QKD network in China extends over 10000 km
In China, there is now an even larger carrier-grade quantum network over 10103 km, both with wired quantum connections and over free space routes with six ground stations. The currently largest QKD network in the world consists of 145 nodes in the backbone network and the 144 fiber links connecting 20 metro networks across 17 provinces and 80 cities. The Trusted Node technology is used to extend the range of the individual connections with an average of 70 km. Of the 145 nodes, 104 nodes act as trusted nodes, which lie between the remaining backbone access nodes. A significant focus is also on hybridization, which is more common in large QKD networks. The network consists of two rings, so that the security of this topology can be used. The ring topology is used for the access nodes, while the connections from the access nodes to the user nodes follow the tree topology to provide multiple users (up to 24) with time division multiplexing. In addition, wavelength division multiplexing or optical switches are also used to multiplex the quantum channels.
Four different high-speed BB84 QKD systems are used: three polarization-encoded and one phase-encoded system. Furthermore, there is also one low-speed BB84 system in place and additionally two CV-QKD systems.
The entire network is controlled by an Operation & Maintenance (O&M) Center, which also takes care of monitoring. The Element Management System (EMS) collects device data locally and forwards it to the O&M Center’s Network Management System (NMS). For routing across domains, 2nd-level QKDN controllers are used to coordinate the 1st-level QKDN controllers of the respective domains. In addition, OTP encryption is supported for secret key rates between 8 and 25 kbps on the four high-speed routes.
The entire QKD network is strictly shielded by its own components and dark fibers in order to avoid data leaks of the tamper-proof generated QKD keys during distribution to the user.
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