Re: A Look at Quantum "Spookiness"

"Daniel Pitts" <googlegroupie@xxxxxxxxxxxxx> wrote in message
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Tao wrote:
"Erops" <erops@xxxxxxx> wrote in message
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A Look at Quantum "Spookiness"

The results of quantum theory were described as "spooky" by Drs.
Einstein, Podalsky, and Rosen because quantum theory seemed to reject
"objective reality". They believed that all observed effects must be
produced by "local" causality. Their conclusion resulted from their
firm
belief that information could not travel faster than the velocity of
light. Indeed, if this were the case, quantum theory would indeed be
"spooky". Quantum theory required, for example, that "paired photons"
maintain polarizations which were opposite in direction . If the
polarization angle of one of the "paired photons" were changed, the
polarization angle of the other photon of the pair must instantaneously
change to match.

Actually this is not a very accurate description of the situation. It is
about determining the polarization, not changing it. The key thing is
that
one can measure the polarization in two directions which are incompatible
observables in quantum mechanics, so the results cannot be explained
merely
by the states the particles started off in. Which direction to measure
can
be chosen by a central controller communicating simultaneously with each
end
of the experiment.

If you read the papers about Aspect's experiment (which verified Bell's
theorem empirically), as I have, you will see Bell's result is only
visible
in the statistics, not in any individual measurement. No-one has found
any
way to use this effect to communicate faster than light, and very few
people
expect this to ever happen.

Although, they have proven conclusivly that the aformentioned effect is
real. Not by statistics, but by concrete mathimatics. Instead of
coupling two photons, they used three photons, and the math became
"Always" (Quantum Spookiness) or "Never" (Einstein Hidden Variables).
Turns out its "Always"

It is possible my intended meaning was not clear. The effect is in the
statistics of the measurements, and can be seen when one collates the
experimental data from both (or all three) afterwards, but at the time,
there is no way for any of the participants to use the effect to communicate
with another at faster than the speed of light.

One article I read on this said that when a participant makes a measurement
it "determines an aspect of reality". This aspect of reality is immediately
known at another point connected by quantum entanglement. The reason this
cannot be used to communicate is that the person who made the measurement
did not specify what the aspect of reality was (for example, whether the
photon was vertically polarised), he merely measured it. From measurements
made at the other end, the other participant cannot determine anything about
what the first person did. We can only be sure that if the other person
measures the vertical polarisation, his measurement will be determined by
the measurement that the first person made.

Is this clear now?


.

Relevant Pages

  • Re: A Look at Quantum "Spookiness"
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  • Re: A Look at Quantum "Spookiness"
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