Google's Quantum AI team demonstrated that magic state cultivation reduced errors by about 40 times on the Willow processor. The team published the paper in Science on Thursday. Google said the protocol produced T-states with a record logical fidelity of 99.99%. Cultivation had previously been tested only in theory and computer simulations.
Only about 8% of attempts passed every check. The chip therefore discarded more than nine out of every 10 attempts to retain one clean state. The experiment used at most 54 of Willow's 105 qubits.
Quantum computers use qubits, which can hold a blend of 0 and 1 and allow machines to explore many answers in parallel. Heat or electrical noise can disrupt qubits and ruin calculations. Error correction spreads information across many qubits so that mistakes can be detected and corrected. Error correction protects simple operations well, but useful programs also need harder operations that cannot be protected in the same way. Quantum computers manufacture magic states for those harder operations, consuming each state when used.
Google said some estimates put the production of clean magic states at up to 95% of a quantum computer's entire capacity. Physicists Sergei Bravyi and Alexei Kitaev introduced magic state distillation in 2004. Distillation converts many noisy magic states into a few clean states but requires large groups of qubits dedicated to that task.
Google researchers proposed magic state cultivation in 2024 as a less costly approach. Cultivation injects a rough magic state into a small patch of the chip and runs a sequence of checks. The process discards every attempt with a detected flaw and continues expanding the states that pass. The researchers' 2024 paper suggested that further distillation "may never be needed in practice."
Cultivation contributed to Gidney's 2025 estimate that RSA-2048 encryption could be broken with under a million noisy qubits. That estimate represented a 20-fold reduction from Gidney's 2019 estimate of 20 million qubits. However, the new experiment does not enable wallet theft. The paper notes that factoring an RSA-2048 key would require magic states with errors around one in 10 billion, roughly a million times cleaner than those achieved.
A Quantum AI whitepaper in March estimated that breaking Bitcoin's elliptic curve cryptography would require fewer than 500,000 physical qubits. Ethereum Foundation researcher Justin Drake and Stanford cryptographer Dan Boneh co-authored the whitepaper. Bitcoin's elliptic curve cryptography prevents someone from deriving a private key from a public address. Google's Quantum Echoes experiment last October achieved the first verified quantum speedup on real hardware.
Cheaper quantum computers would bring useful applications, such as designing drugs and new materials, closer. Cheaper quantum computers would also bring closer the possibility of breaking encryption that protects bank logins and Bitcoin wallets. Google says the next step is running cultivation at a larger scale. The team projects that halving Willow's underlying hardware noise would reduce magic state errors to about two in 100,000. The team says errors in the cultivation process shrink with the cube of the chip's noise level.