Efficient distribution of high-dimensional entanglement through 11  km fiber

High-dimensional entanglement enriches our understanding of entanglement and shows many advantages in quantum communications tasks, so its long-distance distribution is a key technology. Here, we use multicore fiber to distribute four-dimensional (4D) entanglement over 11 km. The observed fidelity is F = 0.921 ± 0.001 , which is feasible for high-dimensional quantum networks. We observed the violation of high-dimensional Bell inequality ( I 4 = 2.635 ± 0.014 ) and steering inequality ( S 4 = 1.900 ± 0.003 ) for a 4D system over a distance of 11 km and finally demonstrated 4D quantum key distribution based on entanglement in proof of principle. Our work provides an experimental platform for high-dimensional quantum technologies and enables the intracity high-dimensional quantum network.