Dear Andrei and colleagues,
I look foreword enthusiastically to our discussion of quantum
information. I certainly agree that the realm of quantum information is
a powerful and effective gateway to investigation of the fundaments of
quantum theory. In particular, I�d emphasize again what Landauer taught
us: that information is always physical. So that, since all measurements
exchange information, all measurements must exchange at least one
physical quantum. (There are no �non-physical� quanta; all have energy.)
This, I�m sure, is a source of � some disturbance of the object
observed...� as you quoted Dirac as telling us, Andrei. (Quantum Theory:
Reconsideration of Foundations, 2001) You also quoted Bohr saying that
for any quantum process there is an essential discontinuity symbolized
by Planck�s quantum action.
I�m convinced that Born got the interpretation of the wavefunction
correct. Quantum theory, as you emphasize, Andrei, is fundamentally
about probability - the probable result of the next measurement. One
mistake, and an almost ineradicable source of confusion, is the
misunderstanding that the wavefunction, Psi, can also always be the
present state of the physical system. One can cite real examples where
both interpretations are not possibly valid simultaneously.
I�ve traced the mistaken notion that Psi is always the state of the
system as far back as Bohm�s book on quantum mechanics. (Does anyone
know an earlier source?) He certainly doesn�t even attempt a proof,
merely citing some special cases. Those special cases seem correct, but
that doesn�t mean that the wavefunction can always be the current state
of the considered object. As you�ve also mentioned, Andrei, one source
of the confusion with quantum theory is the wrong pathways chosen by the
founding fathers of Q. M., cemented by their authority.
Are the conference proceedings from Foundations of Probability and
Physics yet available, Andrei? And, if it�s part of our subject in this
session, may we carefully dissect quantum interference and its meaning
in one of our future discussions?
Cordially,
Michael Devereux
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Received on Fri May 19 07:34:25 2006
