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Original title: From quantum mechanics to the second revolution of quantum technology, the “strange” theory is close to industrialization | New source of popular science: Shangguan News
Summary:Since the end of the last century, the second revolution in quantum technology has emerged in the field of information technology. It is now approaching the stage of industrialization and is intertwined with new generation information technologies such as artificial intelligence. It is expected to generate disruptive innovations.
The Political Bureau of the CPC Central Committee recently conducted the twenty-fourth collective study on the prospects for research and application of quantum technology. What is quantum technology? What is its scientific principle and its development trend? The Jiefang Daily · Shangguan News reporter interviewed many scientists. Since the emergence of the second quantum technology revolution at the end of the last century, a new generation of information technology, such as quantum communications and quantum computing, has reportedly been on the eve of industrialization, which is expected. unleash industrial change with far-reaching influence.
Quantum mechanics uses probability to describe microscopic particles
“The basis of quantum technology is quantum mechanics, which is a theory that helps us understand everything in the world,” said Professor Jin Xianmin, director of the Center for Integrated Quantum Information Technology at Shanghai Jiaotong University. In the eyes of many people, quantum mechanics is very strange, even said to be “misleading”, but in fact, it is one of the best theories to explain natural phenomena in the world from micro to macro.
The so-called quantum is the smallest unit of indivisible physical quantity. If a certain physical quantity cannot change continuously, it can only take a few discrete values and is quantized. It’s like climbing stairs, we can only go up one step, not half. Scientists have discovered that physical quantities in the macroscopic world appear to be continually changing, but in the microscopic world, many physical quantities are quantized. For example, the energy of an electron in a hydrogen atom can only take one basic value: 13.6 electron volts or its 1/4, 1/9, 1/16, 1/25, etc., but not twice or 1/2, 1 3.
Besides quantization, there are many differences between the micro and macro worlds. One of the most incomprehensible characteristics of the microcosm may belong to the state of quantum superposition, which is a basic principle of quantum mechanics. When classical mechanics explains the macroscopic world, it uses the determined values of coordinates and momentum to describe the state of each particle. However, when physicists use this model to describe microscopic particles, they find that classical mechanics fails, because a particle can be in either “0” or “1” state is very different from the certainty of the macro world. Therefore, quantum mechanics uses state vectors to describe the state of particles. In short, the state vector is a kind of probability, which means that the state of the particle is random.
For this elusive randomness, Professor Lu Chaoyang of the China University of Science and Technology used an analogy: some states can be represented by arrows pointing up, down, left and right, so we consider direction as a physical quantity , but there are some The state is a circle. If you measure the direction of the “circle state”, it will become any arrow state with the same probability. In the same way, scientists prepare multiple particles with the same state, and if they repeatedly measure their positions, they will find that the results of each experiment are different.
Academician Pan Jianwei (right) and Professor Lu Chaoyang in the laboratory.
Quantum communication and computing are moving towards industrialization
Using scientific principles such as the quantum superposition state, people can realize secure quantum communication. Pan Jianwei, an academic at the Chinese Academy of Sciences and a professor at the China University of Science and Technology, explained that the signals of classical communication are only 0 and 1. When eavesdropped, neither of these two signals will be disturbed. . For example, when two people are making a call, others may use an error to separate some electrons from the electrons on the communication line and let them into another line to achieve listening, but the caller cannot detect it. Quantum communication is different, it has not only 0 and 1 signals, but also quantum superposition states like 0 + 1 and 0-1. According to the uncertainty principle and the non-clonability principle of quantum mechanics, once a quantum signal is obtained, the quantum superposition state will be altered and can “collapse” into another quantum state. In this way, communicating parties can notice it immediately.
One of the basic principles underlying quantum computing is also the state of quantum superposition. Jin Xianmin explained that because a particle can be in states “0” and “1”, after the “quantum entanglement” interaction between two particles in a state of superposition, there will be 4 states (2 by 2 squared). If 100 particles are quantum entangled, there will be 2 raised to the 100 power state. Such a large number of states allows quantum computers to have super parallel computing capabilities.
Professor Jin Xianmin is looking at the self-made photon integrated chip.
As for the research and development path of quantum computing, the “White Paper on Quantum Information and Quantum Technology (Hefei Declaration)” published in September last year predicts that it will be divided into three stages: the first stage is to achieve the ” quantum superiority “, that is, the computing power for specific problems exceeds the classics. For supercomputers, this phased goal will be realized in the near future; the second phase is to realize a dedicated quantum simulation system with application value; The third phase is to realize a programmable general-purpose quantum computer, which requires the long-term efforts of the global scientific and technological community. “It is estimated that in the next 10 to 20 years, a batch of dedicated quantum simulation systems will be successfully developed for the simulation of catalytic chemical reactions and the preparation of high-temperature superconducting materials,” said Wu Biao, professor at the School. of Physics from Peking University, and its computational efficiency is more efficient than the classical one. Computers are much taller, so the efficiency of scientific research in these fields is expected to improve tremendously, helping scientists develop more and better new drugs, new materials, and other results.
According to Jin Xianmin, since quantum mechanics was gradually established at the beginning of the last century, the first quantum technological revolution emerged in the 1940s, leading to important achievements such as atomic bombs, semiconductor transistors, and lasers. Since the end of the last century, the second revolution in quantum technology has emerged in the field of information technology. It is now approaching the stage of industrialization and is intertwined with new generation information technologies such as artificial intelligence. It is expected to generate disruptive innovations. “International competition for quantum technology is very fierce. The governments of many countries and regions have increased their investment in this field in recent years. The great attention of the Central Committee of the party to quantum technology will force us to march towards the heights. dominant players in international competition “.
Column Editor: Huang Haihua
Text Editor: Yu Taoran
Title Image Source: Xinhua News Agency
