Re: Parallel Universes

From: Wei Dai (weidai@weidai.com)
Date: Wed Feb 12 2003 - 16:31:08 MST

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    On Wed, Feb 12, 2003 at 05:34:26PM -0500, Rafal Smigrodzki wrote:
    > ### What is a deterministic computer?

    It's just a classical Turing machine. All real computers are subject to
    hardware errors, and therefore are not deterministic. I'm assuming that
    the decision maker has access to a truly deterministic computer that does
    not suffer from hardware errors, or can perform deterministic computations
    in his head without error.

    Here's a quote from Greg Egan's "Singleton" (available at
    http://www.netspace.net.au/~gregegan/MISC/SINGLETON/Singleton.html). The
    AI running in the Qusp is an example of someone who can do deterministic
    computations in his head.

    Back in my office, I summoned up a schematic of the device I called the
    Qusp: the quantum singleton processor. The Qusp would employ all the
    techniques designed to shield the latest generation of quantum computers
    from entanglement with their environment, but it would use them to a very
    different end. A quantum computer was shielded so it could perform a
    multitude of parallel calculations, without each one spawning a separate
    history of its own, in which only one answer was accessible. The Qusp
    would perform just a single calculation at a time, but on its way to the
    unique result it would be able to pass safely through superpositions that
    included any number of alternatives, without those alternatives being made
    real. Cut off from the outside world during each computational step, it
    would keep its temporary quantum ambivalence as private and
    inconsequential as a daydream, never being forced to act out every
    possibility it dared to entertain.

    The Qusp would still need to interact with its environment whenever it
    gathered data about the world, and that interaction would inevitably split
    it into different versions. If you attached a camera to the Qusp and
    pointed it at an ordinary object ? a rock, a plant, a bird ? that object
    could hardly be expected to possess a single classical history, and so
    neither would the combined system of Qusp plus rock, Qusp plus plant, Qusp
    plus bird.

    The Qusp itself, though, would never initiate the split. In a given set of
    circumstances, it would only ever produce a single response. An AI running
    on the Qusp could make its decisions as whimsically, or with as much
    weighty deliberation as it liked, but for each distinct scenario it
    confronted, in the end it would only make one choice, only follow one
    course of action.



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