Google Cuts Quantum Errors 40x on Willow Processor

Google has demonstrated a 40-fold reduction in quantum computing errors using its Willow processor, advancing a technology that researchers believe could eventually challenge the cryptography protecting Bitcoin ($BTC). According to Ccn, Google researchers achieved 99.99% logical fidelity while testing purified quantum states on real computing hardware following publication in the scientific journal Science on October 15, 2026.

Magic State Cultivation and Willow

The experiment focused on reducing errors in special quantum states known as magic states, which provide resources needed for operations that ordinary quantum error-correction methods cannot perform on their own. Using the Willow processor, the cultivation process reduced errors by approximately 40 times compared with states created without the method, achieving a record logical fidelity of 99.99% for resulting T-states.

Implications for Bitcoin Security

Bitcoin relies on public-key cryptography and elliptic curve signature systems that could theoretically be targeted by future quantum computers running Shor's algorithm. Blockchain analytics firm Glassnode estimated that approximately 6.04 million BTC, representing 30.2% of the mined supply, had public-key exposure across unspent transaction outputs. Google's earlier research estimated that future cryptographic attacks could require fewer than 500,000 physical quantum qubits.

Key facts

• Google reduced quantum computing errors approximately 40-fold using magic state cultivation on its Willow processor.
• Researchers achieved 99.99% logical fidelity on October 15, 2026.
• Glassnode estimated 6.04 million BTC had exposed public keys, representing 30.2% of mined Bitcoin.
• Coinbase published Bitcoin security recommendations on October 13 regarding legacy coin migration.