Controller-independent bidirectional quantum direct communication

Recently, Chang et al (Quantum Inf Process,14,3515,2015) proposed a controlled bidirectional quantum direct communication protocol using Bell states. In this work, the significance of Bell states, which are being used as initial states in Chang et al. protocol, is elucidated. The possibility of preparing initial state based on the secret message of the communicants is explored. In doing so,the controller-independent bidirectional quantum direct communication protocol has evolved naturally. It is shown that any communicant cannot read the secret message without knowing the initial states generated by the other communicant. Further,intercept and resend attack and information leakage can be avoided. The proposed protocol is like a conversion between two persons without the help of any third person with high-level security.