What is Google Quantum AI Magic State Cultivation on Willow?

Quantum computers use qubits (quantum bits), which can pick up errors from their surroundings, so error correction is used to protect the information. Useful programs also need a specific set of operations that must stay error-corrected, and single-use resources called magic states help create certain operations that are difficult to carry out directly, but some estimates suggest that making magic states could take up much of a future machine’s capacity. Magic state cultivation injects a noisy (error-prone) starting state into a small region of a chip, runs checks, and discards attempts that fail, keeping the states from the attempts that pass. Google Quantum AI researchers developed it in 2024 and have since reported about 40-fold fewer errors in states prepared with it on their Willow processor than in states prepared without it.

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