On 12/11/2012 9:53 AM, Jason Resch wrote:



On Tue, Dec 11, 2012 at 12:48 AM, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    On 12/10/2012 10:01 PM, Jason Resch wrote:


    On Mon, Dec 10, 2012 at 1:35 PM, meekerdb <meeke...@verizon.net
    <mailto:meeke...@verizon.net>> wrote:

        On 12/10/2012 10:16 AM, Jason Resch wrote:


        On Mon, Dec 10, 2012 at 10:30 AM, meekerdb <meeke...@verizon.net
        <mailto:meeke...@verizon.net>> wrote:

            On 12/10/2012 2:56 AM, Bruno Marchal wrote:
            But why isn't "It's a probabilistic world and it obeys the Born 
rule." a
            good explanation.  I'm all for finding a better explanation, i.e. a
            deterministic one.  But simply postulating an ensemble of worlds to 
make
            the probabilities "deterministic" in arbitrary way doesn't strike 
me as
            any improvement.

            It is, as it explains interference, without adding something not 
well
            defined (apparatus, observer) not obeying QM (like with the collapse
            needed to get one physical reality).

            That sounds like prejudice against probabilistic theories.  The
            interference is inherent in the complex Hilbert space states.  The
            interference happens in one world.  As Omnes says, you don't need
            'collapse' you just need to accept that you have calculated
            probabilities.  That's what probability means - some state is 
actualized
            and others aren't.


        How does Omnes explain the EPR experiment without collapse?  It seems 
you need
        to give up not only determinism, but also locality.

        Also, what do you think Omnes would predict as the outcome for Deutsch's
        proposed experiment:

            In Deutsch's thought experiment, an atom, which has a determinate 
spin
            state in one axis, 'left' for example, is passed through a 
Stern-Gerlach
            apparatus which has the possibility of measuring it in another 
axis, as
            either spin 'up' or spin 'down' in this case. This means that the 
atom is
            then in a superposition of 'up' and 'down' states from the 
perspective of
            an observer who has not yet become entangled with it. This 
superposition
            travels to the AI's artificial 'sense organ'. Here it is provided 
with two
            options, it may be detected as either spin 'up' or spin 'down'. The 
AI's
            conscious mind then records the result. The collapse approach 
predicts
            that this will cause the atom to collapse into one determinate 
state, with
            either a determinate 'up' or 'down' (but not 'left' or 'right') 
spin. The
            Everett approach predicts that the mind will branch into two, one 
mind
            will record up and one down (but neither will record 'left' or 
'right').

            The whole process is then reversed so that the atom emerges from the
            entrance to the Stern-Gerlach apparatus and the mind forgets which 
result
            it recorded. This process does not erase any of the AI's other 
memories
            however, including the memory that they did record the atom to be 
in a
            definite state. If a 'left-right' detector was placed at the 
entrance of
            the Stern-Gerlach apparatus then the collapse approach predicts 
that it
            will be detected as being in either a 'left' or 'right' state with 
equal
            probability.


        I think it is wrong in saying that the erasure of which-way information 
(which
        I think is actually impossible for a consciousness, artificial or 
otherwise)
        will leave the atom in an up/down state.


    Isn't that exactly what the quantum erasure experiment shows?

    Quantum erasure requires that the which-way information be eliminated from 
the
    world.  Once an AI consciousness gets the result I think that implies 
entanglement
    with the world and after that the result can't be quantum erased.


What theory of consciousness are you operating under?  CTM or something else?

    I know Deutsch supposes a quantum computer AI can 'know' there was which-way
    information even though the which-way information was quantum erased.  But 
I find
    that doubtful.  And even if it's true, the 'reversal' may bring the atom 
back to 'left'.


That is the proposed result that would prove MWI.

It doesn't prove MWI, it disproves "consciousness causes collapse"; which is a theory no one holds anymore.

If the "left" state is restored always then the universe never collapsed, it split a difference was observed, and a record of observing that difference was stored, then all information pertaining to the result is erased such that the two universes recombine (the split was undone, even though it should have collapsed because the difference was observed).

Only in a Wignerian theory of collapse where 'observed' means by some magic (AI) consciousness.



    Why do you think it is impossible for a conscious process learn the result 
and then
    have that result erased as in the quantum eraser experiment?

    Because I think consciousness must be quasi-classical.  Consciousness needs 
stable
    memory and it needs to interact with its environment - together I think 
that implies
    it must be essentially classical as a computer.


In this case it has stable memory, and is able to interact with its environment, but then all traces of its memory of the which-way result are erased.

It's the 'all traces' which I think make this impossible. But I'm open to seeing the description of the quantum state evolution and how the erasure is accomplished. Has Deutsch published one?

We operate with unstable memories and forget things, and yet are still 
conscious.

    That's one of my reservations about Bruno's oft repeated assertion that he 
has
    proven that matter doesn't exist.


He says matter exists, but that it is not primitive. It can be explained in terms of something more fundamental.

      When pressed he allows that it may exist, but only derivatively within the
    computations of the UD.  But it seems to me likely that it, or something 
very like
    it, must exist (derivatively of not) in order that consciousness exist; that
    'matter' is necessary for consciousness of a human kind to exist.


I think it's appearance is probable for entities such as we who evolved.

I'm saying something more definite. That consciousness requires matter (i.e. a quasi-classical world). This would entail that a pure quantum computer (all proposed quantum computers have classical outputs - for obvious reasons) cannot be conscious.




        You keep asking me about 'collapse', but Copenhagen's physical collapse 
is not
        the same as Omnes epistemic collapse.


    I am sorry.  I don't feel I have a good understanding of what the 
distinction is.

    Omnes looks at it as a mathematical operation used in predicting 
experimental
    results.  That means the 'collapse' is just a change in description, not a 
physical
    process.


If it's not a physical process and only a description of appearances, it sounds more like MWI.

Is MWI just an abstract ensemble invented to give a picture of probability as 
sampling?

Brent

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