Multimode CV‐QKD with non‐Gaussian operations
Mingjian He, Robert Malaney, Jonathan Green · Quantum Engineering · 2020
Non-Gaussian operations have been studied intensively in recent years due to their ability to increase the secret key rate for certain CV-QKD protocols. However, most previous studies on such protocols are carried out in a single-mode setting, even though in reality any quantum state contains multimode components in frequency space. In this work, we investigate the use of non-Gaussian operations in a multimode CV-QKD system. Our main finding is that, contrary to single-mode CV-QKD systems, in generic multimode CV-QKD systems, it is possible to use non-Gaussian operations to increase the optimized secret key rate. More specifically, we find that at losses of order 30dB, which represents a distance of order 160km and the effective maximum distance for CV-QKD, the key rate for multimode non-Gaussian operations can be orders of magnitude higher than single-mode operations. Our results are important for real-world CV-QKD systems, especially those dependent on quantum error correction—a process that requires non-Gaussian effects.