Google’s New Quantum Milestone Puts Bitcoin In Focus

Google demonstrated on its Willow processor a method that greatly reduces errors during the creation of a component essential to universal quantum computing. This advance brings research closer to useful quantum computers, but it does not yet allow breaking the signatures that secure bitcoins.

Google reduces a major quantum error by 40 times

While quantum computing targets bitcoin, the Google Quantum AI team announced on October 15th that it successfully tested the “magic state cultivation” on real hardware. This technique aims to produce very reliable quantum states, necessary for performing certain complex operations on an error-corrected quantum computer.

The results present several precise advances :

• The error rate was reduced by about 40 times compared to untreated states ;
• The researchers achieved a logical fidelity of 99.99% ;
• The experiment was conducted on Willow, Google’s quantum processor ;
• Only 8% of the trials were retained after error detection ;
• The method still needs to work on a much larger scale.

Magic states allow performing operations essential to universal quantum computing. However, their production represents a considerable cost. According to some estimates, it could consume up to 95% of a quantum machine’s capacities, to the detriment of the computations themselves.

Google’s technique acts as a filter. It first places an imperfect state in a small area of the processor, then performs several coordinated measurements to discard defective trials. The retained states are then transferred to a broader error-correcting code.

Google presents this experiment as the first hardware demonstration of a practical solution to this bottleneck. The company, while acknowledging that many technical challenges remain, explains:

This success turns a major theoretical idea into an experimentally demonstrated reality.

BTC remains out of reach of current machines

The announcement does not mean that Willow can recover the private keys of Bitcoin wallets. It improves the quality of a resource needed for future quantum computations but does not provide the number of qubits nor the stability required to perform a complete cryptographic attack.

Bitcoin notably uses the ECDSA signature algorithm on the secp256k1 curve. A sufficiently powerful quantum computer could apply Shor’s algorithm to calculate a private key from a public key. It could then produce a valid signature and transfer funds without the owner’s authorization.

In a study published in 2026, Google researchers estimated that an attack on this cryptography could require at most 1450 logical qubits and about 70 million Toffoli-type operations. With some assumptions on hardware and error correction, fewer than 500,000 physical qubits could suffice to perform the computation in a few minutes.

These estimates remain very far from current capabilities. Corrected logical qubits require many physical qubits because quantum systems remain sensitive to noise and quickly lose the information they manipulate. Google’s demonstration concerns an element of this future architecture, not a cryptographically operational machine.

The 99.99% fidelity also does not correspond to the overall processor precision. It measures the quality of a magic state produced during the experiment. Presenting this figure as proof that a quantum computer would be almost ready to attack Bitcoin would therefore be misleading.

Q-Day nevertheless requires preparing Bitcoin

“Q-Day” designates the moment when a quantum computer will be able to compromise current cryptographic systems. No reliable date allows predicting this event, but a bitcoin migration would require several years of research, development, and coordination.

Not all bitcoins have exactly the same exposure. Funds placed at addresses whose public key has never been revealed benefit from extra protection thanks to hashing. Old reused addresses, pay-to-public-key outputs, and transactions broadcast in the mempool expose their public key more.

A fast enough machine could theoretically calculate a private key between a transaction’s broadcast and its confirmation. Old bitcoins attributed to Satoshi Nakamoto or lost for a long time raise another problem: their owners may no longer be able to migrate their funds to a post-quantum system.

The solution involves new signatures resistant to quantum computing. However, their integration would require a protocol upgrade, new address formats, and a method for transferring existing funds. The community would also have to decide the fate of coins that would never migrate.

Google’s advance does not trigger the Q-Day. Rather, it confirms that several obstacles once theoretical are starting to receive experimental solutions. For Bitcoin, the urgency is not to give in to fear but to prepare a transition before the threat becomes concrete.

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The views, thoughts, and opinions expressed in this article belong solely to the author, and should not be taken as investment advice. Do your own research before taking any investment decisions.