From: *Bruno Marchal* <[email protected] <mailto:[email protected]>>
On 9 Aug 2018, at 14:03, Bruce Kellett <[email protected]
<mailto:[email protected]>> wrote:
Without collapse and FTL potential, or FTL (non-local) hidden
variable theory, how do you interpret the singlet state?
That is actually a rather strange question. How do you think I might
interpret the singlet state? I think that I have been talking about
it here for long enough for you to have worked it out. The singlet
state is a non-separable state that is symmetric under rotations
about the axis between the particles. However, that symmetry will
generally be broken by any interaction with one or other of the
constituent particles.
But it is here that I suspect you introduce some collapse.
The interaction with one particle reduces the symmetry of the
non-separable state so that it becomes separable. You might call this a
"collapse" if you wish, but this is an epistemological collapse, not an
ontological one. It is the nature of the state representing one's
knowledge that changes (the old state "collapses" with the advent of new
knowledge). But that is purely epistemological, and does not involve any
FTL information transfer. It is just as if the probability that your
horse will win the race "collapses" when you find out, after the race
has been run, that it came last!
In particular, the symmetry is broken by the imposition of a
directional magnetic field, as in a Stern-Gerlach magnet used to
measure the spin component of one of the particles in the direct
defined by that external magnetic field.
The singlet is strongly non-separable, so this external interaction
with one of the constituents is instantaneously felt by the other
component particle.
How could this be verified?
It is verified by the Freedman-Clauser and Aspect experiments (and many
other more recent experiments).
Any verification possible will need further interaction, and we can
see only the branche of the universe our own result have spread on.
The verification comes from the results of remote experiments -- and
those results do not change during the time it takes for the
experimenters to come together to compare findings.
That non-local influence is the essence of the non-separability of
the state -- it is a unit, and any interaction with a part is an
interaction with the whole.
That looks magical to me, and as I said, I am not sure this can be
verified. Aspect-like experiment do not verify this for sure.
It might look magical to you, but that is because you have not really
accepted the true weirdness of quantum theory. The Aspect-like
experiments certainly do verify this -- why else do you think that these
experiments were performed?
There is some interesting history here. When Clauser first encountered
the Bell results (through his interaction with people like Abner
Shimony), he thought that quantum mechanics must be wrong, and that the
inequality must be satisfied. His motivation for doing the original
Freedman-Clauser experiment was actually to make his fame and fortune by
proving that quantum mechanics was wrong -- that its predictions for the
singlet sate would not be experimentally verified. History tells a
different story........
Bruce
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