(a), (b), (c), and (d) show the convergence to ground-state energies by the FQE for H2, LiH, H2O, and NH3 molecules, respectively. The numerical simulations are carried out with fixed interatomic distance. The exact value corresponding to Hamiltonian diagonalization energy (red line). The initial state is chosen as the Hartree-Fock product state in all four cases. The final values of the lines for exact ground-state energy (red line) and for the three iteration results, noiseless case (blue line), random noisy case (green line), and Gaussian noisy case (orange line).