Postponing the orthogonality catastrophe: efficient state preparation\n for electronic structure simulations on quantum devices

Abstract

Despite significant work on resource estimation for quantum simulation of\nelectronic systems, the challenge of preparing states with sufficient ground\nstate support has so far been largely neglected. In this work we investigate\nthis issue in several systems of interest, including organic molecules,\ntransition metal complexes, the uniform electron gas, Hubbard models, and\nquantum impurity models arising from embedding formalisms such as dynamical\nmean-field theory. Our approach uses a state-of-the-art classical technique for\nhigh-fidelity ground state approximation. We find that easy-to-prepare single\nSlater determinants such as the Hartree-Fock state often have surprisingly\nrobust support on the ground state for many applications of interest. For the\nmost difficult systems, single-determinant reference states may be\ninsufficient, but low-complexity reference states may suffice. For this we\nintroduce a method for preparation of multi-determinant states on quantum\ncomputers.\n