Google Quantum AI demonstrated a technique called magic state cultivation on its Willow quantum processor, reducing errors 40-fold compared with untreated quantum states and producing T-states with record logical fidelity of 99.99%, according to research published in Science. The advance addresses a major bottleneck in building large-scale, fault-tolerant quantum computers, which could eventually threaten Bitcoin’s elliptic-curve cryptography. A March analysis by Google researchers estimated that fewer than 500,000 physical qubits could be needed to break Bitcoin’s digital signatures in a theoretical attack, potentially deriving a private key from an exposed public key in roughly nine minutes. About 6.9 million BTC could be exposed through publicly revealed keys, including older wallet formats and reused addresses, although no current quantum computer can perform such an attack. Researchers and crypto firms are examining quantum-resistant protections, but migrating Bitcoin would require broad coordination across wallets, custodians, dormant holdings and the decentralized network.