Zurek, Stamp, and the interpretation of QM

Letter to Mike Epperson

Many thanks for sending me the papers of W. Zurek (Decoherence,
Einselection, and

the Existential Interpretation) and P. C. E. Stamp (The Decoherence
Puzzle). Actually,

I had seen several earlier versions of Zurek's paper, which seems to be
aiming at a new

interpretation of QM, essentially different from CI in that it "perhaps
even eliminates the 'collapse' of the state vector". It is based
essentially on environmental decoherence effects (the disappearance of
effects of phase differences) stemming from the action of a large object
(such as a pointer) upon its environment (as illustrated in Fig. 11.3 of
MU). Zurek has pursued this idea diligently for many years, and this
2008 paper emphasizes certain problems with that proposal.

He says on page 2 "we shall describe how decoherence converts quantum
entanglement into classical correlations and how these correlations can
be *used* *by the observer for the purpose of prediction.* This is a
pragmatic application.

He speaks of memories stored in brains, and then on page 5 he begins to
talk about what the observer *knows* and *can know*. But why must he
bring in as an added element *the knowledge of the observer?* Insofar as
the observer is a physical system that is part of the whole physical
universe, evolving in accordance with the Schroedinger equation, the
brain of the observer is represented in QM by a density matrix which,
due to environmental decoherence, is essentially a smear of essentially
classical possibilities.

Yet what any human observer's *knows,* as reflected in his stream of
conscious experiences, corresponds, in general, only to a tiny part of
the smear of essentially classical-type brains that are represented in
the Schroedinger-equation-generated density matrix corresponding to his
brain. If the observer is basically a physical entity, then why are not
similar knowings associated with the other similar parts of the QM
density matrix associated with his brain? It would seem that treating
the human observer as a basically physical entity in a physical world
that evolves always in accordance with the physical (Schroedinger)
dynamics should entail that *each* of the classically incompatible
branches would produce a different associated stream of conscious
experiences. It might therefore be reasonable to say that there is a
separate stream of consciousness associated with each of the classically
disparate branches of the density matrix of the person's brain, and that
these different streams of consciousness exist in parallel, with each
stream unaware of the parallel-existing others. But does it then make
sense to say that the *probability* of experiencing one branch is, say,
ten times greater than the probability of experiencing another branch,
if both streams of conscious are occurring simultaneously? And if *each*
of the appropriate classical parts of the brain is associated with a
separate knowing, then how are *probabilities* unambiguously assigned to
the parts of a *continuous smear* of *overlapping* essentially classical
brain states?

The founder's of QM wrestled long and hard with these questions and
proposed an answer. It is described by von Neumann as his *process 1*,
which is Bohr's "free choice on the part of the experimenter", in
conjunction with the interpretation of the density matrix as a
representation (merely) of *potentialities* for the occurrence of actual
psycho-physical events that link the person's *unique stream of
conscious experiences* to an associated activity in the 'collapsed'
state of his brain. This is the orthodox approach, which is what is used
in actual scientific practice.

In this orthodox approach the inclusion of decoherence effects is
nothing more than a correct including of certain features of von
Neumann's mathematical description of QM. Anyone who proposes an
essentially different way of understanding QM, should, I think, make at
least as clear as the orthodox theory does, the connection between brain
activities and the probabilities of associated streams of consciousness.

Zurek does at the end make an attempt to deal with these questions. He
claims that

the Copenhagen interpretation does not take decoherence into account. I
see little justification in this claim. Interaction with the environment
is a crucial part of von Neumann's formalism. He makes a lot of fuss
about systems that are imbedded in larger systems. When I first looked
at the vN book in 1959 I was acutely aware of the existence of
decoherence effects. And when Heisenberg speaks in 1958 of "interaction
with the measuring device and hence with the rest of the world" he
surely had in mind this transfer/leakage of phase information into the
environment. But the mere inclusion of decoherence effects is not
sufficient to do away with the "process 1" collapse of the quantum
state. The decoherence produces a coordinate-space density matrix that
is quasi-diagonal continuous smear. The QM probability rules then
require the *posing of a specific question* associated with *a* *unique
experience*, whereupon the quantum probability machinery produces, in
connection with an associated collapse, a probability for that unique
experience. No logically satisfactory substitute for this process 1
*intervention* into the Schroedinger dynamics has yet been proposed.
Zurek emphasizes this problem of the selection of unique experience on
page 3, as a difficulty with the no-collapse MWI. Yet he ends up with an
"absence of explicit collapses." (p. 22). The basic problem of unique
experiences with well defined probabilities is not resolved.

I submit that this whole endeavor to eradicate from the physical
dynamics any essential input from mind is a huge step in a backward
direction. Why must the efficacy of *conscious will* be an illusion,
when orthodox QM neatly explains it? Why must Mind, with a capital M, be
subordinate to matter, when matter requires laws, but matter, as usually
conceived, does not itself *make* the laws that it obeys. Why this
continuing retrograde effort to separate physics from the only aspect of
nature that we can be most certain actually exists, and to which it must
be securely connected by any empirically adequate physical theory?

**The Decoherence Puzzle.**

Many thanks for sending this interesting paper. It stresses the possible
complexities

of adequate QM models of solid state systems, particularly with regard
to decoherence.

Of particular interest is the huge (six orders of magnitude) failure
*with respect to decoherence* of the Leggett model for superconducting
systems that works so well with respect to other (non-decoherence)
aspects. This failure strongly suggests the existence of

some source of decoherence other than the usual bath of oscillators.
Stamp stresses the

possibility of some alternative purely physical sources of this
decoherence. But in orthodox QM the process 1 actions are also sources
of both decoherence and classicality: decoherence is increased by the
elimination of interference from paths allowed by the various
non-overlapping projection operators P specified by the process 1; and
classicality is injected by the projections onto the quasi-classical
"coherent" states of the EM field. (See arxiv.org/abs/0803.1625
;0803.1633 ; 0805.0116 ) These states are relatively immune to leakage
of phase information into the open environment. And when Zurek says (p.
17) that neuron states are the "seat" of memory, I would suggest that by
"states" one should mean "density matrix", and that the reduction of
such density matrices to quasi-diagonal form in a coordinate

In the model that I am pushing the *initial* process 1 choice is
supposed to arise from purely physical aspects. To eliminate
anthropocentric aspects one needs to release from any exclusive
connection to human\-\-- and probably even to bio\-\--systems the
process 1 interventions, and make them common features of all suitably
complex systems. But then the possibility presents itself that *process
1* is the needed extra source of decoherence.

I have not explored this possibility, but Stamp's paper provides both
encouragement to do so, and also references to pertinent data that needs
to be explained. Thank you for bringing it to my attention.

References.

W. H. Zurek, arXiv:quant-ph/9805065 February 1, 2008

P.C.E. Stamp, Studies in History and Philosophy of Modern Physics 37
(2006) 467-497 doi:10.1016/j.shpsb.2006.04.003