On 4/06/2016 4:16 am, Brent Meeker wrote:
On 6/3/2016 1:28 AM, Bruce Kellett wrote:
On 3/06/2016 4:39 pm, Brent Meeker wrote:
Scott Aaronson's blog on his debate with Roger Penrose is probably
of interest to the list:/
“Can computers become conscious?”: My reply to Roger Penrose//
//June 2nd, 2016//
//A few weeks ago, I attended the Seven Pines Symposium on
Fundamental Problems in Physics outside Minneapolis, where I had the
honor of participating in a panel discussion with Sir Roger
Penrose. The way it worked was, Penrose spoke for a half hour about
his ideas about consciousness (Gödel, quantum gravity, microtubules,
uncomputability, you know the drill), then I delivered a half-hour
“response,” and then there was an hour of questions and discussion
from the floor. Below, I’m sharing the prepared notes for my talk,
as well as some very brief recollections about the discussion
afterward. (Sorry, there’s no audio or video.) I unfortunately
don’t have the text or transparencies for Penrose’s talk available
to me, but—with one exception, which I touch on in my own talk—his
talk very much followed the outlines of his famous books, The
Emperor’s New Mind and Shadows of the Mind.
/Read the rest at http://www.scottaaronson.com/blog/
This is interesting, and I would like to spend more time on it, but
one thing struck me as I was leafing through....
"The third place where I part ways with Roger is that I wish to
maintain what’s sometimes called the Physical Church-Turing Thesis:
the statement that our laws of physics can be simulated to any
desired precision by a Turing machine (or at any rate, by a
probabilistic Turing machine). That is, I don’t see any compelling
reason, at present, to admit the existence of any physical process
that can solve uncomputable problems. And for me, it’s not just a
matter of a dearth of evidence that our brains can efficiently solve,
say, NP-hard problems, let alone uncomputable ones—or of the exotic
physics that would presumably be required for such abilities. It’s
that, even if I supposed we could solve uncomputable problems, I’ve
never understood how that’s meant to enlighten us regarding
consciousness."
This relates to my current obsession with the universal applicability
of Bell's theorem (and other inequalities such as that of CHSH).
Consider the statement of the Church-Turing thesis: "the statement
that our laws of physics can be simulated to any desired precision by
a Turing machine (or at any rate, by a probabilistic Turing
machine)". This is not true for Bell-type experiments on entangled
particle pairs. To be more precise, the correlations produced from
measurements on entangled pairs at spacelike separations cannot be
reproduced by any computational process. A recent review (arXiv:
1303.2849, RMP 86 (2014) pp419-478) points out that violations of the
Bell inequalities can be taken as clear confirmation the separated
experimenters making the measurements had not communicated: if they
had communicated during the experiment then the inequalities would be
satisfied. The corollary is that there is no possible local
computational algorithm (not involving recourse to the effects of
quantum entanglement) that can produce correlations that violate the
Bell inequalities. In other words, the laws of physics cannot be
simulated to any desired precision by a Turing machine. (I don't
think solving NP problems has anything much to do with it.....)
If the world is a simulation, i.e. is being computed by a Turing
machine, then the computation can implement non-local hidden variables
and violate Bell's inequality in the simulated world (in fact all its
variables would be non-local since locality and spacetime would just
be computed phenomena).
Sure, Bell's theorem only rules out local hidden variables. If you
simulate non-local hidden variables (i.e., get the separated
experimenters to communicate non-locally), then of course you can
reproduce the quantum correlations. But I was under the impression that
the computationalist goal was to eliminate non-locality. Separated
experimenters, with as much computing power as necessary, cannot
simulate the quantum correlations by performing only local computations.
Bruce
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