On 02-06-2017 02:07, Bruce Kellett wrote:
On 2/06/2017 7:28 am, smitra wrote:
On 01-06-2017 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:
Non-locality is not removed in MWI as you appear to believe.
For me the abandon of the collapse is the solution of the EPR
"paradox", and Aspect experience is somehow the confirmation of our
belonging to macrosuperposition.
The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in
Bell's
theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.
Bruce
In the MWI there are only trivial common cause like effects. There is
no non-locality in some mysterious sense like there is in the CI where
somehow there is a non-local effect but you don;t have information
transfer. The mistake most people make when arguing that the MWI
doesn't resolve the problem is that they can't get their head around
the fact that even when Alice and Bob meet and Alice has not yet
communicated everything that's necessary to Bob, that the Alice that
Bob sees has yet to collapse in the branch corresponding to whatever
she is going to say (Bob's consciousness is thus located in many
different branches of Alice, even if the atoms in his body will be in
different states due to decoherence).
I think that either you or someone else said something like this when
this was last discussed. I have a couple of points to make:
1. This is not quantum mechanics, or the many worlds interpretation of
QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.
2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated to
the decohered body. That conflicts with the overwhelming experimental
evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has decohered
having obtained a particular measurement result, all copies (if there
be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one body
and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.
Bruce
Suppose Alice and Bob are robots with classical processors, the states
of each register can only be 0 and 1. Whatever Bob is conscious of must
then be contained in the bitstring that specifies the state his
processor is in. Decoherence has no effect on that bitstring. Until
that time that Bob asks Alice about her setting of her polarizer, Bob's
consciousness is exactly the same across the different branches in which
Alice gives a different answer, despite rapid decoherence.
Real human beings can be expected to fit well within this model. It is
known that there typically is a lot of information present in the
unconscious mind that we're not aware of. So, your consciousness could
be identical across many branches even if your brain had split and the
unconscious mind is already diverging. Take e.g. experiments where you
are making a random choice and on the basis on functional MRI scans the
experimenters are able to predict your choice before you have even made
up your mind.
So, this is same good old QM in the MWI where an observer's
consciousness is modeled as a finite state machine described by a
finite bitstring. We can then work in the basis where the observables
for the bits of the bitstrings are all diagonal, this then corresponds
to the observer having a definite conscious experience.
In practice, what this means is that you can be in a macroscopic
superposition long after decoherence has for all practical purposes made
the superposition inaccessible to be probed using interference or other
experiments.
For example, if a spin is polarized in the positive x-direction and the
z-component is measured, and I'm not aware of the outcome of the result
then my consciousness, as specified by the bitstring that contains all
the information that I'm aware of, cannot possibly contain the result
of the outcome of the measurement before I'm told what the result is.
In a sector where my consciousness is described by bitstring X after
the spin has been measured, the state will have to be of the form:
1/sqrt(2) |X> [|up, Universe(up)> + |down, Universe(down> ]
where Universe(up) and Universe(down) are different states of the rest
of the universe, but my consciousness is described by X and this is not
affected by the decoherence caused by measuring the spin. In general
there will be a summation of such terms where X takes different values
and Universe(up) and Universe(down) will then depend on X, however, I
can only ever find myself in a branch were X takes some definite value,
and any such branch will look like the above state where the norms of
both terms are equal.
Saibal
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