Optimized hierarchical equations of motion for Drude dissipation
  The hierarchical equations of motion theory for Drude dissipation is optimized, with a convenient convergence criterion proposed in advance of numerical propagations. The theoretical construction is on basis of a Pad\'{e} spectrum decomposition that has been qualified to be the best sum-over-poles scheme for quantum distribution function. The resulting hierarchical dynamics under the {\em apriori} convergence criterion are exemplified with a benchmark spin-boson system, and also the transient absorption and two-dimensional spectroscopy of a model exciton dimer system. 
Jin-Jin Ding, Jian Xu, Jie Hu, Rui-Xue Xu, and YiJing Yan
quant-ph cond-mat.stat-mech