Big Step: A fast quantum algorithm for nonce discovery in Proof-of-Work blockchains

Since the emergence of quantum computing, Grover’s algorithm has been widely studied as a method to attack Proof-of-Work (PoW) blockchains. However, it requires multiple oracle and diffuser iterations, causing high computational overhead and ancilla qubit usage. In this paper, we propose a novel quantum algorithm that efficiently finds valid nonces in PoW-based blockchains without iterative amplification. It introduces a non-unitary quantum operator that directly generates a superposition of valid nonces in one step. We also present an efficient quantum circuit implementation and theoretically prove that our algorithm significantly reduces computational resources compared to conventional Grover-based methods.