Quantum Amplifiers Based on Electron Paramagnetic Resonance

Abstract

Already in the first papers on the ammonia maser, it was stated that if the self-excitation condition is not satisfied, the device can serve as an amplifier of microwave power with low intrinsic noises. This is due to the fact that the probability of spontaneous emission in the radio diapason is very low and noises of an amplifier are determined only by the thermal electrical fluctuations in a resonator (actually the working medium is a combination of neutral particles). In spite of the intrinsic noises of the ammonia maser are very small, these devices (and the like) have not got any significant spread because of the extremely narrow bandwidth and the inability of the change of a working frequency, i.e. because of those peculiarities which have made it possible to use them as standards of time and frequency.