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Thread: Questions about Quantum erasure with causally disconnected choice

  1. #1 Questions about Quantum erasure with causally disconnected choice 
    Junior Member
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    Jun 2014
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    Hello,

    Interested mostly-amateur here with some questions about the Quantum erasure with causally disconnected choice experiments conducted in Vienna and the Canary Islands by Ma, Zeilinger et al.

    1. Does the projection event of the system photon's entangled partner occur AFTER the system photon has completed interacting with the interferometer? (I'm assuming it's safe to use terms like before and after since the whole experiment takes place within the same nonaccelerating frame of reference.)

    2. If so, is one possible conclusion that the transactional interpretation of QM is correct and that the experiment manages to break the usual symmetry between events' retarded and advanced waves? In other words, is the environment photon projection event really influencing the system interferometer events that happen BEFORE it?

    3. If one maintains that this reverse causality is NOT occurring, and assuming that Einstein locality is inviolable, what other interpretations can account for the results? The authors state that "no naive realistic picture is compatible with our results because whether a quantum could be seen as showing particle- or wave-like behavior would depend on a causally disconnected choice. It is therefore suggestive to abandon such pictures altogether." That's fair enough, but doesn't really narrow the field of possible pictures that ARE compatible with their results!

    4. Describing an earlier quantum eraser experiment by Scully and Drühl, the authors make this provocative statement: "The presence of path information anywhere in the universe is sufficient to prohibit any possibility of interference. It is irrelevant whether a future observer might decide to acquire it." Assuming this also applies to causally-disconnected versions of the experiment, could detectors 3 and 4 (the ones which detect the polarisation basis of the environment photon) be removed from the Vienna experiment without affecting what's observed at the interferometer? If so, would it matter whether they were replaced with empty space or with black objects (which would absorb the photons, presumably destroying their welcher-Weg information but not measuring anything in the process)?

    Many thanks,

    Sam
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  2. #2  
    Senior Member
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    1. Yes
    2. Most experiments confirm most interpretations of a QM because they are interpretations.
    3. You cannot have realism, locality and free choice all at the same time. Take your pick!
    4. Not sure, would the information really be destroyed?
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