Hi all. In order to access the article I am pretty sure you need to establish an account on physics World. It is free. I did it so long ago I had forgotten. Bruno, I am not sure exactly what you mean by "the existence of the first person indeterminacy in arithmetic", but offhand it seems to me to depedn on a sort of idealism that I do not accept. Incidentally, quantum decoherence is best seen as a sort of thermodynamic effect. There are quantum measurements that can be reversed. I can give some references if anyone wants. John

Professor John Collier Philosophy, University of KwaZulu-Natal Durban 4041 South Africa T: +27 (31) 260 3248 / 260 2292 F: +27 (31) 260 3031 email: colli...@ukzn.ac.za>>> On 2012/06/01 at 02:45 PM, in message <cc50a53f-b07a-4c24-a602-d02c7c891...@ulb.ac.be>, Bruno Marchal <marc...@ulb.ac.be> wrote: Hi John, On 01 Jun 2012, at 13:02, John Collier wrote: > http://physicsworld.com/cws/article/print/2012/may/31/the-quantum-game-of-life > > Sample excerpt: > "Hopes that digital physics might be resurrected in some form rose in > the early 1980s, when Richard Feynman proposed that the blatant gap > between the power and information content of quantum theory and that > of classical computers might be bridged by a new type of computer. > His idea was born out of frustration at seeing classical computers > take weeks to simulate quantum-physics experiments that happen faster > than a blink of an eye. Intuitively, he felt that the job of > simulating quantum systems could be done better by a computer that > was itself a quantum system." He was of course right on that. Actually I don't succeed in getting the paper from the link above. About quantum information, here is an interesting talk by Ron Garrett, quite coherent with the (classical) computationalist theory of mind, on quantum information, seen as information theory on the complex numbers: http://www.youtube.com/watch?v=dEaecUuEqfc Personally I am not (yet?) entirely sure that quantum information is "just" classical information on the complex numbers, I think this is partially true, and theorem like Gleason theorem makes me believe that this is very plausible. Ron Garrett gives a pretty picture of Everett QM (QM without collapse). His account of measurement is rather illuminating (close to the work of Adami and Cerf). Ron Garrett is information theoretic minded, and, with respect to computationalism (comp), has a coherent view of physics. Of course he does not seem aware of the necessity of such a view once we postulate comp, and the fact that this necessitates to take all computations (the one done below our classical comp substitution level) into account, (not just the quantum one) and to justify the quantum interferences from the first person perspective any self-justifying universal number. Comp shows that the qubit ---> bit road (decoherence) is two sided. Technically, due to diagonalization used to make the self-reference, you get the split between truth and justifiable, which provides a tool to distinguish the qualia and the quanta, as different but related mode of information, on the "inverse road" bit --> qubit. I think Ron Garrett explains (very shortly but rightly ) the qubit -> bit justification. Comp provides a reverse of that justification, and this doubled by the communicable/non-communicable (G/G*) splitting: the bit -> quantum-bit, and the bit -> quale-bit*, with the explanation of the fact that the quale bit* can't be quantified nor described (provably so in the ideal case of arithmetically self- referentially correct machine) Comp forces, just to remain coherent, to extend Everett's way of embedding the observer into the physical wave, to his embedding in all arithmetical relations, by first person indeterminacy, with the advantage of explaining a fundamental role to the (universal) person points of view, and hopefully so, to justify QM or refuting comp, or weakening it or constraining it. To be sure computationalism is incompatible with digital physics. If *we* are machine (classical or quantum) then neither the fundamental reality, nor its physical part, can be Turing emulable, despite quantum machine can be Turing emulated. This is more or less a direct consequence of the existence of the first person indeterminacy in arithmetic. Bruno Marchal http://iridia.ulb.ac.be/~marchal/ _______________________________________________ fis mailing list fis@listas.unizar.es https://webmail.unizar.es/cgi-bin/mailman/listinfo/fis Please find our Email Disclaimer here: http://www.ukzn.ac.za/disclaimer/

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