Google shows magic state cultivation working on its Willow quantum chip

Google’s Quantum AI team has shown that magic state cultivation works in practice on its Willow processor. The experiment was published in Science on 15 October 2026, and Google says it is the first time the method has run on physical hardware.

A universal quantum computer, one able to run any quantum program, needs certain operations that are usually made by consuming special inputs called magic states. Each one is gone once used, and making them with few errors is expensive: Google cites estimates that up to 95% of a quantum computer’s capacity could go into producing them.

Cultivation, designed in 2024 by Google’s Craig Gidney, Noah Shutty and Cody Jones, works like a filter. A noisy state is placed in a small patch of the chip, rounds of coordinated measurements check it for errors, and flawed attempts are thrown away. The state that survives is purified while it grows into a larger, usable encoding.

On Willow, cultivated states had about 40 times fewer errors than states prepared without cultivation, and the team reached a logical fidelity of 99.99% for the magic states known as T-states, a record. The paper puts the fidelity at 0.9999 or better while keeping 8% of attempts.

Getting there took new engineering. Noise from drifting electrical equipment and temperature changes in the lab had made the team’s usual benchmark unreliable, so it added extra control and devised a new benchmark that uses cultivation to measure itself.

The team also moved a purified state from one kind of error-correcting code, a colour code, into a larger surface code, a more established scheme. Google says cultivation still has to be shown at a larger scale before it is practical, and that many technical challenges remain.