Quantum communication: an important guarantee for the future autonomous and controllable information security ecosystem

"Quantum" is already a hot research field. As a bystander, you may have used the joke "When in doubt, use quantum mechanics" or paid the IQ tax of "quantum teacup"... But what is quantum technology? Do you know? Focusing on the theme of quantum information technology, the team of Academician Pan Jianwei wrote this popular science article, which gave a relatively complete introduction and outlook on quantum information technology.

Information security is a major strategic area that concerns the national economy and people's livelihood. Traditional information security is achieved through encryption algorithms that rely on computational complexity. However, with the rapid development of computing power, traditional encryption algorithms that rely on computational complexity are facing increasing security risks.

Quantum secure communication based on quantum key distribution is the only communication method that is unconditionally secure in principle to date.

Quantum key distribution refers to the use of quantum states to load information and generate keys through certain protocols. The basic principles of quantum mechanics ensure that the keys cannot be eavesdropped, thereby achieving secure quantum secure communication. The security of quantum secure communication is based on the basic principles of physics and has nothing to do with computational complexity. Even if powerful quantum computers are available in the future, their security will not be threatened.

Quantum secure communication is the first quantum information technology to be put into practical use and industrialized. In addition to the unconditionally secure "one-time one-key" encryption method in principle, the security keys generated by quantum key distribution can also be combined with classical symmetric encryption algorithms to balance security and communication speed. For example, according to the current technical level, quantum key distribution combined with the AES (Advanced Encryption Standard) encryption algorithm can achieve a communication rate of Gbps (exchange bandwidth), while greatly improving the update rate of seed keys and effectively improving the level of communication security. In addition, it can also be combined with the next generation of "PQC (anti-quantum computing cryptography)" to enhance the security of identity authentication, etc.

Development path of wide-area quantum communication

The development goal of quantum communication is to build a global wide-area quantum communication network system. The development route of the wide-area quantum communication network is to realize the metropolitan quantum communication network through optical fiber, then realize the connection between two adjacent cities through repeaters, and finally realize the connection between distant areas through the transfer of satellite platforms.

In terms of metropolitan quantum communication networks, the University of Science and Technology of China has successively built the world's first fully-accessible metropolitan quantum communication network, the first quantum government network, and the first large-scale metropolitan quantum communication network, and in the process has developed related technologies to maturity. The independently developed quantum secure communication equipment has provided information security protection for many important activities.

In terms of inter-city quantum communication networks based on trusted relays, the world's first long-distance optical fiber quantum secure communication backbone network, the Beijing-Shanghai Trunk Line, was fully operational at the end of 2016. The trunk line is more than 2,000 kilometers long, connecting Beijing and Shanghai, and running through Jinan, Hefei and other cities. With the cooperation of financial, government affairs, power and other departments along the line, technical verification and application demonstration of long-distance quantum secure communication are carried out.

Based on the "Beijing-Shanghai Trunk Line" application demonstration, the National Development and Reform Commission approved the "National Wide-Area Quantum Secure Communication Backbone Network" project in February 2018, which will cover important regions such as Beijing-Tianjin-Hebei, Yangtze River Delta, Guangdong, Hong Kong and Macao, Chengdu-Chongqing, and promote the large-scale application of quantum secure communications.

In the field of free-space quantum communication between the satellite and the ground, with the support of the Chinese Academy of Sciences, the University of Science and Technology of China, in collaboration with the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, the Microsatellite Innovation Institute and other units, successfully developed the world's first quantum science experimental satellite "Mozi".

"Micius" was launched into space in August 2016. It was the first in the world to realize quantum communication between the satellite and the ground, and for the first time achieved intercontinental quantum communication over a distance of 7,600 kilometers, fully verifying the feasibility of realizing global quantum communication based on satellite platforms.

With the successful experience accumulated by the "Mozi", the development cost of quantum satellites has been reduced from hundreds of millions of yuan to tens of millions of yuan. It is expected that the miniaturized quantum satellite will be launched in early 2022, laying the foundation for building a low-cost constellation. The weight of the ground receiving station has also been reduced from more than ten tons to about 100 kilograms, which can initially support mobile quantum communications. Combining the "Mozi" quantum satellite and the "Beijing-Shanghai Trunk Line", China has taken the lead in building the prototype of a wide-area quantum secure communication network integrating the earth and the sky, which has become a major landmark event in international quantum information research in recent years.

Application and promotion of quantum communication technology

On October 16, 2020, the Political Bureau of the CPC Central Committee held its 24th collective study on the research and application prospects of quantum technology. General Secretary Xi Jinping presided over the study and pointed out that "we should coordinate basic research, cutting-edge technology, and engineering technology research and development, cultivate strategic emerging industries such as quantum communications, seize the commanding heights of international competition in quantum technology, and build new development advantages". The "Beijing-Shanghai Trunk Line" and the "Mozi" quantum satellite are engineering integration and verification projects based on the basic and applied research results of more than 10 years in my country. They have played a good demonstration effect for the independent research and development of core components, the formulation of relevant application standards, and future large-scale applications, and have steadily promoted the application of quantum secure communications in the fields of commerce and national security.

In terms of core quantum communication devices, China Electronics Technology Group Corporation, University of Science and Technology of China, Shanghai Institute of Microsystem and Information Technology of Chinese Academy of Sciences, etc. have achieved the initial localization of major devices such as single photon detectors and quantum random number generators in the communication band, breaking the barriers of foreign embargoes. In the next 2 to 3 years, through the chipization of key devices, the size of quantum encryption equipment can be reduced to the size of a mobile phone, and the cost can be greatly reduced. In terms of the formulation of relevant application standards, with the active participation of more than 50 scientific research institutions and enterprises in China, national standard organizations such as China Communications Standards Association, National Information Security Standardization Technical Committee, and Cryptography Industry Standardization Technical Committee have compiled a number of national standards and industry standards around the interconnection, security assessment, and application services of quantum secure communication technology. Chinese scholars have broken through the obstacles of Western countries such as the United States and Canada, and initiated the establishment of the world's first standardization organization covering the entire field of quantum information in the International Telecommunication Union, and are currently leading the compilation of a number of international standards.

Development prospects of quantum communication technology

In recent years, Chinese scholars have achieved a number of internationally influential results in the field of single-photon radar: breaking through the quantum efficiency limit of detecting infrared single photons at room temperature, realizing long-range infrared single-photon atmospheric radar detection; achieving continuous detection of atmospheric wind fields day and night, and creating the world record for the longest distance of single-photon imaging at 200 kilometers.

At the same time, single-photon radar can be used to observe objects hidden from sight, that is, "non-line-of-sight imaging", realizing "observing objects through walls", and has broad application prospects in anti-terrorism, riot prevention, emergency rescue and other fields; it has achieved long-distance non-line-of-sight imaging, and for the first time increased the imaging distance from meters to kilometers, greatly promoting the practical development of non-line-of-sight imaging technology.

The single-photon detection technology developed in quantum communication research can also greatly improve the detection sensitivity, detection distance, resolution and other performance of traditional lidar, namely "single-photon radar". Single-photon radar can realize the detection of long-range, high-precision soft targets (atmosphere) and hard targets (objects), and has played an important role in ground mapping, remote early warning, global situational awareness, atmospheric pollution detection and forecasting, aerospace operations and other fields.

Thanks to China's pioneering technical verification and application demonstration of wide-area quantum communication, network technology has initially met the requirements for practical application, the localization of core components and the miniaturization of equipment have been initially achieved, and the conditions for trial implementation in key departments have been met. In the face of fierce international competition, it is now the best time for China to accelerate the application of quantum secure communication and form an asymmetric advantage in information security as soon as possible. Through about 10 years of efforts, China is expected to build a complete wide-area quantum communication network technology system, providing important guarantees for the formation of an independent and controllable national information security ecosystem in the future.