Analysis and control of closed quantum systems based on real-valued dynamics

Abstract

This study aims to facilitate quantum control design by making use of derived real-valued equations, which are equivalent to the Schrödinger equation. First, a pure-state identification approach is presented to show that a quantum state can be determined by a minimum number of real parameters. Second, the real-valued equations are deduced for both two- and three-level systems based on the results of the state parametrisation. The procedure is also extended to n-level systems. Third, with the assistance of the derived real-valued equations, the state transfer problem is investigated based on Lyapunov analysis. The state transfer convergence is analysed. It is further shown how to achieve arbitrary pure state transfers via the Lyapunov method by designing the control. The real-valued equations provide a convenient way for theoretical analysis and control design of quantum systems, and therefore can assist in the implementation of quantum control. The state transfer convergence is analysed. It is further shown how to achieve arbitrary pure-state transfers via the Lyapunov method by designing the control.