  In this paper, we consider N-level quantum angular momentum systems
interacting with electromagnetic fields undergoing continuous-time
measurements. We suppose unawareness of the initial state and physical
parameters, entailing the introduction of an additional state representing the
estimated quantum state. The evolution of the quantum state and its estimation
is described by a coupled stochastic master equation. Here, we study the
asymptotic behavior of such a system in presence of a feedback controller. We
provide sufficient conditions on the feedback controller and on the estimated
parameters that guarantee exponential stabilization of the coupled stochastic
system towards an eigenstate of the measurement operator. Furthermore, we
estimate the corresponding rate of convergence. We also provide parametrized
feedback laws satisfying such conditions. Our results show the robustness of
the feedback stabilization strategy considered in [21] in case of imprecise
initialization of the estimated state and with respect to the unknown physical
parameters.
