Google Says Willow Chip Reduces Magic State Errors by Approximately 40-Fold

Google Quantum AI team published a paper in Science, announcing that a technique called magic state cultivation reduces magic state errors by approximately 40-fold on the Willow processor, producing T states with a logical fidelity of 99.99%. Magic states are one-time resources required to run useful quantum programs; according to estimates cited by Google, the cost of manufacturing magic states can account for up to 95% of a quantum computer's total capacity.

The research notes that traditional magic state distillation, proposed by Sergei Bravyi and Alexei Kitaev in 2004, requires a large number of dedicated qubits; Google's 2024 cultivation approach acts more like a filter: injecting rough magic states into a small chip region, running a series of checks, and discarding attempts detected as defective. In the experiment, about 8% of attempts passed all checks, requiring over 90% to be discarded to retain one clean state. This experiment used at most 54 of Willow's 105 qubits; the paper states that factoring RSA-2048 requires a magic state error rate of about 10^-10, still roughly a million times cleaner than current results. Gidney estimated in 2025 that the cultivation technique reduces the number of noisy qubits needed to break RSA-2048 from 20 million in 2019 to under one million.

[ChainCatcher]