  Phenomenologically important quantum dissipative processes include black-body
friction (an atom absorbs counterpropagating blue-shifted photons and
spontaneously emits them in all directions, losing kinetic energy) and
non-contact van der Waals friction (in the vicinity of a dielectric surface,
the mirror charges of the constituent particles inside the surface experience
drag, slowing the atom). The theoretical predictions for these processes are
modified upon a rigorous quantum electrodynamic (QED) treatment, which shows
that the one-loop "correction" yields the dominant contribution to the
off-resonant, gauge-invariant, imaginary part of the atom's polarizability at
room temperature, for typical atom-surface interactions. The tree-level
contribution to the polarizability dominates at high temperature.

Quantum Physics