Accounting for Errors in Quantum Algorithms via Individual Error Reduction

TL;DR

This paper presents a simple error correction scheme for quantum algorithms that measures observables with and without individual error sources to improve accuracy, especially useful for near-term quantum computers.

Contribution

The authors introduce a novel error accounting method that significantly reduces the required qubit quality for accurate quantum computations.

Findings

Error correction reduces qubit quality requirements by up to two orders of magnitude.

The scheme improves the accuracy of variational quantum eigensolver calculations.

Applicable to various noise sources like damping, dephasing, and thermal noise.

Abstract

We discuss a surprisingly simple scheme for accounting (and removal) of error in observables determined from quantum algorithms. A correction to the value of the observable is calculated by first measuring the observable with all error sources active and subsequently measuring the observable with each error source removed separately. We apply this scheme to the variational quantum eigensolver, simulating the calculation of the ground state energy of equilibrium H$_2$ and LiH in the presence of several noise sources, including amplitude damping, dephasing, thermal noise, and correlated noise. We show that this scheme provides a decrease in the needed quality of the qubits by up to two orders of magnitude. In near-term quantum computers, where full fault-tolerant error correction is too expensive, this scheme provides a route to significantly more accurate calculation