Practical demonstration of high-accuracy electronic structure on a quantum computer

Quantum computing offers a promising path toward accurate electronic structure calculations, especially for systems where classical methods face limitations. However, most quantum demonstrations to date have focused on simplified systems, lacking the quantitative precision required for direct comparison with experiment. In this work, we present a method tailored for implementation on existing and near-term quantum hardware. Our focus is on predicting a quantity that can be directly compared with experiment, enabling a meaningful benchmark of quantum hardware for chemical applications. We use a compact representation that is achieved through physically motivated simplifications of the wavefunction, reflecting a general strategy of adapting the representation to known properties of the system, even though the degree of simplification is system-dependent. We validate this approach by computing the total energy of neutral helium using the Quantinuum H1-1 ion-trap quantum computer, enabling us to determine the ionization potential to within true chemical accuracy of the experimental value. This represents a meaningful step toward practical quantum computational chemistry and establishes a framework for benchmarking future quantum hardware using real-world chemical systems.