报告人简介：Chi-Kwong Li教授是美国威廉和玛丽学院数学系的Ferguson Professor，著名学术杂志Linear and Multilinear Algebra的主编以及 Linear Algebra and Its Applications 的资深编委，2011年度Fulbright奖获得者，国际线性代数学会副主席。

摘要：An n-by-n matrix is a 2-level unitary matrix if it is a unitary matrix obtained from the identity matrix by changing a 2-by-2 submatrix.
It is well known that every n-by-n unitary matrix can be written as a product of no more than n(n-1)/2 2-level unitary matrices. It will be shown that one can impose additional structure on the 2-level unitary matrices so that the decomposition will be more useful in applications such as numerical analysis, tensor analysis, or quantum computing. Related results and open problems will be mentioned.