Some problems with the article by Oluwadare and Oyewumi [Chin. Phys. Lett. 34 (2017) 110301] are discussed. The previously proposed solution of the Schrödinger wave equation in the generalized inverse quadratic Yukawa potential is unsatisfactory for a number of reasons.

The problem of definite information leakage existing in the controlled bidirectional quantum direct communication protocol using GHZ states [Chin. Phys. Lett. 23 (2006) 1680] was pointed out by Ye and Jiang [Chin. Phys. Lett. 30 (2013) 040305]. Then, they proposed two strategies to improve this security bug. However, if the revised versions are analyzed from the viewpoint of information theory, it can be found that they still have the problem of information leakage. That is, three quarters and one half of the information interchanged by the communication parties are leaked out unknowingly in the first and second revised protocols, respectively.

Most recently, Liu and Chen [Chin. Phys. Lett. 30 (2013) 079901] used the tool of information theory to analyze the security of our two improved versions of the MX protocol [Chin. Phys. Lett. 30 (2013) 040305], and they found out that our two improved versions still have the information leakage problem. After revisiting them with the tool of information theory again, with respect to the security, we draw the same conclusion as Liu and Chen. In addition, we point out that how to use a single quantum state as the sole quantum resource to design a bidirectional quantum secure direct communication protocol without information leakage is still a big challenge that needs to be solved.

We point out that the quantum secret sharing (QSS) protocol proposed by Gao et al. [Chin. Phys. Lett. 29 (2012) 110305] has some defects. Thus, some strategies are given to mend them.

We first make a small modification to the improved protocol in order to enhance its efficiency. Secondly, the explanation that our improved protocol can prevent Trent from using the {|Ψ^±₂>,|Φ^±₂>} basis is given.