first order reduced density matrix

例句：

1. 1. In quantummechanics, the first-order reduceddensity matrix is used to describe the stateof a system in the presence of anexternal perturbation.
   在量子力学中，第一阶降密度矩阵用于描述系统在外部扰动存在时的状态。
2. 2.The first-order reduced density matrix isa crucial tool for solving many problems inquantum chemistry.
   第一阶降密度矩阵是解决量子化学中许多问题的关键工具。
3. 3.The first-order reduced density matrix isalso used in the field of quantum computingto simulate the behavior of quantum systems.
   第一阶降密度矩阵还在量子计算领域被用来模拟量子系统的行为。