From: *Bruno Marchal* <marc...@ulb.ac.be <mailto:marc...@ulb.ac.be>>
> On 19 Aug 2018, at 21:36, Brent Meeker <meeke...@verizon.net
<mailto:meeke...@verizon.net>> wrote:
>
>
> But Alice and the detector are not in a singlet state and when you
combine them in a product with the singlet state the result is no long
rotationally invariant.
The rotational invariance of the singlet state has not been broken,
and in principle Alice can get back to it by quantum memory erasure,
unless collapse.
You didn't respond to my earlier post in which I discussed the symmetry
breaking occasioned by Alice's measurement interaction with the singlet
state. I copy the relevant parts of my earlier post here:
"The fact that Alice's interaction with the state is unitary and can be
reversed does not mean that the original symmetry still exists in some
sense. If I place a large weight at some point on the circumference of a
bicycle wheel, the rotational symmetry of that wheel is lost. The fact
that I can reverse the process by removing the imposed weight does not
mean that the altered wheel is still rotationally symmetric in some
wider view."
and later in the same post:
"It seems that you are basing your conviction that all physics is
ultimately local on the idea that all interactions are unitary
transformations of the universal wave function. But that is not
sufficient. You have also to postulate that the wave function itself is
actually local. And we know that that is not true. Because
non-separable, that is, non-local, states do actually exist within the
universal wave function. As Maudlin points out, the basing an argument
for locality on the wave function fails because the wave function itself
is not a local object."
Bruce
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