Quantum secure direct communication based on order rearrangement of   single photons
  Based on the ideal of order rearrangement and block transmission of photons, we present a quantum secure direct communication scheme using single photons. The security of the present scheme is ensured by quantum no-cloning theory and the secret transmitting order of photons. The present scheme is efficient in that all of the polarized photons are used to transmit the sender's secret message except those chosen for eavesdropping check. We also generalize this scheme to a multiparty controlled quantum secret direct communication scheme which the sender's secret message can only be recovered by the receiver under the permission of all the controllers. 
Jian Wang, Quan Zhang, Chao-jing Tang