Feedback preparation of maximally entangled states of two-qubit systems

Bell states play a central role in the field of quantum information. For two-qubit systems, this study proposes a new non-smooth control strategy within the theoretical framework of quantum continuous measurement, and achieves global feedback stabilisation in any target Bell state. For a target Bell state, the authors select one measured observable and two control channels, where the control law associated with one channel is kept constant. They design a non-smooth control law for the other control channel, and prove the stability of the whole closed-loop system. Some simulation experiments show that the control strategy in this paper has a good control effect.