Southwest Quantum Information and Technology

A non-orthogonal quantum eigensolver for strongly correlated quantum chemistry

Presenting Author: James Shee, University of California Berkeley
Contributing Author(s): Unpil Baek, Diptarka Hait, Oskar Leimkuhler, William J. Huggins, Torin F. Stetina, Martin Head-Gordon, K. Birgitta Whaley

A balanced description of static and dynamic correlations in electronic systems with nearly degenerate, low-lying states presents a challenge for classical quantum-chemical algorithms. We present a new hybrid quantum-classical algorithm -- the non-orthogonal quantum eigensolver (NOQE) -- to obtain compact, multi-reference wavefunctions formed from non-orthogonal, dynamically-correlated single-reference states. While on classical devices the evaluation of the required off-diagonal matrix elements would incur an exponentially-scaling step, our quantum algorithm accomplishes this with polynomial cost. We explore various single-reference ansatzes inspired by classical quantum chemistry methods, and demonstrate that the NOQE procedure can capture meaningful amounts of electronic correlation energy in both ground and excited states. NOQE is thus an attractive method for the calculation of multi-reference electronic states of a wide range of molecular systems. Preliminary results from the incorporation of noise models and experiments on quantum hardware will be shared.

Read this article online: https://arxiv.org/abs/2205.09039

(Session 5 : Thursday from 5:00 pm - 7:00 pm)