Towards More Feasible Quantum Networks Based on Cavity-QED and Continuous-variable Codes*

Quantum repeaters (QRs) are the main approach to realize long-distance quantum communication. The main building blocks of conventional QRs are high-efficiency quantum memories (QMs) which are necessary for a practical realization. Here we propose a memoryless QR protocol based on cavity-QED using optical states encoded in one of the rotation-symmetric bosonic codes (RSBCs). Such rotational symmetry enables the fidelity of the transmitted state to be partially restored by doing the syndrome measurement. We evaluate the performance of our repeater protocol by calculating the secret key rate (SKR) in a QKD scenario as our figure of merit. We compare different RSBCs and for the one with the highest SKR calculate the cost coefficient. Those values are comparable with other existing memoryless QR systems. In addition, the performance of other RSBCs is improved adding multiple channels and selecting specific syndrome measurement outcomes by using QMs or cluster states. Next we compare both approaches by determining the tradeoff of the main parameters, such as the coherence time and the gate efficiency. Our results show that that this repeater system might be realized with the state-of-art technology.