RE> quantum neural computer announcement

[Clay Spence x3039]

A comment on Dr. Dyer's comments on Dr. Kak's announcement:

>	2. that quantum-level phenomena could never be adequately simulated
>by a Turing machine (i.e. that reality is not computable).
>
>After reading a number of (non-specialist) books on quantum physics, I am
>not yet convinced of this. ...
>
>But there's an approach that could produce similar results from completely
>deterministic equations -- i.e. chaos theory. ...
>
>In this (albeit hand-waving) case, then, there would exist
>deterministic equations generating wave-like behavior and the whole
>thing could be ultimately simulated by a Turing machine.

Chaos and quantum mechanics are not equivalent; in quantum mechanics a
system has observable properties that one can measure, but in most
interpretations it doesn't make sense to say that the properties had
those values before the measurement was made, e.g., a particle apparently
doesn't have a position until the position is measured.  This has
experimental consequences which have been verified.  (The reference
that comes to my mind [Mermin, 1985] is slightly old, but very
readable).  This kind of effect cannot be produced by a chaotic,
deterministic system of particles.  However, one can simulate a quantum
system on an ordinary computer by solving Schroedinger's equation
numerically and randomly choosing measurement results with probability
given by the squared magnitude of the wave function.  So the conclusion
is correct, "the whole thing could be ultimately simulated by a Turing
machine", to the extent that one can simulate accurately the quantum
system and to the extent that an ordinary computer is like a Turing
machine (I'm not a computer scientist).

I have no idea whether quantum effects could add anything to a
machine's ability to compute or "reason."

Mermin, N.D., 1985.  Physics Today, Vol. 38, No. 4, p.38.

Clay Spence