On 2/06/2017 5:31 pm, smitra wrote:
On 02-06-2017 04:54, Bruce Kellett wrote:
On 2/06/2017 12:00 pm, smitra wrote:
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,
False.
It's trivially true.
Bob's consciousness reflects the results he got. There are only four
branches: '++', '+-', '-+', and '--'. Bob's conscious state is different
for the two Alice '+' branches, and also different for the two Alice '-'
branches. So it is not invariant across Alice's branches.
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.
The definite conscious experience of relevance here is of observing
and recording the result of the spin measurement.
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.
That makes no sense, and is not the case in question. Alica and Bob
make measurements, observe the results and write them in their lab
books. Their subconscious mental states are of no relevance -- we need
look only at their lab books. That is when the non-locality becomes
apparent.
Bruce
There is no problem here because as soon as the spin is measured by
Bob, he becomes entangled with the entangled spin pair; that in either
of his sectors the probabilities for Alice's results are immediately
affected is a rather trivial effect.
It might be trivial, but it is also non-local, which was my point. The
only way this can be avoided is for you to claim that Bell's theorem is
not valid. If that is your claim, then you are no longer talking about
quantum mechanics, and your theory is not valid.
Bruce
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