Quantum Visibility: Imax & Imin Explained

[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

 

[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

 

[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

 

[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