Physics and Astronomy, Electrical and Computer Engineering, Ames Laboratory
Journal or Book Title
Journal of Chemical Theory and Computation
We develop a resource-efficient step-merged quantum imaginary time evolution approach (smQITE) to solve for the ground state of a Hamiltonian on quantum computers. This heuristic method features a fixed shallow quantum circuit depth along the state evolution path. We use this algorithm to determine the binding energy curves of a set of molecules, including H2, H4, H6, LiH, HF, H2O, and BeH2, and find highly accurate results. The required quantum resources of smQITE calculations can be further reduced by adopting the circuit form of the variational quantum eigensolver (VQE) technique, such as the unitary coupled cluster ansatz. We demonstrate that smQITE achieves a similar computational accuracy as VQE at the same fixed-circuit ansatz, without requiring a generally complicated high-dimensional nonconvex optimization. Finally, smQITE calculations are carried out on Rigetti quantum processing units, demonstrating that the approach is readily applicable on current noisy intermediate-scale quantum devices.
American Chemical Society
Gomes, Niladri; Zhang, Feng; Berthusen, Noah F.; Wang, Cai-Zhuang; Ho, Kai-Ming; Orth, Peter P.; and Yao, Yongxin, "Efficient Step-Merged Quantum Imaginary Time Evolution Algorithm for Quantum Chemistry" (2020). Physics and Astronomy Publications. 707.