On 6/3/2016 4:28 PM, Bruce Kellett wrote:
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.
As I understand it, Tegmark proposes that the world is computed, as in a
simulation. Bruno proposes that there are infinitely many threads of
computations which include the experience of infinitely many different
worlds for observers whose experience is computed in those worlds.
"Separate" or "non-local" are attributes of the simulated spacetime and
dynamics.
Brent
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