# Polarization is weird, definitely

John K Clark (johnkc@well.com)
Mon, 28 Apr 1997 13:17:25 -0700 (PDT)

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>> Me:
>>If a beam of light is polarized at 0 degrees and you set your
>>polarizer at X degrees then the number of photons in the beam will
>>be reduced by [cos(X)]^2, for 45 degrees that is 50%. For an
>>individual photon there is a 50% chance it will make it through and
>>a 50% chance it will not, if it does make it through the amplitude
>>has not been changed at all

>Steve Witham <sw@tiac.net>
>Just want to point out that the 50% probability of the photon getting
>through is determined by something called a "probability amplitude,"
>which (in this example) *is* (a complex number with an absolute value
>of) .707...

But the probability of the photon making it through a second polarizer set
the same way as the first is 100%, the probability of it making it through a
second polarizer set 90 degrees from the first is 0%. The same thing is true
of a correlated photon and it doesn't matter how far away it is from me or
even if the two photons were made long before I was born, somehow the photon
"knew" its mate would someday interact with my polarizer and it "knew" what
direction I would set it to. I'm not saying this makes any sense, but it has
been confirmed experimentally.

>MikeRose <mich_ros@alcor.concordia.ca>
>I'm sorry. I am a philosophical and physical lightweight, but....
>"vertical and horizontal" to WHAT? A follower of relativism is
>confused, seeking illumination...

That is indeed a very important question because the reference point actually
determine some of the physical properties of the photon, the really weird
part is that you get to decide what reference point to use yourself, even for
photons made 10 billion years ago. A photon is heading toward you that you
wish to measure. Pick a direction at random, any direction at all, and give
it a name, "horizontal" sounds nice, draw a line perpendicular to it and give
it a name too, I like "vertical". Turn your polarizer to the horizontal
position. If the photon makes it through the polarizer (and there is a 50%
chance that it will) then the photon is polarized 100% in the horizontal
position and always has been, even if it started it's journey from a distant
galaxy to your detector ten billion years before you decided in what
direction to turn it. If the photon doesn't make it through the detector then
the photon was always in the vertical position. The same ridiculous situation
is true for the correlated photon, even though it never came anywhere near