China's quantum space race adds to fraught Sino-US relations

China’s quantum satellite network plans take a great leap forward

In the world of quantum physics and cyber security this is a big deal. China has just successfully tested a quantum satellite network which could lay the foundations for unbreakable communications. “I think we have started a worldwide quantum space race,” said lead researcher Jian-Wei Pan, and he might well be right. But what exactly is a quantum network and how might this latest leap forward impact already tense Sino-US relations?

A long journey

Researchers have, for years, been looking into ways to improve on current encryption systems. The main drawback of them is that with enough computing power encryption can theoretically be cracked. That means that as we develop more and more powerful computers, in time the encryption regarded as highly secure today could be easily undermined by nation states and potentially financially motivated cybercriminals.

Quantum key distribution overcomes these challenges thanks to an idea that sounds like it came straight out of a sci-fi novel. In quantum mechanics, a branch of physics dealing with subatomic particles, pairs of photons created simultaneously remain linked throughout space and time. No matter how far they travel – even light years – or how long they are kept apart, they will share the same properties; something known as “entanglement”.

Everyone’s jumping on the quantum computing bandwagon, but just how close is quantum computing?

This feature could be utilised to securely share the all-important secret key between two parties in order to encrypt and decrypt messages. Crucially – and here’s where quantum mechanics makes this more secure than traditional encryption – any attempt by a third party to intercept these keys would be immediately detected. This is because any attempt to measure a quantum system unpredictably changes that system.

Up until now, scientists have carried out experiments to beam these entangled photons across the earth, via fibre optic cables. However, they need quantum repeaters to amplify the signal every 100 kms or so otherwise the photons lose their entangled state – a drawback which could reportedly offer hackers opportunities to target in the future. Such networks are nevertheless being developed by the likes of Swiss company ID Quantique. However, in the vacuum of space, photons can travel in an entangled state much further.

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