Azuma Koji, Tamaki Kiyoshi, Munro William J
NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
Nat Commun. 2015 Dec 16;6:10171. doi: 10.1038/ncomms10171.
Recent field demonstrations of quantum key distribution (QKD) networks hold promise for unconditionally secure communication. However, owing to loss in optical fibres, the length of point-to-point links is limited to a hundred kilometers, restricting the QKD networks to intracity. A natural way to expand the QKD network in a secure manner is to connect it to another one in a different city with quantum repeaters. But, this solution is overengineered unless such a backbone connection is intercontinental. Here we present a QKD protocol that could supersede even quantum repeaters for connecting QKD networks in different cities below 800 km distant. Nonetheless, in contrast to quantum repeaters, this protocol uses only a single intermediate node with optical devices, requiring neither quantum memories nor quantum error correction. Our all-photonic 'intercity' QKD protocol bridges large gaps between the conventional intracity QKD networks and the future intercontinental quantum repeaters, conceptually and technologically.
近期量子密钥分发（QKD）网络的现场演示为无条件安全通信带来了希望。然而，由于光纤中的损耗，点对点链路的长度限制在百公里以内，这使得QKD网络只能局限于城市内部。以安全方式扩展QKD网络的一个自然方法是使用量子中继器将其与另一个不同城市的网络相连。但是，除非这种骨干连接是洲际的，否则这种解决方案有些大材小用。在此，我们提出一种QKD协议，该协议甚至可以取代量子中继器，用于连接距离在800公里以内不同城市的QKD网络。尽管如此，与量子中继器不同的是，该协议仅使用一个配备光学设备的中间节点，既不需要量子存储器也不需要量子纠错。我们的全光“城际”QKD协议在概念和技术上弥合了传统城市内部QKD网络与未来洲际量子中继器之间的巨大差距。
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