Re: Sociological approach

From: Patrick Leahy <jpl.domain.name.hidden>
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
Received on Mon May 23 2005 - 14:55:17 PDT