Diversity Extraction for Multicarrier Continuous-Variable Quantum Key Distribution

We introduce a diversity extraction for multicarrier continuous-variable (CV) quantum key distribution (QKD). The diversity extraction utilizes the resources that are injected into the transmission by the additional degrees of freedom of the multicarrier modulation. The multicarrier scheme granulates the information into Gaussian subcarrier CVs and divides the physical link into several Gaussian sub-channels for the transmission. We prove that the exploitable extra degree of freedom in a multicarrier CVQKD scenario significantly extends the possibilities of single-carrier CVQKD. The diversity extraction allows for the parties to reach decreased error probabilities by utilizing those extra resources of a multicarrier transmission that are not available in a single-carrier CVQKD setting. The additional resources of multicarrier CVQKD allow the achievement of significant performance improvements that are particularly crucial in an experimental scenario.