 Solution

ID: past-exam-of-the-mathematical-methods-i-course-of-the-university-of-oxford/2015/5/i/solution

(A B)^{†} = B^{†} A^{†} = B A

. Thus

A B is Hermitian if and only if A B = B A .

The necessary and sufficient additional condition is that the two Hermitian matrices commute.

 New to topics? Read the docs here!