China’s ‘Micius’ satellite demonstrates intercontinental quantum key distribution for the first time

Tomasz Nowakowski

China’s Quantum Science Satellite, nicknamed “Micius” (after a fifth century B.C. Chinese scientist) has performed the first intercontinental quantum key distribution by relaying signals between multiple ground stations located in China and Austria.

The test was conducted by a joint China-Austria team of researchers. In a recent study published in Physical Review Letters on January 19, they reported that a decoy-state quantum key distribution between Micius operating in a low-Earth orbit (LEO) and ground stations located in Xinglong, Nanshan (both in China), and Graz (Austria).

“This is the first demonstration of intercontinental quantum key distribution of any kind, and it will stand as a milestone towards future quantum networks,” said Ronald Hanson of the Technical University of Delft in the Netherlands, whose research focuses on long-distance quantum telecommunication for a quantum internet.

Micius was launched into space on August 15, 2016 by a Long March 2D booster. The satellite was built by the Chinese Academy of Sciences (CAS) and weighs around 1,100 pounds (500 kilograms).

The spacecraft is designed to facilitate quantum optics experiments over long distances to allow the development of quantum encryption and quantum teleportation technology.

In order to achieve its scientific objectives, the satellite is equipped with a quantum key communicator, a quantum entanglement emitter, a quantum entanglement source, a quantum experiment controller and processor, and a high-speed coherent laser communicator.

Quantum key distribution (QKD) is a communications method which uses a cryptographic protocol involving components of quantum mechanics. It is based on individual light quanta (single photons) in quantum superposition states that guarantee unconditional security between distant parties. This method is therefore perceived as being more secure than the traditional public key cryptography (which usually relies on the computational intractability of certain mathematical functions).

Now, a team of researchers led by Jian-Wei Pan of the University of Science and Technology of China (USTC) in Hefei, are working to successful demonstrate the use of QKD using laser beams.

As part of the experiment, Micius has relayed quantum encrypted data in the form of images and a video stream between China and Austria – over a distance of 4,700 miles (7,600 kilometers).

“This was, on the one hand, the transmission of images in a one-time pad configuration from China to Austria as well as from Austria to China. Also, a video conference was performed between the Austrian Academy of Sciences and the Chinese Academy of Sciences, which also included a 280 kilometer [174 mile] optical ground connection between Xinglong and Beijing,” the scientists wrote in the paper.

Micius is part of an international project called Quantum Experiments at Space Scale (QUESS), led by Chinese scientists. It aims to establish a quantum-encrypted network – a European–Asian network is planned to be launched by 2020, while a global network by 2030. Pan and his colleagues believe that the latest tests conducted with the use of Micius bring them much closer towards building an ultra-long-distance global quantum network.