Linked by Thom Holwerda on Thu 23rd Feb 2006 18:09 UTC
Geek stuff, sci-fi... Ok, this one is just plain scary. "By combining quantum computation and quantum interrogation, scientists at the University of Illinois at Urbana-Champaign have found an exotic way of determining an answer to an algorithm - without ever running the algorithm. Using an optical-based quantum computer, a research team led by physicist Paul Kwiat has presented the first demonstration of 'counterfactual computation', inferring information about an answer, even though the computer did not run." The research team published their results in Nature.
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Mmhh am I too dumb or...?
by pfortuny on Fri 24th Feb 2006 08:31 UTC
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Do not try to understand "quantum algorithms" as algorithms. They are mere quantum **systems** which, as such **quantum** systems behave in **unpredictable** ways.

They have built up a quite clever experiment which **when interpreted as an algorithm** behaves like stated.

I would not draw any more complicated conclussions from that. Quantum **systems** are just that: complicated systems with random behaviour (though statistically sound, usually, in the long run).

The summary, though, is quite bad:

Although a photon can occupy multiple places simultaneously, it can only make an actual appearance at one location.

Typicall mistake. It is a quantum object; it is not in multiple places but everywhere as a function wave. And in "all the states" at once (ibid.)

We are still to have a Shor's factoring machine. That will be a great day.

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