On 12/12/2012 4:01 PM, Jason Resch wrote:


On Wed, Dec 12, 2012 at 5:15 PM, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    On 12/12/2012 9:25 AM, John Clark wrote:
    On Tue, Dec 11, 2012  meekerdb <meeke...@verizon.net 
<mailto:meeke...@verizon.net>>
    wrote:

        On 12/11/2012 9:31 AM, Jason Resch wrote:

            >>> Everett's QM is not a theory; it's just an interpretations.


        >> Not quite.  Deutsch's proposed experiment with reversible 
computation and
        an AI yields different results for the CI and MWI, thus they are 
theories
        which can be tested and differentiated.
        > Except his proposed experiment relies on a hypothetical quantum 
computer that
        is conscious.


    Yes but Deutsch argues, convincingly I thought, that the reason it's so 
difficult
    to test is not the Many World's theory'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 Deutsch's experiment to prove or disprove the existence of many worlds 
other
    than this one a conscious quantum computer shoots electrons at a metal 
plate that
    has 2 small slits in it. It does this one at a time. The quantum computer 
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 only, and the mind has knowledge of which one. 
Now the
    mind uses quantum erasure to completely destroy the memory of what slits the
    electrons went through. But all other memories and the document remains 
undamaged.

    But why should I think this is possible?  I'd like to see the actual 
mechanism or
    Hamiltonian that allows this.


    And then the electrons continue on their way and hit the photographic 
plate. Now
    develop the photographic plate and look at it, if you see interference 
bands then
    the many world interpretation is correct.

    No, it only means the 'consciousness collapses the wave-function' theory is
    incorrect.  It doesn't follow that MWI is correct.


If observing a definite result doesn't collapse the wave function then what 
does?

Creating a record of it.

I think the experiment is meant to show collapse does not happen. And if there is no collapse then you have the MWI.

MWI has the same problem as decoherence theory (except it tries to ignore it): How or what chooses the basis in which the reduced density matrix becomes approximately orthogonal and what is the significance of it not being exact. Copenhagen said the choice is made by the experimenter and apparently Deutsch agrees with this because he thinks it's significant that his AI is conscious. Decoherence theory hopes to show it is some objective feature of the experiment, e.g. the Schmidt decomposition and purification has been proposed

http://ipg.epfl.ch/lib/exe/fetch.php?media=en:courses:2009-2010:qit:lect5quantinfo0910.pdf

Neither has really said how to deal with the inexactness of orthogonality, but once you assume you can ignore the off diagonal terms then QM just predicts probabilities, as Omnes says.

Brent

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