[extropy-chat] Is Many Worlds testable? (was: cold fusion warms up)

John K Clark jonkc at att.net
Thu Dec 28 07:45:14 UTC 2006

"scerir" <scerir at libero.it>

> Ok, there are even good physicists which believe in MWI, not as an
> interpretation of quantum phenomena, upon measurements, but as an
> _ontology_, that is: real worlds. Simple experiments can show, imo, they
> are wrong.

Huh? If simple experiments can prove them wrong then they're not very good
physicists now are they. I don't think the MWI is more provable or
un-provable then any other interpretation; but I want to make a prediction,
I predict it will become more popular. It may not be science and Popper may
not approve but Human Beings need to form a mental picture to figure out how
things work. If a Quantum Computer could be built you'd have to understand
it pretty well to program it, and the many world way would probably be the
clearest way to think about it: a huge (perhaps infinite) number of worlds
all with a computer in it working on a bit of the problem.

But actually I think MWI is testable. I've communicated with David Deutsch
about this and he proposes an experiment to see if the MWI is right or not;
it wouldn't be easy but he thinks the experiment will actually be performed
in the first half of this century. The reason it's so difficult to test is
not many world's 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.

In the Deutsch test a conscious quantum computer shoots electrons at
a metal plate that has 2 small slits in it. It does this one at a time.
After leaving the plate the electrons hit some photographic film, but do not
look at the photograph until later. The quantum mind has detectors near
each slit so it knows which slit the various electrons went through.
The quantum mind now signs a document saying that it has observed each
and every electron and knows what slit each electron went through. It is
very important that the document does not say which slit the electrons
went through, it only says that they went through one slit and one slit
only, and that the mind has knowledge of which slit.
After the electrons pass the plate but before they hit the photographic
film (just place the film a long way away to give you time)
the mind then uses quantum erasure to completely destroy his memory
of which slit the electrons went through. The only part remaining is the
document. Now develop the photographic plate and look at it. According
to Deutsch 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 interpretation is correct.

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 when the electrons hit the photographic film but
their influence will still be felt, you'll see indications that the electron
went through slot A only and indications that it went through slot B only,
and that's what causes interference.

   John K Clark

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