● Covered by 1 source · 1 reportMedium impact1 negative
Spin Audit Questions Accuracy of Quantum Chemistry Benchmarks for Iron-Sulfur Clusters
Key points
- SQD/QSCI benchmarks on iron-sulfur clusters were audited for spin state convergence.
- No audited execution returned the named singlet at a competitive energy.
- The lowest root found had an ⟨S²⟩ of 1.37, not near a singlet state.
- The audit recommends including measured spin moments in future benchmarks.
Audit of Quantum Chemistry Benchmarks
A recent audit examined the spin state convergence of Sample-based Quantum Diagonalization (SQD, also known as QSCI) benchmarks. These benchmarks, particularly those on [2Fe-2S] and [4Fe-4S] iron-sulfur clusters, have been presented as key evidence for the utility of quantum chemistry in practical applications.
Convergence Issues Identified
The audit investigated whether, upon energy convergence, the calculations actually converged to the target spin state. Using methods such as rotation-invariant spin audits, exact determinant-space ⟨S²⟩, and invariant S²-Gram spectra, the study found that none of the audited executions achieved the named singlet state at a competitive energy.
For instance, at the largest published dimension (5.625×10⁷ determinants), the numerically stable lowest root was approximately 170 mHa below the published energy but exhibited an ⟨S²⟩ value of 1.37, which is not indicative of a singlet state. Furthermore, the released hardware samples showed no energy advantage over uniform-random controls.
Implications for Quantum Chemistry
These findings suggest that the reported energy convergence in some quantum chemistry benchmarks may not accurately reflect convergence to the desired chemical state. This has implications for the interpretation and reliability of results from these methods, particularly in complex systems like iron-sulfur clusters.
The audit recommends that measured spin moments become a mandatory output for future quantum chemistry benchmarks to ensure the accuracy and validity of the reported states.
Reproducibility and Data Availability
The authors have provided a comprehensive archive containing the paper, analysis scripts, result archives, and a reproduction map. This allows other researchers to reproduce and verify the audit's findings. Large companion files, including the flagship-dimension amplitude archive and certification vector blocks, are also available with SHA-256 hashes for integrity checking.
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Reporting from
A new audit of Sample-based Quantum Diagonalization (SQD/QSCI) benchmarks on iron-sulfur clusters found that calculations did not converge to the target spin state, despite energy convergence. This raises concerns about the reliability of these headline quantum chemistry demonstrations, suggesting that reported energies may not correspond to the intended chemical states.