This year's government work report will "vigorously promote the construction of a modern industrial system and accelerate the development of new quality productivity" as the top priority of the government's work in 2024, and the importance of promoting the accelerated growth and expansion of new quality productivity is self-evident.
It is worth noting that "quantum technology", as an important part of the future industry in the new quality of productivity, has been mentioned twice in the government work report, and the government work report mentioned in the 2023 work review that "innovative achievements in frontier fields such as quantum technology continue to emerge", and in the future, it will "open up new tracks such as quantum technology and life sciences". In 2024, quantum technology industry innovation is expected to continue to receive policy support.
Photo courtesy of Professor Han Zhengfu: Interviewee
In the process of research and development of quantum information technology, what are the key technical problems that need to be solved? How will the development of quantum communication technology affect people's daily life and work methods? In this regard, Xiaokang magazine and China Xiaokang Network interviewed Han Zhengfu, chief scientist of Anhui Wentian Quantum Technology Co., Ltd. and professor of University of Science and Technology of China. He began to engage in the research of quantum cryptography technology in 1989, and was one of the earliest researchers engaged in quantum information technology in mainland China, undertaking major projects such as the key R&D project of the Ministry of Science and Technology from 2018 to 2023, such as "Research on Key Technologies for High-performance Quantum Key Distribution". He has won the first prize of Anhui Natural Science Award and the first prize of Technological Invention Award of the Ministry of Education. He has served as the deputy leader of the National "863" Program Quantum Information Theme Expert Group, and is currently the director of the Quantum Cryptography Professional Committee of the Chinese Cryptologic Society.
Quantum communication moves from myth to practicality
China's Xiaokang Network: Could you briefly introduce the concept and development process of quantum information technology?
Han Zhengfu: Strictly speaking, quantum information technology is an information processing method that uses quantum states to encode information, or a technology that uses quantum states to process information on behalf of information.
The information technology we use now, most of the coding uses voltage or light intensity, sending a high voltage pulse to represent "1", and then sending a low voltage pulse to represent "0", using a strong light to represent "1" in communication, and then using weak light to represent "0" - this is the current information technology means. But at the quantum level, we use "quantum states" to represent information, and quantum states also come in various forms, one of which can represent "1" and the other "0". When the computer processor processes the information, the traditional electronic computer is processed according to the voltage "0" and "1", and the calculation process is to let the logic gate jump back and forth between the high voltage and the low voltage according to the set law, which is the basic program of electronic information technology, and it must conform to the basic rules of classical physics, that is, electromagnetism.
Quantum states are used to represent information, and since quantum states are not classical physical quantities, the laws that satisfy it are no longer the laws of electromagnetism, but the laws of quantum mechanics. When processing quantum information, because the information represents the quantum state, which is different from voltage, it has different advantages from traditional information technology, but also has certain disadvantages. So many years of research on quantum information is to give full play to its advantages and avoid its shortcomings.
From the perspective of the underlying logic, the quantum information network is not the same thing as the current electronic information grid, and at the machine level, it is not a concept at all. Traditional computers and mobile phones, strictly speaking, have no way to run quantum information, and must rebuild a set of quantum hardware, form a quantum processor, and then install software to make it work, in order to completely do the processing and transmission of quantum information.
In 1984, Charles Bennett of the United States and Gillette Basard of the University of Montreal in Canada jointly proposed the first and most famous quantum key distribution protocol - BB84 protocol. Quantum key distribution uses the unique quantum properties of microscopic particles, such as the indivisibility of single photons and the non-replicability of unknown quantum states, to ensure the non-eavesdropping of keys in principle, thereby ensuring the security of information transmission. The BB84 protocol pioneered the quantum information industry to use it for key distribution and thus secure communication.
In addition, we can use the new method of quantum state coding to develop another type of computer that is completely different from today's electronic computers, and it has the advantage of being able to easily deal with some of the complex problems that we often encounter. For example, more accurate weather forecasting, the relationship between people and stocks, earthquake and avalanche prediction, etc. In the field of traditional electronic computers, these are complex problems that are difficult to solve. But in the field of quantum computers, these problems are relatively less difficult, and they can speed up the computation by a large margin.
We can also use quantum technology to solve some basic measurement problems. For example, it is used to define the length, to define the magnitude of the light intensity, and to directly measure the magnitude of the current, and the measurement accuracy is much more accurate than the traditional method. Therefore, where high-precision measurements are required, quantum technology can be used to make measurements, which is called quantum measurement. Of course, there are also technologies such as quantum imaging and quantum lithography, which are not currently mainstream. Are there any new directions in the future? There must be, but there are no mainstream research directions at present.
From 1984 to 1990, quantum information gradually attracted the attention of the international academic community, after 2000, it was confirmed that quantum technology can do things that traditional computing and traditional communication could not do in principle, and after 2010, it became an international hot spot, and quantum information technology research was vigorously carried out.
China's Xiaokang.com: At present, what are the application scenarios in the field of quantum communication?
Han Zhengfu: In terms of development history, the quantum information industry has existed for nearly 40 years, but so far, except for some applications of quantum communication, other aspects have yet to enter the real application scenarios.
At present, there are not many application scenarios, such as quantum communication, the core of which is quantum key distribution, which solves some problems that cannot be solved by traditional cryptography. After the concept of quantum computers came out, it has theoretically been proved that the cryptographic technology in use is not safe, and quantum computers can crack it once they come out. In the future, we need to fully enter the quantum level and use quantum cryptography to deal with quantum computers. At the quantum level, encryption and cryptography can reach the same level with each other, so security is more guaranteed.
At present, quantum cryptography technology has been applied in many industries, such as customs and border inspection, the financial industry, and the public security department involves the personal identity and privacy of thousands of households to protect information, which can also be solved with quantum cryptography. In fact, wherever there is communication and data at scale, quantum cryptography can be used. In terms of pure quantum information processing, it is necessary to wait for the development of quantum computers before quantum methods can be used to process them. For example, in the screening and development of drugs, quantum computers can be used to simulate or optimize first, thus greatly speeding up drug research and development; in the meteorological industry, if quantum computers are used, the weather can be predicted more accurately.
Quantum cryptography is already in use, and in 2018 our product was used at a border checkpoint. There are also some applications in other fields, and the technology used here is quantum key distribution, or quantum communication. Accurate measurement of large currents is very important for the power grid, at least in relation to charging. Now with quantum measurement, the accuracy is more accurate, and the engineering is more convenient, and it is still in the rehearsal stage.
China's Xiaokang Network: What is the current progress of the research and development of quantum computers around the world?
Han Zhengfu: At present, the biggest difficulty of quantum computers lies in how to implement the hardware, because the quantum state is particularly fragile and easily disturbed by the surrounding environment, so we have to isolate it, isolate it to a certain extent, and control it to make a quantum computer. In the last decade or so, the world has been trying to do this, but there is no technology that can meet the needs of ideal quantum computing.
For example, the use of ions to make quantum computers, which are currently too large and too expensive, and superconducting quantum computing has become very popular in recent years, and is considered to be the most likely technology to make the first quantum computer. At the end of 2023, Harvard University will provide another set of quantum computers based on bound atoms, claiming to be able to make 48 logical bits, which is a height that other technologies cannot reach at present, but we will wait and see where this technology can eventually go. In addition, semiconductor quantum computers, which are similar to traditional electronic computers, are slow, but their scalability and manufacturing processes are very mature, and it is difficult to determine whether they can catch up.
Quantum computers are too difficult to expect to solve problems in a short period of time.
What are the advantages and limitations of quantum communication compared with traditional communication methods?
Han Zhengfu: The biggest advantage of quantum communication is that it can control the security of the entire communication process, or whether my information has been eavesdropped on by others or leaked, I know. At present, the biggest limitation is that if it is used on the ground, it must have optical fiber, and it is not possible to use wires for quantum communication. Light can only be transmitted directly in the air, and both ends of the transmission and reception must be visible, and can only be transmitted at a direct viewing distance. The so-called quantum satellite is to transmit a set of quantum states from the satellite to the ground to achieve quantum communication, and the current limitations are still relatively large.
Reshaping communication and data security in the post-quantum era
In 2018, the Key Laboratory of Quantum Information of the Chinese Academy of Sciences at the University of Science and Technology of China made important progress in the research of Loopback Differential Phase Quantum Key Assignment (RRDPS).
Han Zhengfu: Before 2018, in the quantum key distribution protocol, how to find out whether the key was eavesdropped during transmission depends on the traces left by the enemy when eavesdropping on the information in the process of transmitting from A to B or from B to A. By detecting the size of the bit error, we can know the amount of information that the eavesdropper may eavesdrop, and we can use some mathematical means to eliminate the information that the enemy eavesdrops, so as to leave the security information, so all quantum key distribution needs to know how big the bit error rate of the system is. And if the bit error rate is high, the system will not work well.
The biggest difference in the RRDPS solution is that it does not need to detect how many bit errors there are to a certain extent, and can tolerate higher bit error rates. In practical applications, where the interference is relatively large, it is impossible to distinguish whether the bit error is interfered with or really eavesdropped by the enemy. Therefore, the advantage of the RRDPS protocol is that it can tolerate large bit errors, and can obtain safe information when the bit errors are large. In 2018, we theoretically perfected the security proof of the protocol and implemented the scheme experimentally, solving the difficult problem of how to achieve the RRDPS scheme as close to the ideal as possible with the least amount of equipment.
"Xiaokang" China Xiaokang Network: What is the core technology system of Wentian Quantum?
Han Zhengfu: Wentian Quantum has a full range of technologies such as point-to-point quantum cryptography communication technology, quantum cryptography communication networking technology, and quantum cryptography communication core devices, and has built a complete core technology system of quantum cryptography communication with independent intellectual property rights. In the 90s of the last century, we have gained a foothold in the world, and from 2000 to 2010, we applied for some technical patents, laying the foundation of the entire intellectual property rights of Wentian Quantum. Therefore, in terms of safety, integrity and reliability of equipment, Wentian Quantum is one of the best manufacturers in the world.
Looking to the future, Han Zhengfu said that the next five years will be the stage of comprehensive application of quantum communication technology, and it should be able to be popularized in 10 years. Photo courtesy of the interviewee
In 2022, you and your collaborators achieved 833 kilometers of optical fiber quantum key distribution, increasing the world record of secure transmission distance by more than 200 kilometers, and taking an important step towards realizing 1,000 kilometers of land-based quantum secure communication. Can you tell us more about the significance of this achievement?
Han Zhengfu: Quantum key distribution, or quantum communication, is limited by distance. Under certain technical conditions, there is a limit to the distance it can transmit. Previously, it was only possible to do about two or three hundred kilometers, and the limit distance was about five hundred kilometers. In China's vast territory, this is a shortcoming. For example, in Northern, Central, Eastern, and Southern China, the distance between the two cities will not exceed 300 kilometers, and the previous quantum communication distance is sufficient. However, in the great northwest, such as Gansu, Qinghai, Tibet, and Xinjiang, the distance between the two cities may be seven or eight hundred kilometers, or even thousands of kilometers.
Since 2019, it has taken us about three years to increase the limit distance of quantum key distribution to 833 kilometers at one time. This distance can basically solve the communication problem between most cities in the mainland, so its value is still quite large, and it represents the highest international level at that time.
China's well-off network: What are the current challenges and problems faced by quantum communication technology, and how to solve these problems?
Han Zhengfu: At present, the biggest problem we are facing is how to combine it with real-world applications? From the beginning of 2015 to the present, we have spent about five to ten years doing user education, and the vast number of practitioners in the information industry now know the concept of quantum information, but how to use it? Some breakthrough ideas and thinking are still needed. At present, we do not have such a deep understanding of user needs, and we still need to learn some specific industry knowledge, such as medical, financial and other industries, what special needs they have, and then think about how to give full play to the advantages of quantum. After a new technology is developed, it will have an impact on the traditional industry, and the traditional industry will inevitably have resistance, which is a difficult problem for the promotion of new technology.
China's well-off network: What are the differences in research progress at home and abroad in the field of quantum communication?
Han Zhengfu: In a macro sense, quantum communication is about 3~5 years ahead of Europe and the United States. Quantum measurement and quantum computing may be about 5~10 years behind in general, and I am not sure whether my judgment is accurate.
Quantum technology explores the future
Xiaokang: What is your view on the current commercialization process of quantum communication technology?
Han Zhengfu: First, objectively speaking, the whole industry is a bit chaotic. There are too many companies engaged in this industry now, and some are catching up with the boom to enter this track.
Second, how to perfectly combine quantum communication technology with commercialization and use it is an open question.
Third, now the national level attaches great importance to it, so the publicity is also relatively large, which is a positive promotion for the industry.
Fourth, in terms of application scenarios, competition with traditional technologies is still weak. It is hoped that the state can increase its impetus and provide application scenarios. In general, quantum communication technology has entered some application scenarios and solved some problems. The quantum technology industry is really moving at a rapid pace.
China's Xiaokang Network: What kind of future will quantum communication lead mankind to?
Han Zhengfu: In the next 10 to 20 years, quantum communication may change the current information security model. The current information security landscape is chaotic, and so many fraudsters are able to carry out their fraud schemes because they have easy access to our information. With the use of quantum technology, I believe that I can solve some of these problems. With the theoretical security of the information system, we can concentrate on solving some problems that are not very reassuring, which will promote the information security industry. Quantum information allows us to achieve ideal security step by step.
How will the development of quantum communication technology affect people's daily life and work style?
Han Zhengfu: From a technical point of view, especially security technology, we don't want users to feel uncomfortable, the best way is to put security invisible, so that you can get security without feeling. From this point of view, we can't change the lives of human beings, or we are not willing to change the way of life of human beings at all.
However, from the point of view of being able to ensure safety gradually, people can relax their precautions. At a further level, with the advent of quantum computers and quantum communications, what will our lifestyles become? It's not easy to imagine, and I can't give a more accurate prediction.
What is the development direction of quantum communication technology in the future?
Han Zhengfu: First of all, it will be used in some occasions involving high secrets, and at present, it is gradually being used in the commercial field. The next five years will be the stage of full application of quantum communication technology, and it should be able to be popularized in 10 years.
China's Xiaokang Network: Please share your prospects and expectations for the development of quantum communication technology in the future.
Han Zhengfu: This is true of the development of any technology, the earliest technology may have the lowest indicators and the most limitations. At present, our technology is able to cover almost all needs, but it is certainly not in a good state.
The follow-up should be the direction of how to solve the problem and how to meet the actual needs. All the direction of our technological development must follow the direction of meeting the needs and realizing the needs of information security. Therefore, the technology developed independently from the perspective of scientific research may trigger a boom in the academic community in a short period of time, but it is not market demand, and it must be tested by the market.
Quantum cryptography technology is needed in almost all information-related industries, such as the process of communication, storage, and processing...... As for how to use it, whether it is used well, how is the user experience, and from the perspective of the enterprise, it is this kind of problem that needs to be solved.
END
Source: "Xiaokang", China Xiaokang Network
Author: Sun Yuanyuan
Editor: Liu Yanhua
Review: Gong Zimo
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