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I have a very basic understanding of what GPU's and quantum computers are good at. To me, it seems like they overlap, but maybe this isn't completely true. GPU's are good for graphics which requires a lot of calculations being done in parallel, and quantum computers are good at doing lots of calculations in parallel. Would that make a quantum computer good at everything a GPU does, even gaming, video rendering, etc. or only the very specific tasks like finding factors of large numbers? (even if it couldn't do these things now, is it theoretically better at doing them so maybe it could out perform a standard computer in the future)

Thank you for your response.

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closed as off-topic by Brandon Enright, JamalS, David Hammen, ACuriousMind, Kyle Kanos Jan 25 '15 at 15:41

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    $\begingroup$ Your comparison (parallel computation) only makes sense in the most superficial way. Once you get past waving your hands they're completely different. $\endgroup$ – Brandon Enright Jan 25 '15 at 6:30
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    $\begingroup$ I'm voting to close this question as off-topic because it belongs on Theoretical Computer Science. cstheory.stackexchange.com $\endgroup$ – Brandon Enright Jan 25 '15 at 6:31
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    $\begingroup$ Limiting your question to rendering 3D graphics, I think the basic difference is that while quantum computers are good at searching a large problem space for a single answer, rendering an image involves finding many independent "answers" (pixel or fragment color values). I'd speculate that quantum computing might be terrific for simultaneously modelling the many paths light takes to arrive at a point (giving a pixel its brightness), but that it wouldn't suit creating a whole image in parallel. I'm very much just speculating though. $\endgroup$ – Qubei Jan 25 '15 at 7:00
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    $\begingroup$ "...quantum computers are good at doing lots of calculations in parallel..." That is not really the right way to think about what quantum computers do. Quantum computers are different. Two of the interesting known algorithms are Grover search and Shor's factoring algorithm. $\endgroup$ – DanielSank Jan 25 '15 at 7:30
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What a quantum computer can do it take lots of results and options and do them in parallel, and then if you can figure out how to get bad or wrong results to cancel each other, then you can efficiently combine them all together and get the right answer. It's being able to efficiently combine all the things done in parallel that is useful and special.

For instance the Shor algorithm for factorization is useful not because it is a parallel method for finding factors (we already knew ways to do that for classical computers), but it's useful because it figures out a way to do it in ways where wrong answers can cancel and right answers rise to the top, synthesizing all the different work done. That's what gets you so much good results so quickly. If you don't have a good way to do that, you can lose your results from decoherence faster than you can do the work and then its no help at all to have a quantum computer.

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