Original URL: http://www.theregister.co.uk/2011/12/02/diamond_quantum_computing_entanglement/

Quantum computing comes closer as diamonds get spooky

Boffins 'entangle' synthi-gems at room temperature

By Lewis Page

Posted in Science, 2nd December 2011 12:40 GMT

International boffins are chuffed today to publish cunning research in which they demonstrate quantum entanglement - the "spooky action at a distance" so disliked by Einstein - between a pair of small synthetic diamonds: and, this is the clever bit, at room temperature rather than in a cryogenic chamber or similar, so bringing the long hoped-for quantum computer hardware that bit nearer.

The scientists write:

Entanglement is usually fragile in room-temperature solids, owing to strong interactions both internally and with the noisy environment. We generated motional entanglement between vibrational states of two spatially separated, millimeter-sized diamonds at room temperature. By measuring strong nonclassical correlations between Raman-scattered photons, we showed that the quantum state of the diamonds has positive concurrence with 98% probability. Our results show that entanglement can persist in the classical context of moving macroscopic solids in ambient conditions.

The entanglement was achieved and demonstrated in the two diamonds using a complicated setup of lasers and beam splitters such that a given photon could be in either diamond, so entangling them. Physicists have demonstrated entanglement many times before, but generally have needed to use very cold environments to avoid "noise" corrupting the experiment. It's also unusual to be able to entangle large, physically visible objects like diamond crystal, as opposed to individual atoms or similar.

All this is important to the IT world because entangled objects can function as quantum on-off devices, or "qubits". Qubits aren't just 1 or 0 like regular classical bits: they could contain a whole load of info.

Entangled qubits would theoretically also be the dog's bits, as they might be used to build hard-to-understand yet puissant "quantum computers". Quantum computing has been modelled and theorised, and it's known could it be achieved it would offer some interesting possibilities: not least the breaking of current encryption and, of course, the chance of new and provably unbreakable crypto to replace it.

Doing this sort of thing at normal temperatures with normal-ish objects means that the boffins, led by Ian Walmsley of Oxford uni, get a headline in prestigious boffinry journal Science for their work. Unfortunately it seems that we won't be getting our quantum computers just yet.

"I am not sure where this particular work will go from here," Andrew Cleland, a rival quantum boffin in California, tells rival journal Nature. "I can't think of a particular use for entanglement that lasts for only a few picoseconds."

But Walmsley for his part insists that "diamond could form the basis of a powerful technology for practical quantum information processing". ®