Even spookier entangled particles.

[Sean Lynch]

On Fri, Sep 16, 2016 at 10:13 PM, jim bell <jdb10987 at yahoo.com> wrote:

> https://www.yahoo.com/news/entangled-particles-reveal-
> even-spookier-action-thought-125723794.html
> <https://www.yahoo.com/news/entangled-particles-reveal-even-spookier-action-thought-125723794.html?soc_src=mail&soc_trk=ma>
>

I'm by no means an expert in quantum physics, which makes my lack of
surprise at this fairly uninteresting, but it seems to me these results are
completely compatible with the time-symmetric interpretation of quantum
mechanics. If I understand it correctly, according to TSQM the particle
already "knows" about its future interactions to the extent that quantum
information is preserved through any intervening interactions. So in the
case of photon-splitting, the photons leave their source with polarizations
that are aligned with (or opposite) the axis on which they will be
measured. You could say the information "propagates" in both temporal
directions, but I think it makes more sense to think of the particle's
entire timeline as a single entity.

According to the papers I've read on TSQM, it makes (or made) no
predictions that are different from the Copenhagen interpretation. This
experiment seems like it may be the first to show a difference. Not
necessarily because of any predictions, but because of the additional
mental contortions required to hang on to the Copenhagen interpretation.
There's still no ability to send "real" information faster than light or
backward in time, though. I say this only because of the purported
equivalence between TSQM and Copenhagen, not because I have any idea why it
should be the case. Intuitively, it seems like it could be related to the
(quantum) information-theoretic version of entropy that you get with
reversible computations. Or maybe even just real entropy, since TSQM still
"behaves" as if it's nondeterministic from our perspective, since we can
never know enough about a system to know its "true" internal state. So
somehow everything conspires to prevent us from setting up a system that
would carry some piece of information back in time that we care about.

I guess another way to look at it is that the universe is a solution to
some kind of differential equation. Possible solutions that contain
paradoxes aren't valid, so they don't happen. Not via some shift in some
"unified" timeline ala Star Trek, but through colossal numbers of tiny
shifts that disperse any information that we're trying to send back in time
that would cause any kind of paradox at any scale. The result is a universe
that appears to have an arrow of time at any scale we can actually measure,
appears to mostly follow General Relativity, etc. Until you get to scales,
large and small, where the exact underlying geometry starts to matter.

Come to think of it, if paradoxes are what's important, the ability to send
information back in your own timeline (i.e. within your own past light
cone) is all that matters. If there is no privileged reference frame, this
also means you can't send information into spacelike regions of your own
light cone, because if two entities do that then you can arrange things to
send information into your own past light cone. But if there IS a
privileged reference frame, say, the reference frame of the CMB, where you
can't send information into *its* past light cone, then you can send
information faster than light but still not into your own past. Recall that
the Lorentz transformations were initially introduced to (successfully)
explain how light could appear to always be moving the same speed even with
a luminiferous ether, but then Einstein discarded the luminiferous ether
because he realized it wasn't necessary, not because there was any evidence
that contradicted it.

I may well be misinterpreting what TSQM says, so please don't discard it on
the basis of my uninformed interpretation! Go read up on it and THEN
discard it ;-)
http://jamesowenweatherall.com/SCPPRG/AharonovPopescuTollaksen2010PhysToday_TimeSymQM.pdf
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