Spin audit of SQD/QSCI quantum-chemistry benchmarks on iron–sulfur clusters

Researchers at Pure State Labs conducted a critical audit of sample-based quantum diagonalization (SQD) benchmarks on iron–sulfur clusters, questioning whether previous demonstrations actually converged to their target spin states. Their analysis found that none of the audited executions returned the claimed singlet state at competitive energies, with the lowest energy solution showing a spin value of 1.37 rather than the expected singlet, and no advantage over random controls. The authors recommend that measured spin moments become a mandatory benchmark output for quantum chemistry calculations.