Controller-independent quantum bidirectional communication using non-maximally entangled states

In the recent past, Mohapatra and Balakrishnan (Quantum Inf Process 16:147, 2017) proposed a controller-independent bidirectional quantum direct communication protocol using Bell states. In this work, we show the possibility of the achieving same protocol with non-maximally entangled states without compromising on the security and the efficiency of the protocol. We exploit the degree of entanglement as an additional security parameter. By doing so, the eavesdropper always gets detected in the initial stages of the protocol in the case of an intercept and resend attack. On the other hand, there is only 25% chance that the eavesdropper goes undetected in the initial stages of the protocol proposed by Mohapatra and Balakrishnan. Thus, the proposed protocol can be implemented with the viable physical resources.