Figure 4
From: Finding low-energy conformations of lattice protein models by quantum annealing
Embedding problem instances into hardware.
Graph representations of (a) the four-qubit unembedded energy function (Eq. 6) and (b) the five-qubit expression (Eq. 7) as was embedded into the quantum hardware. In graphs (a) and (b), each node denotes a qubit and the color and extent of its glow denotes the sign and strength of its corresponding longitudinal field, hi. The edges represent the interaction couplings, Jij, where color indicates sign and thickness indicates magnitude. Since we want the two qubits representing q4 (q4 and q4′) to end up with the same value, we apply the maximum ferromagnetic coupling (J = −1) between them, which adds a penalty whenever this equality is violated. These maximum couplings are indicated in the figure by heavy lines. For the case of Experiment 3, the reconstruction of the binary bit stings representing the folds in Fig. 3, from the five-qubit experimental measurements can be recovered by qexp3 = 010010q10q2q3|q4q4′, with qi = 0 (qi = 1) whenever si = 1 (si = −1).
