The Birkhoff theorem for unitary matrices of prime dimension
arXiv:1509.08626 · doi:10.1016/j.laa.2015.12.005
Abstract
The Birkhoff's theorem states that any doubly stochastic matrix lies inside a convex polytope with the permutation matrices at the corners. It can be proven that a similar theorem holds for unitary matrices with equal line sums for prime dimensions.