Below Threshold: What Google's Willow Chip Actually Proved
In December 2024, Google published a Nature paper announcing that their Willow chip demonstrated quantum error correction below the threshold — the point at which larger codes become more reliable, not less. The headline about “10^25 years of classical computation” was technically true and mostly a distraction. The real result is more important and less flashy: for the first time, a quantum processor demonstrated that logical error rates decrease exponentially as the code grows. This is what scalable quantum computing looks like at its first credible step.