Alice & Bob announced a theoretical estimate that a fault-tolerant quantum computer with about 29,588 physical qubits could solve the elliptic-curve problem behind Bitcoin signatures in 61.8 minutes. The estimate relies on specialized “cat qubits” and is not evidence that existing quantum computers can crack Bitcoin keys; building a machine that can reliably perform the calculation remains a major engineering challenge.
The estimated attack would take longer than Bitcoin’s roughly 10-minute average block interval, limiting its immediate practicality against ordinary transactions awaiting confirmation. Coins with already-exposed public keys could face a greater threat because an attacker would not necessarily have to finish before the next block. Previous estimates put about 6.9 million BTC in that potentially exposed category.
