Quantum Bitcoin mining study: 51% attack threat negligible

A new study from Zach Manson and Barry C. Sanders, published on arXiv (2607.23952), tackles a pressing question in cryptocurrency security: could quantum computers threaten Bitcoin's consensus mechanism? The researchers built a game-theoretic model simulating two independent, aggressive miners equipped with purpose-built quantum computers, competing against each other and a classical Bitcoin network. They extended existing frameworks to compute full payoff matrices, deriving optimal quantum mining strategies for scenarios where miners can restart their search when quantum measurements fail to yield a valid block.

The paper's key innovation is the 'Aggressive Quantum Mining Strategy,' which realistically captures how rational quantum miners would behave when competing for block rewards. Despite the computational advantages quantum machines might offer in searching for nonces, the results show that the optimal strategies have a negligible effect on the 51% attack threshold. In other words, even with two sophisticated quantum miners operating optimally, the network's security against majority attacks remains effectively intact. The work spans 53 pages with 17 figures, and the authors have released code for replication. This finding provides important evidence that proof-of-work cryptocurrencies like Bitcoin may be more resilient to quantum threats than previously feared, helping guide future research on post-quantum blockchain security.