We investigate the distillability problem in quantum information in
\bbC^d\ox\bbC^d. A special case of the problem has been reduced to proving a
matrix inequality when d=4. We investigate the inequality for two families of
non-normal matrices. We prove the inequality for the first family with d=4
and two special cases of the second family with d≥4. We also prove the
inequality for all normal matrices with d>4.Comment: 19 pages, comments are welcom