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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