Robustness of Energy Landscape Controllers for Spin Rings under Coherent Excitation Transport

S O’Neil, FC Langbein, E Jonckheere, SG Shermer. Robustness of Energy Landscape Controllers for Spin Rings under Coherent Excitation Transport. Research Directions: Quantum Technologies, Volume 1, e12, 2023.
[DOI:10.1017/qut.2023.5] [arXiv:2303.00142] [PDF]

The design and analysis of controllers to regulate excitation transport in quantum spin rings presents challenges in the application of classical feedback control techniques to synthesize effective control, and generates results in contradiction to the expectations of classical control theory. This paper examines the robustness of controllers designed to optimize the fidelity of an excitation transfer to uncertainty in system and control parameters. We use the logarithmic sensitivity of the fidelity error as the robustness measure, drawing on the classical control analog of the sensitivity of the tracking error. Our analysis shows that quantum systems optimized for coherent transport demonstrate significantly different correlation between error and the log-sensitivity depending on whether the controller is optimized for readout at an exact time T or over a time-window T ± ∆/2.

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