Quantum networks are being built to send fragile quantum particles—entangled photons—through the same fibre-optic cables that already carry internet traffic, but the technology to switch, route, and purify those particles on demand does not yet exist. This project tackles a core problem: entanglement, the quantum link that enables secure communication and connects quantum computers, is currently hard to produce and even harder to direct. Today’s experimental networks can generate entanglement, but they cannot dynamically route it to different users or adjust how much entanglement each user receives—like a telephone exchange that can only make one call at a time. The researchers will build a portable, fibre-based source of hyper-entangled photons, then develop switching elements (a LAQN gateway and a quantum-enabled reconfigurable optical add-drop multiplexer) that let operators connect users in local and metropolitan networks, adjusting the entanglement rate like bandwidth. They will also demonstrate entanglement swapping over distances beyond a single city, and use frequency qubits to clean up noise in polarisation qubits—a technique called entanglement distillation. If successful, this work could turn quantum networking from a lab curiosity into a practical infrastructure layer, enabling secure communications and distributed quantum computing over existing fibre without requiring new cables.
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Quantum networking is an emerging technology that leverages the principles of quantum mechanics to transmit and exchange quantum information among different users. It offers many key advantages over classical networks, including enhanced communication security, efficient scaling of quantum computing power by interconnecting quantum computers, and high-precision synchronisation across networks. For these reasons, quantum networking is a significant area of research and development. While the potential benefits of quantum networks are significant, there are numerous technical challenges to address to realise it. 1) Integrated quantum and classical network architecture: the network infrastructure is essential and requires significant technological advancements adaptable to the existing fibre infrastructure to achieve useful, cost-effective and robust quantum networks. 2) Dynamic connectivity: producing entanglement is still a non-trivial task and the entanglement photons are precious resources in the quantum network. Dynamic connectivity of entanglement will ensure the on-demand delivery of valuable entanglement resources, as well as entanglement rate adjustment similar to the offering of various bandwidths in classical communications. This supports efficient allocation of the entanglement. 3) Long distance and robust reach: It is important to support long-distance and robust entanglement in the future quantum network. It will require innovative approaches such as low-loss infrastructure, bright entangled photon source, entanglement swapping and purification. This project will focus on developing novel solutions to create robust, scalable and dynamic entanglement-based networks which operate over the real-world deployed fibre infrastructure. We will first develop a portable, fibre-based hyper-entangled photon source that can be deployed in real-world environments. We will also focus on developing switching elements for interconnecting users in the local area access quantum network (LAQN) and metropolitan area quantum network, known as LAQN gateway and quantum-enabled reconfiguration optical add-drop multiplexer (Q-ROADM). The switching elements will support the entanglement-based quantum link connection at two different hierarchical network layers, offering dynamic connectivity between users and adjusting the ‘bandwidth’ of the entanglement rate. We will further demonstrate dynamic entanglement swapping beyond the metropolitan scale, which is a crucial technology to extend quantum network distances when quantum memory becomes more feasible. In addition, the team will work together to demonstrate controlled-NOT (CNOT) gate operation between frequency and polarisation qubits carried by the hyper-entangled photon pairs, and use frequency qubits to purify polarsation qubits for entanglement distillation. This is essential for maintaining robust and high-quality entanglement over long distances.
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