On 2/28/2012 2:38 PM, Stephen P. King wrote:
On 2/28/2012 1:32 PM, meekerdb wrote:
On 2/28/2012 7:43 AM, Quentin Anciaux wrote:
Dear Bruno,

Let me see if my thoughts are correct as I can best write them. COMP is the conjunction of "Yes Doctor", the Church Thesis and Arithmetic Realism, correct? I am now not sure of the definition of "Digital physics" given this thread so far... From what I can tell, Yes Doctor is built on the idea of functional substitutability at some level or scale for physical systems, such that a given algorithm will run on any functionally equivalent physical system; it is basically a restatement of computational universality. This idea shows us that our consciousness is not dependent on a particular form of physical system if and only if our consciousness is algorithmic or computable in the Turing sense. I am agnostic on this because I do not see any evidence (pace Tegmark) that our brain's implementation of consciousness does not involve quantum entanglement.

This is ambiguous. Tegmark showed that quantum decoherence of ion locations in neural processes is much faster than neural signaling, therefore brain processing is almost all classical. It is classical *because* there is quantum entanglement between the ions and the environment. It is quantum entanglement with an environment (something with many degrees of freedom) that produces decoherence and classical behavior. If you substitute for some neurons a silicon chip that is designed to be functionally identical, that "functionally identical" means it acts as a classical device to implement a certain computational algorithm. Of course it will be quantum entangled with its environment because that's what makes it classical.

Maybe you meant you that you think brain processes may involve quantum coherent superpositions - but that's what Tegmark refuted.

Dear Brent,

Not so fast! Tegmark's argument only holds, if it can be experimentally verified that is, _only_ for ion transport based processes. Consider theexperimental evidence <http://newscenter.lbl.gov/feature-stories/2010/05/10/untangling-quantum-entanglement/> for quantum entanglement in the photosynthesis process in algea, does that not make you pause just a little bit in making your proclamation?
Also see http://arxiv.org/abs/1012.4059 (dec. 18, 2010), Focus on quantum effects and noise in biomolecules <http://dx.doi.org/10.1088/1367-2630/13/11/115002> , http://arxiv.org/abs/1104.2337 for the latest on the topic. Classicality is not so easy to assume any more. I may seem unusually confident but I do have indirect knowledge, via personal friend, of the latest work at UC Berkeley on this question.



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