X-Message-Number: 14993
From: "Pat Clancy" <>
Date: Wed, 22 Nov 2000 15:31:07 -0800
Subject: Re: Clancy, brief comment

Robert Ettinger wrote:

> >A Turing machine cannot implement [calculate?] quantum reality; 
> 
> I don't know why not (although of course not in real time). A human 
> mathematician with enough pencils and paper and longevity could, in 
> principle, eventually find successive quantum states of any system, so a 

> Turing computer could also, to any desired degree of accuracy. I and others 
have
> pointed out other problems, of course.

Calculating successive states is not the same as implementing quantum 

reality - so your "[calculate?]" in my statement I would not agree with. Sure a
computer can calculate quantum states - that's the kind of thing computers 
were invented to do. But physical/quantum reality happens at infinite 

precision, and the infinite precision "calculations" of reality happen instantly
- 
for a computer, such calculations are non-terminating. Furthermore, in QM 
you cannot just calculate the positions and momenta of particles as they 
evolve through time, you have to calculate a wave/probability function that 
emanates from each "particle" and then becomes entangled with the wave 
function of everything else it encounters, in a spreading and exponential 
growth of complexity that would quickly overwhelm the computational ability 
of a computer the size of the universe. But even if you could do that, you 
then have to deal with the collapse of wave functions when appropriate, which 
involves essentially instantaneous collapse of entangled wave functions. And 
I don't think you can escape these problems by saying that your simulation 

would not run in real time, i.e. that you could in theory simulate sequentially
those things that were instantaneous in reality, since I think your program 
would again be in a non-terminating loop trying to calculate the interactions 
between interacting wave functions that were collapsed instantly.

Pat Clancy

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