A Chinese satellite launched Tuesday will test the viability of data links that cannot be eavesdropped on, potentially leading to a revolution in defense communications.

The satellite carries a so-called quantum system, which sends a series of single photons to receiving stations on Earth. Any attempt to intercept the beam destroys it.

“The idea is to use quantum information stored in the state of a photon to transmit an encryption key between parties,” quantum physicist Andrew Truscott of the Australian National University said by email.

“What makes the process uncrackable is the quantum nature of the light and the fact that any eavesdropper will destroy the quantum state of the photon — and in turn render the information gathered useless.”

If it works, the system may have a range of applications, from spy satellites delivering their images to Earth, to embassies reporting back to their governments and submarines taking orders while deep beneath the waves.

The satellite, named QUESS, is the world’s first designed around quantum exploration and is expected to be followed by others from China.

At its closest swing-by, it will be only 500 km from a receiving station.

The principle has been proven on Earth in fiber optics but is untested in space. Obstacles that must be overcome include the satellite’s speed — it orbits every 90 minutes — and interference from sunlight, moonlight and light noise from cities, all of which are stronger than the beam’s single photon, chief project scientist Pan Jian-wei told the science journal Nature in January.

The satellite’s equipment must also point precisely at a telescope on the ground for the link to work.

Separately, China’s Xinhua News Agency quoted Pan as calling the project a huge leap forward for the nation, marking a transition from Beijing being a “follower” in information technology to taking the lead role in what may be the science of the future.

China’s ambitious space program has already notched up a range of successes, including a successful test of an anti-satellite missile and a probe that reached the moon.

It is not the only nation to look at quantum communications. Teams in Japan and other nations are also working on it.

“This type of communication is the future for secure encryption,” ANU’s Truscott said.

But he added, since it has only been demonstrated over distances of around 100 km, the idea that it will work over the distances needed for satellite communication “is not a foregone conclusion.”

The QUESS satellite will orbit at an altitude 100 km higher than the International Space Station and will initially talk to ground stations in Beijing and Urumqi, Xinjiang province, Xinhua said.

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