Ghislaine Coulter-de Wit

Superdense coding exploits shared entanglement to encode two classical bits into a single qubit. This concept can be incorporated into quantum secure direct communication, where message transmission and eavesdropping detection are combined into a single protocol without prior key generation. Building on the results of Wu, Long, and Hayashi [Phys. Rev. Appl. 17, 064011, (2022)], we analyze the security of scenarios in which an eavesdropper may hold the purification of the shared entangled state. We extend the previous result by incorporating statistical errors into the estimation of the distributed entangled state and, thus, make a further step in the security analysis of superdense coding.