The energy dierence at ε = 1.6 meV between the (2,0) states indicated as e [rst-excited state, no. 2 in Fig. A main conclusion form the VFCI results in Fig. is that, for a given V z , the energy gaps between the spin singlet and and spin triplet states in the (2,0) conguration are drastically suppressed compared to the orbital (single-particle) gap of hω 0 = 0.40 meV = 96.719h GHz associated with the non-interacting limit; see, e.g., the spin-singlet-spin-triplet gap, E ⊕ ST , at ε = 1.60 meV between the ground and rst-excited states (denoted as g and e, respectively), which is E ⊕ ST ≈ 4.05h GHz in Fig. ) and E ⊕ ST ≈ 6.09h GHz in Fig. ). This quenching of the gaps, which recently was observed experimentally in Si (but also in GaAs ) DQD qubits, is the result of strong-electron correlations and of the formation of Wigner molecules. Namely, the ensuing spatial localization of the electrons within the left or right QD reduces the Coulomb repulsion between them, a process that leads to the convergence of the energies between the states with symmetric and antisymmetric space parts.