# 问题：

Show that the tensor product of two unitary operators is unitary.

## 解答

$(A \otimes B)^{\dagger}(A \otimes B)=\left(A^{\dagger} \otimes B^{\dagger}\right)(A \otimes B)=\left(A^{\dagger} A\right) \otimes\left(B^{\dagger} B\right)=I \otimes I=I$；

#### 参考

[1]www.qtumist.com