Quantum Secure Direct Communication with Private Dense Coding Using a General Preshared Quantum State

For real-world quantum communication, how perfect does a system actually need to be? Here researchers propose a private dense-coding framework using a general preshared quantum state, for quantum secure direct communication that unifies a large number of protocols aimed at secure classical communication using quantum resources. This study provides a detailed performance analysis for the framework in both the asymptotic and nonasymptotic cases, and a better upper bound on information leakage in the finite-length setting. For practical application, the authors also propose an efficient method for implementation, under certain assumptions.