Google's Quantum Error Cut Lowers Estimate for Bitcoin-Breaking Machine

A Google research paper in Science dated October 15 describes a method that slashed errors on the company's Willow chip by roughly 40 times, which the firm calls a first-of-its-kind solution to a significant quantum computing challenge.

A future quantum computer might be able to break the cryptography safeguarding Bitcoin (BTC). Current devices remain far too weak. Google's technique, the firm says, could lower the size required for such a hypothetical machine.

How Google Cultivated a Cleaner Magic State

Quantum computers rely on specific operations built from elements known as magic states. Google notes that generating clean versions of these states might, by some estimates, consume as much as 95% of a machine's capacity.

Google's technique, dubbed magic state cultivation, uses a process of elimination. The Willow chip begins with an imprecise, flawed state, performs multiple checks, and eliminates each unsuccessful outcome. The remnants are then cultivated into a significantly purer state.

States created with this cultivation method on the Willow chip exhibited roughly 40 times fewer errors compared to standard generation. Google states this achieved a record fidelity of 99.99%, an indicator of precision.

The team argued that, if the technique scales, it could drastically cut the size of a machine needed for useful work. Google has employed this machine-size metric before when evaluating the danger posed to Bitcoin.

“This work is the first demonstration of a practical solution to one of quantum computing’s most severe resource bottlenecks. It demonstrates, on real hardware, that we can efficiently create these crucial magic states,” the team wrote in a blog post.

The Bitcoin Calculation Implied by Google’s Work

In theory, a sufficiently advanced quantum machine could derive a Bitcoin wallet’s private key from its public key. Last March, Google calculated that an attack of this kind would require less than 500,000 qubits.

Such an operation also demands tens of millions of magic-state-dependent steps. The cultivation approach has already reduced a comparable projection. In 2025, Google’s Craig Gidney applied the method to downsize the theoretical machine able to break RSA, a common encryption standard.

Google’s existing chip, Willow, contains just 105 qubits, a figure vastly beneath the 500,000 threshold. The company acknowledged this constraint.

“Of course, we still need to demonstrate magic state cultivation at a larger scale to make it realistic for practical quantum computing, and plenty of technical challenges remain,” the Google team stated.

Despite this, specific coins would be simpler to target should such a machine emerge. Glassnode figures place 6.04 million BTC, representing 30.2% of all Bitcoin ever mined, in wallets where public keys are exposed. The total value of this hoard stands at approximately $494 billion, given a Bitcoin price of $81,857, which had risen 1.19% in the prior day.

The bulk of those coins remain mobile and could be shifted to more secure locations. Yet a study from June predicted that roughly 2.3 million BTC lack this possibility. These assets are lost, dormant, or originate from the very earliest era of Bitcoin.

The fate of these stranded coins has yet to be settled. Coinbase described it as a knotty problem in an October 13 article addressing Bitcoin’s migration toward quantum-resistant cryptography.

The exchange enumerated possibilities reaching from immobilizing old coins to creating reclaim tools for their owners. It additionally advocated a phased plan permitting active wallets to adopt quantum-resistant protections ahead of schedule. Coinbase characterized the piece as a contribution to an ongoing debate, not a definitive stance.

A migration commenced in 2026, according to the June study, might conclude between 2029 and 2031. That timeframe would precede even a best-case 2035 debut for a machine capable of breaking codes. Google did not offer a schedule for scaling up its own technique.