Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!edcastle!aipna!cstr!tim From: tim@cstr.ed.ac.uk (Tim Bradshaw) Newsgroups: comp.ai Subject: Re: Artificial vs. ''real'' intelligence Message-ID: Date: 11 Jul 90 21:40:14 GMT References: <1990Jul2.182411.4441@king.mcs.drexel.edu> <600@dlogics.COM> Sender: news@aipna.ed.ac.uk Organization: CSTR, University of Edinburgh Lines: 41 In-reply-to: dsa@dlogics.COM's message of 10 Jul 90 20:05:40 GMT >>>>> On 10 Jul 90 20:05:40 GMT, dsa@dlogics.COM (David Angulo) said: > In article , tim@cstr.ed.ac.uk (Tim Bradshaw) writes: >> I have a paper by Deutch where he proves something he >> calls the `physical Church-Turing principle': >> >> Every finitely realizable physical system can be perfectly >> simulated by a universal model computing machine operating by >> finite means. >> > Well, I only majored in Physics in college. I do not even pretend to be > an "expert." Also, I haven't read this reference and perhaps you're > misquoting it; however, I don't think that this is possible as current > physical theories do not explain everything known about the universe so > if this guy can perfectly model the universe I would think that the > physics community would look on him like a god. No, this isn't what he's saying, and yes, I should have made it clearer. He's interested in the functions that can be computed by a physical system or a computing machine -- in the sense that, for instance, one can design a classical physical system that will calculate sin(x) given x, but you cannot write a program for a Turing machine which will do this. Loosely he says that a computing machine `perfectly simulates' a physical system if a mapping can be set up such that they calculate the same functions for a given program on the machine. His claim is then that for quantum mechanical systems that obey certain fairly general and plausible conditions then there exists some program under which the universal quantum computer will perfectly simulate such a system. This is *not* the same as giving the program of course -- all he's saying is that a program exists, which is a much lesser claim. This is in Proc Roy Soc London sometime early eighties (paper's at home). --tim Tim Bradshaw. Internet: tim%ed.cstr@nsfnet-relay.ac.uk UUCP: ...!uunet!mcvax!ukc!cstr!tim JANET: tim@uk.ac.ed.cstr "Quis custodiet ipsos custodes?"