On Mon, Dec 10, 2012 at 1:35 PM, meekerdb <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> 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?  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?

> 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.


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