When it comes to sending information securely, there is one technique that leaves all other in the shade. Quantum key distribution makes it possible to send messages with perfect secrecy. And since this is guaranteed by the laws of physics, secrecy doesn’t get better than that.
So it’s no wonder that governments, the military and commercial organisations all over the world are interested in exploiting this trick. Indeed, commercial quantum key distribution over optical fibres is already in use in various places and researchers have demonstrated quantum key distribution through free space over distances of up to 144 km.
But what of water? It’s easy to imagine that submarines might want to exploit this kind of communication as might underwater sensor networks or autonomous underwater vehicles and so on. But that raises an obviosu question: is it possible to communicate through seawater using this ultimate form of quantum security?
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