Title: Quantum secure direct communication based on order rearrangement of single photons
Abstract: We present an improvement of the protocol proposed by Lucamarini and Mancini [M. Lucamarini, S. Mancini, Phys. Rev. Lett. 94 (2005) 140501] with techniques used in the protocol presented by Zhu et al. [A.D. Zhu, Y. Xia, Q.B. Fan, S. Zhang, Phys. Rev. A 73 (2006) 022338], namely the secret transmitting order of particles.