# Re: Can someone explain why this doesn't work?

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On 23 Jul 2013, at 16:00, Jason Resch wrote:```
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When there are two polarizers A and C, which are rotated by 90 degrees to each other then no photons will pass through both polarizers. However, if we insert polarizer B at a 45 degree offset to A and C then 1/4 of the photons will make it through.
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Now let's say we have two entangled photons travelling away from each other. If we send photon #1 through polarizer A right before photon #2 goes through polarizer B, right before photon #1 goes through polarizer C, then if I understand entanglement correctly that implies some of the time photon #1 will make it through polarizer C. Is that correct?
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Yes. Relatively to you.

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To me it seems that must be incorrect, because it would enable super luminal communication.
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In a single universe, it looks like there is such a communication, but the math shows that you cannot use it to send information (like with quantum teleportation).
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But if you look at this in the Everett picture, you can see that there are no superluminal communications at all. By choosing some angle of some polarizer, you determine the type of partitioning of the multiverse you will stay in. May be you can do the computation yourself, and you might be inspired by the computation that Steve Price does in his "Everett FAQ".
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By sending a continuous stream of entangled photons in opposite directions and changing the orientation of B between 0 and 45 degrees, you could cause photons at C to stop with 100% or 75% probability. This cannot be so then what is wrong with the above assumptions of how the three polarizer experiment works with entangled photons?
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I think that you are using implicitly the "uniqueness of outcome" somewhere. Not much time to do the details for now, but I might do it later if nobody does it. But you can do it, also, as this needs only a minimal amount of QM. Of course this will not prove that Everett is always "local" in general. For this you can take a look on some paper by Tipler, or more rigorous one by Deutsch and Hayden, but even this is criticized by some physicists.
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Bruno

http://iridia.ulb.ac.be/~marchal/

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