From: *Bruno Marchal* <marc...@ulb.ac.be <mailto:marc...@ulb.ac.be>>
On 20 Aug 2018, at 13:18, Bruce Kellett <bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au>> wrote:
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.”
OK, but when the heavy object is removed, at that moment, the symmetry
is back. Then, when Alice makes the measurement, the symmetry is lost
from her point of view, but the general symmetry of the state has not
changed. It is only not retrievable by Alice (unless quantum erasure,
amnesia, etc.).
Bruno, you have not made the least effort to understand the point I made
above, or to respond to it intelligently. It is difficult to believe
that you are actually discussing this in good faith. You just keep
repeating your own misunderstandings of the situation. The measurement
that Alice makes destroys the symmetry. That is all there is to it.
There is not some wider symmetry that is preserved.
Bruce
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