Google tests magic state cultivation on Willow, reports 40-fold error reduction

Google Quantum AI says it experimentally demonstrated a method called magic state cultivation on its Willow quantum processor, in work reported in Science on October 15. The method addresses a difficult part of fault-tolerant quantum computing: preparing resource states needed to carry out certain error-corrected operations.

Google reports a 40-fold reduction in errors for the cultivated states compared with states prepared without cultivation, and a logical fidelity of 99.99% for T-states. The researchers also transferred an encoded state between a small color code and a surface code, a step toward making the technique fit existing hardware designs. These are experimental results for a particular protocol and device, not evidence that a broadly useful fault-tolerant quantum computer is already operating.

The distinction matters because resource-state preparation can consume a substantial share of a future quantum computer's physical capacity. Google says the technique must still be demonstrated at larger scale, with technical challenges unresolved. The announcement advances a quantum-computing component rather than releasing a new AI model or a commercial computing service.