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Splitting wavefunctions

  1. Oct 30, 2014 #1
    I just found out about this via Twitter:

    I'm too tired to have got my head around all the details, but it looks as if there's a fascinating new experimental perspective on what a "measurement" in QM actually is.

    DOI for the original journal article: 10.1007/s10909-014-1224-3
  2. jcsd
  3. Oct 30, 2014 #2


    Staff: Mentor

    Interesting article and phenomena.

    Don't agree with it's conclusion though:

    'No one is sure what actually constitutes a measurement. Perhaps physicists can agree that someone with a Ph.D. wearing a white coat sitting in the lab of a famous university can make measurements. But what about somebody who really isn't sure what they are doing? Is consciousness required? We don't really know.'

    These days its when de-coherence has occurred.

    Interesting to see if some bright spark can do a de-coherence analysis.

    Indeed it may reveal something deep and important - one never knows.

  4. Oct 31, 2014 #3


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    Science Advisor

    It is known for a long time that liquid helium can show quantum properties at a macro scale, which is not very surprising given that liquid helium has a very low temperature (4 K), making decoherence rather ineffective. The experiment described above seems to be nothing but yet another example of this general feature of liquid helium. Without causing decoherence, the helium cannot cause a quantum measurement - that's all.

    Indeed, they say:
    "The experiments we have performed indicate that the mere interaction of an electron with some larger physical system, such as a bath of liquid helium, does not constitute a measurement," Maris said. "The question then is: What does?"

    My answer:
    Interaction with any matter which causes decoherence (i.e. almost any other material, especially if not very cold), constitutes a measurement.
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