The transmission efficiency analysis for quantum secure direct communications over noisy channels

The concept of quantum secure direct communication (QSDC) is to distribute secure message directly between distant users securely, which is an important branch of quantum information science. The purpose of QSDC is to investigate the large capacity of quantum channels and fast speed of information transmission. However, the fidelity of qubits and the efficiency of QSDC will inevitably be affected by the channel noise and the decoherence of the quantum system. In this work, we focus on the performance of QSDC under different noisy channels, and investigate the evolution of quantum states. By numerically studying the performance for two QSDC protocols, we show the efficiency of information transmission over different noisy channel models.