State transfer of a two-qubit open quantum system via improved bang-bang control

Fast state transfer of quantum system is one of the effective robust control problems that often appear in practice, which is good for efficiency improving and decoherence suppression caused by the environment. In this paper, we mainly discuss the fast transfer of quantum state in a two-qubit system. By analyzing the advantages and disadvantages of the existing Lyapunov control, we propose that the quantum state transfer can be accelerated by minimizing the Lyapunov function, and give three optimized control field design methods. For the problem of a two-qubit open quantum system, numerical simulation results indicate the effectiveness of the method. Not only the state transfer time is shortened, but also the high-frequency oscillation that occurs in bang-bang control is effectively avoided.