Quantum networks, integrating quantum communication, quantum metrology and distributed quantum computing, could provide secure and efficient information transfer, high-resolution sensing and an exponential speed-up in information processing1. Deterministic entanglement distribution over long distances is a prerequisite for scalable quantum networks2-5. However, the exponential photon loss in optical fibres prohibits efficient and deterministic entanglement distribution. Quantum repeaters6, incorporating entanglement swapping4,7,8 and entanglement purification9-11 with quantum memories, offer the most promising means to overcome this limitation in fibre-based quantum networks. Despite numerous pioneering efforts12-25, a critical bottleneck remains, as remote memory-memory entanglement suffers from decoherence more rapidly than it can be established and purified over long distances. Here we demonstrate memory-memory entanglement between two nodes connected by 10 km of spooled fibre surviving beyond the average entanglement establishment time. This is enabled by the development of long-lived trapped-ion memories, an efficient telecom interface and a high-visibility single-photon entanglement protocol26,27. As an application, we report a proof-of-principle device-independent quantum key distribution demonstration with finite-size analysis over 10 km and a positive key rate over 101 km in the asymptotic limit, with both distances exceeding previous work by more than 2 orders of magnitude28-30. Our work provides a critical building block for quantum repeaters and marks an important step towards scalable quantum networks.

Gammaherpesvirus is a subfamily of herpesvirus, distinct phylogenetically from alphaherpesvirus and betaherpesvirus and characterized by its oncogenic subtypes, including Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus1. It broadly infects humans and other vertebrates and causes various diseases and malignancies2,3. However, no specific antiviral agents are available for each subtype or the whole family. gB is a common fusion protein that is vital for herpesvirus infection and is an ideal target for broad vaccine development; however, a lack of structural and mechanistic understanding of gB hinders this effort4. Here we report the molecular basis of broad gB binding and cross-genus virus neutralization by an antibody, Fab5. This antibody confers effective protection against authentic virus challenges in immunocompetent mice, non-human primates and humanized mice with murine, rhesus and human gammaherpesvirus. Cryo-electron microscopy structures reveal that Fab5 targets a conserved and vulnerable epitope of gammaherpesvirus gB that is antigenically exposed in both pre-fusion and post-fusion states. This finding not only demonstrates that Fab5 is a cross-genus antibody that is broadly reactive to gammaherpesvirus infection and pathogenesis progression, but also offers insights into potential common mechanisms for herpesvirus infection and facilitates the development of broad-spectrum vaccines against gammaherpesviruses.