2022 Nobel Prize in Physics announced: Three scientists awarded for their research in the field of quantum entanglement

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This article is from WeChat public account: Huipu (ID: fanpu2019) , author: Xue Peng, title map from: Visual China

At 11:45 on October 4, 2022 local time in Sweden (17:45 on October 4, Beijing time) , the Nobel Prize Committee announced that the 2022 Physics Prize will be awarded to French physicist Alain Aspect and American physicist John F. Clauser and Austrian physicist Anton Zeilinger for “verifying that quantum does not obey Bell’s inequality with entangled photons, and pioneering quantum information science”.

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The Nobel Prize Committee stated in its official introduction that quantum mechanics now has a wide range of research fields, including quantum computers, quantum networks and secure quantum encrypted communication.

Anders Irbäck, Chairman of the Nobel Committee for Physics, said: “It is becoming increasingly evident that a new quantum technology is emerging. We can see that the research of entangled states by the laureates is very important, even going beyond the fundamentals of explaining quantum mechanics. question”.

Xue Peng, a professor at the Beijing Computational Science Research Center, guessed this year’s winners in advance. She told “Fu Pu” that the three winners were well deserved.

The following is Professor Xue’s introduction to the popular science of this year’s award-winning work.

In 2010, three physicists, Alain Aspect of France, John Clauser of the United States, and Anton Zeilinger of Austria, “because of their Fundamental concepts and experimental contributions to the foundations of quantum physics, in particular a series of increasingly complex tests of Bell’s inequalities, have won the Wolf Prize “.

In 2019, 2020 and 2021, the popular science website Inside Science of the American Physical Union predicted that the three physicists will win the Nobel Prize in Physics for three consecutive years.

Einstein believed that quantum entanglement, the super-distance interaction, was inconceivable and violated the special theory of relativity. Instead of a thought experiment proposed by his Princeton assistants, Boris Podolsky and Nathan Rosen, it is known as the EPR paradox. Particles whose A and B are spin 1/2 are described, and the initial total spin is zero.

Assuming that the particle has two possible spins, namely |up> and |down>, then, if the spin of particle A is |up>, the spin of particle B must be |down>, in order to keep the overall conservation, vice versa. At this time we say that these two particles constitute a quantum entangled state.

Two particles A and B are flying in opposite directions, they are getting farther and farther apart… No matter how far apart, they should always be |up>|down> related. Two particles are measured on both sides by observers Alice and Bob, respectively.

According to quantum mechanics, each particle should be in some superposition state, say |up>, |down> with 50% probability each, as long as Alice and Bob have not made measurements. Then, if Alice measures A, the superposition of A collapses in an instant, eg, to |up>.

Now, here comes the problem: since Alice has already measured that A is |up>, B must be |down> for conservation reasons. However, at this time, A and B are already very far apart, say tens of thousands of light-years. According to the theory of quantum mechanics, B should also have half the probability of |up> and |down>. Why can it be done? Always select | Down > What? Unless there is some way of “communicating messages” between A and B particles in a timely manner?

Even assuming they can sense each other, that seems to be an instantaneous signal at a distance! And this action at a distance is contrary to the theory of relativity that the speed of light cannot be surpassed. So this constitutes a paradox.

Therefore, he believes that quantum mechanics is incomplete, and he hopes to establish a more general theory of local realism to make up for the deficiencies of quantum theory and eliminate the action at a distance. As the successor of Einstein’s thought, Bohm introduced “hidden variables” in 1952, and formed a completely decisive theory on the basis of local realism – local hidden variable theory. The following is to verify whether the quantum mechanics theory is correct and complete or whether the local hidden variable theory is correct and complete.

The experimental verification of Bell’s theorem is a physical experiment designed to test which of the quantum mechanics theory and the local hidden variable theory is correct.

The birth of Bell’s inequality announced the local controversy of quantum mechanics theory, from pure speculation with philosophical color to scientific theory that can be falsifiable by experiment. Although Bell, as a follower of Einstein, his original intention to study the theory of hidden variables was to prove that the non-locality of quantum mechanics was wrong, all subsequent experiments showed that the predictions of the local hidden variable theory were wrong, and the quantum theory was wrong. The predictions are consistent with the experiments.

In 1972, John Clauser and Stuart Freedman completed the first Bell’s theorem experiment at the University of California, Berkeley, due to the existence of a locality loophole, that is, the distance between entangled particles is too small to explain the non-locality of entanglement, The results were not convincing.

In 1982, Alan Aspect et al improved the Bell’s theorem experiment of Clauser and Freedman at Paris 11 University, and the experimental result violated Bell’s theorem.

In 1998, Anton Zeilinger and others completed Bell’s theorem experiments at the University of Innsbruck, Austria, completely eliminating the local loopholes, and the experimental results are decisive.

In 2015, Ronald Hanson’s research group at Delft University of Technology in the Netherlands reported their experiments to verify Bell’s inequality in a diamond color center system. To avoid locality holes, simply place two diamond color centers in two labs 1.3 kilometers apart. Using entangled photon pairs and entanglement exchange techniques, they achieved entanglement between electrons in diamond color centers.

The time required for the direct optical communication between the two color centers is about 4.27 microseconds, and the time to complete an experiment is 4.18 microseconds, which is 90 nanoseconds less than the optical communication time, so the locality loophole is solved.

In addition, the measurement efficiency of color centers is as high as 96%, and the measurement loopholes are also blocked. In conclusion, they claim to have achieved a loophole-free experiment verifying Bell’s inequality, supporting quantum theory with 96% confidence (2.1 standard deviations) , thereby falsifying the local hidden variable theory.

In 2016, the Big Bell Test was launched and more than 100,000 volunteers were called from around the world.

In the experiment, all volunteers need to continuously choose based on personal free will to form binary random numbers, and press 0 or 1 quickly and randomly in the clearance game, and continuously generate a data stream of more than 1,000 bits per second within 12 hours. , all recorded in the Internet cloud, and distributed in real time and randomly to relevant research groups distributed around the world to control the Bell inequality test experiments of these research groups.

The Big Bell Experiment believes that human beings have true free will. Through the free will of a large number of participants, the Big Bell Experiment closes the loophole of free choice in a wider range and strongly denies Einstein’s principle of locality.

This article is from WeChat public account: Huipu (ID: fanpu2019) , author: Xue Peng

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