Explicitly correlated wavefunctions as classical seeds and property references for sample-based quantum diagonalization beyond the Born–Oppenheimer approximation
Year: 2026
Type: preprint
Abstract: This work evaluates how well hybrid classical–quantum simulation methods capture not only the energy of small atomic and molecular systems, but also their other properties: contact densities, molecular structure, and state identity — the spin sector a computed state actually lives in. It employs explicitly correlated Gaussian (ECG) wavefunctions both as references for evaluating these properties and as classical seeds for sample-based quantum diagonalization (SQD), on the simulator and on IBM quantum hardware. Our testbeds — positronium hydride, the muonic heliumlike ions, the HD+ molecular ion, and the positronium anion and molecule — realize three typical failure regimes: boxes that lack the property no matter how configurations are selected, boxes that hold it exactly with no selection needed, and the middle regime where the selection itself decides. In every regime the property error dwarfs the energy error: a subspace can converge the energy to microhartrees while misstating an annihilation rate, a bond length, or the spin by whole percent. Property fidelity, not energy, is the discriminating test of a multicomponent simulation.
Author: Chancé, Alain
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7208710347