Re: Quantum Computers [was Read any good books lately?]

From: John Clark (jonkc@worldnet.att.net)
Date: Tue Aug 17 1999 - 11:22:07 MDT


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hal@finney.org <hal@finney.org> On Tuesday, August 17, 1999 Wrote:

>This points up an ambiguity in the MWI, which is, when do other universes
>exist? That is, when does the universe split? You can give two answers.
>One is that it splits whenever there is an alternative which is explored
>in the quantum realm. The other is that it splits whenever there is
>a measurement which causes what would conventionally be called wave
>function collapse.

I've never heard of that second version of the MWI before, I always
thought it's entire advantage was that it didn't have to explain what
a measurement is. Do the two-slit experiment, but instead of using film to
stop the photons after they pass the slit, let them head out into infinite space.
If Many Worlds is correct then the entire universe splits into 2 when the
photon hit's the 2 slits and never recombines. There is nothing special
about you the observer, you split just like everything else, you know that
the photon went through one and only one slit, but of course you have
no way of knowing which one. Now let's do the more usual two-split experiment
and put the film back in. The universe splits just as it did before when it passed
the two slits, but when the photon hits the film and it no longer exists in either
universe then the 2 are identical and fuse back together again. Looking back
we find evidence that the photon (or electron) went through both slits and
this causes an interference pattern. Again there is nothing special about an
observer in this, the same thing would happen if nobody looked at the film,
or even if you used a brick wall instead of film, because the important thing
is not that the photon makes a record (whatever that is) but simply that it is
destroyed. Mind has nothing to do with any of this so I don't need to
explain it, or measurement, or representation, or consciousness.

  John K Clark jonkc@att.net

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