虑在外界激光脉冲控制下的含近简并能级多能级系统的量子动力学,该多能级系统模型包括了 一个基态和多个激发态,其中假设基态与各个激发态之间都存在跃迁。 研究了不同激光脉冲场控制下的基态到近简并多能级激发态的布居转移。研究表明,在脉冲激光很短时, 所考虑的多能级系统可以约化为一个二能级系统,并得到了在激光脉冲为多频弱场和单频强场时有效二能 级系统参数的近似解析公式。以上结果可以推广到有多组近简并能级的多能级系统,用来鉴别有效控制维数, 简化设计系统的控制策略。

Considering dynamics of a pulse-driven finite-dimensional quantum system with near degenerate eigenstates, the multi-level system model includes one ground state and a number of excited states, in which the transitions exist between the ground state and any excited state. Population transfer induced by different kinds of pulses in this multi-level system were investigated. It is noted that in the case of both weak and strong fields, the quantum system can be reduced to a two-level system. Analytical relations between the original system and the reduced system are obtained for weak fields with multi frequencies and strong fields with one frequency. These results can be generalized to a multi-level system with several sets of near-degenerated eigenstates, and the conclusion can be utilized to identify the effective dimension of a quantum multi-level system controlled by laser.