Polarization Eraser & Entanglement

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SUMMARY

The discussion centers on the concept of polarization erasure and entanglement as outlined in Eberly's 2002 paper on Bell inequalities and quantum mechanics. The proposed experiment involves sending an incident beam from entangled photon pairs into a beamsplitter, resulting in outputs X and Y that maintain entanglement post-recombination. The conversation highlights the theoretical implications of combining streams from Alice and Bob, suggesting that if (Alice X + Bob Y) and (Bob X + Alice Y) could be combined, they would exhibit entanglement, challenging traditional interpretations of quantum mechanics. The experiment has not been conducted, and references to its feasibility remain scarce.

PREREQUISITES
  • Understanding of quantum entanglement principles
  • Familiarity with beamsplitter functionality in quantum optics
  • Knowledge of Bell inequalities and their implications
  • Basic grasp of polarization states in quantum mechanics
NEXT STEPS
  • Research the experimental setups for polarization erasure in quantum optics
  • Study the implications of Eberly's theories on Bell inequalities
  • Explore Ryff's critique of Eberly's derivation and its impact on quantum mechanics
  • Investigate the concept of combining quantum streams and its theoretical outcomes
USEFUL FOR

Quantum physicists, researchers in quantum optics, and students studying advanced quantum mechanics concepts will benefit from this discussion, particularly those interested in the nuances of entanglement and polarization phenomena.

DrChinese
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Following Fig. 1 in the following paper:

Eberly (2002): Bell inequalities and quantum mechanics

In an ideal case (this is far from easy to do): Send an incident beam from one side of entangled photon pairs into a beamsplitter, and then recombine the outputs back into a single stream. Let's call the outputs of the beamsplitter as X and Y, where X and Y are orthogonal. The theory is that the recombined stream X+Y will still evidence entanglement, as the polarization has been erased.

In the next step, let's do the same thing for both Alice and Bob. You end up with 4 outputs from the 2 beamsplitters, which are before erasure:

Alice X
Alice Y
Bob X
Bob Y

1. So if you take the recombined streams (Alice X + Alice Y) and (Bob X + Bob Y), they are still entangled. As far as I know, this experiment (as described by Eberly in more complex versions) has not been performed. Does anyone know of a reference on this?

2. Here is a strange one: Alice X and Bob X are identical streams, as are Alice Y and Bob Y. I believe that theory would say that (Alice X + Bob Y) and (Bob X + Alice Y), if they could be combined, would be entangled! Were that true, it would indicate that the probability waves are "real" even though the observable properties apparently are not. Any thoughts? Has anyone seen anything on this?
 

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Probably no one has bothered with experiment described by Eberly because his derivation is erroneous as explained by Ryff here http://arxiv.org/pdf/0902.1724"
 
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