  We investigate the optical properties of (Cd,Mn)Te quantum dots (QDs) by
looking at the excitons as a function of the Mn impurities positions and their
magnetic alignments. When doped with two Mn impurities, the Mn spins, aligned
initially antiparallel in the ground state, have lower energy in the parallel
configuration for the optically active spin-up exciton. Hence, the
photoexcitation of the QD ground state with antiparallel Mn spins induces one
of them to flip and they align parallel. This suggests that (Cd,Mn)Te QDs are
suitable for spin-based operations handled by light.
