The idea continues to be somewhat controversial - as is the one that your nose might be doing a bit of quantum biology.

BBC: Perfume chemist

But to exploit the fullest security allowed by the peculiar rules of quantum mechanics, each "bit" of information in the key should be encoded onto exactly one photon, sent through air or down a fibre.

BBC: Quantum key distribution with single photons

"In a very naive way, the advantage of quantum computing is that by being a little bit of zero and a little bit of one, you can do two calculations at once, " says Raymond Laflamme, a researcher at the Los Alamos National Laboratory in New Mexico.

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Such a quantum repeater uses groups of three photons for each bit of the message.

ECONOMIST: Quantum information technology