MOUNTAIN VIEW, Oct. 17 -- Early readings from Google's quantum chip looked wrong, and research scientist Emma Rosenfeld traced the fault to drifting electrical equipment and temperature swings in the lab, according to Google's account of the experiment. Fixing it produced a result that Google published in Science on Thursday.

Google Quantum AI says its Willow processor made "magic states," a scarce resource that quantum computers consume as they run, at 99.99 percent logical fidelity, with a roughly 40-fold drop in errors compared with uncultivated states. Google has chased the error problem for years, and its 2023 error-correction result showed errors falling as qubit counts rose.

The stakes are about cost. Magic states can be used onl...