Improving the accuracy of the energy estimation by combining quantum annealing with classical computation

TL;DR

This paper presents a hybrid approach combining quantum annealing and classical computation to improve the accuracy of ground state energy estimates in quantum chemistry, enabling more reliable results.

Contribution

It introduces a method to enhance quantum annealing accuracy by using classical pre-estimations and measurable energy statistics to validate results.

Findings

The combined method improves energy estimation accuracy.

Expectation value and variance thresholds guide QA reliability.

The approach is experimentally feasible for quantum chemistry applications.

Abstract

Quantum chemistry calculations are important applications of quantum annealing. For practical applications in quantum chemistry, it is essential to estimate a ground state energy of the Hamiltonian with chemical accuracy. However, there are no known methods to guarantee the accuracy of the estimation of the energy calculated by quantum annealing. Here, we propose a way to improve the accuracy of the estimate of the ground state energy by combining quantum annealing with classical computation. In our scheme, before running the QA, we need a pre-estimation of the energies of the ground state and first excited state with some error bars (corresponding to possible estimation error) by performing classical computation with some approximations. We show that, if an expectation value and variance of the energy of the state after the QA are smaller than certain threshold values (that we can calculate from the pre-estimation), the QA provides us with a better estimate of the ground state energy than that of the pre-estimation. Since the expectation value and variance of the energy can be experimentally measurable by the QA, our results pave the way for accurate estimation of the ground state energy with the QA.