Measurement Reduction in Orbital-Optimized Variational Quantum Eigensolver via Orbital Compression

TL;DR

This paper introduces an orbital compression technique for the variational quantum eigensolver (VQE) that enhances accuracy and reduces measurement costs in quantum chemistry simulations on near-term quantum devices.

Contribution

The authors develop an orbital-optimized VQE framework using orbital compression with frozen natural orbitals and split virtual orbitals to improve accuracy and efficiency.

Findings

FNO-OO-VQE and SVO-OO-VQE improve variational accuracy.

Measurement costs are substantially reduced.

Effective in simulating molecular dissociation and decomposition energies.

Abstract

The variational quantum eigensolver (VQE) has emerged as one of the leading quantum algorithms for solving electronic structure problems on near-term noisy intermediate-scale quantum devices. However, its practical application to quantum chemistry remains challenging due to the limited coherence time, imperfect quantum gate fidelity, and the large number of measurements required, which together confine current electronic structure simulations to relatively small active spaces. In this work, we present an orbital-optimized VQE framework based on orbital compression, designed to improve the accuracy of electronic structure calculations while maintaining relatively small active spaces. Frozen natural orbitals (FNO) and split virtual orbitals (SVO) are first employed to construct compact active spaces for VQE simulations, leading to the FNO/SVO-VQE approach. Orbital optimization is then incorporated to further recover electron correlation effects, resulting in the FNO/SVO-OO-VQE methods. We apply the proposed method to simulate potential energy surfaces for molecular dissociation and the activation energy of formaldehyde decomposition. Numerical results demonstrate that both FNO-OO-VQE and SVO-OO-VQE improve the variational accuracy while substantially reducing measurement cost.