Figure 2: The examined problem instance and its energy spectrum.

(a) Depiction of the 16-qubit problem instance studied, with corresponding values of h_i and J_ij. Each circle represents a qubit and each line represents a coupler. The coupling between any two qubits not connected by a line is zero. (b) The energy scales Δ_i(s) for all i and (s) near the anticrossing. (c) The lowest energy levels of the Hamiltonian, relative to the ground-state energy E₀, as a function of s. States corresponding to the global minimum (green) and the superposition of the 256 local minima (blue) are labelled. The calculated minimum gap is g_min/k_B=0.011 mK and δE/k_B=50.5 mK. Inset: the lowest two energy levels near the anticrossing. (d) Measured instantaneous probabilities of occupying (green symbols) and (blue symbols) for T=19.9 mK and t_f=100 ms. At the anticrossing, both probabilities are ≈0.5. The dashed red line marks the theoretically predicted position of the anticrossing. The error bars depict the s.e.m., assuming each sample is independent.