Bitcoin Quantum Attack Cost Halved to 1,151 Qubits [2026]

A quantum computer that can forge a Bitcoin signature does not exist, and nobody serious claims one is coming this year. But the engineering target for building one just got smaller. A paper posted to arXiv and obtained ahead of publication by CoinDesk on September 10, 2026, shows that a team of more than 100 contributors, drawn from the Ethereum Foundation, Theta Labs, StarkWare and several other organizations, cut the estimated computing resources needed to break the elliptic-curve cryptography protecting Bitcoin and Ethereum wallets by more than half. The new circuit needs 1,151 logical qubits and roughly 1.3 million Toffoli gates to perform one arithmetic step inside Shor’s algorithm, the quantum routine that could eventually recover a private key from a public one.

That is a narrow, technical result. It is also the kind of number that custodians, exchanges and protocol developers watch closely, because it feeds directly into how urgently the broader cryptocurrency industry needs to migrate away from the cryptography both chains have used since launch. This piece breaks down what changed, what it does not change, and why the gap between “theoretically weaker” and “practically breakable” still spans years rather than months.