today, the idea of ​​quantum key distribution has been experimented at a distance of thousands of kilometers.
Specifically, the quantum key distribution experiment uses satellite to transmit quantum signals, and the ground receiving method, when the "Mozi" quantum satellite transits, establishes an optical link with the Hebei Xinglong ground optical station, and the communication distance is from 645 kilometers to 1200 kilometers.
According to the experimental results of "Mozi No.", on the communication distance of 1200 km, the quantum decoy source on the satellite transmits an average of 40 million signal photons per second, and an over-track docking experiment can generate a 300kbit security key, and the average code rate can be Up to 1.1kbps.
Behind these data is a comparison result, that is, the transmission efficiency of the "Star Quantum Key" is 20 orders of magnitude higher than the traditional technology, that is, the same distance to the ground Fibre Channel, that is, the trillions of times.
Reviewers of Nature magazine praised Starland's quantum key distribution as "impressive achievement" and "it consTItutes a milestone in the field", and called "m. Undoubtedly, it will cause high interest among scientists and the general public in the fields of quantum information and space science, and lead to extremely extensive coverage in the public media."
(2) Quantum teleportation experiment: the traditional fiber repeating work requires 380 billion yearsAnother article by Pan Jianwei published by Nature on August 10th is about quantum teleportation, which uses quantum entanglement to accurately transfer the unknown quantum state of matter to distant places, but the object itself does not need mobile.
According to Carl Zimlers, this is the "most famous but mysterious" aspect of quantum mechanics. He said that in this experiment, the Pan Jianwei team showed how to use photons in entangled states to achieve this.
Specifically, when the "Mozi" quantum satellite transits, it establishes an optical link with the Tibet Ali ground station at an altitude of 5,100 m. The ground source produces 8000 "quantum teleportation cases" per second, and the ground transmits entangled photons to the satellite. The experimental communication distance ranges from 500 km to 1400 km. All six states to be transmitted exceed the classical limit with a confidence of more than 99.7%. .
According to Pan Jianwei, assuming that this work is repeated in the same length of fiber, it takes 380 billion years—that is, 20 times the age of the universe—to observe one case.
"These results represent a major breakthrough in the continuous exploration of long-distance quantum communications," said Nature Reviewer. "This goal is very novel and challenging, and it represents a major advance in the real-world implementation of quantum communication solutions."
On June 16th, when China took the lead in realizing the two-dimensional quantum entanglement distribution of the “thousand-kilometer-level†star field, Pan Jianwei mentioned that when it was not made (this experiment), there was a lot of suspicion outside, and now it takes so much time to make it. Now, internationally, they all said that they should "catch up as much as possible".
As one American colleague said, although the first spacecraft and the first satellite were made by the Soviet Union, the United States was the first to land on the moon. They feel that as long as they work hard, they can catch up with China in the field of quantum. Pan Jianwei said, "So, we don't dare to slack off."
Nowadays, when the scientific task of the "Mozi" quantum satellite is completed, Bai Chunli said the same meaning: "Innovation never ends, and it is not allowed to slack off. If you do not advance, you will retreat. ."
He said that at present, we maintain a leading position in the field of quantum communication research, but the competition is becoming increasingly fierce. The United States has released a new quantum research program. The EU and Japan are also stepping up their research. In the new round of scientific research competition, the situation and pressure we face will be greater than ever.
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