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

Illustration of the three cooperating ground stations (Graz, Nanshan, and Xinglong). Listed are all paths used for key generation and the corresponding final key length.

Illustration of the three cooperating ground stations (Graz, Nanshan, and Xinglong). Listed are all paths used for key generation and the corresponding final key length. Image Credit: Pan et al., 2018.

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.

One-time-pad file transfer. A picture of Micius or Schrödinger was transferred between Beijing and Vienna one-time-pad encrypted with a secure key with a length of 5.34 or 4.9 kB, ensuring unconditional security. Binary view of pictures and keys are depicted where each pixel represents one byte of data or key encoded in a 256 color scale. Each side encrypted or decrypted the picture with a simple bitwise xor operation.

One-time-pad file transfer. A picture of Micius and Schrödinger were transferred between Beijing and Vienna one-time-pad encrypted with a secure key with a length of 5.34 or 4.9 kB, ensuring unconditional security. Binary view of pictures and keys are depicted where each pixel represents one byte of data or key encoded in a 256 color scale. Each side encrypted or decrypted the picture with a simple bitwise xor operation. Image Credit: Pan et al., 2018.

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.

 

 

 

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Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.

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