What would be outcome of experiment?

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Discussion Overview

The discussion revolves around the outcomes of a proposed experiment involving entangled photons, specifically focusing on the effects of manipulating polarization before and after a polarizing beam splitter (PBS). The scope includes quantum mechanics concepts, experimental design, and interpretations of entanglement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes an experiment where entangled photons are manipulated by rotating polarization and potentially destroying entanglement before detection.
  • Another participant questions whether rotating polarization by 45° instead of destroying entanglement would make predicting outcomes easier.
  • A different participant clarifies that rotating polarization does not affect entanglement and suggests that detection terminates entanglement, implying that additional polarizers could be used to explore outcomes.
  • One participant argues from a quantum mechanics perspective that changing polarization properties after the PBS could alter the experiment's outcome due to the nature of the wavefunction.
  • Conversely, the same participant notes that from a local realism perspective, changing properties after detection should not affect outcomes, unless unfair sampling is assumed.

Areas of Agreement / Disagreement

Participants express differing views on whether changing polarization after the PBS can influence the outcomes of the experiment, indicating unresolved debate on the implications of quantum mechanics versus local realism.

Contextual Notes

The discussion includes assumptions about the nature of entanglement, the role of detection in terminating entanglement, and the implications of manipulating polarization, which remain unresolved.

zonde
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What would be outcome of such experiment:
We take EPR photon experiment where we direct one entangled photon to Bob's side and the other to Alice's side. We rotate polarization of photon at Alice's side by 22.5°. At both sides we direct photon to PBS and detect them in two detectors.
Only difference is that at each side before detection at one of two detectors we destroy entanglement of photon (if it's can be done).
 
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Would it be easier to predict outcome of EPR like experiment if instead of destroying entanglement we would rotate polarization by 45° before all four detectors (but after PBS)?
 
It is not clear what you are asking of the experiment.

You can rotate Alice and Bob (using say wave plates) and that will not affect their entanglement. If they are not entangled, you will not expect any special correlation over and above chance. Using a PBS with 2 detectors on each side, entanglement is terminated when you detect them. You could put additional polarizers in front of the detectors and after the PBS, and play with them that way I guess.
 
The question is that: from QM perspective - is it possible to change outcome of experiment by changing polarization properties after PBS?
It seems to me that it is possible because entangled pair of photons is wavefunction over all paths including paths after PBS. And changing wavefunction may change outcome of experiment.

But from local realism perspective it would seem that changing polarization properties after PBS should not change outcome because if photon is there then changing it's properties does not change the fact that it is there. Unless of course we assume unfair sampling at detectors.
 

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