I've been studying Bell's theorem out of curiosity tonight after watching a BBC documentary about quantum mechanics (The secret of quantum physics - 1. Einsteins nightmare).(adsbygoogle = window.adsbygoogle || []).push({});

The episode ended on Bell's theorem disproving locality and showing Einstein to be wrong. So I went and did a little research into the experiment.

I found this great article by Gary Felder explaining how it worked and breaking it down into bitesize chunks, I'm sure many of you will have seen this before: http://www.felderbooks.com/papers/bell.html

I've only been studying this over the last couple of hours so let me know if my understanding is flaky in places!

Anyway, onto my question:

A photon that is entangled with another will change it's partners polarisation once it's reached the detector and measured along some orientation. I'm happy with that. So photon A is measured which instantly affects photon B.

Now, what would happen if we could measure the two photons at EXACTLY the same time. I realise this would be impossible to do in reality but I supposed we could explore it in theory.

So, photon A is measured and affects photon B, but at the same time the opposite is occurring; photon B is measured and is also affecting photon A. In my mind I have a kind of logic loop occurring, where the photons are constantly switching polarisation due to the change in it's entangled pair changing which in turn changes the photons again, plus this is all instantaneous, does physics break? If one measurement effects the other, which photon would be effecting which. Has this been scenario explored before?

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# Bell's theorem & entanglement

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