Limebeer, D. J.N.Anderson, B. D.O.2026-01-022026-01-020191-2216ORCID:/0000-0002-1493-4774/work/174739809https://hdl.handle.net/1885/733803076An upper bound is derived for the McMillan degree of all H** infinity -optimal controllers using vector interpolation theory. The advantage of this method is that interpolation theory leads directly to a degree bound on all optimal closed loops. With this in hand, it is relatively easy to obtain a bound on the controller degree. A novel result on the degree of all optimal solutions to the matrix Nevanlinna-Pick problem.6en19870023562756