Key points are not available for this paper at this time.
The quantum theory of noise in lossy electrical circuits is extended to systems which are not in thermal equilibrium. The theory is applied to microwave molecular amplifiers (masers) and predicts a correction to the classically calculated noise figure which can be identified with spontaneous emission from the molecules of the active medium. The correction is small at ordinary temperatures but becomes significant at very low temperatures.
Marcel Müller (Mon,) studied this question.