----- Original Message -----
From: "Patrick Leahy" <[EMAIL PROTECTED]>
Subject: Re: Sociological approach
Date: Mon, 23 May 2005 19:50:15 +0100 (BST)
> QM is a well-defined theory. Like any theory it could be proved
> wrong by future experiments. My point is that R. Miller's
> suggestions would definitely constitute a replacement of QM by
> something different. So would aet.radal's (?) suggestion of
> information tunnelling between macroscopic branches. The crucial
> point, which is not taught in introductory QM classes, is the
> theory of Quantum decoherence, for which see the wikipedia article
> and associated references (e.g. the Zurek quant-ph/0306072).
> This shows that according to QM, the decay time for quantum
> decoherence is astonishingly fast if the product ((position
> shift)^2 * mass * temperature) is much bigger than the order of a
> single atom at room temperature. Moreover, the theory has been
> confirmed experimentally in some cases.
> Since coherence decays exponentially, after say 100 decay times
> there is essentially no chance of observing interference phenomena,
> which is the *only* way we can demonstrate the existence of other
> branches. "No chance" meaning not once in the history of the
> universe to date.
> No existing animal is small enough or cold enough to participate
> directly in quantum interference effects (i.e. to perceptibly
> inhabit different micro-branches simultaneously), hence my claim
> that your "behaviour system", whatever it is, must be in the
> fully-decohered regime.
> I have to backpedal some though, because by definition an
> intelligent quantum computer would be in this regime (in practice,
> by being very cold). I certainly don't want to imply that this goal
> is known to be impossible.
> NB: I'm in some terminological difficulty because I personally
> *define* different branches of the wave function by the property of
> being fully decoherent. Hence reference to "micro-branches" or
> "micro-histories" for cases where you *can* get interference.
> Paddy Leahy
> Dr J. P. Leahy, University of Manchester,
> Jodrell Bank Observatory, School of Physics & Astronomy,
> Macclesfield, Cheshire SK11 9DL, UK
> Tel - +44 1477 572636, Fax - +44 1477 571618
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