# 问题：

Show that the Pauli matrices except for $I$ have trace zero.

$Pauli$矩阵$X,Y,Z$的迹为零.

## 解答

$\operatorname{tr}\left[\begin{array}{ll}0 & 1 \\ 1 & 0\end{array}\right]=\operatorname{tr}\left[\begin{array}{ll}0 & -i \\ i & 0\end{array}\right]=\operatorname{tr}\left[\begin{array}{ll}1 & 0 \\ 0 & -1\end{array}\right]=0$.

#### 参考

[1]www.qtumist.com