Quantum benchmarking at QCE26 turned into an audit

This guide follows 55 talks on quantum benchmarking, error mitigation and classical simulation at IEEE Quantum Week 2026 in Toronto. The best results came from the people who check quantum claims. On Monday 14 September, in a workshop in Room 718A of the Metro Toronto Convention Centre, Salvatore Mandrà of Google Quantum AI described a classical simulation of a 56-qubit run by Quantinuum, a rival firm. It kept pace with the quantum machine. Mandrà said it also showed up errors in Quantinuum’s first published data, which the firm later revised. An ordinary computer had checked a quantum one and found a fault in its record. For quantum benchmarking, the job of measuring what these machines can do, the roles had been reversed. Every claim about a quantum computer rests on a measurement, and today’s machines are noisy. Each gate has a small chance of going wrong, qubits slowly lose their state and readout sometimes returns the wrong bit, so the longer a circuit runs, the more its answer fades toward random noise. Quantum benchmarking measures how bad this is. Some tests take the machine part by part, as with the error rate of one gate, while others run whole circuits…