This discussion reminded me of an discussion
of total internal reflection in a QM class many
years ago. The discussion concerned the fact that
if you have a piece of glass in which total internal
reflection is taking place, and then put the surface
of a second block of glass very close to the surface
of the first block,but with an air gap inbetween,
you get transmission and it is no longer
total internal reflection. Our instructor would say,
(tongue is cheek, I'm sure.)
Well, when there is no second block, the photon
sticks it head out the glass, takes a look and sees
nowhere to go and so goes back into the first glass block.
However, if there is a second piece of glass, the photon say,
I can make that jump, and leaps into the second piece of
glass (transmission)
The instructors way of saying the following, I guess.
The photon wavefunction has a part of it extending outside the surface
(barrier) of the frist glass block. When there is just air outside the
block, the probablity of transmission is zero across that 'barrier'.
However when a second glass block exist nearby, and a portion of
the photon's wavefunction exists in the second block, then there
is some real probablity of transmission across the air barrier to
the second glass block.