General methods to control right-invariant systems on compact Lie groups and multilevel quantum systems

TL;DR

This paper introduces three control design methods for right-invariant systems on compact Lie groups, enabling precise or arbitrarily accurate state steering, with applications to quantum systems and electrical networks.

Contribution

It presents new, simple control strategies that guarantee arbitrary constructive control on compact Lie groups, including multilevel quantum systems, with efficiency improvements.

Findings

Exact control under certain conditions

Control with arbitrary accuracy without complex estimation

The combined method outperforms individual approaches in examples

Abstract

For a right-invariant system on a compact Lie group G, I present two methods to design a control to drive the state from the identity to any element of the group. The first method, under appropriate assumptions, achieves exact control to the target but requires estimation of the `size' of a neighborhood of the identity in G. The second method, does not involve any mathematical difficulty, and obtains control to a desired target with arbitrary accuracy. A third method is then given combining the main ideas of the previous methods. This is also very simple in its formulation and turns out to be generically more efficient as illustrated by one of the examples we consider. The methods described in the paper provide arbitrary constructive control for any right-invariant system on a compact Lie group. I give examples including closed multilevel quantum systems and lossless electrical networks. In particular, the results can be applied to the coherent control of general multilevel quantum systems.