Fig. 7: Comparison of VQD with different parameter β and VQE/AC for phenol blue.

Energy deviations ΔE (in kcal mol−1) from the exact values for S0 at the FC (a), S1 at the FC (b), S0 at the CI (c), and S1 at the CI (d) were calculated using the SA-CASSCF method. The errors in energy obtained by the statevector and noisy-QASM simulators are shown in red and blue, respectively. Detailed values are shown in Supplementary Table 4.