Google Quantum AI Cuts Magic State Errors 40-Fold on Willow Processor

Google Quantum AI published a paper in Science on Thursday showing that a technique called "magic state cultivation" cut errors about 40-fold on its Willow processor, producing single-use magic states with 99.99% logical fidelity. According to Google, some estimates place the cost of producing clean magic states—single-use resources consumed during complex quantum operations that standard error correction cannot protect—at up to 95% of a quantum computer's entire capacity. Unlike traditional magic state distillation proposed in 2004, which requires large dedicated qubit factories, Google's 2024 cultivation method acts as a filter on a tiny patch of the chip; however, only about 8% of attempts passed every check, meaning the hardware discards more than nine out of every 10 tries. While hardware validation of cultivation backs earlier theoretical estimates that RSA-2048 encryption could be broken with under 1M noisy qubits and Bitcoin's elliptic curve cryptography with fewer than 500k physical qubits, this experiment used at most 54 of Willow's 105 qubits and remains roughly 1M times noisier than the 1-in-10B error rate needed to factor RSA-2048. "On Google Quantum AI's Willow processor, our protocol achieved an extraordinary 40-fold reduction in errors relative to un-cultivated states. And we got T-states with a record logical fidelity of 99.99%." — Google Quantum AI