where the off-diagonal Förster interaction is given by V F , and the direct Coulomb binding energy between the two excitons, one on each dot, is on the diagonal and given by V XX . The ground state energy is denoted by ω ω 0 , and Δ Δ ω ω ≡ ≡ ω ω 1 − − ω ω 2 is the difference between the excitation energy for dot I and that for dot II. These excitation energies and inter-dot interactions are all functions of the applied field F.