Google cut by roughly twenty times the number of physical qubits considered necessary to break Bitcoin’s cryptography, shifting the threat from a problem in the 2040s to a preparation window between 2030 and 2035. Under the group’s assumptions, a key could be extracted in nine minutes, compared with Bitcoin’s average ten-minute block time, with an estimated hijacking probability of 41%. More than six million BTC, representing about 30% of the supply and $500 billion to $600 billion, are held at addresses whose public keys are already visible. Tezos, Algorand and QRL already have post-quantum implementations, while BIP-360 replaces neither ECDSA nor Schnorr signatures, does not automatically migrate existing funds and is not expected to be completed before 2033. Ethereum targets full protection by 2029, but Bitcoin still has no official process for selecting post-quantum algorithms or coordinating a migration timeline.
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