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Bell's Theorem and the detector

  1. Feb 25, 2012 #1
    Edgardo thanks for posting the links to Bell's Theorem. I read the first one and it was a clear description of Bell's experiment.

    I have a question (or an alternative explanation for the difference in probabilities between mathematical calculations and experimental results in the Bell's experiment) which I am posting in a new thread because:

    For some, I am sure, valid, but unknown, reason that thread has been lock.

    Bell's Theorem, for example in the link below:

    Spooky Action at a Distance – An Explanation of Bell’s Theorem by Gary Felder

    shows how the actual results (in this case 1/2) are lower than the mathematically derived probability (in this case 5/9).

    it is then concluded that this is only possible if the photons were quantum entangled.

    However is it not possible that the detectors are effecting the property/behavior/spin of the photons (at the time of detection or an infinitesimally small time prior to detection) in such a way as to change the probability from 5/9 to 1/2.

    for example:

    in the Dirac Three Polarizers Experiment it seems that the polarizer(s) might not just be simply filtering, but also modifying the spin of, the photon.

    or another example (and this is by no means a description of how photons spin is modified) to illustrate this conceptually:

    consider a vertical slot (i.e. perpendicular to surface of ground/earth) at which coins are flung by a precision machine at 45 degrees (to the ground/earth). now some of the coins might actually pass through the slot because of the dynamics of the forces between the circumference of the coin and the perimeter of the slot.

    in short: is it not possible that the detection equipment is biasing the probabilities?
    Last edited: Feb 25, 2012
  2. jcsd
  3. Feb 25, 2012 #2
    Of course. If a photon meets a polarizer it has a chance to pass through according to Malus' Law. If it passes through the polarizer then that photon is then polarized at the same angle i.e. it then has a 100% chance to pass through a subsequent polarizer set at the same angle.

    This is where the "spooky action at a distance" comes from. It seems that a measurement at polarizer A sets the polarization of photon A at a certain angle, and therefore does the same to (entangled) photon B. But then you can't say that any particular measurement precedes the other, maybe the measurement of photon B came first.
    Last edited: Feb 25, 2012
  4. Feb 25, 2012 #3
    how about this thought/idea:

    the measurement at A sets the polarization of photon A and the measurement of B (independently) sets the polarization of photon B in a same/correlated manner?

    i.e. you don't need to assume any kind of quantum entanglement i.e. any kind of non-local nonlocal quantum correlations because:

    A and B had similar initial conditions to begin with (at the time of their generation/birth/creation) and hence the polarizers effect them in the same way, which could result in some kind of biasing in probabilities...

    just playing devil's advocate.....to complete a full proof test of quantum entanglement....

    for example twins (humans not photons...;)...) behavior (tastes, preferences, personality) will tend to be more closely correlated (with each other) than the general population
    Last edited: Feb 25, 2012
  5. Feb 25, 2012 #4
    What you're describing there is a local Hidden Variables theory. Which is precisely what Bell showed couldn't reproduce the predictions of QM.
  6. Feb 25, 2012 #5
    actually you are correct Joncon, for a moment/day I forgot. thanks for reminding

    i'll close this thread

    just one thought (and this might be a weak argument):

    in the experiment (in the link above) position 1 & 3 are assumed similar (yay-boo-yay), the probabilities are assumed to be additive.....maybe positions 1 & 3 are not totally similar/additive but a bit less than that.....
    Last edited: Feb 25, 2012
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