The "uncrackable codes" made by exploiting the branch of physics called quantum mechanics have been sent down kilometres of standard broadband fibre.

This "quantum key distribution" has until now needed a dedicated fibre separate from that used to carry data.

But a new technique reported in Physical Review X shows how to unpick normal data streams from the much fainter, more delicate quantum signal.

It may see the current best encryption used in many businesses and even homes.

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