Thursday, 11 December 2014

quantum mechanics - What's wrong with this experiment showing that either FTL communication is possible or complementarity doesn't hold?


The assumptions are:




  • Alice and Bob have perfectly synchronized clocks

  • Alice and Bob have successfully exchanged a pair of entangled photons


The idea is simply to have Alice and Bob perform the Quantum Eraser Experiment (doesn't need to be the delayed choice).


Alice and Bob agree on a specific time when Bob's photon will be between the "path marker" (which is usually just after the slits) and the detector.


If Alice acts collpasing the wave-function on her photon, the interference pattern will disappear. If not it won't.


Alice and Bob can be spatially separated...


What am I misunderstanding?


The only meaningful difference from this spatially separated quantum eraser experiment to one done on tabletop is that you won't be able to use a coincidence detector, but that is not impeditive to identifying the interference pattern, just will make errors more probable. Which we should be able to deal with a appropriate protocol...


There is a experimental paper with a small amount of citations pointing out to the breaking of complementarity in a very similar setup: http://www.pnas.org/content/early/2012/05/23/1201271109





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