On 17 February 2014 09:02, Bruno Marchal <marc...@ulb.ac.be> wrote: May be I should not have, as we can use the intensional Church's thesis, > for the UD. But we can formally make a difference, and some can exploit it. > In fact the difference between computation and computability is more > general than between physical computation and physical computability. > Computability a priori concerns only the class of functions that we can > compute. > It has been proved that such class is the same for all know universal > system, from Babbage machine to the quantum computer. But each system > computes in a priori very different ways. Combinators are computed by > following two simple reduction laws (like Kxy = x, Sxyz = xz(yz)), > arithmetic computes by adding and subtracting one, register machine compute > by erasing or adding one in some register, quantum computations processes > on waves, etc. > But all systems can imitate all systems. Combinators and their reduction > can implement a program computing like a quantum processor (althou with a > superexponential slow down, which does not matter in the UD*, though). > > Now for some reason, I didn't get that immediately, and for a time I > believed that QC could violate the intensional Church thesis, notably due > to strict parallelization, use of arbitrary complex coefficients, and > entanglement. I was just wrong. > > In fact, even if some quantum computation was necessary for the mind to > exist, comp should still able to justify this, by a necessary back and > forth above and below the substitution level, which indeed must already > play some role in the stabilization of the histories (the measure). In fact > comp predicts already the existence, formally, of comp-quantum > computations. But it is an open problem if it is isomorphic to quantum > computation. Today, it is even an open problem if such > comp-quantum-computation violates Church thesis (which I find not quite > plausible, to be sure). >
OK, I see. Thanks. David -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
