It is shown that bremsstrahlung can give rise to a loss of coherence for quantum systems. Here a particular mechanism is analyzed, which makes use of the formal properties of the infrared radiation in QED. A charged particle goes through a scattering process into a superposition of two kinematically distinct states. The scattering also gives rise to the emission of a cloud of soft photons, and it is precisely this process that washes out the interference term between the two final states.

• Received 22 October 2002

DOI:https://doi.org/10.1103/PhysRevA.67.042702