On 4/26/2018 3:41 PM, Bruce Kellett wrote:
From: *John Clark* <[email protected]>
On Thu, Apr 26, 2018 at 2:02 PM, <[email protected]> wrote:
>
/ How many times must I remind you that Feynman explained that
very clearly.
/
42.
>
/Please repeat it. AG/
I originally sent this on December 14 2017:
David Deutsch proposed a test of Many Worlds about 30 years ago in
his book "The Ghost In The Atom", but it would be very difficult to
perform. The reason it's so difficult to test is not the Many
World's theory fault, the reason is that the conventional view says
that conscious observers obey different laws of physics, many worlds
says they do not, so to test who's right we need a mind that uses
quantum properties. Quantum Computers have advanced enormously over
the last 30 years so I wouldn't be surprised if it or something very
much like it is actually performed in the decade or two.
An intelligent quantum computer shoots photons at a metal plate one
at a time that has 2 small slits in it, and then the photons hit a
photographic plate. Nobody looks at the photographic plate till the
very end of the experiment. The quantum mind has detectors near each
slit so it knows which slit the various electrons went through. After
each photon passes the slits but before they hit the photographic
plate the quantum mind signs a document saying that it has observed
each and every photon and knows which slit each photon went
through. It is very important that the document does not say which
slit any photon went through, it only says that they went through one
slit and one slit only and the mind has knowledge of which one. There
is a signed document to this effect for every photon it shot.
Now the mind uses quantum erasure to completely destroy its memory of
which slit any of the photons went through; the only part remaining
is the document which states that each photon went through one and
only one slit and the mind (at the time) knew which one. Now develop
the photographic plate and look at it. If you see interference bands
then the many world interpretation is correct. If you do not see
interference bands then there are no worlds but this one and the
conventional quantum interpretation is correct.
This works because in the Copenhagen interpretation when the results
of a measurement enters the consciousness of an observer the wave
function collapses, in effect all the universes except one disappear
without a trace so you get no interference. In the many worlds model
all the other worlds will converge back into one universe because
information on which slit the various photons went through was the
only thing that made one universe different from another, so when
that was erased they became identical again and merged, but their
influence will still be felt, you'll see indications that the photon
went through slot A only and indications it went through slot B only,
and that's what causes interference.
Quantum erasure involves more than just forgetting what happened. What
about Zurek's "many records in the environment". If you know what
happened, many traces of that result remain -- even if your memory is
erased. Deutsch on the wrong track, yet again!
Deutsch knows the difference, and he specifies quantum erasure, which
implies that the detection of welcher weg is never classical, i.e. it
is not decohered into the environment since if it were it could not be
quantum erased. Which is the point of my remark that maybe all that
would be proved is that quantum "detection" can't be conscious. I'm
pretty sure consciousness is a purely classical phenomenon. So
Deutsch's scheme to detecting welcher-weg but erasing the knowledge may
retain the interference pattern but just prove that quantum knowledge is
not conscious...something Borh might well say.
Brent
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