High-rate quantum networks with energy-time entanglement

Quantum entanglement networks have garnered significant attention due to the inherent security provided by quantum physics. The networks aim to connect a multitude of users with a high secure key rate (SKR). Fully connected networks have been demonstrated using wavelength-division multiplexing architectures. However, the SKR of such networks remains challenging due to the limited brightness of quantum photon-pair sources and the loss introduced by cascaded filtering components. We present high-rate quantum entanglement networks that leverage a broadband quantum light source with high brightness and an industry-grade flexible wavelength-selective switching technique with uniform loss. By implementing the BBM92 protocol, we achieve an SKR of 28.19 kbps in a four-user network, representing a two-order-of-magnitude improvement over previous implementations. After transmission through a 40-km fiber spool, the SKR remains as high as 3.58 kbps and stays positive over distances up to 250 km. Furthermore, the flexibility of our scheme is illustrated by constructing a six-user network, achieving SKRs of 4.21 kbps and 0.45 kbps without and with a 40-km fiber spool, respectively. These results demonstrate a practical approach to enhancing the SKR and scalability in entanglement-based quantum networks, offering a feasible solution for deploying metropolitan and backbone quantum communication systems.