Polarization is digital, sort of

John K Clark (johnkc@well.com)
Tue, 6 May 1997 11:15:06 -0700 (PDT)


On Thu, 01 May 1997 Hara Ra <harara@shamanics.com> Wrote:

>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.

You are 100% correct.

>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.

Teue, but it's not relevant, at least not very relevant, if you're talking
about an individual proton. The concept of probability starts to get
fuzzy and not very rigorous when you talk about individual one of a kind
events. If I say there is only a 25% chance that it will rain tomorrow and it
turns out to be a rainy day, was I wrong? If it doesn't rain was I right?
If that was the only information you had and I never made another prediction
it would be difficult to form a conclusion about my competence as a weather

I'm sure I'll hear from the Bayesian people about that remark.

>The point is that quantum values are indeterminate, which means not
>fixed until measured!

Maybe, but the Copenhagen interpretation is not the only one consistent with
the facts.

>>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.

As I said, even if you instantly change something on the other side of the
universe you can not use this effect to exchange energy or information,
the effect is real however, as can be seen in Quantum Cryptography. You can
also make a destructive measurement on one photon and learn something about
the other without harming it.

John K Clark johnkc@well.com

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