On 11/6/2014 10:52 AM, Bruno Marchal wrote:
On 05 Nov 2014, at 18:56, Richard Ruquist wrote:
Bruno: The differentiation can't go faster than light
Richard: How is that consistent with the EPR experiments?
Where is the inconsistency? EPR and Bell assumes unicity of the outcomes. But like the
indeterminacy, the non locality is an illusion due to the fact that people share the
entanglement, once they make measurement.
let 0 = 0' + 1'
and
1 = 0' - 1'
This describes the maximally incompatibe bases for some qubit (spin of electron, for
example, or photon polarization). I assume all this is multiplied by 1/sqrt(2).
0 can be seen equivalently as an infinity of computations in which the particle and its
"doppleganger" are all in state 0, or mixture of one half computations where there are
in state 0' and in state 0.
By the tensor product x, (paul x 0) can be seen as either Paul in front of a particle in
state 0, in an infinity of computations, or one halve of paul in front of 0' and one
have in front of 1'.
Now the EPR state 00 - 11 is more amazing, 'course, as it is equivalent to 0'0' - 1'1',
and to 0"0" - 1"1" and this for all bases {0,1}, {0',1'}, {0", 1"}, ...
If Alice and Bob makes measurement on their particles, their projects themselves in the
partition of the possibilities described by the quantum state. If you can show me
something non local occurring in a branch or in a computation, I would be interested.
All what I see are correlation, which looks non local only because we focus on one
computations instead of looking at the entire wave.
The wave is non-local. I think this causes confusion to students because the wave is
extended in space, i.e. has values for different spacial points at the same time. But
this is different from the physicist's meaning of non-local which refers to
faster-than-light signaling or causation.
It would be long to make the development, right now, but I intent to let my students
search for something non local.
It might be clearer or simpler with teleportation, where you see in the finale four
Alices obtaining each one among the four times two bits as result of her measurement of
their two qubits (the one teleported, and the one she share entangled with the one Bob
keeps, to stay in quantum touch with Alice), and you see those four Alice communicating
the two bits by classical means in the four universes (equivalent class on the infinity
of one), on which she was projected coherently with Bob.
And all this does not depend of the choice of the bases to describes the whole thing,
once you make the decomposition so as to be able to read the diaries of Alice and Bob
(whose brains is supposed to exploit some particular bases).
The puzzle is why that particular basis and not some other. Zurek's quantum Darwinism
seems like part of the answer. I hope that comp+UD might answer the question of whether
the classical bases we observe are the only possible ones for sentient beings.
Brent
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