Applications of Feedback Control in Quantum Systems

TL;DR

This paper introduces feedback control in quantum systems, highlighting its unique aspects, applications like noise reduction, stabilization, adaptive measurement, and specific examples such as cooling and state-preparation.

Contribution

It provides an accessible overview of quantum feedback control, connecting classical control theory with quantum applications, and discusses recent practical implementations.

Findings

Feedback control differs significantly between quantum and classical systems.

Adaptive measurement is a key application of quantum feedback control.

Feedback techniques enable cooling and state-preparation in nano-electro-mechanical systems and trapped atoms.

Abstract

We give an introduction to feedback control in quantum systems, as well as an overview of the variety of applications which have been explored to date. This introductory review is aimed primarily at control theorists unfamiliar with quantum mechanics, but should also be useful to quantum physicists interested in applications of feedback control. We explain how feedback in quantum systems differs from that in traditional classical systems, and how in certain cases the results from modern optimal control theory can be applied directly to quantum systems. In addition to noise reduction and stabilization, an important application of feedback in quantum systems is adaptive measurement, and we discuss the various applications of adaptive measurements. We finish by describing specific examples of the application of feedback control to cooling and state-preparation in nano-electro-mechanical systems and single trapped atoms.