Reference-State Error Mitigation: A Strategy for High Accuracy Quantum Computation of Chemistry

Decoherence and gate errors severely limit the capabilities of state-of-the-art quantum computers. This work introduces a strategy for reference-state error mitigation (REM) of quantum chemistry that can be straightforwardly implemented on current and near-term devices. REM can be applied alongside existing mitigation procedures, while requiring minimal post-processing and only one or no additional measurements. The approach is agnostic to the underlying quantum mechanical ansatz and is designed for the variational quantum eigensolver. Up to two orders-of-magnitude improvement in the computational accuracy of ground state energies of small molecules (H2, HeH+, and LiH) is demonstrated on superconducting quantum hardware. Simulations of noisy circuits with a depth exceeding 1000 two-qubit gates are used to demonstrate the scalability of the method.

Automated summary

This work introduces a strategy called reference-state error mitigation (REM) for quantum chemistry, which can be implemented on current and near-term devices. REM can be applied alongside existing mitigation procedures with minimal post-processing and additional measurements. The method is designed for the variational quantum eigensolver and shows significant improvement in the computational accuracy of ground state energies of small molecules on superconducting quantum hardware. Simulations of noisy circuits with a depth exceeding 1000 two-qubit gates demonstrate the scalability of the method.