When the system transitions to the (2,0) charge con-guration, this scheme is modied because the spinsinglet-spin-triplet degeneracies are lifted; however, the hallmark family of 16 states persists and is easily traceable in the spectra (see Figs. the case of two electrons conned in a tunable double quantum dot, oers also a most eective tool for analyzing the spectra of Si qubits with more than two wells and/or more than two electrons; it can also be straightforwardly extended to the case of bilayer graphene QDs . The Y n (y) are the eigenfunctions of a one-dimensional oscillator in the y direction, and the X µ (x ≤ 0) and X µ (x > 0) can be expressed through the parabolic cylinder functions U [γ k , (-1) k ξ k ] , where ξ k = x ′ k 2m * ω xk /h, γ k = (-E x + h k )/(hω xk ), and E x = (µ+0.5)hω x1 +h 1 denotes the x-eigenvalues. The matching conditions at x = 0 for the left (k = 1) and right (k = 2) domains yield the x-eigenvalues and the eigenfunctions X µ (x). The n indices are integer numbers. The µ indices are in general real numbers, but their number is nite.