High-dimensional entangled quantum networks with adaptive subspace division

Quantum communication networks are essential for secure information transfer and distributed quantum technologies. High-dimensional entanglement is a promising resource for such networks because it can increase the information capacity and offer greater potential. However, its practical advantages have not been fully explored, and existing demonstrations have not shown clear benefits over two-dimensional networks under realistic conditions. Here, we demonstrate a metropolitan-scale high-dimensional entangled network with active subspace division, showing potential practical benefits in key rate, flexibility, and noise resilience. Using hybrid polarization-time-bin encoding, we distribute high-dimensional entanglement over single-mode fiber channels. The transmission distance exceeds previous network-level high-dimensional implementations by three orders of magnitude, while active phase compensation supports long-term stable operation. Our network can also coexist with classical signals, and its reconfigurable subspace division provides the adaptability needed for practical quantum networks. These results show a practical route toward large-scale, high-performance quantum communication networks.