A Question On Quantum Entanglement
Imagine that you have a beam of photon pairs that are polarization-entangled and in a single beam, and have opposite polarizations. This beam goes to a polarizing beam splitter (PBS - not to be confused with public broadcasting service), so that one photon of each pair goes straight through and the other is reflected 90 degrees left. After each of the resulting beams are polarizing filters oriented at 45 degrees and anti-45 degrees relative to the plane of the PBS.
Will both photons from each pair either (both) be transmitted or blocked? The question boils down to whether the PBS breaks the entanglement.
Now imaging a variation. After the PBS, the vertical beam goes to another PBS (PBS2) oriented in the same plane. 100% of the photons will then be transmitted because, due to the first PBS, they are all vertical in that plane. None of them will turn 90 degrees left (don't want no Rush Limbaugh photons!). If, however, the horizontal beam that turned left at the first PBS reaches a polarizing filter oriented at 45 degrees, they and their entangled partners will then have definite polarizations relative to the 45 degree plane, and that will mean that the "vertical" beam will split at PBS2.
This experiment is very similar to the Quantum Eraser (QE). The difference is that the initial beam is filtered into vertical and horizontal, and relies on entanglement being maintained afterwards. The QE supposedly can't be used for communication as it requires a classic information channel - the "coincidence detector," which is essentially an AND gate between detectors that filters out only pairs of photons. I still wonder whether it's possible to get around that, but there have been experiments that show it isn't possible. The experiment outlined above is sort of an attempt to make an even simpler experiment to test it out.
This is your brain on quantum mechanics.
Any questions?
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