Robust $H_\infty$ Coherent-Classical Estimation of Linear Quantum Systems
For quantum control engineers, this work provides a method to improve estimation robustness in uncertain quantum systems, though the improvement is incremental over existing classical approaches.
This paper develops robust H∞ coherent-classical estimators for linear quantum systems with parameter uncertainties, demonstrating that these estimators outperform purely-classical estimators in disturbance-to-error performance and robustness to uncertainty.
We study robust $H_\infty$ coherent-classical estimation for a class of physically realizable linear quantum systems with parameter uncertainties. Such a robust coherent-classical estimator, with or without coherent feedback, can yield better disturbance-to-error performance than the corresponding robust purely-classical estimator for an uncertain plant. Moreover, coherent feedback allows for such a robust coherent-classical estimator to be more robust to uncertainty in comparison to the robust classical-only estimator.