Google's Willow chip just shrank a 95% quantum overhead to a 99.99% magic trick 🪄

Google's Quantum AI team said Thursday it cut a major class of quantum errors roughly 40-fold on its Willow processor using a technique called magic state cultivation, marking the first time the method has worked on actual hardware rather than in theory or simulation. The result appeared in a paper published Thursday in Science, and Google framed it as evidence that further distillation of these so-called magic states "may never be needed in practice."

Quantum computers run on qubits, which can hold a blend of 0 and 1 at once but are highly sensitive to noise. Error correction spreads information across many qubits so mistakes can be caught and fixed, but a subset of harder operations cannot be protected the same way. Those operations require clean "magic states," single-use resources that have historically consumed up to 95% of a quantum machine's capacity, according to Google. The standard fix, magic state distillation, was laid out by Sergei Bravyi and Alexei Kitaev in 2004 and works by boiling many noisy states down into a few clean ones, but it demands sprawling qubit factories.

Cultivation, which Google researchers proposed in 2024, takes a different approach. A rough magic state is injected into a small patch of the chip and run through a chain of checks; failed attempts are discarded and surviving states are grown. "On Google Quantum AI's Willow processor, our protocol achieved an extraordinary 40-fold reduction in errors relative to un-cultivated states. And we got T-states with a record logical fidelity of 99.99%," Google said. The company added that only about 8% of attempts passed every check, meaning the chip discards more than nine of every 10 tries to produce a usable state.

The technique is one of the drivers behind a 2025 estimate by researcher Gidney that cracking RSA-2048 encryption could be done with under one million noisy qubits, a 20-fold reduction from his 20 million-qubit estimate in 2019. A March 2026 Google whitepaper co-authored with Ethereum Foundation researcher Justin Drake and Stanford cryptographers extended similar math to $BTC's elliptic curve cryptography, putting the bar at under 500,000 physical qubits. Willow currently has 105. Ethereum, Zcash, Sui and Near have published quantum-resistance plans, and Coinbase spent the week arguing that wallet migration should begin now, though no live network has demonstrated a break of existing cryptography.

Breaking RSA-2048 still requires error rates on the order of one in 10 billion, about a million times cleaner than what Google reported, and Drake has separately argued that AI-driven mathematics could threaten elliptic curve keys on classical machines before quantum hardware catches up.