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From this title, we can see that they are both proud, ignorant, and abandoned.
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This video was released on December 21, 2021 and has reached 208,000 views
Highlights:
Recently, people's daily published an article "China University of Science and Technology releases new results!" 》。 In fact, this is the result of a collaboration between my colleague and friend Professor Peng Xinhua's team and German scientists, who told me about it a few months ago. On November 18, 2021, the paper was finally officially launched in Nature Physics, so the media began to publicize it.
The paper is titled "Search for axion-like dark matter with spin-based amplifiers."
Uh, what's that talking about? Ordinary people may have difficulty in understanding one of these key words. The editor of the People's Daily must have been the same, since he couldn't understand it at all, he simply gave up treatment, and the headline only wrote a "New Achievements Released by the University of Science and Technology of China!" ", the end of the exclamation point, as for what the result is not mentioned at all. From this title, we can see that they are both proud, ignorant, and abandoned.
Let me explain. First, the result is the search for dark matter. The so-called dark matter is the invisible matter. Why believe it exists when you can't see it? Because invisible means it doesn't participate in electromagnetic interactions, but we already know that it participates in gravitational interactions. It is not felt in everyday life, but on cosmic scales it is often found that the actual gravitational effect is much stronger than that of visible matter. For example, the rotation of galaxies, astronomers have long found that galaxies seem to rotate too fast, if there is only visible matter in the galaxy, then they should have disintegrated long ago. The most convenient explanation for this is that there is dark matter, which holds galaxies together.
Based on these observations, it is now generally accepted that visible matter accounts for less than 5% of the entire universe, while dark matter accounts for about 27%. So what's more than 60%? It is dark energy that is more wonderful than dark matter, a force that accelerates the expansion of the universe. Therefore, the People's Daily reported that "dark matter accounts for about 85% of the mass composition of the universe," but so far no direct evidence of the existence of dark matter has been found." "This refers to about 85 percent of visible matter plus 27 percent of dark matter, excluding dark energy."
Then, what exactly is dark matter? Not yet known, this is one of the most important unsolved mysteries of whole physics. There are many conjectures about it, such as "weakly interacting massive particles" (WIMP for short, which means "coward"). Another conjecture that has attracted a lot of attention is the "axion", and a variety of axial-like particles, which are all light pseudo-scalar particles. This article searches for dark matter of these axions.
In order to find dark matter, countries have laid out a series of national or even world-class experimental detection programs (http://news.ustc.edu.cn/info/1055/77600.htm), such as the Alpha Magnetic Spectrometer AMS led by Ding Zhaozhong, the AdMX experiment on axle dark matter led by the University of Washington in the United States, and the "Wukong" satellite DAMPE led by the Purple Mountain Observatory of the Chinese Academy of Sciences. PandaX and CDEX at China's Jinping Underground Laboratory and CERN's Solar Axis Telescope CAST, among others. But so far, no definitive evidence of the existence of dark matter has been found.
So what are the results of these experiments? Their typical result is that the upper limit of the dark matter parameter is depressed. For example, if a theoretical model predicts that an average of one event will be seen once a month under certain conditions, but the observations are not seen once a year, then this model can be excluded. Or for any model to survive, it needs to meet the quantitative limits of these experiments.
Dmitry Budker
Peng Xinhua et al. contrasted mainly with CASPEr, which is an abbreviation for the Cosmic Axion Spin Precession Experiment, the cosmic axion spin precession experiment, which is also the name of a cartoon elf. The author of CASPEr, Professor Dmitry Budker of Germany, and a collaborator of Peng Xinhua's paper. The CASPEr works on the principle that tiny oscillations of the dipole moment of atomic nuclear power can be induced through the cosmic axion background, and in the perpendicular magnetic and electric fields, this oscillation causes the nuclear spin to precede, which in turn induces a small but perhaps detectable oscillating magnetic field (Nobel laureate Wilczek: Where will particle physics go? |). Mr. Sai). If found, this is evidence of the existence of the axion. Of course they haven't found it yet, but they've pressed the upper limit of the spin coupling of the axion to the kernel to a very low level, specifically 10^(-2)GeV^(-1), which is the best value before.
Then, what are the results of Peng Xinhua and others? They invented a new method of quantum precision measurement, which lowered this upper limit by 5 orders of magnitude and was lower than the so-called cosmic astronomical limit 5* 10^(-8) GeV^(-1), which means that any astronomical method is not as accurate as theirs. What's even more interesting is that their method is still desktop-style, that is, a table can be put down, and it is a small experiment, which is much cheaper than the previous dark matter detection experiments.
You can look at these two pictures. The previous one is a dark matter boundary given by a large astronomical observation, which is high enough that dark matter particles swim in it, with hippie smiles. The latter is the new boundary given by Peng Xinhua and others, this boundary is much lower, and the dark matter particles seem to be pressed under the Five Elements Mountain. The abscissa of these two plots is the mass of the dark matter particles, expressed in energy units eV, because the mass multiplied by the square of the speed of light is energy. The minimum upper limit they get is 2.9*10^(-9) GeV^(-1), which appears at 67.5 feV.
In the detection principle, they used a new spin amplification effect to achieve the best sensitivity of the nuclear spin magnetic sensor to date with a gaseous xenon and rubidium atom mixing vapor chamber. In short, they can achieve ultra-high sensitivity magnetic field detection.
Some people may ask, can this achievement win the Nobel Prize? The answer is: not yet, because it has only improved the detection accuracy of a certain type of dark matter candidate by 5 orders of magnitude, and has not yet found dark matter. If dark matter is found, it is, of course, far from a Nobel Prize problem, but a scientific revolution. However, at present, it is still in the stage of "if you want to do a good job, you must first use it.".
Finally, I can tell you that quantum precision measurements can not only be used to detect dark matter, but also play a role in many parts of everyday life. For example, magnetic resonance imaging in medicine now requires a strong magnetic field, which is very unfavorable for people who wear pacemakers, and with their technology, magnetic resonance imaging with zero magnetic field can be achieved. In my recently published popular science book" "A Brief Introduction to Quantum Information", I introduced this magnetic resonance imaging with zero magnetic field. It not only eliminates the requirement for magnetic fields, but also greatly reduces costs, which is expected to be a boon for many patients.
In addition, quantum precision measurements can be used to probe other new physics beyond the Standard Model. If one day it is reported that Chinese scientists have found a fifth basic interaction, please do not be surprised.