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Quantum Visibility

  1. Oct 24, 2014 #1

    What does visibility in interference mean? in quantum mechanics?
    V = Imax-Imin/Imax+Imin

    but which part of the interference does Imax and Imin refer to?

  2. jcsd
  3. Oct 24, 2014 #2


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    With a 50/50 mixture of left (L) and right (R) in the Young slits the probalility on the screen is
    ##L(x) \overline L (x) + R(x) \overline R (x)## you have no interference.
    in the pure case the probability is
    ##[L(x) + R(x)] \overline {[L(x) + R(x)]}##
    These are special cases of
    ##L(x) \overline L (x) + R(x) \overline R (x) + V[L(x) \overline {R(x)} + R(x) \overline {L (x)}]## for V = 0 and V = 1.
    Take V = 0.7 and see what it gives with a graph plotter
  4. Oct 24, 2014 #3

    but what is the meaning of visibility? does visibility means chance of seeing interference?

    is the V in your equation the visibility? there is a minus sign in the intensity form

    are L(x) and R(x) operators?

  5. Oct 24, 2014 #4


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    No L(x) and R(x) are the probability amplitudes that the photon hits the screen at x after having passed thru the Left slit (or the Right slit)
    Suppose now that behind the slits there is a device that let 80% of the photon pass thru the unmodified Young slits but that every 20% it randomly obturates one of the slits.
    We will have V = 0.8
    The probability curve on the screen will be sandwiched between two envelopes.
    It will look like that
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