How China’s quantum satellite aims to defeat hacking

Photo credit: Xinhua.

On Tuesday, China did something rather remarkable: it launched what it says is the world’s first quantum communications satellite. The satellite, nicknamed “Micius,” will help China conduct an experiment in hack-proof quantum communications.

Why should you care?

This technology is in its infancy, and if it works, for now it will still be wildly expensive. But in the long run, quantum communications systems could help us transmit data over large distances much more securely than current systems. If you’ve ever been concerned that someone else might be snooping on your messages, then you should be interested in quantum communication technologies, which could make snooping impossible.

How does the current system work?

Currently, if you want to send information securely, you send an encrypted message. To read the encrypted message, the recipient will need a key, which means you have to send that too. The problem is that if someone’s snooping on you and they intercept the key transmission, they can now easily decrypt and read your message. Even worse, because your recipient will still receive the key, you probably won’t be aware that you’re being spied on and your message is no longer safe.

How does this new quantum satellite system work?

In theory, it works like this: China will send an encrypted message from one location to another through normal communication channels. It will pass the “quantum” key to decrypt that message to the satellite in the form of photons set in specific quantum states. The satellite will then pass that quantum key down to the message recipient. Like so:

Icons via StockUnlimited.

This approach makes the key far more difficult to snoop, tap, or “hack” because of the properties of photons in quantum mechanics. Any attempt to observe the quantum key as it’s being transmitted would be unsuccessful, because according to the uncertainty principle any observation changes the quantum states of the photons, rendering the key useless. The end result: the attempted snooper ends up with a broken key. And because the recipient will also have received that worthless key, the two parties now know that someone is trying to spy on them.

Is the satellite doing anything else?

The quantum communications system the satellite is testing is probably more likely to affect your life in the reasonably-short-term than anything else it’s doing. But the satellite is going to help China conduct some other quantum-physics-related tests, including tests on long-distance quantum entanglement and a test of long-distance quantum teleportation.