Quantum Blockchain Survey: Foundations, Trends, and Gaps
Quantum threats fundamentally undermine the cryptographic foundations of classical blockchains. This paper establishes the first unified analytical framework to systematically survey post-quantum blockchain (PQBC) and quantum blockchain (QBC) research, comparing their security guarantees, scalability, and deployment feasibility across cryptographic primitives, architectural design, and implementation constraints. Methodologically, it integrates post-quantum cryptography, quantum entanglement, and quantum key distribution (QKD) protocols, and proposes a multidimensional technical evaluation model. Key contributions include: (1) identifying critical open challenges in hardware compatibility, consensus mechanisms, and network-layer integration; (2) constructing a structured knowledge taxonomy; and (3) pinpointing core research gaps—particularly migration pathways for quantum-resilient transition and lightweight consensus under quantum resource constraints—thereby providing both theoretical foundations and practical guidance for the evolution of quantum-secure blockchains.