# Re: collapsing quantum wave function

From: Stathis Papaioannou <stathispapaioannou.domain.name.hidden>
Date: Sun, 12 Jun 2005 21:14:11 +1000

Russell Standish writes:

[quoting Norman Samish]
> > Suppose we take ten apparently identical ball bearings and put stickers
>on
> > each with the identifiers "1" through "10." We leave the room where the
> > balls with stickers are, and a robot removes the stickers and mixes the
> > balls up so that we don't which ball is which. However, the robot
>remembers
> > which sticker belongs on which ball. We come back into the room and
>pick
> > one ball at random to destroy by melting it in an electric furnace. If
>at
> > this point we ask "What is the probability that the destroyed ball is
>ball
> > '3'?" we can truthfully answer "My memory tells me that the destroyed
>ball
> > has a one in ten probability of being '3.' "
> >
> > However, by reviewing the robot's record we can see that "6" was, in
>fact,
> > the one destroyed.
> >
> > Does this mean that the quantum wave functions of all ten balls
>collapsed at
> > the moment we viewed the record and observed what happened to "6"? Or
>did
> > the wave function never exist, since the robot's record always showed
>the
> > identity of the destroyed ball, irrespective of whether a human observed
> > this identity or not?
>
>Yes and no. In a 3rd person description of the situation, the
>Multiverse has decohered into 10 distinct universes at the moment the
>robot decides which ball it picks up. What about the 1st person
>description? According to the interpretation I follow, the observer is
>in fact superposed over all 10 branches, and only collapses into a
>single branch the moment the observer becomes aware of the robot's
>record.
>
>A more conventional physics interpretation would have the conscious
>observer as belonging to a definite branch since the Multiverse
>decohered, but not knowing which. I understand that David Deutsch
>holds this interpretation, for example.
>
>There is certainly no 3rd person experiment that can be done to
>distinguish between these two interpretations, and the only 1st person
>experiment I can think of relates to tests of quantum immortality. I
>find it hard to believe the "no cul-de-sac" conjecture would hold in
>the latter case.

If you accept that it makes no first person difference whether there is one
or many instantiations of the same observer moment - that it is all one
observer moment - then it becomes meaningless to ask whether the observer
belongs to just one or to a superposition of all of the instantiations. How
would QTI distinguish between the two interpretations?

--Stathis Papaioannou

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Received on Sun Jun 12 2005 - 07:15:22 PDT

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