Quantum Says 30,000 Qubits Could Break a Bitcoin Key in an Hour

Alice & Bob, a quantum computing company, announced Thursday that a machine using roughly 30,000 of its cat qubits could recover a Bitcoin private key in about an hour. A preprint posted to the IACR Cryptology ePrint Archive targets secp256k1, Bitcoin’s signature elliptic curve, and sets 29,588 physical qubits and 61.8 minutes as ceilings. Cat qubits use Alice & Bob’s superconducting approach, which limits bit-flip errors in hardware and lowers the physical-qubit count for each logical qubit; the estimate assumes no bit-flips. The company’s 2023 estimate for a 256-bit elliptic curve logarithm was 126,133 cat qubits and nine hours. Because the hour-long attack exceeds Bitcoin’s 10-minute block time, transactions in progress stay out of reach, the company said.