density matrix

例句：

1. 1.The density matrix of the system is critical for understanding its behavior.
   该系统的密度矩阵对于理解其行为至关重要。
2. 2. In quantum mechanics, the density matrix is used to describe the state of a particle.
   在量子力学中，密度矩阵用于描述粒子的状态。
3. 3.The density matrix is calculated using the Schrödinger equation.
   密度矩阵是通过薛定谔方程计算得出的。