From: John Clark (jonkc@worldnet.att.net)
Date: Tue Aug 17 1999 - 22:55:36 MDT
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Doug Jones <random@qnet.com> Wrote:
>There's your fallacy- detectors at the slits perturb the wave
>function of the electrons, and destroy the interference pattern.
It's possible to put detectors near each slit and tell which one the
electron went through, but if you do that the interference pattern
disappears. Copenhagen explains this by saying that the
"measurement" (nobody knows exactly what that is) collapses the
wave function, many worlds explains it by saying that the
two universes do not converge as they would if the detectors
were not there because now there is a difference between
the two, there is a physical difference in the brain of the observer,
one has a memory of the electron going through slit A and the
other has a memory of slit B. Both theories give the same correct
results so we can't distinguish between them with this experiment.
So let's change things a little, use quantum erasure so both
brains forget the results of the measurement, both brains have
the same memory and so are now physically identical; the two
universes are now identical too. If Copenhagen is right the wave
function has already collapsed and so the quantum erasure will
have no effect on the result of the experiment, there will still be no
interference pattern. If many worlds is right then the two universes
will converge and you will see evidence that the electron went
through slot A and evidence that it went through slot B, in other words
you will see an interference pattern. There is a clear cut difference
between the two theories that can be tested for.
>It's the detector, not whatever looks at the *output* of the
>detector, that matters. Erasing the recording of the output does
>not eliminate the interaction that the detector had with the
>electrons earlier.
I can see that you're absolutely positively 100% certain of that,
but we'll have to actually perform the experiment to see if you're
also correct.
John K Clark jonkc@att.net
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