Optimized Dynamical Decoupling in {\Xi}-Type n-Level Quantum Systems
  In this paper, we first design a type of Bang-Bang (BB) operation group to reduce the phase decoherence in a {\Xi}-type n-level quantum system based on the dynamical decoupling mechanism. Then, we derive two kinds of dynamical decoupling schemes: periodic dynamical decoupling (PDD) and Uhrig dynamical decoupling (UDD). We select the non-diagonal element of density matrix as a reference index, and investigate the behavior of quantum coherence of the {\Xi}-type n-level atom under these two dynamical decoupling schemes proposed. At last, we choose a {\Xi}-type six-level atom as a system controlled, and use the decoupling schemes proposed to suppress the phase decoherence. The simulation experiments and the comparison results are given. 
Linping Chan and Shuang Cong
quant-ph