On 27 Apr 2016, at 06:49, Bruce Kellett wrote:
On 27/04/2016 1:51 pm, Brent Meeker wrote:
On 4/26/2016 8:38 PM, Jesse Mazer wrote:
OK, let's say experimenter A measures particle 1, and experimenter
B measures particle 2. Any given copy of particle 1 has a "label"
that says something about the state of 2--we can imagine that the
copy of particle 1 carries a little clipboard on which is written
down both its own quantum state, and a quantum state it assigns to
particle 2. When that copy of 1 is measured, it not only adjusts
its own state (to an eigenstate of the measurement operator), it
also adjusts the state it has written down for 2. You seem to be
assuming, in effect, that when a copy of 1 adjusts what it has
written down for the state of 2 on its own clipboard, this must
mean that copies of 2 also instantaneously adjust what they have
written down about *their* own state. However, in a copying-with-
matching scheme, there's no reason this need be the case!
That's pretty much the many-universes model that Bruno proposes.
But it's non-local in the sense that the "matching scheme" must
take account of which measurements are compatible, i.e. it "knows"
the results even while they are spacelike separated.
Exactly, the model assumes the results it is trying to get. It is
not a local physical model because the statistics do not originate
locally.
The statistic did originate locally. Alice and Bob did prepare the
singlet state locally, and then travel away. They are in infinitely
many worlds, and in each with opposite spin. The cos^2(theta) is given
by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> -
1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling
that you talk like if Alice or Bob reduce the wave after their
measurement, but they just localize themselves in the relative
branches. Like Jesse said: no "matching" between copies of measurement-
outcomes at different locations takes place at any location in space-
time that doesn't lie in the future light cone of both measurements.
Only if a reduction of the wave occur would a genuine action at a
distance have to take place to keep up the cos^2(theta). In the MWI,
we keep it intact because 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>
describes a global state of the multiverse. There is a form on non
separability, but it does not use non local action. It uses only the
fact that the many Alice and Bob are in the same branches and remains
in the same branches when travelling away of each other in each
branch, but they both cannot know in which branch they are, and what
is the spin of their respective particles. They do know that they are
correlated by 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>, but that is all
they can know.
Bruno
Bruce
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