What is the quantum world like? For those who have never been exposed to this aspect, the impression of quantum mechanics is the fantasy concept in every science fiction movie. Many people firmly believe that the knowledge inside is correct. Let me give you a brief introduction. Understand what the quantum world is like.
What is the quantum world like? 1 Before exploring the magical quantum world, we should first review the classic world, which is the world of our daily life. Before the 20th century, our understanding of the classic world mainly came from Sir Newton, who was one of the two most famous scientists in human history.
Newton's early life was rather miserable. He was born in a small village in England. His father died three months before he was born. At the age of 3, his mother got married again, and Newton was raised by his grandmother. Newton resented his mother for abandoning himself and even wanted to set fire to his stepfather's house. It was not until he 10 that his stepfather died that his mother moved back to live with him. /kloc-When he was 0/6 years old, his mother asked him to drop out of school and help his family with farm work. Fortunately, the headmaster of middle school loves talents so much that he goes to his house to lobby. It's a pity that a clever child like him doesn't study. In addition, his uncle also said that he would help financially, so Newton returned to school. We should thank this great middle school principal: without him, Sir Newton would have repaired the earth all his life.
Newton/Kloc-was admitted to Trinity College of Cambridge University at the age of 0/8. This is one of the most famous universities in the world. Children should know that there is a great prize in the world called the Nobel Prize, which includes six categories: physics, chemistry, physiology or medicine, literature, peace and economics. So far, the teachers and students of Trinity College of Cambridge University have won 32 Nobel Prizes. You know, Asia as a whole, with 48 countries and a population of more than 4 billion, has won less than 30 Nobel Prizes. However, winning so many Nobel Prizes is not the main reason why Trinity College is famous. The real reason why this college is famous is that there is a Newton here.
Newton graduated from Cambridge University at the age of 22. When a great plague broke out in England that year, Newton returned to his family's farm to take refuge. During his two years of refuge, he made three major discoveries that have influenced future generations for hundreds of years, namely calculus, spectroscopy and gravity. One of the most important reasons why Newton was able to create such a miracle was that he worked very hard. For example, once he invited a friend to dinner at home, and when his friend came, he found Newton working in the study. My friend waited and waited, but he couldn't come out, so he ate a chicken himself and left with a pile of bones. Newton came out of the study and saw the bones on the plate, and suddenly realized, "I thought I didn't eat, but I had already eaten." Say that finish, he went back to work in the study.
Two years later, Newton returned to Cambridge and became the second Lucas professor of mathematics at the age of 26. Since then, Newton's life has been smooth sailing: at the age of 29, he was elected as an academician of the Royal Society, at the age of 46, he was elected as a member of the British Parliament, at the age of 56, he became the director of the Royal Mint, and at the age of 60, he became the president of the Royal Society. Newton was the first scientist to be knighted in history, and also the first scientist to enjoy the treatment of state funeral in history. After his death, a poet specially wrote a poem praising him, which said, "The laws of nature are hidden in the darkness. God said,' Leave Newton alone', and then the world will have light. "
Why did Sir Newton gain such a high reputation? Because he wrote a very great academic book called Mathematical Principles of Natural Philosophy.
In this book, Sir Newton established a brand-new discipline called classical mechanics, also called Newtonian mechanics. Its core is Newton's three laws and the law of universal gravitation.
Newton's first law says that if there is no external force, an object will always maintain its original state of motion. Children often have this experience in their daily lives: you are very happy to play games at home, and you will definitely feel bored when your mother suddenly asks you to go outside to do sports; For example, if you are having fun outside and your mother suddenly asks you to go home for dinner, you will definitely not want to. Similarly, a stationary object will never move if you don't push it; An object moving in a vacuum will not stop unless you make it stop. In physics, we call the characteristic that an object wants to keep its original state of motion inertia, so Newton's first law is also called the law of inertia.
Newton's second law says that force can change the speed of motion of an object. We can imagine that a stationary object will move when you push it; A moving object, if you catch it, it will stop. Another point is crucial: the greater the mass of an object, the greater the force required to change its state of motion. For example, there is a toy car coming towards you. To stop it, all you have to do is reach out and grab it. But if a car really comes towards you and you want to stop it, most people can't. You must be a superhero like Superman. We can regard Newton's second law as a lazy law: the lazier a person is, the greater his inertia and the harder it is to change. Similarly, the greater the mass of an object, the greater the inertia, and the more difficult it is to change.
Newton's third law says that if you apply a force to an object, you will get an equal and opposite reaction from the object. For example, many children, especially boys, like to hit the ball. When you hit the ball, you will feel pain in your hands. This is because when you bat the ball, your hand exerts a force on the ball, and the ball will in turn give your hand an equal reaction. The harder you clap your hands, the more painful your hands will be, because the reaction of your opponent will increase accordingly.
In addition to these three laws of motion, Sir Newton also discovered a new law about force, which is called the law of universal gravitation. It says that there is mutual attraction between any two objects with mass, and its size is directly proportional to the product of the mass of the two objects and inversely proportional to the square of the distance between the two objects. This kind of power is everywhere in the whole universe. For example, it is this force that makes ripe apples fall from trees. For another example, it is this force that makes the moon go around the earth and the planets go around the sun. This ubiquitous attraction is called gravity.
These laws are simple, right? But don't underestimate these simple laws. With them, we can predict when the sun will rise in the east, when the moon will be round and when it will be short. These predictions can be accurate to minutes, seconds, or even shorter time. In the macro world, that is, the world of our daily life, from the sun, the moon and the stars to the rivers, lakes and seas to the daily necessities, these laws discovered by Sir Newton can be accurately described.
Because of the great success of Newtonian mechanics, scientists before the 20th century generally believed that Newton's three laws and the law of universal gravitation were the ultimate truths that dominated the whole universe. One of the representatives is the famous French mathematician and physicist Laplace.
Laplace went to Paris with a letter of recommendation at the age of 18, hoping to meet the famous scientist D'Alembert. D'Alembert treated him as a little boy and shut him out. Laplace sent a paper he wrote to D'Alembert. After reading the newspaper, D'Alembert took a 180 degree turn, 180. He not only met Laplace immediately, but also offered to be his godfather. Later, he was even recommended to teach in a military school. Therefore, when you are good enough, the best recommender is actually yourself.
In that military school, Laplace had a close relationship with a short student. He was Napoleon, the general who had a great influence on Europe in the future. As Napoleon reached the peak of French power step by step, Laplace followed suit. When Napoleon proclaimed himself emperor, he was even appointed as the French Minister of the Interior, equivalent to the Minister of Public Security of China. Unfortunately, although Laplace is a master in scientific research, he is a complete failure in administration. After only six weeks as home secretary, Napoleon was dismissed.
Laplace is a faithful believer in Newtonian mechanics. He once said that we can regard the present state of the universe as the result of its past and the cause of its future. If a wise man can know all the forces and the motion state of all objects at a certain moment, then the future will appear in front of him like the past. This wise man, whom Laplace called omniscient and omnipotent, was later called "Laplace demon". This view that Newtonian mechanics is strong enough to determine the future is called determinism, which has been the mainstream view in academic circles until the 20th century.
The best example of determinism is Laplace's own story. He calculated the motions of all the planets in the solar system with Newtonian mechanics, and then wrote a book called Celestial Mechanics, which was dedicated to Napoleon who ascended the throne. After reading the book, Napoleon asked him, "Your books are all about things in the sky. Why don't you say a word about God? " Laplace replied, "Your Majesty, in my theory, there is no need to assume the existence of God."
However, after the 20th century, scientists found that Newtonian mechanics actually only applies to the macro world of our daily life, but it doesn't work in the micro world with extremely small scale.
Children, come and do a simple thinking experiment with me. A stone, broken with a hammer, will become a small stone; This small stone can also be broken into smaller stones. If you keep knocking, you will eventually knock out the smallest stone, and no matter how you knock, you can't divide it any more. This smallest "stone" is called an atom. The concept of atom was put forward by the ancient Greeks more than 2000 years ago. However, the atom mentioned by the ancient Greeks is completely a philosophical speculation. The first person to explain the concept of atom scientifically was the famous Austrian physicist Boltzmann.
Tell an interesting story about Boltzmann. Boltzmann is a very strange teacher. He doesn't like to write on the blackboard in class, but he keeps talking on the podium alone. Some students complained to him that, teacher, you have to write formulas on the blackboard in the future, and we can't remember them just by talking or not. Boltzmann agreed. But the next day, he talked in class again, and finally concluded: Look at this problem, one plus one equals two. Then he suddenly remembered his last promise to the students, so he picked up the chalk and wrote "1+ 1=2" on the blackboard.
Boltzmann has always believed that the world is made up of atoms, and based on this, he founded a discipline called statistical mechanics. But at that time, people generally did not believe in atomism, so in academic circles, Boltzmann had a large number of opponents. These people attacked atomism all the year round, and even directly attacked Boltzmann himself, which made him feel very painful. Boltzmann once felt that he was "a weak person who struggled with the trend of the times." But Boltzmann was not alone. A young German scientist stood by him. However, Boltzmann was so proud that he felt that the Germans who supported him were nobody and didn't care. However, this German scientist is none other than Planck, who will be called "the father of quantum theory" in the future.
Now scientific research has proved that atoms do exist. However, its volume is very small, only one billionth of 1 meter. How small is it? If everyone on the earth becomes as small as an atom, stacking them one by one is not as tall as a child with a height of 1 m. But atoms are not the most basic particles. At the center of the atom, there is a positively charged nucleus, which is only one tenth of the size of the atom. Outside the nucleus are negatively charged electrons, which are small in size.
As we have said, all substances in the world are made up of atoms. Besides atoms, there is a common thing, that is light. Scientists discovered as early as the19th century that light is actually a wave traveling at the speed of light. What is a wave? Wave is a phenomenon that something vibrates in the process of propagation. For example, water waves are produced by the vibration of water. For another example, sound waves are generated by air vibration. Waves also have energy: the higher the frequency, the shorter the wavelength and the higher the energy.
In the picture above, the colored part in the middle is the light that our eyes can see, which is called visible light. Beautiful rainbows often appear in the sky after rain. There are seven different colors of rainbows: red, orange, yellow, green, blue, indigo and purple. The frequency range of visible light is between red light and purple light. Red light has the lowest frequency, the longest wavelength and the lowest energy. Purple light has the highest frequency, the shortest wavelength and the highest energy. Less energy than red light is infrared, which can be used to make night vision devices, remote control televisions and air conditioners. Less energy than infrared ray is microwave, which can be used to heat objects. The microwave oven in our home uses the characteristics of microwave energy to heat objects. There is something lower than microwave energy, and that is radio. Our TV, radio, mobile phone and wireless network signals are all transmitted by radio.
What I just said was the light of imbecility. Let's talk about high-energy light first. More powerful than violet light is ultraviolet light. If we stay in the sun for a long time, our skin will get sunburned, and what burns us is ultraviolet rays. Above ultraviolet energy is X-ray. X-rays have strong penetrating power. When we went to the hospital for a physical examination and took X-rays, we used X-rays. Higher energy than X-rays is gamma rays. Gamma rays are very high in energy, so they can be used as special scalpels to operate on patients.
As we said just now, scientists discovered that light is a wave traveling at the speed of light as early as19th century. But in 1900, the aforementioned Planck made an amazing discovery: the energy of light emitted by thermal radiation of an object is not continuous, but a part, the size of which is equal to the frequency of light multiplied by a small constant, called Planck constant. What we call "quantization" actually means that the physical quantities themselves are discontinuous and always distributed one by one. In other words, in the quantum world, there is always a minimum value of physical quantity, which can't go to zero directly like the classical world. This great discovery opened the door to the quantum world, and Planck won the Nobel Prize in Physics in 19 18.
There is an interesting story about Planck. After winning the prize, Planck was often invited to give lectures at universities. Because the contents of the report are the same, over time, his driver can also say it. Once, the driver told Planck that I had memorized your report and asked me to listen to the next class. Planck agreed. So in the next speech, the driver replaced Planck to make a report, which was successfully completed. However, in the following audience questioning session, some viewers asked a technical question, which directly stumped the driver. Fortunately, the driver responded quickly and replied: "This question is very simple. Even the driver under my stage can answer it. Let him tell you. " Then Planck, who was sitting under the stage, came on stage to save the scene.
1905, the great physicist Einstein took another step forward on the road of human understanding of the quantum world. He pointed out that light is actually a particle called a photon.
We have told you that there are two most famous scientists in human history. One of them is Sir Newton, and the other is Einstein. Like Sir Newton, Einstein's early life was not smooth. Einstein was born in a Jewish family in Germany. In order not to serve in the German army, he went to a university in Switzerland to study. As a result, I failed in the college entrance examination in the first year and was admitted to Zurich Institute of Technology in the second year. Einstein was so arrogant that he often didn't attend lectures during his college years. To make matters worse, the university classroom at that time was not like this. When you are in a large class, there are dozens or even hundreds of students in a classroom. If you don't go, the teacher may not find out. But when Einstein went to college, there were only 10 students in a classroom. If you don't go, the teacher will catch one. Because Einstein often doesn't go to class, his teacher is very dissatisfied with him. At that time, Weber, the head of their physics department, criticized Einstein for not listening to other people's opinions. This led to a very serious consequence, that is, when Einstein graduated, he did not find a job in the university.
Two years after graduating from college, Einstein had a hard time. He used to teach in middle schools, tutor children, and even worked as an unemployed person for a while. Later, with the help of a college friend's father, I found a stable job in Bern Patent Office. The salary of this job is not high, but it is relatively free, which gives Einstein time to engage in the physics research he loves.
1905, Einstein, who was originally unknown, suddenly entered people's field of vision. In a year, he made three discoveries that shocked the world, namely, special relativity, Brownian motion and photoelectric effect. Because of Einstein's magical performance, people later called 1905 "Einstein's miracle year". Among Einstein's three discoveries, photoelectric effect is the second step on the way to understand the quantum world. Einstein won the Nobel Prize in Physics with 192 1
-This article is selected from "Telling Children about Quantum Mechanics" by li miao Democracy and Construction Press. Please read the original text for details.
What is the quantum world like? 2 What is quantum? According to quantum theory, quantum is the most basic unit of matter and the most basic carrier of energy, and they are inseparable. If a thing has the smallest indivisible basic unit, we can say that it is quantized, and the smallest unit is called quantum. All well-known molecules, atoms, electrons, photons and other microscopic particles are a form of quantum expression.
Why is quantum technology important?
First of all, after the establishment of quantum mechanics, it became the theoretical framework of the whole microphysics, which brought one success after another. Quantum mechanics explains chemistry. The periodic table of elements, chemical reactions, chemical bonds and the stability of molecules are all caused by the laws of quantum mechanics.
Quantum mechanics helps us understand the universe. Our universe spans various scales, from light to elementary particles, to nuclei, and then to condensed matter composed of atoms, molecules and a large number of atoms. Quantum mechanics plays an important role in understanding these aspects, so it has become the basis of modern technology.
On the microscopic scale, the unification of various basic forces is an important issue in theoretical physics, which depends on quantum mechanics. Other unsolved mysteries, such as dark matter and dark energy, also depend on quantum mechanics.
Many astronomical phenomena, such as stellar luminescence, white dwarfs and pulsars, solar neutrino oscillation, cosmic background radiation and even the origin of cosmic structure, are all due to the laws of quantum mechanics.
Many material properties, such as conductor, insulator, magnet, superconductivity, etc. Quantum behavior derived from electrons. Quantum mechanics has brought rich technologies and applications, and profoundly changed human civilization and history. It allows us to get new energy from nuclear energy, and also allows us to use solar energy more effectively. Nuclear bombs have influenced world history, and nuclear power is the peaceful use of nuclear energy.
Quantum mechanics provides the hardware foundation for the information revolution. The principles of laser, semiconductor transistor and chip all come from quantum mechanics. Quantum mechanics also makes it possible for new technologies such as information storage of magnetic disks and optical disks, light emitting diodes, satellite positioning and navigation. Without quantum mechanics, the Internet and smart phones would not exist. Quantum mechanics also provides analytical tools for materials science and technology, medicine and biology, including X-ray, electron microscope, positron annihilation, optics and magnetic resonance imaging.
As early as 1990s, Lederman, winner of the Nobel Prize in Physics, pointed out that quantum mechanics contributed one-third of the GDP of the United States at that time. Today, this ratio is even higher. For our country, the market prospect of quantum technology is also quite broad and the development speed is extremely fast. As far as China's quantum communication industry is concerned, the market scale of 20 17 will reach1800 million yuan, and it is expected to reach 80.5 billion yuan by 2023.
Comparatively speaking, China is still in the stage of catching up with the world's advanced level in the field of quantum computing. In the field of quantum communication, China has been at the forefront of the world. In 20 16, the successful launch of Mozi experimental satellite in China marked the beginning of quantum communication industrialization in China. In 20 17, the world's first long-distance quantum secure communication backbone network "Beijing-Shanghai trunk line" was officially completed and opened. Compared with traditional communication methods, quantum communication has the characteristics of long-term and high security, which can fully meet the confidentiality requirements of information transmission in sensitive fields such as government affairs, national defense and finance. At the same time, the quantum communication industry is also the first brand-new industry opened by China in modern times, which is of milestone significance.
The so-called quantum communication is simply a communication technology that uses the relevant principles of quantum mechanics to solve information security problems. Among them, a famous principle is quantum entanglement. Generally speaking, the value of a physical quantity in a quantum system cannot be determined in advance, but depends on what measurement basis is adopted; Furthermore, for two particles in quantum entanglement, the measurement result of one particle will instantly determine the state of the other particle, no matter how far apart they are. This "ghostly action at a distance" called by Einstein is the theoretical basis of quantum communication.
The traditional communication method is based on encryption algorithm or encryption technology. If the computing power is strong enough to crack the encryption algorithm, there is a risk of being eavesdropped. The unique characteristics of quantum make it have "innate advantages" such as unclonability and uncertainty. Using quantum "key" to transmit information, the encrypted content will not be deciphered, and the eavesdropper will be caught, which provides a solution to solve the "bottleneck" of information encryption.
Running hard towards the dream of secure communication —— Mozi quantum science experimental satellite China was launched in August 20 16, and the success rate of satellite-ground quantum key distribution has reached 10 kbps in 20 17 years, which successfully verified the feasibility of satellite-ground quantum key distribution. At present, after system optimization, the code rate of key distribution has reached the order of 100 kilobits per second (kbps), which has preliminary practical value.
1120km! In 2020, "Mozi" quantum science experimental satellite made new achievements: scientists used "Mozi" as the source of quantum entanglement, distributed quantum entanglement to two distant places, and realized quantum key distribution based on entanglement for the first time in the world-laying an important foundation for the practical application of quantum communication.
Nowadays, the world is experiencing a great change once in a century, and scientific and technological innovation is one of the key variables. Specific to the field of quantum science and technology, it is still necessary to strengthen the top-level design and forward-looking layout, improve the policy support system, accelerate the breakthrough of basic research and key core technologies, cultivate high-level talent teams, and promote collaborative innovation in Industry-University-Research. These tasks can not only rely on the hard work of scientific and technological workers, but also require the strategic judgment, high support and overall coordination of party committees and governments at all levels, and require government departments at all levels to attach great importance to the development of scientific and technological innovation, learn new knowledge and master new trends.
We expect that in the new round of scientific and technological revolution and industrial transformation in the world, China can seize the commanding heights of international competition in scientific and technological development and build a new development advantage-quantum technology will become one of the brightest pearls.