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The computer that works best when it's switched off

... I don't know what to say about this NewScientist piece (no 2539, 25-Feb-2006, p 21). I mean, it's freaky isn't it. Check out the film, What The Bleep Do We Know, to blow your mind even more!
The computer that works best when it's switched off

Even for the crazy world of quantum mechanics, this one is weird. A quantum computer program has produced an answer without actually running.

The idea behind the result, suggested in 1998, is to put a quantum computer into a "superposition", a state in which it is both running and not running. It's as if you asked Schrodinger's cat to hit "Run". You would sometimes get an answer out of the computer even though the program did not run.

Now researchers from the University og Illinois at Urbana-Champaign have improved on the original design and built a non-running quantum computer that really works. They send a photon unto a system of mirrors and other optical devices, including a section that runs a simple program by changing the properties of the photon.

The new design includes a quantum trick called the Zeno effect. Repeated measurements stop the photon from entering the actual program, but allow its quantum nature to flirt with the program's components - so it can become gradually altered even through it never actually passes through (Nature, vol 439, p 949).

"It is very bizarre that you know your computer has not run but also know what the answer is," says team member Onur Hosten.

This scheme could have an advantage over straightforward quantum computing. "A non-running computer produces fewer errors," says Hosten. That idea should have technopobes nodding enthusiastically.