We present high-precision quantum computing simulations of three-body atoms (He and ${\mathrm{H}}^{-}$) and molecules $({\mathrm{H}}_2{}^{+} \text{and} {\mathrm{HD}}^{+})$, the latter being studied beyond the Born-Oppenheimer approximation. The noniterative disentangled unitary coupled-cluster variational quantum eigensolver (NI-DUCC-VQE) [M. Haidar et al., Quantum Sci. Technol. 10, 025031 (2025)] is used. By combining a first-quantized Hamiltonian with a minimal complete pool of Lie algebraic excitations, we construct a compact Ansatz with a gradient-independent construction, avoiding costly gradient evaluations and yielding efficient computational scaling with both basis size and electron number. It enables rapid convergence, and no barren plateaus are observed in the tested systems. Energy errors as low as ${10}^{-11}$ a.u. with state fidelities only limited by arithmetic precision are achieved in only a few thousand function evaluations in all four systems. These results make three-body atoms and molecules excellent candidates for benchmarking and testing on current noisy intermediate-scale quantum devices. Further, our approach can be extended to more complex systems with larger basis sets, taking advantage of the efficient scaling of qubit requirements to study electronic correlations and nonadiabatic effects with high precision. We also demonstrate the applicability of NI-DUCC-VQE for simulating higher-order effects such as relativistic corrections and hyperfine interactions.

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• Atomic & molecular structure
• Quantum algorithms & computation
• Quantum algorithms for chemical calculations
• Atoms
• Molecules
• Schroedinger equation
• Variational approach