Optimal Noise Suppression of Phase Damping Quantum Systems via Weak Measurement

One qubit subjected to the effect of phase damping in a two-level quantum system with arbitrary pure initial state is studied in this paper. The aim of this paper is to find the optimal control scheme to correct the qubit back as close as possible to its initial state. The strength-dependent measurements and control correction rotation in different bases are designed to protect the arbitrary pure state of qubit. The authors design the optimal weak measurement strength to achieve the best trade-off between gaining the information of the system and the disturbance through measurement.The authors study the suppression of phase damping in two cases: There is and isn't the y component in initial state. The authors deduce the optimal parameters and performances of the control schemes for the various initial state situations. Simulation results demonstrate the effectiveness of the proposed control schemes.