On 06 Nov 2014, at 20:20, meekerdb wrote:
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.
?
The wave obeys the SWE, it has to be local (in the configuration
space, which is were the wave is living, and the EPR-Bell-Aspect
lesson is that we must take the whole wave seriously. What *seems* non
local is the partial trace of the wave (or correspoding operator) or
the projection that we can see in our branche. I would say.
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 is clear that such communication-at-a-distance cannot occur with
the Bell inequality violation, although it means that there is a "true
(3p- indeterminacy", in case there is reduction of the wave packet.
But with the MWI, we have no "true randomness" (other than the
computationalist FPI), nor, I think, do we have any form of true
correlation at a distance, except the one brought by sharing entangled
particles (which type of correlation exists also in the classical
realm).
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.
But computationalism start from the classical reality (or logic). We
need bits, but they are simply extracted from the universal system we
start (like arithmetic), then the quantum is the first person plural
reality that we can share when observing our body and environment
below our substitution level. Zurek's quantum darwinism seems to be
directly implied by the "comp-darwinisme" on *all* computations, when
seen from inside. It illustrates how well the physical reality
complies to the computationalist demand of explaining the physical by
the sharing of computation above the substitution level. Of course we
need to derive the SWE from it, in the exact same way. We can't
postulate the quantum, like in physics. Comp makes Everett correct
(very plausibly) but incomplete. The wave *is* phenomenological too,
if we buy the idea that brains are Turing-emulable without change in
consciousness or in the first person reports.
Bruno
Brent
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