Google’s experiment with the Willow processor reduced the error rate of special quantum states by 40 times, reigniting debate over when quantum computers capable of threatening cryptocurrency security might be developed.
According to The Block, Google Quantum AI announced on October 15 that it had successfully tested a method called “magic state cultivation” on its Willow processor. The work targets one of the major bottlenecks in developing powerful, reliable quantum computers.
Quantum computers need special quantum states called “magic states” to perform a wide range of operations. Preparing these states at high quality requires considerable resources; some estimates suggest that up to 95 percent of a machine’s capacity could be devoted to this task.
Error rate fell 40 times in the experiment
The method, which Google researchers began developing in 2024, works like a filter. A quantum state prepared in a small chip region is controlled through coordinated measurements; faulty attempts are discarded to produce a state with a lower error rate.
In the Willow experiment, the error rate of quantum states processed this way was 40 times lower than that of unprocessed states. For states called T-states, logical fidelity—the measure of how closely they match the target quantum state—also reached 99.99 percent.
According to the researchers, larger-scale experiments are still needed before the method can be used in practical, fault-tolerant quantum computers.
How close is crypto’s feared “Q-day”?
Q-day is a term used for the point at which quantum computers become powerful enough to break some of the cryptographic security methods in use today. Such a capability could threaten not only the digital signatures that authorize cryptocurrency transactions, but also public-key systems across internet and financial infrastructure.
Nic Carter, co-founder of Castle Island Ventures, believes AI-powered improvements are accelerating progress in quantum computing. In Carter’s view, Google’s experiment is another example of this trend; however, there is no imminent threat, and engineering challenges remain before large-scale, fault-tolerant machines can be built.
Alex Pruden, CEO of Project Eleven, points to a different consideration: Since this method was already assumed in earlier calculations, the experiment does not necessarily have to move up the Q-day timeline. According to Pruden, the results confirm the assumptions behind current resource estimates, making those estimates more credible.
This long-term risk is also driving the crypto sector to develop security methods resistant to quantum attacks. Google’s result does not mean that a wallet’s encryption has been broken today; it shows progress on one of the technical steps needed to achieve that capability in the future.
Not investment advice.