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Problem with quantum entanglement of photons

  1. Jan 18, 2012 #1
    I'm trying to follow the logic to the quantum theory of the entanglement of light. I'd like to ask a question about one of several problems I'm having with the entanglement.

    Photons (Light) have orthogonal electric and magnetic waves.

    In discussions of polarization of light for the entanglement of photons I find no reference to the magnetic waves, even in discussions of "hidden variables".

    Also, the "polarization paradox" discussions seem to ignore the magnetic wave component.

    (By polarization paradox I mean a 45° polarizer between an H and V polarizer will restore light)

    It seems the magnetic component can predict the electric component, and vice versa.
    Likewise, the polarization paradox experiments seems to show there is information at 45° (between the orthogonal magnetic and electric waves).

    Either I missed something, or the magnetic component needs to be accounted for in the polarization of photons.

    Thanks in advance for setting me straight on this particular entanglement issue.
  2. jcsd
  3. Jan 18, 2012 #2


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    In quantum field theory of light, the electric-magnetic field corresponds to only one of many possible bases in which quantum states can be expanded. Another useful basis is the number-of-photons basis. So entanglement can be described in any of these bases, but when you use one basis you don't need to use the other one. It's a matter of personal choice. I hope it answers your question.
  4. Jan 18, 2012 #3
    Thank you for your reply Demystifier, you have addressed my larger, unstated questions which do include photon detection as well (from your example; the number-of-photon basis).

    Please allow me to rephrase my smaller question:

    The explanations for photon entanglement that I have read appear to have chosen the electric-magnetic basis in order to use polarization data as evidence for photon entanglement.

    The explanations (I've seen) seem incomplete, since only the electric component of the basis is discussed during the generation photon polarization data.

    In terms of bases in general, it seems the electric and magnetic waves could form a basis for a vector, say at 45°, which may explain:

    1) the polarization paradox experiments


    2) the apparent mystery expressed at how polarization information in the photon appears to be lost and then restored again during other experiments.

    ... without the need for a hidden variable.

    At any rate, to me the entanglement polarization data seems suspect when there appears to be no accounting for the magnetic component of the selected electric - magnetic basis.

    Question rephrased:

    When the electric - magnetic basis is used to explain quantum entanglement of photons from polarization data, why does the magnetic part seem to be ignored?

    Thanks again to all in advance for helping me with this question.
  5. Jan 21, 2012 #4
    Maybe I have an answer to my own question.

    as per the above, when an electric - magnetic wave reacts with a molecule in a polarizing structure, any "charge" of the molecule appears in relative motion to the magnetic component of the incident light / photon. This would result in a force along the plane of the electric component.

    For ordinary discussions of polarization, it may be sufficient to consider only the electric plane / component of the electric - magnetic wave.

    Possibly some anomalies found with light / photon polarizing data measured in the electric component plane, are a result of the magnetic component of the incident light / photon.

    I'll go with this for now and see where it ends up.
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