back to article What are quantum computers good for?

The problem with trying to explain quantum computing to the public is that you end up either simplifying the story so far as to make it wrong, or running down so many metaphorical rabbit-burrows that you end up wrong. So The Register is going to try and invert the usual approach, and try to describe quantum computing at a more …

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    1. Anonymous Coward
  1. Havin_it
    WTF?

    Er...?

    Maybe I'm misunderstanding, but I think the 0/1 usage is jumbled on p2?

    If the broken machine only outputs 1, how does "might have to input 500 numbers before the output changed from 0 to 1 (or vice versa)" make sense? If it had been outputting 0 up until then, then it would have to be the working machine and she was a bit of an idiot to have kept punching in numbers!

    And what's with the "000...0" terms? You throw that in cold, what does it mean? An indeterminate number of zeroes?

    It's too late to prevent my brain dribbling down my lapels, but if you're aiming to accessibly explain the concept to laypeople, please try to avoid goofs such as this (appears to be).

  2. Anonymous Coward
    Anonymous Coward

    Tired

    I just spent my lunchtime reading through this, I think I know less than when I started

    I'm certainly more tired!

  3. corn

    Similar topic-

    http://www.lulu.com/us/en/shop/nick-rugai-phd/computational-epistemology-from-reality-to-wisdom/hardcover/product-18771255.html

    It's all still beyond my understanding but this book was interesting.

  4. Crisp
    Coat

    As Deepak Chopra taught us,

    Quantum physics means anything can happen at any time for no reason!

  5. rrtucci
    FAIL

    This article is full of false statements:

    Here are some

    (1)"a quantum computer is exponentially more efficient at performing Fourier Transforms than a classical computer."

    That is totally false. A QC can calculate faster than classical computers only "quantum" Fourier transforms, not "classical" Fourier transforms. They are quite different. For a classical Fourier transform, you can "print" all N components of the answer at once, for a quantum Fourier transform, you can print ONLY ONE of the N components of the answer. The other N-1 components are lost when you print just one of them.

    (2)"Today, the problem is approached by sampling, using the Metropolis algorithm on a classical computer. The European/Canadian group propose an alteration to that algorithm that uses a quantum computer to obtain the samples."

    Again, very misleading.

    The statement refers to the following paper:

    http://arxiv.org/abs/0911.3635

    Quantum Metropolis Sampling

    K. Temme, T.J. Osborne, K.G. Vollbrecht, D. Poulin, F. Verstraete

    The problem with this paper is that it is not very honest. It doesn't tell

    you that their QC algorithm is no faster than classical!. There are QC algorithms, which PREDATE the Temme et al al algorithm and which can sample faster than the Temme et al algorithm. Those algorithms use Szegedy operators. (See, for example, the work of Pawel Wocjan). The Temme et al paper doesn't compare their algorithm with those because they know they would look quite bad in the comparison.

    (3)"Another example is here: a quantum algorithm for solving linear equations (where you have a matrix and a known vector, and wish to compute an unknown vector)."

    That is totally false. Again, with the classical algorithm for solving LE, you can print all N components of the answer, but with the quantum one you can print ONLY ONE component. Equating these two algorithms is quite disingenuous. Check out this post by Eric Dexler, one of the most prominent figures of nanotech

    http://metamodern.com/2009/11/10/quantum-computing-sorry-no-speedup-in-solving-linear-systems/

  6. Dick Pountain
    Angel

    Yeti

    I have pictures of a yeti using a quantum computer but I daren't show them to anyone in case they disappear.

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