Behavior of quantum coherence of Ξ-type four-level atom under bang–bang control

In this paper, we have studied the bang–bang (BB) decoupling scheme to suppress the phase decoherence, the amplitude decoherence and the general decoherence in a four-level Ξ-type atom system. The corresponding dynamical decoupling groups are given for designing the decoupling pulse sequences to suppress these three kinds of decoherence, respectively. Results show that in a proper time scale, the decoupling operations suppress the decoherence effectively. Especially in the ideal limits, it can suppress the decoherence completely. We also give the time scale in which the BB control works well. Numerical simulations show that, the larger cycle times N, the better effect of the BB decoupling operations under a fixed time scale.