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Some people think that the superposition state is a state similar to a blind box, and the result has been determined before the blind box is removed, but you just don't know it. Wrong, not so!
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This video was released on December 22, 2021 and has nearly 2,000 likes
Highlights:
On November 19, 2021, the University of Science and Technology of China posted an interesting message (http://news.ustc.edu.cn/info/1055/77557.htm): Our university posted on Science... Instead of sending a paper, I sent a review article. That is to say, other scientists do a study, publish a paper, and then the scientists of our school make a comment on it and introduce its background and significance to the reader.
The important achievements of mainland scientists that I have introduced in the past are often accompanied by such review articles. It was someone else who judged us, and this time we were judging others. This is an interesting thing, because the first person who is qualified to be rated in Science is, of course, the famous people in the field. Therefore, we can understand that the interaction between mainland scientists and scientists from other countries is already a two-way street, and everyone sits on an equal footing.
Let's take a closer look at this work. The author of this review article is Professor Wang Xing'an and his doctoral supervisor Academician Yang Xueming, who have done a lot of internationally renowned work in the field of molecular reaction dynamics, and this review is a paper published in the same period in the journal Science, richard N. Zare, a foreign academician of the Chinese Academy of Sciences. The gist of this work was to realize the two states of the D2 molecule, the hydrogen molecule composed of two deuterium atoms, and to observe the difference between the two states.
The first of these two states is that the D2 molecule has a state of definite orientation, taking an angle of 45 degrees or -45 degrees relative to a reference axis. That is, if the reference axis is in the 0 o'clock direction on the clock, then the connection between the two D atoms in the D2 molecule can point to the direction of 1.5 o'clock or to the direction of 10.5 o'clock. These are two different states, but their orientation is both deterministic, and both belong to the category of orientation determination. We call this state of orientation determination a unordered state.
The second state is the superposition of these two states in the first. What is superposition? Anyone who has read my popular science book " A Brief Introduction to Quantum Information " can understand that this is a phenomenon peculiar to quantum mechanics , and there is no word superposition in Newtonian mechanics. The two states with an orientation of plus or minus 45 degrees are superimposed to obtain a state without determining the orientation. Measuring its orientation to this state will give 45 degrees with half the probability and -45 degrees with half the probability, so we call it a biaxial state.
We need to emphasize that the biaxial state is a real state, just as real as the mono-axis. Some people think that the superposition state is a state similar to a blind box, and the result has been determined before the blind box is removed, but you just don't know it. Wrong, not so! The correct understanding is that the superposition state is a real state, it really exists in the blind box, and it is only when you open the blind box and make a measurement that it undergoes a mutation and becomes one of the two possible outcomes.
What is the difference between these two understandings? The difference can be expressed in a number of experimental methods, such as this article using a method similar to the double-slit interference in optics.
Inelastic scattering occurs with He atoms and D2 molecules to measure the angular distribution of the product. If the D2 molecule is a mixture of two unannoidal states, that is, half 45 degrees plus half -45 degrees, then the resulting angular distribution is similar to the addition of the results of two single-slit experiments, that is, there are two bright stripes, which are continuous transitions in the middle, and there are no light and dark stripes. If the D2 molecule is in a biaxial state, that is, the superposition of two uniaxial states rather than mixing, then the angular distribution is similar to the result of double-slit interference, with two of the brightest stripes, but several light and dark stripes in the middle, especially in the middle that are completely black. You see, the difference is immediate, right?
The significance of this study in principle is to show the wave-particle duality of matter. For technical significance, let's excerpt the report on HKUST's homepage:
Laser preparation of specific quantum states and oriented molecules technology has reflected its significant advantages and scalability, in the future experiments, combined with advanced laser quantum state preparation and molecular space orientation technology, scientists will be able to carry out further precision dynamic measurement of hydrogen exchange and other reactions through cross-molecular beam experiments, with the help of laser state selection "double slit experiment" in-depth understanding of the quantum interference behavior and stereodynamics of primitive reactions, and is expected to achieve stereoscopic quantum dynamics control of ternary chemical reactions in the future.