Fig. 6: The relationship between acetone VQE results and the number of hardware-efficient ansatz layers.
From: Quantum simulation of preferred tautomeric state prediction
a, b are the results when Gaussian-initialized parameters are used while c and d are the results when initial states are the HF states. All the x-axes represent the number of hardware-efficient circuit layers. For a and c, the y-axes represent VQE energy errors of the keto or enol form of acetone, and the dashed lines represent chemical accuracy (Chem. Accu.). For b and d, the y-axes represent the energies relative to the keto form (so VQE energies, CCSD energies, and exact energies of the keto form are set to zero). Note that the exact energies (Exact in the legend) are the results from exact diagonalization of the active-space Hamiltonian for each tautomer, and CCSD full in the legend represents the CCSD energy of the full system relative to the keto form.
