Researchers at the University of Science and Technology of China (USTC) have reported establishing quantum entanglement between two remote quantum memory nodes connected by 420 km of optical fiber — a distance described in the original post as raising the 'load-bearing wall' for future intercity quantum networks.
Why this matters
- Quantum repeaters need matter memories. Long-distance quantum communication ultimately relies on entangling quantum memories at different nodes, not just distributing photonic entanglement, so that entanglement can be stored, swapped, and extended across a network.
- From tens to hundreds of kilometers. Prior memory-to-memory entanglement demonstrations typically operated over much shorter fiber spans. Reaching 420 km pushes this into a range relevant to connecting neighboring cities.
- Bottleneck addressed. Fiber attenuation and finite memory lifetime are the main obstacles to entanglement distribution at metropolitan scale. The result shows that photon-mediated entanglement can be successfully transferred to two storage nodes across a real fiber channel of hundreds of kilometers.
Implications
The achievement is framed as a foundational step toward quantum repeater chains and, eventually, an intercity quantum internet — enabling applications such as long-distance quantum key distribution with trusted-node-free security, distributed quantum computing, and entanglement-based sensor networks.
> Note: The source post contained a title only, with no experimental body text. For protocol details (wavelengths, memory platform, fidelity, storage time) and the corresponding publication, refer to the original announcement from USTC.