Xinhua News Agency, Beijing, February 22 (Reporter Liu Zhen) The reporter learned from the Beijing Institute of Quantum Information Science on the 22nd that my country's scientific research team proposed the unidirectional quantum direct communication theory and successfully developed a practical system, creating a stable transmission record of 2.38kbps in the 104.8km standard optical fiber communication experimental test. Quantum direct communication has moved from theoretical concept to practical application stage.

This research was completed by the Beijing Institute of Quantum Information Science and related teams of Tsinghua University and Northern University of Technology. The relevant results papers have been published in the academic journal "Science Progress".

Quantum direct communication was originally proposed by the Long Guilu team of Tsinghua University. It uses quantum states to achieve secure communication, with five major features: eavesdropping perception, blocking eavesdropping, compatibility with existing networks, simplifying management processes, and hidden transmission, providing a new solution to ensure the security of information transmission.

How to use quantum states with extremely low energy and extremely susceptible to interference to achieve safe and reliable communication in quantum channels with high noise, high loss and eavesdropping risks has always been a core problem that needs to be overcome in this field. Previous research adopted a two-way protocol, and both parties to the communications needed to conduct round-trip transmission of quantum states, resulting in huge system losses, which seriously restricted the improvement of communication performance.

"In 2022, we created a world record of 100 kilometers of quantum direct communication, but the rate is only 0.5bps, and we can only transmit messages with very few words." Long Guilu, a professor at Tsinghua University, introduced that one-way transmission can shorten the transmission distance of quantum states by half and greatly reduce losses, which is the key to improving the performance of quantum direct communication.

In this study, the scientific research team successfully broke through a series of key technologies such as high-noise and high-loss channel coding, channel mask capacity increase, and high-speed quantum state modem and demodulation. They proposed a theoretical method of unidirectional quantum direct communication, and used the same set of optical quantum states to simultaneously realize the secure transmission and key negotiation of information, successfully solved the technical problems of quantum direct communication, and also completed the development of practical communication terminals. Compared with the 2022 system, the speed is 4760 times higher, greatly improving the performance of quantum direct communication.

"This research results have opened a new journey of practical construction of quantum direct communication. In the future, quantum direct communication systems are expected to be widely used in areas such as government affairs and finance that require extremely high information security, and effectively enhance communication security." Long Guilu said.