Shortcuts for adiabatic and variational algorithms in molecular simulation
Phys. Rev. A 114, 042619 – Published 20 October, 2026
DOI: https://doi.org/10.1103/rpnt-v9mr
Abstract
Quantum algorithms offer a promising route toward computational advantage, but current implementations remain constrained by limited coherence and gate errors, making circuit complexity and noise sensitivity critical considerations. Here we develop a shortcut-to-adiabaticity strategy for molecular ground-state preparation and apply it to both digitized adiabatic quantum computing and the variational quantum eigensolver. In the adiabatic framework, we construct an approximate counterdiabatic (CD) Hamiltonian using a nested-commutator expansion. For the molecular systems considered, the CD correction accelerates state preparation and improves energy convergence in the fast-evolution regime, enabling a target accuracy to be reached with a lower implemented-operator count. In the variational setting, we introduce the adiabatic gauge Ansatz, obtained by promoting the Pauli-string components generated by the approximate adiabatic gauge potential (AGP) to independent variational generators. We further propose a reduced variant that retains only Pauli generators with weight not larger than 2, substantially reducing the Ansatz size while maintaining competitive accuracy over the regimes considered. Benchmarks on and show that the proposed Ansätze achieve accuracies competitive with established approaches such as the unitary coupled-cluster Ansatz with single and double excitations (UCCSD). Experiments on the IBM_basquecountry superconducting quantum processor, together with simulations under depolarizing noise, show that the reduced CD-inspired Ansatz yields smaller energy discrepancies than the UCCSD under the noise conditions considered. Overall, our results demonstrate how AGP-inspired operator structures can be used to balance accuracy and implementation cost in molecular simulations on current noise-limited quantum hardware.
