Systematic Semistochastic Heat-Bath Configuration Interaction (SHCI) Benchmarks for Catalytically Relevant Strongly Correlated Systems

Quantum computing has long identified catalytic systems such as FeMoco, cytochrome P450, iron–sulfur clusters, and Ru-based complexes as promising targets for quantum advantage. However, rigorous classical baselines remain inconsistent due to varying problem definitions and convergence standards. Here, we present systematic Semistochastic Heat-Bath Configuration Interaction (SHCI) benchmarks across these flagship systems. By carefully converging the variational selection threshold and perturbative corrections, we obtain reproducible classical reference data including ground-state energies, Hartree–Fock overlaps, and detailed performance metrics (determinant counts, wall-clock time, etc.). Our results suggest that CYP450 and Ru clusters are classically tractable within sub-millihartree accuracy, whereas FeMoco and Fe–S clusters approach the edge of classical feasibility, marking credible milestones for early fault-tolerant quantum algorithms. These findings sharpen the practical boundary of quantum advantage and establish transparent, high-accuracy baselines for algorithm validation and resource estimation in quantum computational chemistry.