  A simple variation of the traditional Young's double slit experiment can
demonstrate several subtleties of interference with polarized light, including
Berry and Pancharatnam's phase. Since the position of the fringes depends on
the polarization state of the light at the input, the apparatus can also be
used to measure the light's polarization without a quarter-wave plate or an
accurate measurement of the light's intensity. In principle this technique can
be used for any wavelength of photon as long as one can effectively polarize
the incoming radiation.
