On September 28, 2022, Maison Clouatre and John Valasek of VSCL, in tandem with Mark Balas of the Texas A&M Mechanical Engineering Department and Vinod Gehlot of NASA Jet Propulsion Laboratory, published the paper “Linear Quantum State Observers” in IEEE Transactions on Quantum Engineering. This paper develops fundamental results for using linear observers to infer an unknown state of a quantum dynamical system. The theoretical contributions of the article are three-fold:
- A quantum observability test is provided in terms of two “quantum observability matrices”. This test is shown to be more computationally efficient than testing the Kalman observability matrix of the same quantum system.
- A canonical quantum state observer is derived, which guarantees that the observer error tends to the unobservable space of any quantum system with positive operator valued measure (POVM) output.
- The canonical observer preserves the Hermiticity of the observer’s state. This allows one to efficiently project the observer’s state onto the set of valid quantum density matrices while
retaining the convergence rate of the observer.
This publication is part of VSCL’s ongoing work in the area of control for quantum information systems. The early access version of the article can be viewed on IEEE’s website: https://ieeexplore.ieee.org/document/9904875.