Dear Dr. Schlosshauer,

Thank you for your kind reply.

> If you have specific questions for Cramer, maybe you could send
> him an email?

I sure did,

http://God-does-not-play-dice.net/Cramer.html

Let me share with you my comments on your two recent papers, and try to explain why I like Cramer's Transactional Interpretation of QM. I believe it is still a "shut up and calculate" interpretation of QM, but it reveals much more from the quantum realm than W. Zurek's speculations [Ref. 1].

It seems to me that Cramer's TI does not suffer from the notorious tails problem [Ref. 1, p. 30): "in any region in space and at any time  t  > 0, the wave function will remain nonzero if it has been nonzero at  t  = 0 (before the collapse), and thus there will be always a part of the system that is not "here"."

Also, it does not play with the human brain, and hence does not suffer from the genuine Catch 22 paradox that is imbedded in other interpretations of QM. What I mean by 'Catch 22 paradox' is that the human brain is part of the environment (or Feynman's 'the rest of the universe'), "where the perception of denumerability and mutual exclusiveness of events must be accounted for" [Ref. 1]. All other interpretations of QM bypass this genuine paradox, as if the human brain could be shielded from all ambiguities in Process II or the Schrödinger dynamics alone [Ref. 2]. Hence I think Cramer's TI does not suffer from the basis problem either [Ref. 2].

In the context of the  "Copenhagen hegemony" [Ref. 3], for example, *any* macroscopic cat states of our neurons would be lethal (hence the importance of the tails problem). If you measure a quantum system, the very first thing that will happen is that your brain and the quantum system will be entangled, and *nothing* would have any definite state whatsoever, 'the rest of the universe' included. Hence your brain will break down and could never recall that there is such thing as Process I or 'projection postulate', not to mention the Born rule [Ref. 3]. You'll be damn dead. Hence you utterly need some "point-like" state to initiate the measurement, but such a well-defined "point-like" state can be miraculously obtained only *after* the measurement. Hence the Catch 22 paradox.

I can't see how Cramer's TI would actually *derive* the Born rule, however [Ref. 3]. Perhaps John Cramer would elaborate.

To sum up, I agree with Henry Stapp that "the basis problem is *the* problem that any interpretation of quantum theory must resolve in some way" [Ref. 2]. I believe the basis problem can be solved only by something that pertains to 'the rest of the universe', which is why I like Cramer's TI and speculated on the Born rule from his perspective,

http://God-does-not-play-dice.net/Krasnikov.html#Born

The issue is far from clear, of course,

http://God-does-not-play-dice.net/energy.html#gravity

http://God-does-not-play-dice.net/Barbara.html#imaginary

http://God-does-not-play-dice.net/Knuth.html#note

Best regards,

Dimi Chakalov
--
http://God-does-not-play-dice.net
 

References

[Ref. 1] Maximilian Schlosshauer, Decoherence, the Measurement Problem, and Interpretations of Quantum Mechanics, quant-ph/0312059 v3
 

[Ref. 2] H.P. Stapp, The basis problem in many-worlds theories,
quant-ph/0110148 v2; Can. J. Phys. 80(9), 1043 (2002).

"(O)ne chooses a single set of vectors that can be used to represent a state and thus one chooses a single *preferred* way of representing a state as the sum of vectors in the Hilbert space."
...

"But the entire construction depends crucially on the idea that a particular well-defined set of preferred basis states is specified by the evolving non-collapsing quantum state of the universe.
...

"The values associated with the preferred basis vectors are supposed to be "possessed" by the systems, or to exist within nature.
...

"Indeed, the basis problem is *the* problem that any interpretation of quantum theory must resolve in some way. Thus the central idea of the Copenhagen interpretation was to imbed the quantum system in a larger system that specifies the preferred basis by bringing in "measuring devices" that are set in place by a classically conceived process. In von Neumann’s formulation there is the infamous "Process I", which likewise lies outside the process governed by the Schroedinger equation.
...

"The quantum state would be, to first order, a superposition of a continuum of slightly differing classical-type worlds with, in particular, each measuring device, and also each observing brain, smeared out over a continuum of locations, orientations, and detailed
structures. But the normal rules for extracting well defined probabilities from a quantum state require the specification, or singling out, of a *discrete set* (i.e., a denumerable set) of orthogonal subspaces, one for each of a set of alternative possible experientially distinguishable observations. But how can a particular discrete set of orthogonal subspaces be picked out from an amorphous continuum by the action of the Schroedinger equation alone?
...

"This fact poses a problem in principle for any deduction of probabilities from the Schroedinger dynamics alone: how can a specific set discrete orthonormal subspaces be specified by the continuous action of the Schroedinger equation on a continuously smeared out amorphous state?"
 

[Ref. 3] Maximilian Schlosshauer, Arthur Fine, On Zurek’s derivation of the Born rule, quant-ph/0312058 v3

"Decoherence provides a mechanism, termed environment-induced superselection, in which the interaction of S with E singles out a preferred basis in HS [20]; however, a fundamental derivation of the
Born rule must of course be independent of decoherence to avoid circularity of the argument."
...

"We cannot derive probabilities from a theory that does not already contain some probabilistic concept; at some stage, we need to "put probabilities in to get probabilities out". (...) Moreover, any derivation of quantum probabilities and Born’s rule will require some set of assumptions that put probabilities into the theory. In the era of the "Copenhagen hegemony", to use Jim Cushing’s apt phrase, probabilities were put in by positing an "uncontrollable disturbance" between object and apparatus leading to a brute quantum "individuality" that was taken not to be capable of further analysis."