Having successfully demonstrated long-distance quantum key distribution (QKD) during daylight, Chinese scientists have vowed to continue their work to enhance its application including in satellites.
The long-distance free-space QKD could only be available during the night, "as the background noise during the daylight is typically five times greater than that during the night," prohibiting quantum communication in transmission under conditions of high channel loss over long distances, Peng Chengzhi, a senior scientist at the University of Science and Technology of China and a member of the research team, told the Global Times on Wednesday.
"Our experiment has proved the feasibility of satellite-based quantum communication in daylight, and laid a foundation for a satellite-constellation-based global quantum network," Pan Jianwei, an academician with the Chinese Academy of Sciences, who leads the research team, was quoted by the Xinhua News Agency on Tuesday as saying.
As a solution to overcome the background noise, the research team chose a wavelength of 1,550 nanometers and developed free-space single-mode fibre-coupling technology and ultra-low-noise upconversion single-photon detectors to achieve the daytime distribution.
The new technology was announced on Monday in the journal Nature Photonics.
China is now way ahead of the world in the field of quantum communication development, Peng said.
The research team will continue to work on improving the practicability of QKD, such launch of satellites at higher orbit and construction satellite constellation, Peng said.
And to increase the link efficiency, they need to develop new techniques including larger-size telescopes, better acquiring, pointing, and tracking systems, and wave-front correction through adaptive optics, which are on the agenda of the research team, according to Peng.
Peng also revealed the team's ultimate goal of "providing a global quantum network consisting of a quantum satellite constellation and existing ground fibre networks."
Quantum communication is believed to be "ultra-secure" as a quantum photon can neither be separated nor duplicated. Accordingly, it is impossible to wiretap, intercept or crack information it transmits.
China is striving to set up the first-ever global quantum communication network by around 2030, through linking a satellite constellation consisting of dozens of quantum satellites and ground-based quantum communication networks.
