Towards a function-scalable quantum network with multiplexed energy-time entanglement

TL;DR

This paper demonstrates a scalable quantum network by multiplexing energy-time entanglement to support quantum time synchronization and quantum cryptography simultaneously over a 120 km fiber link, enhancing compatibility and security.

Contribution

It introduces a compatible implementation of quantum synchronization and cryptography using multiplexed energy-time entanglement, enabling scalable and secure quantum networking.

Findings

Achieved sub-picosecond quantum time synchronization over 120 km fiber.

Implemented dispersive-optic quantum key distribution with 73.8 bits/sec secure key rate.

Effectively mitigated delay attacks through parallel synchronization.

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 across a network to support a variety of quantum applications. However, current quantum protocols often develop independently, leading to incompatibilities that limit the functional scalability of the network. In this paper, we showcase a compatible and complementary implementation of two distinct quantum applications, 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-optic link is demonstrated, which achieve sub-picosecond synchronization stability based on the quantum two-way time transfer protocol. Simultaneously, this synchronization provides the required timing for implementing dispersive-optic quantum key distribution with an average finite-size secure key rate of 73.8 bits per second, which can be employed to safeguard the security of the transferred timing data. Furthermore, thanks to the compatibility, potential asymmetric delay attacks in the link, which are detrimental to the accomplishment of secure key distribution, can be effectively mitigated by the parallel quantum time synchronization procedure. Our demonstration marks a substantial leap towards unlocking the full potential of energy-time entanglement and paves the way for a resource-efficient, function-scalable, and highly compatible quantum network.