Thousands of kilometers away, quantum entanglement is still there. China experiment answers Einstein’s puzzle
China continues to lead in quantum communication research.

　

　　On June 16th, Chinese scientists took the lead in successfully realizing the two-way quantum entanglement distribution between the satellite and the ground in the world by using the "Mozi" quantum science experimental satellite, and on this basis, they realized the nonlocality test of quantum mechanics that strictly met the "Einstein localization condition" on the spatial scale, which laid a reliable technical foundation for the future experimental research on large-scale quantum networks and quantum communication, as well as the experimental test of the basic principles of physics such as general relativity and quantum gravity in outer space.

　

This achievement was made by a research team composed of Pan Jianwei, a professor at China University of Science and Technology, and Peng Chengzhi, a colleague, in collaboration with Wang Jianyu Research Group of Shanghai Institute of Technical Physics, Institute of Microsatellite Innovation, Institute of Optoelectronic Technology, National Astronomical Observatory, Purple Mountain Observatory, National Space Science Center, etc., with the support of the strategic pilot science and technology project of space science of China Academy of Sciences. On the same day, relevant achievements were published in the international authoritative academic journal Science in the form of cover papers.

　

Two entangled quanta, no matter how far apart, can affect each other instantly.

　

On August 16th, 2016, China successfully launched the first quantum science experimental satellite "Mozi", which is one of the first scientific experimental satellites in the space science pilot project of China Academy of Sciences.

　

Quantum is the smallest and indivisible unit of energy in the physical world. Quantum entanglement is one of the two wonderful properties of quantum. "It is a quantum state composed of two (or more) particles. No matter how far apart the particles are, measuring one of them will inevitably affect other particles. Two entangled quanta are like a pair of telepathic twins. No matter how far apart they are, on the order of thousands of kilometers or more, as long as the state of one of them changes, the state of the other person will also change. " Pan Jianwei said, "This phenomenon is called nonlocality of quantum mechanics. The nonlocality of quantum entanglement is one of the most magical phenomena in quantum mechanics. "

　

Einstein called quantum entanglement "ghostly action at a distance", and he thought that this effect may be manipulated by some so-called "hidden variable" that people may not understand for the time being. So, is Einstein right?

　　

In 1964, physicist john bell put forward an experimental scheme, which can be tested. "This is the quantum entanglement distribution experiment. Let a machine emit the prepared pairs of entangled particles (usually photons) in two directions, and then randomly measure the polarization direction of entangled photons at different angles. " Peng Chengzhi, a researcher at the University of Science and Technology of China, the chief engineer of the scientific application system of the quantum science experimental satellite and the deputy chief engineer of the satellite system, said, "If the measurement results meet the Bell inequality, Einstein is right; Otherwise, it is proved that the nonlocality of quantum mechanics is real. "

　　

To verify whether quantum entanglement exists at a longer distance, we need to experiment in space.

　　

In the quantum entanglement distribution experiment, in order to ensure the space-like separation of measurement events, scientists always place two detection devices at a certain distance. Every time they finish a round of experiments, they will think, if the distance is farther, does quantum entanglement still exist?

　

However, because quantum entanglement is very fragile, it will decay with the transmission distance of photons in optical fiber or in the surface atmosphere. In other words, if this experiment is done on the ground, the transmission distance cannot be too long.

　

"Even with the most advanced ideal single-photon detector, point-to-point quantum communication in 1200 km optical fiber can only transmit one bit every 30,000 years. Just like a team with 1 million people, there may be only a few people left in the end, and it took a long time to reach the destination. " Pan Jianwei said, "This leads to the low efficiency of information transmission over a long distance, so the previous quantum entanglement distribution experiment only stayed at a distance of 100 kilometers."

　

How can we further extend the distance of quantum entanglement distribution? Pan Jianwei said that there are two ways in theory at present. One is to use quantum relay, that is, to divide the transmission into several segments to reduce the loss of each segment, and solve this problem by means of "quantum relay". However, at present, this approach is still seriously restricted by factors such as quantum storage life and readout efficiency, so it can not be applied in practice.

　

"The other is to use the satellite platform. Because in space, there is basically a vacuum near the orbit of the satellite, and most of the air is attached to the surface of the earth. Therefore, if entangled photons are emitted from space to the ground, the interference will be relatively small and the loss will be small. Combined with the transfer of satellites, it is expected to realize ultra-long-distance quantum entanglement distribution on a global scale. " Pan Jianwei said, "Our research team decided to use this way to extend the distance of quantum entanglement distribution, and in 2003, we proposed a scheme to realize long-distance quantum entanglement distribution by using satellites."

　

When the satellite transits through the border, it realizes the two-way quantum entanglement distribution between the satellite and the ground in 1200 kilometers.

　

How is this experiment conducted?

"When the Mozi crossed the border, it established optical links with two ground stations, Delingha Station in Qinghai and Gaomeigu Station in Lijiang, Yunnan." Wang Jianyu, a researcher at Shanghai Institute of Technical Physics, Chinese Academy of Sciences, executive deputy chief engineer of quantum science experimental satellite engineering and commander-in-chief of satellite system, said that the entanglement source load on the satellite generates 8 million entangled photon pairs per second, and the establishment of optical link can establish quantum entanglement between two stations over 1,200 kilometers on the ground at the speed of one pair per second, and the transmission attenuation of this quantum entanglement is only one trillion times that of the lowest loss ground optical fiber of the same length.

　　

Pan Jianwei said: "Under the condition of closing the localization loophole and measuring the selective loophole, the experimental results we obtained violated Bell’s inequality with four standard deviations, that is, the quantum mechanical nonlocality test that strictly meets Einstein’s localization condition was realized on the spatial scale of thousands of kilometers."

　

Reviewers of Science magazine praised the achievement as "a major technological breakthrough with potential practical application and the importance of basic scientific research".

　

Pan Jianwei said that using the developed quantum entanglement distribution technology, the research team is conducting experiments to create keys to realize information transmission between heaven and earth. At present, one of the main challenges of quantum communication is how to distinguish and receive the signals of quantum satellites when there are a large number of optical photons in the daytime, so as to realize quantum communication. Other important scientific experimental tasks of Mozi satellite, including high-speed satellite-ground quantum key distribution and teleportation of satellite quantum, are also under intense and smooth progress. It is expected that more scientific achievements will be released one after another this year.

　

Our reporter Wu Yuehui People’s Daily (June 17, 2017, 04 edition)

　http://paper.people.com.cn/rmrb/html/2017-06/17/nw.D110000renmrb_20170617_7-04.htm

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From March 20th to April 6th at 8: 00 a.m, the Legislative Affairs Commission of the National People’s Congress Standing Committee (NPCSC) received a total of 37,560 opinions. Among them, 37,067 opinions were put forward through websites such as China People’s Congress Network, 100 opinions were published in newspapers such as People’s Daily and Legal Daily, and 393 letters were received. On March 27th, we announced to the media the first stage of the draft labor contract law for comments. From March 28th to April 6th, compared with the first stage, the number of opinions received increased significantly, which shows that all sectors of society attach importance to and pay attention to this law. In addition to continuing to put forward opinions on the scope of application of the draft, the short-term labor contract, the probation period and the standard of economic compensation, the opinions at this stage mainly reflect the following aspects:

First, the purpose of labor contract legislation should seek a balance between the rights and interests of workers and the rights and interests of enterprises. Some opinions suggest that law is the regulator of social relations and social interests, and any legislation is the allocation of rights and obligations and social interests. Legislators must find a combination point among multiple interest subjects and strive to find a balance of interests among various interest subjects, especially between the opposite parties in the same contradiction. As far as labor relations are concerned, the laborer is weak at any time. However, if legislation excessively expands the rights and interests of laborers and increases the responsibility of enterprises, it will bind the autonomy of employing people in enterprises, make it difficult to implement flexible management of survival of the fittest, affect the optimal allocation of human resources, and ultimately affect the market competitiveness of enterprises. "If the skin doesn’t exist, the hair will be attached." If the enterprise collapses, the workers will lose their jobs, and it is impossible to protect the rights and interests of workers. On the other hand, if the protection of workers’ rights and interests is not in place and there are too few requirements for corporate responsibility, it will affect the supply of labor force and is not conducive to the formation of a high-quality and healthy workforce. Therefore, labor contract legislation should establish a correct legislative concept, find an appropriate balance between citizens’ labor rights and interests and employers’ rights and interests, and ensure that labor relations are not unbalanced.

Two, in some cases, the existence of oral labor contracts should be allowed. The form of labor contract cannot be limited to written form. Now is the information age, and there are many forms of signing contracts. Labor contracts should be allowed to use electronic documents, oral contracts and other forms. As long as factual labor relations exist, they should be protected by law, and the emphasis on written forms may be detrimental to protecting the interests of workers. In particular, for part-time employment, employment with a short contract period or the contents of the contract have not changed much, it should be allowed to sign the contract orally.

Third, everyone has different views on the provisions of non-competition. Some people think that if the employer needs to keep business secrets, it can agree on non-competition when signing a labor contract with the employee, and at the same time agree with the employee to pay economic compensation for non-competition when the labor contract is terminated or dissolved. Some people think that the restriction of non-competition is not conducive to the flow of talents, and the termination of the labor contract means that the workers will lose their jobs, so it is suggested to cancel the restriction of non-competition. Some people think that the standard of liquidated damages for non-competition in the draft is too low, which will inevitably lead to the consequences of malicious poaching between enterprises in the same industry; Some people think that the economic compensation paid by the employer is too high, and it is suggested to refer to the non-competition clauses of other countries and modify the economic compensation to 50% of the annual wage income. If the laborer violates the non-competition restriction, in addition to paying liquidated damages, he should also pay compensation if he has caused economic losses to the enterprise.

Four, some people think that the provisions of the draft on the conclusion of a labor contract without a written form may be abused. If this provision is made, some workers may deliberately not sign a labor contract with the employer to achieve the purpose of signing an open-ended labor contract. It is suggested that the situation of not concluding a labor contract in written form should be clarified. Some people also think that this provision will use the employer to apply an open-ended labor contract in disguise without signing a written labor contract deliberately to achieve the purpose of arbitrarily dissolving the labor contract. Because according to the provisions of article 32 of the draft, the employer is subject to fewer restrictions when it terminates the open-ended labor contract. It is not conducive to achieving the original intention of stabilizing labor-employment relations and effectively protecting the legitimate rights and interests of workers.

Five, the labor contract law shall limit the overtime work of the employer. Many workers report that some enterprises now work overtime regularly and universally. Some workers work more than ten hours a day, six days or even seven days a week, and there is no overtime pay. Some enterprises calculate overtime when determining the workload, and they can’t finish the work quota without overtime, so as to maliciously avoid paying overtime, which seriously damages the rights and interests of workers and affects their health.

Six, the draft should make a special chapter on collective contracts. Some trade union organizations and the masses have suggested that a collective contract is an agreement on the rights, responsibilities and obligations of both employers and employees. Collective contract is the basis of labor contract and the soul of labor contract law. The practice in many countries has proved that the collective contract is an effective measure to ensure the workers’ negotiating status, and it is also the cornerstone to stabilize labor relations. At the present stage, when the supply and demand of labor force in China are unbalanced and workers are in a weak position, the measure to coordinate labor relations and make them harmonious is to promote and standardize collective contracts. Therefore, while legislating to standardize the labor contract, we should also standardize the collective contract. At present, it is difficult to introduce the collective contract law, so we should make a special chapter on the collective contract in the labor contract law.

Seven, the legislation should be clear about the supervision responsibility of the labor and social security department on the labor contract. Many problems in labor relations are not that there is no law, but that the law is not enforced. The provisions of the labor law have been relatively comprehensive, but problems such as arbitrarily terminating labor contracts, defaulting on wages, and not giving employees social insurance still occur in practice, indicating that the law has not been implemented well. There are laws that are not enforced, and no matter how good the laws are, it is useless. Some opinions suggest that law enforcement agencies should be given more effective law enforcement power, and at the same time, it is clear that safeguarding the rights and interests of workers is the statutory duty of the labor security department. If the labor department fails to perform its statutory duties, it should bear corresponding legal responsibilities. The provisions of the draft on the responsibility of labor and social security departments are not clear enough, so it is suggested that legislation should make clear provisions on this.

Eight, continue to discuss the issue of labor dispatch, put forward opinions and suggestions. Some suggestions should further regulate labor dispatch. First, improve the entry threshold of labor dispatch; The second is to clarify under what conditions, in which positions and types of work, the employer can use the form of labor dispatch; The third is to clearly divide the responsibilities of labor dispatching units and receiving units; Fourth, clearly stipulate the time limit for labor dispatch, and prohibit employers from using dispatched labor for a long time; Fifth, strict legal responsibility should be imposed, and severe punishment should be imposed on the labor dispatching unit and the receiving unit for shirking each other or maliciously colluding to infringe upon the legitimate rights and interests of workers.
(Provided by the National People’s Congress Standing Committee (NPCSC) Legal Affairs Committee)

　　have/reap a bumper/copious/rich harvest

　　Less than a month before the 2023 college entrance examination, the college entrance examination work was put on the agenda. On May 9, the Ministry of Education and relevant departments held a video conference on the safety of the 2023 national college entrance examination. The Minister of Education made arrangements for the 2023 college entrance examination, emphasizing the prevention of cheating on mobile phones as the top priority of this year’s college entrance examination.

　　This year’s college entrance examination is the first one after the Covid-19 epidemic, which means that the epidemic has little impact on the college entrance examination, and we will concentrate on the "safe college entrance examination". One of the arrangements for the "Safe College Entrance Examination" is to strengthen comprehensive management, and preventing mobile phone cheating is the top priority of this year’s college entrance examination security. To this end, the Ministry of Education emphasizes that mobile phones cannot be brought in, used or sent out.

　　The reason why preventing mobile phone cheating is the top priority of college entrance examination security is because everyone has a mobile phone today. If the prevention is not strict, the mobile phone will easily become a cheating tool. More importantly, in recent college entrance examinations, although it is explicitly forbidden for candidates to bring wireless communication devices such as mobile phones into the examination room before the college entrance examination, and metal detectors are supplemented during security inspection, and various measures are taken to shield wireless signals, mobile phone cheating cases still occur.

　　For example, in the college entrance examination in 2021, a candidate in Hubei illegally brought his mobile phone into the examination room. In the examination, he hid the mobile phone under the draft paper to shoot questions, and distributed it to a training institution to seek answers at the beginning of the examination. In the college entrance examination in 2022, a candidate in Gansu illegally brought his mobile phone into the examination room. After the examination, he took the test paper and sent it to QQ group for an answer. These events have aroused social concern and affected the reputation of the college entrance examination.

　　The college entrance examination is a life test for the majority of candidates. Only a standardized college entrance examination order can ensure the fairness of the college entrance examination. Although the mobile phone cheating in the above cases failed to achieve the goal, it still revealed that the security of the college entrance examination seemed to be well deployed, but in fact there were some loopholes. In order to maintain the fairness and justice of the college entrance examination, preventing mobile phone cheating has been mentioned in an important position in this year’s college entrance examination.

　　The so-called "no entry" is to strengthen the security inspection of test sites and prevent candidates from bringing their mobile phones into the examination room from the source. If the security personnel of the test center are serious and responsible for their work, and with the help of advanced technology such as metal detectors, candidates with mobile phones can be found in time and prevented from entering the examination room.

　　"I can’t use it" means to strengthen the responsibility of the invigilator in the examination room. Even if candidates carry their mobile phones through the security clearance, they will not have the opportunity to use them in the examination room, which is a supplementary defense against possible security omissions. "Unable to transmit" means to improve and upgrade the wireless signal shielding equipment, so that even if candidates use mobile phones in the examination room, they cannot achieve the purpose of obtaining answers.

　　In order to maintain the order and fairness of the college entrance examination, this year, the safety of the college entrance examination was clearly defined, and specific requirements were put forward to form a "full chain" supervision at the test sites. The effect is worth looking forward to. First, "taking the prevention of mobile phone cheating as the top priority of the college entrance examination this year" is a shock to candidates with cheating tendency. Second, this will further compact the supervision responsibility of the three links and ensure that mobile phone cheating cases will not appear.

　　However, considering that the total number of candidates is likely to exceed 10 million this year, the number of candidates in some provinces has increased, and the idea that individual candidates still cheat on mobile phones is not ruled out. At the same time, considering that there are as many as seven or eight thousand test sites in the national college entrance examination, it is not excluded that there are omissions in the security inspection of individual test sites. In addition, there are hundreds of thousands of college entrance examination rooms every year, and there are more than one million invigilators, not to mention the negligence of invigilators.

　　After the Ministry of Education emphasized that preventing cheating on mobile phones should be the focus of this year’s college entrance examination security, all localities must make further detailed arrangements to truly pursue secrecy and prevent one from being sparse. There are still more than 20 days before the college entrance examination. I hope that all relevant departments at all levels, the person in charge of each test center and each invigilator can make full preparations, strictly perform their duties and responsibilities, guard the discipline and fairness of the college entrance examination, and hand over satisfactory answers to the majority of candidates and the public.

　　Photo courtesy/vision china