A Remark on Witten Effect for QCD Monopoles in Matrix Quantum Mechanics

In a recent work (hep-th/9905198) we argued that a certain matrix quantum mechanics may describe 't Hooft's monopoles which emerge in QCD when the theory is projected to its maximal Abelian subgroup. In this note we find further evidence which supports this interpretation. We study the theory with a non-zero theta-term. In this case, 't Hooft's QCD monopoles become dyons since they acquire electric charges due to the Witten effect. We calculate a potential between a dyon and an anti-dyon in the matrix quantum mechanics, and find that the attractive force between them grows as the theta angle increases.