  We develop the theory of conductance of a quantum dot which carries a spin
and is coupled via RKKY interaction to another spin-carrying quantum dot. The
found dependence of the differential conductance on bias and magnetic field at
fixed RKKY interaction strength may allow one to distinguish between the
possible ground states of the system. Transitions between the ground states are
achieved by tuning the RKKY interaction, and the nature of these transitions
can be extracted from the temperature dependence of the linear conductance. The
feasibility of the corresponding measurements is evidenced by recent
experiments by Craig et al. [cond-mat/0404213].
