Modular network for high-rate quantum conferencing

One of the main open problems in quantum communication is the design of efficient quantum-secured networks. This is a challenging goal, because it requires protocols that guarantee both unconditional security and high communication rates, while increasing the number of users. In this scenario, continuous-variable systems provide an ideal platform where high rates can be achieved by using off-the-shelf optical components. At the same time, the measurement-device independent architecture is also appealing for its feature of removing a substantial portion of practical weaknesses. Driven by these ideas, here we introduce a modular design of continuous-variable network where each individual module is a measurement-device-independent star network. In each module, the users send modulated coherent states to an untrusted relay, creating multipartite secret correlations via a generalized Bell detection. Using one-time pad between different modules, the network users may share a quantum-secure conference key over arbitrary distances at constant rate.The ability of modern society to move towards quantum communications is dependent on the capacity to realize quantum networks with the ability to securely transmit and share information over long distance and among multiple users. The authors propose a protocol for a scalable quantum network made of modules each consisting of continuous-variable measurement-device independent applied to quantum key distribution, allowing to perform secure quantum conferencing among an arbitrary number of users.

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