论文标题
强大量子态制备的模型预测控制
Model predictive control for robust quantum state preparation
论文作者
论文摘要
量子技术中的关键工程挑战是对量子动态的准确控制。在理论和实验紧密匹配时,基于模型的最佳控制方法已显示出非常有效的。因此,通过基于模型的控制,实现高保真量子过程需要仔细的设备表征。在基于冷原子的量子处理器中,可以很好地表征哈密顿量。对于在毫克尔文温的温度下运行的超导量子位,哈密顿量的特征却没有那么良好。对物理学(即模式差异),连贯的干扰以及噪声损害传统基于模型的控制不正确。这项工作介绍了用于量子控制应用的模型预测控制(MPC)。 MPC是一个闭环优化框架,(i)通过合并测量反馈来继承自然的干扰拒绝,(ii)利用基于有限的摩托车模型的优化来控制复杂的多输入,在状态和输入约束下的多输入,多输出动力学系统,以及(iii)足够灵活地与其他现代控制策略相协调。我们展示了如何使用MPC在量子态制备的代表性示例中生成实用的优化控制序列。具体而言,我们证明了一个量子,一个弱的量子量子和正在串扰的系统,即使模型不足,MPC也可以实现成功的基于模型的控制。这些示例展示了为什么MPC是量子工程控制套件的重要补充。
A critical engineering challenge in quantum technology is the accurate control of quantum dynamics. Model-based methods for optimal control have been shown to be highly effective when theory and experiment closely match. Consequently, realizing high-fidelity quantum processes with model-based control requires careful device characterization. In quantum processors based on cold atoms, the Hamiltonian can be well-characterized. For superconducting qubits operating at milli-Kelvin temperatures, the Hamiltonian is not as well-characterized. Unaccounted for physics (i.e., mode discrepancy), coherent disturbances, and increased noise compromise traditional model-based control. This work introduces model predictive control (MPC) for quantum control applications. MPC is a closed-loop optimization framework that (i) inherits a natural degree of disturbance rejection by incorporating measurement feedback, (ii) utilizes finite-horizon model-based optimizations to control complex multi-input, multi-output dynamical systems under state and input constraints, and (iii) is flexible enough to develop synergistically alongside other modern control strategies. We show how MPC can be used to generate practical optimized control sequences in representative examples of quantum state preparation. Specifically, we demonstrate for a qubit, a weakly-anharmonic qubit, and a system undergoing crosstalk, that MPC can realize successful model-based control even when the model is inadequate. These examples showcase why MPC is an important addition to the quantum engineering control suite.