Quantum noise and its evasion in feedback oscillators
Abstract
We study an abstract model of an oscillator realized by an amplifier embedded in a positive feedback loop. The power and frequency stability of the output of such an oscillator are limited by quantum noise added by two elements in the loop: the amplifier, and the out-coupler. The resulting frequency instability gives the Schawlow-Townes formula. Thus the applicability of the Schawlow-Townes formula is extended to a large class of oscillators, and is shown to be related to the Haus-Caves quantum noise limit for a linear amplifier, while identifying the role of quantum noise added at the out-coupler. By illuminating the precise origin of amplitude and frequency quantum noise in the output of an oscillator, we reveal several techniques to systematically evade them.
Cite
@article{arxiv.2304.03716,
title = {Quantum noise and its evasion in feedback oscillators},
author = {Hudson A. Loughlin and Vivishek Sudhir},
journal= {arXiv preprint arXiv:2304.03716},
year = {2023}
}