Experts used China's quantum satellite -- Quantum Experiments at Space Scale (QUESS) -- to verify quantum-secure time transfer for the first time, which laid a foundation for building a safe satellite navigation system.

The study published on Nature Physics was jointly accomplished by Professor Pan Jianwei from the University of Science and Technology of China and his colleagues.

High-precision time synchronization plays an important role in fundamental science and real-life applications, including navigation and positioning.

The current time synchronization techniques have shown to be vulnerable to sophisticated adversaries. Therefore, there is a compelling need for new methods to distribute high-precision time information securely.

The quantum communication technology can bring new solutions, said Pan. Based on the principle of quantum "non-cloning," time transfer technology with a single photon as a carrier can fundamentally ensure the security of the signal transmission process.

In physics, the no-cloning theorem states that it is impossible to create an identical copy of an arbitrary unknown quantum state.

The research team led by Pan proposed a satellite-based quantum-secure time transfer (QSTT) scheme, in which a single photon is used as the carrier for both the time transfer and the secret-key generation, offering quantum-enhanced security for transferring the time signal and time information.

By using QUESS, experts performed a satellite-to-ground time synchronization using single-photon-level signals and achieved a quantum bit error rate of less than 1 percent and a time-transfer precision of 30 ps, Pan said.

China launched QUESS, nicknamed "Micius" after a 5th Century B.C. Chinese philosopher and scientist, on Aug. 16, 2016. (Xinhua)