Global feedback stabilization of quantum noiseless subsystems

In this paper, we investigate the state preparation problem of quantum noiselsss subsystems for the quantum Markovian systems via quantum feedback control. The controlled dynamics we consider are given by the so-called stochastic master equation including the coupling terms with the environment. We formulate the problem as a stochastic stabilization problem of an invariant set. This formulation allows us to utilize the stochastic Lyapunov technique and derive a globally stabilizing controller. The effectiveness of this method is evaluated by applying it to the 3-qubit systems subject to the collective noise.