On 21/11/2017 12:36 am, Bruno Marchal wrote:
On 17 Nov 2017, at 23:18, Bruce Kellett wrote:
The singlet state is intrinsically non-local.
I am not sure what that means, but I can imagine this could make sense
in the "one-world" hypothesis, not much in many-worlds, still less in
many-computations.
The singlet state is intrinsically non-local because it involves two
particles without specifying any particular separation. Because the
singlet requires both particles, it is clearly non-separable -- it
cannot be explained by the purely local properties of the individual
particles. Non-separability means that changing one of the particles
influences the other 'instantaneously'. That is non-locality.
A simple argument is that any experimental set-up showing a
non-locality can be simulated by a classical (local) computer, and the
simulated observer(s), like all the Bob-Alice pair we get, will all
(the majority) describe an apparent non-locality, despite we, looking
patiently at the whole emulation will see that there are none.
That argument has been debunked by Brunner et al, arxiv:1303.2849
It actually has nothing to do with whether people meet or not - it
describes a situation which explicitly violates Einstein's notion of
local realism: the state of one of the entangled pair is not
separable from the state of the other distant particle.
Non-separability here implies non-local influence, or simple
non-locality. The attempt to claim that non-separability does not
imply non-locality is mere verbal gymnastics, with no physical content.
The singlet state does not describe one pair, but an infinity of
pairs, having spin (say) in all directions, but correlated in all the
case verifiable by Bob and Alice when they can interact. I would say.
That is a complete misrepresentation of the situation. Only one pair is
necessary. You are confusing 'pairs' with the rotational symmetry of the
singlet state, and that is your continuing egregious error.
Bruce
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