Ground test of satellite constellation based quantum communication

TL;DR

This paper demonstrates daytime satellite-based quantum key distribution over 53 km using advanced noise suppression techniques, marking a significant step towards a global quantum communication network with satellite constellations.

Contribution

It introduces a novel daytime quantum communication experiment with a satellite-like setup, overcoming sunlight noise with new technology, and shows feasibility for satellite constellations.

Findings

Successful 53 km daytime quantum key distribution

Overcame sunlight noise using 1550 nm wavelength and ultralow noise detectors

Demonstrated potential for satellite constellation-based global quantum network

Abstract

Satellite based quantum communication has been proven as a feasible way to achieve global scale quantum communication network. Very recently, a low-Earth-orbit (LEO) satellite has been launched for this purpose. However, with a single satellite, it takes an inefficient 3-day period to provide the worldwide connectivity. On the other hand, similar to how the Iridium system functions in classic communication, satellite constellation (SC) composed of many quantum satellites, could provide global real-time quantum communication. In such a SC, most of the satellites will work in sunlight. Unfortunately, none of previous ground testing experiments could be implemented at daytime. During daytime, the bright sunlight background prohibits quantum communication in transmission over long distances. In this letter, by choosing a working wavelength of 1550 nm and developing free-space single-mode fibre coupling technology and ultralow noise up-conversion single photon detectors, we overcome the noise due to sunlight and demonstrate a 53-km free space quantum key distribution (QKD) in the daytime through a 48-dB loss channel. Our system not only shows the feasibility of satellite based quantum communication in daylight, but also has the ability to naturally adapt to ground fibre optics, representing an essential step towards a SC-based global quantum network.