Information Leakage Problem in High-Capacity Quantum Secure Communication with Authentication Using Einstein–Podolsky–Rosen Pairs

The information leakage problem often exists in bidirectional quantum secure direct communication or quantum dialogue. In this work, we find that this problem also exists in the one-way quantum secure communication protocol Chin. Phys. Lett. 32 (2015) 050301. Specifically, the first bit of every four-bit message block is leaked out without awareness. A way to improve the information leakage problem is given.