Benchmarking Adaptive Variational Quantum Eigensolvers

• Published in: Frontiers in chemistry 2020-12, Vol.8, p.606863-606863
• Main Authors: Claudino, Daniel, Wright, Jerimiah, McCaskey, Alexander J, Humble, Travis S
• Format: Article
• Language: English
• Subjects: ADAPT-VQE; Chemistry; potential energy scan; quantum chemistry; quantum computing; state fidelity; VQE
• ISSN: 2296-2646; 2296-2646
• DOI: 10.3389/fchem.2020.606863

By design, the variational quantum eigensolver (VQE) strives to recover the lowest-energy eigenvalue of a given Hamiltonian by preparing quantum states guided by the variational principle. In practice, the prepared quantum state is indirectly assessed by the value of the associated energy. Novel adaptive derivative-assembled pseudo-trotter (ADAPT) ansatz approaches and recent formal advances now establish a clear connection between the theory of quantum chemistry and the quantum state ansatz used to solve the electronic structure problem. Here we benchmark the accuracy of VQE and ADAPT-VQE to calculate the electronic ground states and potential energy curves for a few selected diatomic molecules, namely H , NaH, and KH. Using numerical simulation, we find both methods provide good estimates of the energy and ground state, but only ADAPT-VQE proves to be robust to particularities in optimization methods. Another relevant finding is that gradient-based optimization is overall more economical and delivers superior performance than analogous simulations carried out with gradient-free optimizers. The results also identify small errors in the prepared state fidelity which show an increasing trend with molecular size.