March 01, 2006

Physics and Interrogation

Cosmic variance has a non-physicist friendly explanation of one component of a story on Quantum Computing released earlier in the week.

From the,

A quantum computer at a US University has solved a computational problem without running a program. Scientists at the University of Illinois at Urbana-Champaign gleaned the answer to an algorithm by combining quantum computation and quantum interrogation (a technique that makes use of wave-particle duality to search a region of space without actually entering that region) in an optical-based quantum computer through a process called "counterfactual computation".

The explanation –

Quantum mechanics, as we all know, is weird. It’s weird enough in its own right, but when some determined experimenters do tricks that really bring out the weirdness in all its glory, and the results are conveyed to us by well-intentioned but occasionally murky vulgarizations in the popular press, it can seem even weirder than usual…

Let me make a stab at explaining, perhaps not the entire exercise in quantum computation, but at least the most surprising part of the whole story — how you can detect something without actually looking at it. The substance of everything that I will say is simply a translation of the nice explanation of quantum interrogation at Kwiat’s page, with the exception that I will forgo the typically violent metaphors of blowing up bombs and killing cats in favor of a discussion of cute little puppies.

Read in full here. (via

A-level physics was interesting, but sadly no university offered Physics minus math as a option.

- 6 comments by 2 or more people Not publicly viewable

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  1. That's because physics is applied maths…

    01 Mar 2006, 13:13

  2. I hate maths

    01 Mar 2006, 15:00

  3. Leighton Joskey

    So does that mean this computer will answer my questions before I ask them, so long as I don't look at it?

    01 Mar 2006, 17:19

  4. Leighton: Well it depends on the nature of the query you're seeking a solution to. The answer to life, the universe and everything may be a bit of a stretch at present.

    01 Mar 2006, 22:11

  5. Ah, don't you just loooove quantum physics? Actually I dislike it, but not as strongly as waves….

    16 Mar 2006, 10:07

  6. Damn you first years! shakes fist and cries

    16 Mar 2006, 12:06

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