关于酉阵之和是酉阵的充要条件

The Necessary and Sufficient Condition About Sum of Unitary Matrices Is Unitary Matrix

给出了两个酉阵（部分酉阵或准酉阵）Ａ 与Ｂ之和Ａ＋ Ｂ仍是酉阵（部分酉阵或准酉阵）的充要条件，同时给出Ａ 与Ｂ的关系式．

Let A,B be unitary matrix(partial unitary matrix or para unitary matrix).In this paper,we give sufficient and necessary condition for A+B is unitary matrix (partial unitary matrix or para unitary matrix).Meanwhile,related expressions of A and B are also given.