Improved Quantum Optimal Control in Dynamic Control Field

Matthew Grace, Wayne M. Witzel, Malcolm S. Carroll +1 more

Hirmay Sandesara, Alok Shukla, Prakash Vedula

Ze-Xia Huang, You-Hong Yu

According to the specialty of quantum systems, the reliability or the efficiency of a general optimal control scheme leave much to be desired. In this paper, we develop a special improved quantum optimal control method for using dynamic control field, which can be implemented as fast convergent algorithms. The relations among, convergence speed and iteration step parameters are analyzed in detail through a three-level ¦® system simulation experiments. Theoretical analysis show that this new algorithm exhibits significantly superior to the classical quantum optimal control method and the Krotov method in reliability and convergence rate.

T. S. Mahesh, Priya Batra, M. Harshanth Ram

Tak‐San Ho, HERSCHEL A. RABITZ

The control of quantum dynamics is often concerned with finding time-dependent optimal control fields that can take a system from an initial state to a final state to attain the desired value of an observable. This paper presents a general method for formulating monotonically convergent algorithms to iteratively improve control fields. The formulation is based on a two-point boundary-value quantum control paradigm (TBQCP) expressed as a nonlinear integral equation of the first kind arising from dynamical invariant tracking control. TBQCP is shown to be related to various existing techniques, including local control theory, the Krotov method, and optimal control theory. Several accelerated monotonic convergence schemes for iteratively computing control fields are derived based on TBQCP. Numerical simulations are compared with the Krotov method showing that the new TBQCP schemes are efficient and remain monotonically convergent over a wide range of the iteration step parameters and the control pulse lengths, which is attributable to the trap-free character of the transition probability quantum dynamics control landscape.

Xiaodong Yang, Yunrui Ge, Bo Zhang +1 more

High-fidelity control of quantum systems is crucial for quantum information processing, but is often limited by perturbations from the environment and imperfections in the applied control fields. Here, we investigate the combination of dynamical decoupling (DD) and robust optimal control (ROC) to address this problem. In this combination, ROC is employed to find robust shaped pulses, wherein the directional derivatives of the controlled dynamics with respect to control errors are reduced to a desired order. Then, we incorporate ROC pulses into DD sequences, achieving a remarkable improvement of robustness against multiple error channels. We demonstrate this method in the example of manipulating nuclear spin bath via an electron spin in the nitrogen-vacancy center system. Simulation results indicate that ROC-based DD sequences outperform the state-of-the-art robust DD sequences. Our work has implications for robust quantum control on near-term noisy quantum devices.