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In theory, does a quantum computer have the capacity to generate truly random numbers

  1. Jul 22, 2009 #1
    as opposed to pseudo-random numbers?
     
  2. jcsd
  3. Jul 23, 2009 #2
  4. Jul 23, 2009 #3
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    it depends on whether there are hidden variables or not. We still don't know. (Although this post may start yet another debate over whether there are hidden variables and whether most scientists think there are, or not).

    Also, the generation of random or pseudo-random numbers is not the claim to fame for quantum computers. The same thing can be done by simply watching nuclear decay.
     
  5. Jul 23, 2009 #4
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    Well, the question was "according to theory," not "according to fact"...and according to Bell's theorem,

    No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.

    I'm not saying theory is correct, but this is the answer according to theory..
     
  6. Jul 23, 2009 #5
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    Well I do take exception to that statement of Bell's, but also there is the possibility of non-local hidden variables, which is not addressed by it (and I happen to be a non-local hidden variable-ist at heart, fwiw).

    EDIT: But i should also point out that i disagree with Bohm, as well. I'm just a difficult guy to please.
     
    Last edited: Jul 23, 2009
  7. Jul 23, 2009 #6
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    Can you elaborate on the difference between local and non-local, and why you believe in non-local? I'm also a difficult guy to please :tongue:
     
  8. Jul 23, 2009 #7
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    Non-local in this context means disobeying our (rather classical) concept of causality.

    Note that we never raise an eyebrow at a local process that, if separated by some distance, we would call spooky (disobeying causality). Two local particles are welcome to interact in a variety of ways as long as they obey certain laws after they are done interacting. Our current understanding, however, places certain restrictions on how those particles should behave together if there is a distance between them. So the concept of distance and finite light speed is paramount in the definition of causality. Entangled particles are spooky simply because they behave as if they are local yet they are apparently not.

    The two most obvious examples of non-locality are entanglement and Mach's principle. "Entanglement" and "non-local" appear all over the place in literature, but "Mach's principle" and "non-local" don't show up much together. Mach's principle is ignored because its an old unanswered question we've come to mostly ignore, not because it isn't profoundly important. It is our decision to ignore Mach's principle that is preventing us from understanding some things.

    There must be something that mediates Mach's principle and mediates the communication between entangled particles. Or our concept of distance and time need to be reviewed (and that's what I think needs to be done, and i have some ideas on that). In either case, the interactions that mediate those things might very well be the non-local hidden variables that force QM to be a statistical theory.
     
  9. Jul 23, 2009 #8
    Re: In theory, does a quantum computer have the capacity to generate truly random num

    Random number generation has nothing to do with quantum computers. We could create true quantum random number generators easy enough (easy in theory, getting it all to work well enough and stable enough would be an engineering feat, assuming it's even possible). For an explicit example (although, this is almost certainly not the most convient way to implement this in the real world) say you want to generate a truly random x bit number: Pass a stream of electrons through a z-oriented stern-gerlach box (which I will just call SGz), take the Sz+ stream and for each electron pass it through an SGx machine, if it comes out Sx+ call that bit a 1, if it comes out Sx-, call that bit a 0. Tada. You've generated a truly random number (there is an exactly, truly random, 50-50 change that the Sz+ electron will come out of the SGx as + or -).
     
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