Google's Willow Chip Cuts Quantum Errors 40-Fold, Renewing Focus on Old Bitcoin Wallets
Key Takeaways
- •Google's Willow quantum chip cut errors roughly 40-fold when preparing magic states using a new cultivation technique, achieving a record fidelity of about 99.99%, according to findings published in Science.
- •Magic states are needed to run the non-Clifford gates behind algorithms like Shor's, and some estimates suggest up to 95% of a quantum computer's capacity could go toward producing them, a cost Google says its new method lowers.
- •Bitcoin's oldest holdings face greater theoretical risk because the network's early transaction format exposed public keys on the blockchain, and lost coins cannot be relocated to stronger protections by their owners.
- •Google estimated in March that a quantum computer fewer than 500,000 physical qubits could break Bitcoin and Ethereum wallet cryptography, and experts say the new result does not shift Q-Day timelines but makes those earlier estimates more credible.
- •Post-quantum preparation is progressing, with Coinbase describing Bitcoin's transition as complex and multi-year, NIST finalizing its first post-quantum standards in 2024, and Google setting an internal goal to adopt post-quantum cryptography by 2029.
Google said its Willow quantum chip cut errors about 40-fold when preparing “magic states,” specialized resources that quantum computers need to run certain advanced calculations. The findings were published this week in the journal Science.
The result came from a technique called magic state cultivation, which Google says now works on the Willow chip and reached a record fidelity of about 99.99%. Magic states are what allow error-corrected quantum computers to run the non-Clifford gates required for algorithms such as Shor's, which is why their production cost is a major factor in estimates of how large a machine would need to be. The announcement has drawn close attention from the cryptocurrency industry because a large enough quantum computer could, in theory, work out bitcoin secret keys — and some of the network's oldest coins have exposed public keys.
🚨JUST IN: Google may bring Bitcoin's Q-Day sooner than expected after its Willow chip cuts quantum errors 40x. Google says a technique called “magic state cultivation” now works on its Willow chip, cutting errors about 40x with a record 99.99% accuracy. Q-Day is the moment a… pic.twitter.com/6fquMJURPH
— Coin Bureau (@coinbureau) October 15, 2026
Some estimates say up to 95% of a quantum machine's capacity could go toward producing magic states. Google says its new method lowers that cost.
How Google's Cultivation Method Works
Cultivation starts with a rough, noisy state on a small part of the chip. Researchers then run measurements to check for errors and throw out flawed attempts. Google reported about 99.99% fidelity, which shows how closely the finished states matched the target. That number applies only to the states that passed inspection.
Willow kept about 8% of its attempts after the checks. For every 100 tries, about eight made it through.
Google researchers Craig Gidney, Noah Shutty and Cody Jones began developing the approach in 2024. The team says larger demonstrations are still needed before it can support practical quantum computing.
Why Bitcoin's Oldest Wallets Face More Risk
A large quantum computer running Shor's algorithm could, in theory, work out a secret key from a public key. Mathematician Peter Shor published the method in 1994, but nobody has demonstrated it at that scale.
Some of bitcoin's oldest holdings have had their public keys exposed since they were mined. That visibility traces to the network's early design: bitcoin's first transaction format paid directly to public keys, leaving them fully visible on the blockchain, while newer address types hash the public key and reveal it only when a coin is spent. Lost coins add to the problem because their owners cannot move them to stronger protections.
In March, Google estimated that a quantum computer with fewer than 500,000 physical qubits could break the wallet cryptography used by Bitcoin and Ethereum. That estimate already assumed efficient magic state production.
Experts Weigh In on Q-Day Timelines
Q-Day is a shorthand for the moment a quantum computer could break the cryptography protecting existing wallets. Experts offered differing views on whether the new result moves that timeline.
Nic Carter of Castle Island Ventures said there is no imminent threat, but noted that AI is speeding up progress on error correction. Project Eleven CEO Alex Pruden said the result does not shift Q-day timelines because earlier estimates assumed the technique. He said it makes those estimates more credible.
Old coins have also been moving. On Oct. 7, 100.02 BTC untouched since July 2010 moved, worth about $8.5 million — coins that had been dormant for more than 15 years. Such transfers do not prove holders are reacting to quantum fears, since coins can move for wallet changes or sales.
Earlier this week, Coinbase published technical priorities for Bitcoin's post-quantum transition, calling the process complex and multi-year. Post-quantum cryptography refers to methods designed to withstand attacks from quantum computers, and the U.S. National Institute of Standards and Technology finalized its first standards for such methods in 2024. Google, for its part, has set an internal goal of moving to post-quantum cryptography by 2029. The larger demonstrations Google's team said are still needed, together with the multi-year transition Coinbase outlined, are the near-term markers to watch.
Source: CoinCentral
