We derive a quantum linear Boltzmann equation from first principles to describe collisional friction, diffusion, and decoherence in a unified framework. In doing so, we discover that the previously celebrated quantum contribution to position diffusion is not a true physical process, but rather an artifact of the use of a coarse-grained time scale necessary to derive Markovian dynamics.
Kamleitner I and Cresser J. Phys. Rev. A 81, 012107 (2010). Copyright (2010) by the American Physical Society. The original article can be found at [http://link.aps.org/doi/10.1103/PhysRevA.81.012107].