Polychromatic continuous-variable quantum communication network enabled by optical frequency combs

Abstract

Polychromatic resources have transformed classical communication networks by boosting rate and scalability; quantum communication networks are reaching a similar inflection point. Here, we report a polychromatic continuous-variable quantum communication network enabled by optical frequency combs. The multi-mode density matrices constituted by polychromatic quantum networks are studied. We incorporate finite mode isolation into the security analysis to bound Eve’s accessible information and compute the total network secret key rate. It is demonstrated that, compared to other multiplexing techniques, polychromatic quantum networks can theoretically achieve a secret key rate without decreasing with the increase in users. In the experiment, direct-transmission type and round-trip type quantum communication networks were built using optical frequency combs and dual-comb interference detection technology. The Gaussian-modulated continuous-variable quantum key distribution (CV-QKD) protocol has been validated, with a network capacity of 19 and a total secret key rate of 8.75 Gbps at a uniform distance of 5 km (asymptotic case), 0.82 Mbps at 120 km (finite-size effect), 89.10 Mbps at 40 km (composable security), 13.66 Mbps at 40 km (composable finite-size security). This implementation not only provides technical support for a high-speed multi-node quantum network, but also provides a solution for the future quantum Internet with continuous variables.