  The problem of the reflectance of a photon by a metallic mirror whose
position is treated quantum mechanically is considered. The interaction between
the metallic surface and the light is treated classically. It is shown that the
reflectance depends on the spread of the wavefunction describing the reflecting
surface along its normal. Considering this decrease on the mirror reflectance,
it is shown by first principles that it is impossible to achieve a highly
entangled state between a photon and a mirror when the photon can be reflected
only once.
