Towards a Function‐Scalable Quantum Network With Multiplexed Energy‐Time Entanglement

Abstract Quantum networks, which hinge on the principles of quantum mechanics, are revolutionizing the domain of information technology. The vision for quantum networks involves the efficient distribution and utilization of quantum resources to support diverse applications, yet existing protocols face compatibility issues that limit the functional scalability. In this paper, a framework is proposed for the compatible and complementary implementation of quantum time synchronization and quantum cryptography, by multiplexing the same energy‐time entangled biphotons and quantum channel. A proof‐of‐principle experiment between two independent nodes across a 120 km fiber is demonstrated, which achieves sub‐picosecond synchronization stability based on the quantum two‐way time transfer protocol. Simultaneously, this synchronization provides the required timing for enabling dispersive optics quantum key distribution with an average finite‐size secure key rate of 73.8 bits per second. Furthermore, the performance degradation induced by asymmetric delay attacks in the quantum channel is effectively mitigated by the parallel quantum time synchronization procedure. This work advances energy‐time entanglement potential and paves the way for a resource‐efficient, function‐scalable, and highly compatible quantum network.