Quantum Calculation: Google takes a step with its Willow chip and revives debate on Bitcoin

A reduction of errors by forty on Google's Willow chip

Google Quantum AI unveiled in the journal Science on Thursday, October 15, 2026, an experimental result obtained on its Willow processor, reports the Journal du Coin and Decrypt. Researchers in the technology group have implemented a process that reduces the errors generated in creating specific states necessary for advanced quantum calculations by about 40 times.

This technical announcement comes as the cryptoactive world wonders about the future vulnerability of its cryptographic mechanisms. According to CoinDesk, the debates surrounding the quantum threat for Bitcoin usually focus on the raw size of the theoretical machines, often neglecting the material fraction essential for the simple preparation of calculations.

On the markets, Alphabet's share closed at $340.59 on October 16, 2026, showing a 2.47 per cent decline according to Yahoo Finance data. For its part, the price of Bitcoin stood at 72,652.00 euros on October 17, 2026 in the morning, down 0.69% over 24 hours according to CoinGecko's readings.

The technique of "cultivation" facing the burden of magical states

Quantum calculations are based on qubits, which are particularly unstable in the face of heat, tremor and parasitic signals, CoinDesk recalls. To stabilize the system, the designers group together several physical quadits to form logical quadits protected against disturbance. However, certain essential instructions, called T-doors, cannot be executed directly by this classic correction mechanism, says the Journal du Coin. Without these operations, quantum calculators would do no better than a conventional computer.

The execution of T doors requires the manufacture of single-use resources called "magic states". According to Decrypt and Le Journal du Coin, the production of these ephemeral components can mobilise up to 95% of the total capacity of a quantum machine. In 2004, Sergei Bravyi and Alexei Kitaev had imagined a distillation approach, requiring the development of complex plants of quibs on chips.

To overcome this constraint, Google uses a method called "cultivation", theorized in 2024 by Craig Gidney and his colleagues. According to the Journal du Coin, the team led by Emma Rosenfeld and Craig Gidney injected a raw state onto the Willow chip before performing a series of strict checks and eliminating failed tests. The experiment used no more than 54 of the 105 physical quarbits of the migrant processor from a color code of distance 3 to a surface code of distance 5.

The resulting T states show a 99.99% fidelity, which corresponds to a 40-fold breakdown of errors compared to non-filtered states, notes the Journal du Coin. This drastic selection nevertheless has a modest yield: Decrypt and CoinDesk report that 92% of attempts are ruled out, only a rate of about 8% of states victoriously passing the verification stages.

Estimates of resources to threaten Bitcoin cryptography

The impact of these advances is of direct concern to block chain security. According to a white paper published in March 2026 by Google, co-edited with Justin Drake and Dan Boneh and quoted by Decrypt and the Coin Journal, a superconducting quantum machine with less than 500,000 physical qubits would be enough to break the elliptical cryptography used by Bitcoin and Ethereum. This theoretical work already incorporated the hypothesis of a successful cultivation of magical states.

The theoretical material threshold required to break a dry keyp256k1 was estimated at 813 logical quibits at the end of August, reports the Journal du Coin. At the same time, estimates of the factorization of an RSA-2048 key have declined sharply over the years, from 20 million noisy qubits in 2019 to less than one million in May 2025 under the impetus of Craig Gidney's calculations.

However, the Willow chip currently has only 105 physical quibits, Decrypt recalls. In addition, sources point to the considerable gap between current experience and actual piracy. Breaking an RSA-2048 encryption would require an error rate of about one in ten billion, which implies an accuracy of about one million times higher than the level observed on Willow, according to Decrypt and the Journal du Coin.

The Journal du Coin nevertheless mentions a law of scale from the scientific publication: anomalies decrease with the cube of material noise. Thus, reducing the noise on Willow by half would compress the error ratio to about two per 100,000. Google has however specified that this method of cultivation still needs to be proven on a wider scale and requires developments to fit into real-time operations.

Exhibition of old addresses and recent fund movements

The theoretical threat particularly concerns certain categories of Bitcoin addresses. CoinDesk explains that a conventional transaction requires a secret key to validate the transfer and then exposes the corresponding public key to the public registry. Using the algorithm presented in 1994 by mathematician Peter Shor, an attacker with an operational quantum computer could reconstruct the private key from the public key to sign fraudulent transactions.

A physically stored recovery phrase does not protect against this risk, as public data is already on the chain, CoinDesk recalls. If later address formats hide the public key under a digital footprint (or hash) until the first expense, Bitcoin's oldest assets have public keys exposed since their creation by mining. Lost units whose secret keys have disappeared can never be transferred to new secure formats, remaining exposed to future attacks.

These vulnerabilities fuel network transfers. On October 7, 2026, 100.02 BTC sleeping since July 2010 were transferred after more than 16 years of inactivity, worth about $8.5 million, reports CoinDesk. During August 2026, six immobile portfolios from 2011 to 2014 had also moved BTC 553.59, or nearly $40 million at that time. CoinDesk notes, however, that these transactions alone do not show a quantum-related panic, with portfolio reorganizations or sales being other common explanations.

Sector preparations and institutional timetable

Faced with this technological trajectory, the cryptoecosystem is stepping up its preventive measures. According to Decrypt, Coinbase defended the need to start moving without delay to resistant systems, while the Sui network experimented with quantum-protected transactions in a test environment. Other protocols such as Ethereum, Zcash and Near are also preparing adaptation strategies.

On Bitcoin, the Corner Journal reports that community initiatives are under consideration, including BIP-360 and BIP-361 proposals. Circle has also been broadcasting since August a public table measuring the distance between the laboratory-demonstrated qubits and the number required to break current algorithms.

Government agencies also set strict deadlines. The National Institute of Standards and Technology (NIST) is planning to depreciate vulnerable cryptographic protocols after 2030, before issuing a ban after 2035, recalls the Journal du Coin.

Finally, Decrypt reports a warning from researcher Justin Drake in early October 2026. The latter recommended that large Bitcoin holders forward their assets to blank addresses that had never signed a transaction. According to Decrypt, Justin Drake believes that advances in mathematics guided by artificial intelligence could compromise elliptical curves on standard computing hardware in the space of "months and not years", exposing the cryptographic industry to a simultaneous double pressure combining IA and quantum calculation.