Researchers from Alice & Bob and their co-authors estimated that a quantum computer using superconducting cat qubits could solve the cryptographic problem behind Bitcoin’s signatures with about 29,600 physical qubits in 62 minutes. This is a theoretical estimate, not a demonstrated attack, and quantum computers capable of it do not currently exist.
Such an attack could potentially derive a private key from a known public key. Estimates cited in the study put 6.26 million BTC in wallets with exposed public keys, but that does not mean the coins can be stolen today. The main resource estimates assume no bit-flip errors, equivalent to a qubit-state lifetime of about 100 years.
