Re: Polarization is digital, sort of

Hara Ra (
Thu, 01 May 1997 22:56:31 -0700

John K Clark wrote:
> 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, if fact nothing at
> all about the photon has been changed because it has ALWAYS been polarized at
> exactly 45%. I don't claim this is a sensible way to run a universe, but it
> has been conformed experimentally, some call it "Quantum Weirdness".
Wrong. You can run your photon through a set of filters, each of which
is 45 degrees turned relative to the previous filter. If the photon was
originally at 45 degrees, it will always be blocked by the second filter
in the series. What actually happens is that each filter takes out 50%
of the incident photons, and the second filter therefore passes 25% of
the photons, the third passes 12.5%, etc. The point is that quantum
values are indeterminate, which means not fixed until measured!

> Some atoms produce 2 photons of the same polarization but traveling in
> opposite directions, so if you measure the polarization of one you know the
> polarization of the other.

Sure, if the other photon hasn't interacted with something, which you
can't know faster than light speed.

| Hara Ra <> |
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