Quantum Visibility

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1. Oct 24, 2014

suma

Hi,

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?

thanks

2. Oct 24, 2014

naima

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

3. Oct 24, 2014

suma

thanks,

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?

thanks

4. Oct 24, 2014

naima

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