Improved “bidirectional quantum secure communication protocol based on a shared private Bell state”

In 2009, Shi et al. [Opt. Commun. 282 (2009) 2460-2463] proposed a bidirectional quantum secure communication protocol based on a shared private Bell state. The protocol allows two legitimate users to exchange their secret messages simultaneously and is free from information leakage. This work tries to use random permutation on photons to reduce the communication cost and enhance the quantum bit efficiency on Shi et al.'s protocol.