Quantum systems can be controlled by other quantum systems in a reversible way, without any information leaking to the outside of the system-controller compound. Such coherent quantum control is deterministic, is less noisy than measurement-based feedback control, and has potential applications in a variety of quantum technologies, including quantum computation, quantum communication and quantum metrology. Here we introduce a coherent feedback protocol, consisting of a sequence of identical interactions with controlling quantum systems, that steers a quantum system from an arbitrary initial state towards a target state. We determine the broad class of such coherent feedback channels that achieve convergence to the target state, and then stabilise as well as protect it against noise. Our results imply that also weak system-controller interactions can counter noise if they occur with suitably high frequency. We provide an example of a control scheme that does not require knowledge of the target state encoded in the controllers, which could be the result of a quantum computation. It thus provides a mechanism for autonomous, purely quantum closed-loop control.
Comparing and correcting robustness metrics for quantum optimal control
Pritzker School of Molecular Engineering, University of Chicago（芝加哥大学普里茨克分子工程学院）；Department of Computer Science, University of Chicago（芝加哥大学计算机科学系）；California Institute of Technology（加州理工学院）；Johns Hopkins Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）
A proposal of adaptive parameter tuning for robust stabilizing control of $N$--level quantum angular momentum systems
镇定控制综合是控制理论和工程中的核心课题之一，在实际应用中往往要处理不可避免的不确定性。在这项研究中，我们提出了一种自适应参数调整算法，用于$N$级量子角动量系统的鲁棒稳定量子反馈控制，该系统具有由Liang，Amini和Mason提出的鲁棒稳定控制器[SIAM J. Control Optim.，59（2021），pp. 669-692]。所提出的方法保证了局部收敛到目标状态。数值实验表明，在适当选择学习参数的情况下，该算法具有整体收敛性。
Robust Quantum Controllers: Quantum Information -- Thermodynamic Hidden Force Control in Intelligent Robotics based on Quantum Soft Computing
Institute of System Analysis and Management, Dubna State University（杜布纳国立大学系统分析与管理研究所）；Joint Institute for Nuclear Research (JINR)（联合核子研究所）；Moscow State University of Geodesy and Cartography (MIIGAiK)（莫斯科测绘大学）；Yamaha Motor Co. Ltd.（雅马哈发动机株式会社）
