Re: Washington Post Magazine article on ID

From: Randy Isaac <>
Date: Mon Feb 27 2006 - 10:58:43 EST


    Welcome to the discussion list! From the heading, I suspect your note may have only come to me rather than to the entire list so I will copy this to the listserve to ensure everyone receives it.

    Thank you for your comments. That's an excellent perspective. I agree.

  ----- Original Message -----
  Sent: Sunday, February 26, 2006 9:10 PM
  Subject: Re: Washington Post Magazine article on ID

  In a message dated 2/26/2006 8:12:57 PM Eastern Standard Time, writes:
    I assume you're referring to Deutsch's comment in an article in Frontier in 1998:
    "To predict that future quantum computers, made to a given specification, will work in the ways I have described, one need only solve a few uncontroversial equations. But to explain exactly how they will work, some form of multiple-universe language is unavoidable. Thus quantum computers provide irresistible evidence that the multiverse is real. One especially convincing argument is provided by quantum algorithms — even more powerful than Grover’s — which calculate more intermediate results in the course of a single computation than there are atoms in the visible universe. When a quantum computer delivers the output of such a computation, we shall know that those intermediate results must have been computed somewhere, because they were needed to produce the right answer. So I issue this challenge to those who still cling to a single-universe world view: if the universe we see around us is all there is, where are quantum computations performed? I have yet to receive a plausible reply."

    Personally, I don't buy it. Not that I can answer his question either. First, I'm skeptical that such a computation would or ever could be done. Secondly, if it could, I'm not so sure the "somewhere" is relevant in quantum algorithms. Those results don't exist in the same way as classical results.

  Hi, let me introduce myself to this list, since this is my first time posting. I'm a theoretical physicist who lives in Orlando, Florida, and I work for NASA at the space center here. My work is usually in the field of statistical mechanics, but I dabble in science issues that intersect the Christian faith as much as time permits.

  I'd like to weigh in on this. I think the fallacy in Deutsch's argument is that he assumes the maximum information content of the universe is on the order of the integer number of atoms. One might reply that most of the information content "per atom" could be of a cardinality greater than the integers, and that the rich information usefulness "per atom" has never been tapped prior to quantum computing. Hence there is no reason to assume that this computation is taking place anywhere other than within this universe, within the information-rich Hilbert space of the wavefunctions themselves.

  Every view of QM has a way to explain how the computation takes place (or predicts that it will fail to take place), and Deutsch is doing some circular reasoning by assuming his view of QM is correct, failing to acknowledge that the other views are self-consistent and have not been invalidated by any test. For example, the copenhagen interpretation (CI), which says that wavefunction collapse occurs when a "measurement" is made, implies that most of the information of an atom is lost at the wavefunction collapse. The outcome of the measurement is therefore a tiny fraction of the information that originally existed in the wavefunction -- so much less information as the cardinality of the integers compared to the cardinality of the real numbers (in other words, an order of infinity). From that perspective the universe is vastly richer in information "per atom" than what we can ever measure by classical means, and only quantum computing taps into the full information available within a single universe.

  The CI is rightfully criticized because it treats the observer as if he were not a part of the QM system -- as if the observer is the only classical object interacting with a wavefunction world and causing it to collapse. But theists who hold that a spirit or soul really exists as a non-physical thing interacting with the physical universe won't agree that this is any less elegant than the idea of a multiverse. In fact, to many people some version of CI seems vastly more elegant.

  There are those like physicist Paul Davies who (apparently holding to some sort of non-local hidden variables theory) believe that quantum computing will never work for exactly the reason Deutsch raises. Davies believes wavefunctions cannot avoid decoherence when the information content exceeds the total (classical?) information content of the universe.

  Both of these interpretations, CI (or some version of CI) and non-local hidden variables theories, are on equal grounds and as likely to be true from a purely scientific perspective as the multiverse interpretation. Hence, Deutsch's comments are unfounded.

  best regards,

  Phil Metzger
Received on Mon Feb 27 20:45:19 2006

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