Free field-matter commutation relations in operator radiation reaction theory

Resonant light scattering is considered in the Heisenberg picture by making use of operator radiation reaction theory. A crucial commutator between matter and free-field variables is shown to vanish, and the validity of the quantum fluctuation-regression theorem, like that of the optical Bloch equations which govern the reduced atomic density matrix, is firmly established, apart from renormalization difficulties, within the rotating wave approximation.