Controlling open quantum systems: Tools, achievements, and limitations

TL;DR

This paper reviews recent advances in optimal control theory for open quantum systems, focusing on strategies to mitigate decoherence and utilize the environment to enhance quantum device performance.

Contribution

It provides a comprehensive overview of optimal control methods applied to open quantum systems, highlighting new techniques and potential future directions.

Findings

Optimal control can mitigate decoherence effects.

Control strategies can exploit environmental interactions.

Recent methodological advances improve device operation.

Abstract

The advent of quantum devices, which exploit the two essential elements of quantum physics, coherence and entanglement, has sparked renewed interest in the control of open quantum systems. Successful implementations face the challenge to preserve the relevant nonclassical features at the level of device operation. A major obstacle is decoherence which is caused by interaction with the environment. Optimal control theory is a tool that can be used to identify control strategies in the presence of decoherence. We review here recent advances in optimal control methodology that allow for tackling typical tasks in device operation for open quantum systems and discuss examples of relaxation-optimized dynamics. Optimal control theory is also a useful tool to exploit the environment for control. We discuss examples and point out possible future extensions.