Critical Limitations in Quantum-Selected Configuration Interaction Methods · HackerPapers discussions

Critical Limitations in Quantum-Selected Configuration Interaction Methods — HN submission

Thu, 06 Aug 2026 22:50:09 GMT

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

Author here. Background, for anyone who hasn't followed this fight: IBM's iron–sulfur SQD results (Sci. Adv. 2025) are one of the flagship "quantum computers are useful for chemistry now" claims, and a published critique (arXiv:2501.07231) argues the quantum samples never beat classical selected-CI at matched cost. That argument is still live. Both sides have been arguing about energies. Neither measured which electronic state these calculations actually converge to. So I measured it. ⟨S²⟩ comes out between 4.7 and 7.0 depending on the system and the subspace size, where the target these…

19 points; 1 discussion reply on HN. Paper and source history. A submission is not an endorsement.

Critical Limitations in Quantum-Selected Configuration Interaction Methods — HN submission

Wed, 29 Jul 2026 13:13:16 GMT

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

9 points; 6 discussion replies on HN. Paper and source history. A submission is not an endorsement.