Boffins develop quantum-computer building block

US boffins have made two widely separated atoms communicate their properties to one another in a phenomenon famously referred to by Albert Einstein as "spooky action-at-a-distance" and by others as "quantum teleportation".

In a paper published today by prestigious boffinry journal Nature, a crack team of eggheads, led by professor Christopher Monroe (then of the University of Michigan, now at Maryland), "entangled" two ytterbium atoms using a fibre-optic thread - in quantum style, not literally, duh.

"When entangled objects are measured, they always result in some sort of correlation, like always getting two coins to come up the same, even though they may be very far apart," Monroe said. "Einstein called this 'spooky action-at-a-distance,' and it was the basis for his nonbelief in quantum mechanics. But entanglement exists ..."

In this case the entangled rare-earth atoms were about a metre apart* in linear ion traps, but Monroe said that once the entanglement was complete the fibre link could be dispensed with and the entanglement would persist even if one atom was "(carefully) taken to Jupiter".

This is not unlike Terry Pratchett's well-known proposal to use royalty for communication, on the basis that as soon as a king dies his his son is instantaneously the king. This could allow faster than light communication across interstellar distances, as it's well known that royalness can be measured by simple means involving peas and mattresses.

Obviously the sensitivity would need to be refined in order to distinguish between a king and a mere prince, and (depending on the available supply of monarchs) it might be useful to be able to use kings to send messages more than once.

Pratchett informs us, if memory serves, that plans for experiments involving the careful torturing of a small king - and presumably at the reception end, some kind of advanced pea and bedding rig, perhaps involving a Hello! magazine editor - were interrupted by the pub closing.

Research hasn't languished since then, though, as Monroe and his fellow boffins seem to have performed a similar trick with relatively cheap, obtainable and easy-to-work-with ytterbium ions.

Sadly, however - very sadly - we aren't getting our faster-than-light starships or even communications just yet. Quantum teleportation theory - despite its promising name - requires an ordinary classical comms link as well as the miracle quantum one, rather limiting its potential.

But boffins - and maybe the rest of us - aren't disappointed, because entangled atoms can function as quantum on-off devices, or "qubits". Qubits aren't just 1 or 0 any more than a king in a box with a cat and some poison is just dead or alive: 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 thought that 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.

In fact, spooky-action-at-distance has been demo'd before; but Monroe & Co get a piece in Nature - not their first, either - because these methods could actually be used in building quantum IT kit.

"This linkage between remote atoms could be the fundamental piece of a radically new quantum computer architecture," says Monroe.

"Now that the technique has been demonstrated, it should be possible to scale it up to networks of many interconnected components that will eventually be necessary for quantum information processing."

Huh. We'd still like our starship, though. Brain-hurting boffinry detail from the Trapped Ion Quantum Computing group here.®

*roughly the snout-to-tail distance of a mature female Vietnamese potbellied pig, or 0.5 pico-Bills (Bill Gates's money in $1 bills end to end), or about half a standard walrus.