“Science everyone” | 40,000 words dry goods! You can understand the quantum information

Yu Lanfeng, Ph.D., University of Science and Technology of China, Associate Professor, National Laboratory of Microscale Material Science, Hefei, China University of Science and Technology, President of Science and Technology and Strategy. In recent years, you must see more and more “quantum” related to the news of science and technology. August 16, 2016, China launched the world’s first quantum science experimental satellite “Mozi”, it is a global sensation. But if you want to understand the quantum science, on the network to see and most of the mysterious and mysterious, inexplicable argument, what “no one knows how quantum mechanics” friends, “the role of space”, “God does not Dice “, the more confused. You can not help but whispered: perhaps so deep things, it is beyond the scope of my understanding? “Mozi” Quantum satellite launch on this, this article would like to say: Do not give up treatment! Okay, it’s a joke. The practical meaning is that quantum science is perfectly understandable and is by no means anything that can not be spoken. Just read this article carefully, I believe you will be able to get a very in-depth understanding of this subject. Depth to what extent? At least more than the vast majority of media reporters and people who eat melons. Later to see the relevant news, you will understand what is the matter, what is the background, what kind of meaning. After all, the essence of science is plain, any reason can be explained to the people. If you are tired of all kinds of trickery speculation, really want to learn some “dry goods”, then this article is definitely your food. Of course, reading this article is not as easy as drinking a chicken soup. Full text nearly 40,000 words, you may need to be divided several times to finish. And this article is about genuine scientific principles, really want to thoroughly understand, or need to have a certain basis, and focus on thinking. What kind of foundation does it need? Perhaps the level of high school … … If you really very hard to read, maybe junior high school also! (Pupils: do not discriminate against us!) Keke, no matter what your basis is what, as long as carefully read and think about this article, you will certainly be harvested. Well, let’s start this quantum journey. Buckle the seat belt, we have to start! What is the “quantum” Quantum science is mysterious, first of all the name is a big reason. See the word “quantum”, many people in the “unaware”, the first reaction is to understand it as a particle. But as long as the people who have been in secondary school, we know that we often see the material is composed of atoms, atoms and is composed of nuclei and electrons, the nucleus is composed of protons and neutrons. What exactly is the quantum? Is it smaller than the atomic, electrons? It is not. Quantum with atoms, electrons can not be relatively large, because it is intended to be a mathematical concept. Just as “5” is a number, “3 apples” is a kind, you ask “5” and “3 apples” which big, how does this answer? The correct answer can only be: they are not the same category of concepts, can not be compared. What is the meaning of the mathematical concept of quantum? Is the “smallest unit of discrete change”. What is “discrete change”? We count the number of people, there can be a person, two people, but can not have half a person, 1/3 individuals. When we step up, we can only step up one step, two steps, and not the first half, one third step. These are “discrete changes”. For the number of people, a person is a quantum. For the steps, a step is a quantum. If something can only be distorted, we say it is “quantum”. on the steps with the “discrete change” relative to the “continuous change.” For example, you in a section of the road, you can go to 1 meter position, you can also go to 1.1 meters position, you can go to the location of 1.11 meters, and so on, any distance between the middle can come, this is the ” Continuous change “. Obviously, discrete and continuous changes in daily life are a lot of existence, the two concepts themselves are easy to understand. So why does the word “quantum” become so important? Because people find that discrete change is an essential feature of the microscopic world. Discrete changes in the microscopic world include two categories, one is the material composition of the discrete changes, one is the physical volume of the discrete changes. First look at the first class, the material composition of the discrete changes. For example, light is composed of a photon, you can not separate half a photon, 1/3 photon, so the photon is the light quantum. Cathode ray is composed of an electronic, you can not separate half an electron, 1/3 electrons, so the electron is the cathode ray of the quantum. In this case, you seem to be able to take the quantum to the atomic, electronic comparison, but this does not make much sense, because it is with your problem and change. Atom, electrons, protons, neutrons, neutrinos These words themselves correspond to certain particles, and the word quantum corresponds to different particles in different contexts (if it corresponds to particles). And there is not some kind of particle specifically called “quantum”! Look at the second class, the physical volume of the discrete changes. For example, the energy of electrons in a hydrogen atom can only take -13.6 eV (eV is “electron volts”, an energy unit) or its 1/4, 1/9, 1/16, etc., in general, -13.6 eV (-13.6 / n 2 eV, n can take 1, 2, 3, 4, 5, etc.), and can not take other values, such as -10 eV, -20 eV. We can not say what the quantum of electron energy in the hydrogen atom is (because it is not the change of the equidistant distance), but it is said that the energy of the electron in the hydrogen atom is quantified and lies at the “energy level”. The energy of electrons in each atom is quantum, and this is a common phenomenon. Hydrogen atoms are found away fromAfter the change is an essential feature of the microscopic world, the scientist founded a physics theory that accurately describes the microscopic world, which is “quantum mechanics”. Now you can see how the name comes, and it is to emphasize the universality of discrete changes in the microscopic world. After the emergence of quantum mechanics, people called the traditional Newtonian mechanics “classical mechanics”. For the general public, quantum mechanics sounds like a frontier. But for the relevant professional (physics, chemistry) researchers, quantum mechanics is a very old theory, – has been more than a century! The origin of quantum mechanics in 1900, the German scientist Planck (Max Planck) in the study of “black body radiation” problem, found that the radiation must carry the energy as a discrete change in order to launch consistent with the experimental formula. On this basis, Albert Einstein, Niels H. D. Bohr, Louis V. de Broglie, Werner K. Heisenberg, Erwin RJA Schrodinger, Paul AM Dirac, and others have proposed a new concept that extends the application of quantum mechanics step by step. By the 1930s, the theoretical building of quantum mechanics had been largely established to quantitatively describe most of the microscopic world’s phenomena. Second, the ubiquitous quantum mechanics Quantum mechanics and relativity is the twentieth century two scientific revolution, the human world outlook had a strong shock. But the visibility of the public, quantum mechanics seems to be much lower than the theory of relativity. The reason may be that the theory of relativity is mainly created by Einstein, the image of the lone hero is easy to remember and spread, and the main contributors to quantum mechanics have few, not a unique spokesperson. Einstein and the theory of relativity were known to women and children, and heard of quantum mechanics in the “Schrodinger’s cat”, “Heisenberg measured principle” these words, has been regarded as a scientific enthusiast. However, most people do not know is that the scope of the application and the number of researchers, quantum mechanics far more than the theory of relativity. In other words, relativity is a relatively famous and less used theory, quantum mechanics is a less famous and more used theory. Why is this so? Look at these two theories play a role in the conditions to understand. Relativity has a fundamental importance in the case of objects moving close to the speed of light and strong gravitational conditions. But how many opportunities do you have in your daily life? In most cases, the object of our study is still at low speed, the earth’s gravitational field is not strong. So the current theory of relativity, limited to cosmology, heavy elements of chemistry, atomic clock, global positioning system and a few areas. While the other side, describing the microscopic world must use quantum mechanics, the nature of macroscopic material is determined by its microstructure. Therefore, it is necessary to use quantum mechanics not only to study the microscopic objects of atoms, molecules and lasers, but also to study the properties of macromolecule conductivity, thermal conductivity, hardness, crystal structure and phase transition. Many of the most basic problems are the quantum mechanics that can be answered before it appears. For example: why the atom can remain stable, for example, the hydrogen atoms in the electrons do not fall on the nucleus? (Because the energy of the electrons in the hydrogen atom is quantified, the lowest can only take -13.6 eV, and if it falls on the nucleus it becomes negative and infrains below this value.) Why is the atomic atom forming molecules, Hydrogen atoms H converged into a hydrogen molecule H 2 ? Why do atoms have different combinations, such as carbon atoms can be combined into graphite, diamond, football, carbon nanotubes, graphene? Why does salt NaCl form ionic crystals? Why are some substances very stable, and some substances are prone to chemical reactions? Why some substances such as copper can be conductive, some substances such as plastic is not conductive? Why do some substances such as silicon are semiconductors? Why do some substances, such as mercury, become superconductors at low temperatures? The Why is there a phase change, such as water at 0 degrees Celsius below the ice, 0-100 degrees Celsius between the liquid, more than 100 degrees Celsius gasification? Why change the composition of steel, can create a variety of special steel? Why are lasers and luminous diodes glowing? Why can chemists synthesize new substances much more than nature’s original species? Why do you know the elements of the distant planet by observing the spectral lines in the universe? … … modern society fruitful technical achievements, almost all with quantum mechanics. You open an electrical appliance, the conductivity is explained by quantum mechanics, power, chip, memory, and display works based on quantum mechanics. Into a room, the nature of steel, cement, glass, plastic, fiber, rubber is determined by quantum mechanics. The process of burning a plane, a ship, a car, and a fuel is determined by quantum mechanics. The development of new chemical processes, new materials, new drugs, are inseparable from the quantum mechanics. It can be said: rather than ask what quantum mechanics can be used to do, it is better to ask it can not do! The above is on the scope of the application of comparative quantum mechanics and relativity. Another observation angle is the number of people studying and studying. Now all the students of physics and many related professions (especially chemistry) learn quantum mechanics, and only students who study general theory of relativity, such as theoretical physics and astronomy, have a lot of students studying special relativity. The research activity of quantum mechanics is also much higher than relativity. In the media reports you will find that the quantum field is changing, the field of big news is to verify Einstein 100 years ago to predict the gravitational wave! double black hole merged to produce gravitational waves Third, the emerging quantum information Since the emergence of quantum mechanics has been more thanFor a century, why has it been so hot recently in the media? The answer is: Quantum mechanics and information science interdisciplinary – Quantum information. Why can these two disciplines cross? Because quantum science is an available mathematical framework for information science. The purpose of quantum information is to use the characteristics of quantum mechanics to achieve the classic information science can not achieve the function, such as will never be cracked confidential method (that is, later to explain the “quantum cryptography”), science fiction film ” Surgery “(yes, the transmission is in principle can be achieved, and its professional name is called” quantum teleportation “). As the classic information science, including communication and computing two major themes, quantum information research can also be divided into two blocks: quantum communication and quantum computing. Quantum information Subjects Quantitative development of quantum information, the quantum into a public opinion hot words. In the scientific community is rarely used in the “quantum technology” this argument, because as mentioned earlier, all the technological achievements of modern society are inseparable from the quantum mechanics, where there is no “quantum” technology? Scientists prefer to use well-defined “quantum mechanics” and “quantum information” and other terms. When you see “quantum technology” in the media, it often refers to quantum information. Fourth, the operation of the micro-world operation manual You may have heard a lot of rendering quantum mechanics how difficult to understand the argument, such as “even Einstein can not understand the quantum mechanics,” “Feynman said, no one understands quantum mechanics.” But for beginners, these statements are somewhat misleading, will let you think that quantum mechanics is a metaphysics, Zen machine, a kind of riddling or sophistry of something. In fact, quantum mechanics is a clear set of mathematical frameworks that can be compared to an operating manual for micro-world operations. Millions of scientists and technicians around the world are familiar with the operating manual, just as millions of plumbers are familiar with pipeline operations around the world. According to this operating manual, we can make accurate predictions of the operation of the microscopic world, with the experiment in line with the very good, often accurate to the decimal point after the 9th or more. British physicist Dirac’s famous “quantum mechanics principle” so hard to understand what is it? Is this operating manual “why” is this, this is a philosophical level of the problem. And this manual is itself very clear. Like you get the “nine yin scriptures”, although do not understand why many places inside so write, but you can become a master of martial arts training. From an information sciences point of view, quantum mechanics can take advantage of three points that are very violating the everyday experience of the macro world: stacking, measuring, and entangling. We may call it “three upanishads”. This is not to say that only three of the quantum mechanics, of course, there are other, but the relationship with the information science is not so big, this article is not introduced. Although these three esoteric violations of “common sense”, but many of the micro-world experiments have already verified their correctness. When you read the following, whenever you feel “how could this”, “this is not nonsense,” remember that these principles are not a scientist’s whim to the wall fictional, but has been nearly a hundred years Experiments have repeatedly proved that its application covers almost all things around us. So, in the current context of knowledge, the scientific community regarded these principles as truth. If you want to ask, “If these theories are wrong,” the answer is: your TV can not open the machine, the phone can not pass the letter, the computer can not even things, light can not send light. So, do you want these theories to be wrong, or is it right? Here I have to explain the specific “three upanishads”, which use some mathematical symbols, – because it is the easiest way to understand. If you use the daily language to describe, will pay a lot of tongue, but also said unclear. Many articles are more and more confused, is the reason. And the use of mathematical language to describe, you can accurately and concise understanding of the “three upanishads.” If you really want to understand the quantum information, beyond the level of the crowd, you must cross this psychological barrier, brave to face mathematics. After doing so, you will find that, in fact, not difficult, you can do it! 1 2 3 4 5 6 7 Next page

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