Gao, QingZhang, GuofengPetersen, Ian2023-09-050005-1098http://hdl.handle.net/1885/298219This work extends the previous quantum projection filtering scheme in Gao et al. (2019), by adding an optimality analysis result. A reformulation of the quantum projection filter is derived by minimizing the truncated Stratonovich stochastic Taylor expansion of the difference between the true quantum trajectory and its approximation on a lower-dimensional submanifold through quantum information geometric techniques. Simulation results for a qubit example demonstrate better approximation performance for the new quantum projection filter.This work was supported by the Alexander von Humboldt Foundation of Germany, the National Natural Science Foundation of China (No. 61903016), the Hong Kong Research Grant council (RGC) grant (No. 15206915), and the Air Force Office of Scientific Research, *United States and the Naval Research Global, *United States under agreement number FA2386-16-1-4065.application/pdfen-AU© 2019 The authorsQuantum filtersQuantum projection filtersStratonovich stochastic Taylor expansionsQuantum information geometry202010.1016/j.automatica.2019.1087162022-07-24