China has effectively transmitted ‘unbreakable’ code in an effort to build ‘hack-proof’ communications. This is the first-time quantum key distribution has been achieved from a satellite to the ground.
The quantum satellite, Micius, shot messages to two ground stations – one in Xinglong and the other in Nanshan – from varying distances between 645 km and 1,200 km. The message was secured through quantum physics, which meant that any endeavour to listen in on the message would cause detectable changes.
The quantum satellite was originally launched two years ago with the goal of eventually developing a “hack-proof” communications system. The first trial of its laser-based communications system was completed in June this year.
The satellite is named after an ancient Chinese scientist and philosopher who performed optical experiments in the 5th century BC. The satellite weighs more than 1,322 pounds.
Using satellites removes some of the limitations that ground-based systems have in relation to quantum communications. The quantic laws dictate that any attempt to gauge these key properties permanently transforms them. By encoding a key to encrypt data using entangled photons, it is conceivable to send messages in full confidence that they have reached their recipient free of obstruction. In theory, then, it should be impossible to hack.
Ground-based encryption systems that utilise entangled photons have been accessible for years. Nevertheless, the greatest distance over which these messages can be sent safely is around 200 km. This is due to a limitation with the fibre-optic cables through which they travel, as messages gradually weaken over increasing lengths.
Repeater stations can relieve issues relating to distance, but that introduces weak points that attackers may target to scoop up messages. By contrast, laser signals sent through the atmosphere or via satellites in space can travel substantially further before being weakened.
Data transmission rates with satellites are approximately 20 orders of magnitude more effective than fibre-optic cables. If the satellite-based quantum key distribution could be integrated with quantum networks in major metro areas, it could enable quantum cryptography on a global scale. That, for example, can meet demands such as making an absolute safe phone call or transmitting a lot of banking information over private networks.
China is also working to build up a substantial ground-based network that also uses quantum communication to secure messages. The Micius test was one of a few experiments bringing the idea of a worldwide quantum internet nearer to completion, but there are many challenges to be addressed before widely adopting this technology.
What do you think of quantum satellites? Is this a technology you can see ‘taking-off’ in the next decade?