Quantum secure direct communication based on single particles

A quantum secure direct communication scheme based on single particles is proposed. In our scheme, we define a new Y-basis which is different from the traditional Z-basis and X-basis in BB84. Then we use the Pauli I operation and Z operation to encode the secret message into the single particles. Compared to Pauli X operation and Pauli Y operation, the merit of Pauli Z operation is that it only rotates the phase of the particle and not change the polarization of the particle, so its implementation will be easier than that of Pauli X operation or Pauli Y operation. Therefore, our scheme will be more practical than the existing schemes.