Google’s Willow quantum chip has reduced errors by approximately 40-fold when preparing “magic states,” a specialized quantum resource that researchers say is essential to building machines powerful enough to crack Bitcoin wallets, according to results published in Science on October 16.
Magic states are quantum states consumed during calculations and must be continuously produced. Google’s method produces clean states by starting with a rough version, checking for errors, and discarding flawed attempts. The company achieved 99.99% fidelity in finished states that passed inspection, though only 8% of preparation attempts succeeded.
The advancement addresses a costly bottleneck in quantum computing. Bitcoin wallets use a secret key to approve payments and a matching public key for network verification. A sufficiently large quantum computer running Shor’s algorithm, first published in 1994, could theoretically work backward from the public key to recover the secret key, allowing an attacker to sign transactions as the owner.
In March 2026, Google estimated that a superconducting quantum computer with fewer than 500,000 physical qubits could break Bitcoin and Ethereum wallet cryptography. That estimate assumed efficient magic-state production. Under one modeled attack scenario, 500,000 magic states per second would be required, with the complete attack lasting 9 minutes after the public key becomes available.
Quantum computers store information in qubits, which are extremely fragile and prone to errors from heat, vibration, and stray signals. Engineers organize physical qubits into groups that detect and correct errors, creating logical qubits. Willow’s 40-fold error reduction tests part of Google’s March approach rather than providing an additional 40-fold cost reduction on top of earlier work, according to reporting by CoinDesk.
In September 2026, researchers published work cutting the workload of a core calculation used in quantum attacks, though that research covered one component of the attack and excluded complete attack and physical hardware costs.
Some Bitcoin payment formats hide the public key behind a hash until the owner spends. Lost coins with exposed public keys present a problem because owners cannot move them into stronger protections without the keys. On October 7, 100.02 BTC untouched since July 2010 moved after 16 years, valued at approximately $8.5 million at the time. In August 2026, six wallets inactive since 2011 to 2014 moved 553.59 BTC, worth roughly $40 million.
