China sets new world record in high-rate quantum key distribution

Chinese scientists have developed a high-speed quantum key distribution (QKD) system to generate secret keys at a rate exceeding 110 Mb/s over a 10 km standard optical fiber, setting a new world record in the field.

File photo: CFP

It is of great significance to the large-scale application of quantum communication and quantum network, according to Xu Feihu, a professor at the University of Science and Technology of China (USTC).

Xu said that previously the highest secret key rate (SKR) among the international academic community was about 10 Mb/s over a 10 km standard optical fiber.

A research team led by Chinese physicists Pan Jianwei, known as China's "father of quantum," and Xu Feihu developed a QKD system that is able to generate secret keys at a record high SKR of 115.8 Mb/s over a 10 km standard optical fiber, and distribute keys over up to 328 km of ultralow-loss fiber. The system has been running stably for over 50 hours.

The research findings, in collaboration with researchers from Chinese institutes and universities including the Shanghai Institute of Microsystem and Information Technology of the Chinese Academy of Sciences, the Jinan Institute of Quantum Technology and the Harbin Institute of Technology, were published in the journal Nature Photonics on Tuesday.

QKD can provide fundamentally proven secure communication. The SKR, the rate at which the secret key is generated, is a key figure of merit for the application of any QKD system, which has so far been limited to about a few megabits per second.

Concerning the new world record, Xu noted that such abilities are attributable to a multipixel superconducting nanowire single-photon detector with an ultrahigh counting rate, an integrated transmitter that can stably encode polarization states with low error, a fast post-processing algorithm for generating keys in real-time and the high system clock rate operation.

According to the researchers, the results demonstrate the feasibility of practical high-rate QKD, which can meet the needs of high-bandwidth communication and thus open the possibility for widespread applications of quantum communication.