Original URL: http://www.theregister.co.uk/2000/08/15/boffins_unveil_worlds_most_powerful/

## Boffins unveil world's most powerful quantum computer

Based on... er... just five atoms

Posted in Business, 15th August 2000 10:11 GMT

Researchers from Stanford University, the University of Calgary and IBM have built what they claim is the most advanced quantum computer to date - a staggeringly powerful beast that uses all of five atoms to store and process data.

The team of boffins used the computer to find the period of a mathematical function, one of the basic maths building blocks of modern cryptography, doing so in the equivalent of a single CPU cycle. By contrast, a traditional microprocessor would have had to run many iterations of the software to come up with the answer.

Don't expect to see this kind of processing power on the desktop anytime soon, though. Quite apart from quantum computing's relative uselessness when it comes to applications that don't require much number crunching - ie. most desktop apps - the researchers reckon that taking the number of atoms from five to between seven and ten will take two years at least.

"A quantum computer could eventually be used for practical purposes such as database searches - for example searching the Web could be sped up a great deal - but probably not for more mundane tasks such as word processing," IBM's Isaac Chuang, the research team leader, told Reuters.

Quantum computing works by using an atom's quantum spin state - essentially the direction it's rotating in - as a way of storing binary data: spin up equals 1, spin down equals 0. Quantum theory, however, states that unobserved particles can spin in both directions simultaneously - it's called 'superposition' - a single direction only emerges when someone one measures it.

Bizarre, we know, but that's what the statistical calculations behind the theory say, and since it's what makes the quantum computer work, who are we to argue?

Superpositioning allows the quantum computer to simultaneously store multiple bit patterns, or states, depending on the number of particles in the system. The number of states equals two multiplied by itself for each particle. In the IBM system, with its five atoms, that makes for 2 x 2 x 2 x 2 x 2 = 32 states. The upshot is that the IBM machine can apply a calculation to 32 sets of numbers in a single go.

Hence the interest of the US National Security Administration and Department of Defense in the team's work. Quantum computing will theoretically make short work of the most complex cryptography codes - codes that would take current computer systems decades to break. Guess who's funding the quantum computing team's work... ®

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