Re: Plaga's paper

Date: Sat, 28 Oct 1995 15:45:46 -0700
From: Vic Stenger <vjs@uhheph.phys.hawaii.edu>
To: quantum-d@teleport.com
Subject: QUANTUM-D: Re: Plaga's paper

I just read Plaga's paper.  It's nicely written and the introduction gives 
a good, concise summary of the different quantum interpretations. His 
explanation of the proposal is also very clear.

One of the problems I have always had with the various interpretations of
QM is that they did not offer any practical empirical tests to decide
between them.  MWI has a formalism that is valid independent of whether
the parallel worlds are "real" or not.  In fact, the many histories view
can use the same formalism and simply say that only one world exists,
selected by chance.  The Bohmian interpretation can also use the same
formalism and simply say that the choice of which world is real is made by
deterministic (but unfortunately superluminal) hidden variables yet to be 
discovered. 

Plaga makes it clear that the test he proposes is indeed on the concept 
that all the parallel worlds exist "in reality."  While tests have been 
proposed before, this is claimed to be feasible with existing technology.

I have not yet studied that part of the paper in sufficient detail to 
judge this claim, and would like to hear what experts in the experimental 
techniques involved have to say.

But it seems on the right track.  Do an experiment and see.  My money is 
on a negative result because I think the MWI is an uneconomical, bizarre 
way to explain the paradoxes of QM when they can easily be explained with 
the simple expedient of eliminating the arrow of time at the quantum 
scale, that is, doing away with forward-time causality.

************************************************************************
Victor J. Stenger
Professor of Physics
Department of Physics and Astronomy                 Phone: (808)956-2942
2505 Correa Road                                      Fax: (808)956-2930
University of Hawaii at Manoa                 vjs@uhheph.phys.hawaii.edu
Honolulu, HI 96822
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On Wed, 25 Oct 1995, john baez wrote:

> What do people think of Plaga's paper, "Proposal for an experimental test 
> of the many-worlds interpretation of quantum mechanics," available as
> quant-ph/9510007?  (If you don't know how to get stuff from quant-ph,
> check out the file preprint.info in the directory pub/baez, available
> by anonymous ftp from math.ucr.edu.  Or just fire up your WWW browser
> and go to http://xxx.lanl.gov/)
> 
> Here's the abstract:
> 
> The many-worlds interpretation of quantum mechanics
> predicts the formation of distinct parallel worlds
> as a result of a quantum mechanical measurement.
> Communication among these parallel worlds
> would experimentally rule out alternatives to
> this interpretation.
> A procedure for ``interworld'' exchange of information and energy,
> using only state of the art quantum optical equipment, is described.
> A single ion is isolated from its environment in an ion trap.
> Then a quantum mechanical measurement
> with two discrete outcomes is performed on another system,
> resulting in the formation of two parallel worlds.
> Depending on the outcome of this measurement the ion
> is excited from only one of the parallel worlds before the
> ion decoheres through its interaction
> with the environment. A detection of this excitation
> in  the other parallel world is direct
> evidence for the many-worlds interpretation.
> This method could have important
> practical applications in physics and beyond.
> 
> 
> Is this paper actually interesting?
> John Baez
> 
>