China tests hack-proof quantum satellite communications

In the first trial of a communication system designed to be hack-proof, China has sent a stream of quantum encryption keys from a satellite to earth.

The trial marks the first time space-to-ground quantum key distribution (QKD) technology has been successful, according to the official Xinhua news agency.

The laws of quantum mechanics mean that any attempt to intercept communications will introduce anomalies that can be detected immediately.

QKD uses quantum mechanics to guarantee secure communication for two parties to share secret keys for encrypting and decrypting messages.

If intercepted or measured, the quantum state of the key will change, and the information will self-destruct according to the system’s designers.

News of the test – detailed in the journal Nature – comes a year after China launched the world’s first quantum satellite, called Micius, and has been hailed as a milestone by reviewers.

The Micius test is one of several experiments “bringing the concept of a global quantum internet closer to fruition”, wrote Robert Bedington, Juan Miguel Arrazola and Alexander Ling in a review, reports Information Age.

Quantum communications hold the promise of making the internet more secure than ever as a means of exchanging confidential data.

Satellite-based QKD promises to establish a global-scale quantum network by “exploiting the negligible photon loss and decoherence” in space, the journal says.

Before the test, which appears to have been carried out earlier this year, the achievable distance for QKD was limited to a few hundred kilometres, owing to the channel loss through optical fibre and air.

In the test, the satellite sent quantum keys up to 1,200km, which, according to the experiment’s lead scientist, Pan Jian-Wei, is 20 times more efficient than using optical fibre over the same distance.

Xinhua quoted him as saying that could meet the demand of making an absolutely safe phone call or transmitting a large amount of bank data, according to Reuters.

The news agency said there were “enormous prospects” for applying this new generation of communications in defence and finance.

China is also working to establish a large ground-based network that also uses quantum communication to protect messages, reports the BBC.

Although there are quantum key-based networks operating in the US and Europe, most are reportedly research projects that are not being developed with commercial partners.