Two-Step Efficient Quantum Dialogue with Three-Particle Entangled W State

This paper we proposed an efficient quantum dialogue scheme by using three-particle entangled W state. In this scheme, the legitimate user Alice and Bob can exchange their secret messages with the help of unitary operations, and each W state can carry two bits of secret messages. Almost all the emitted particle can be used to carry the secret message besides the decoy photons, the intrinsic efficiency for qubits approaches the value 100 %. By joining the decoy particle checking technique and the step-transmitting idea to ensure the safety and reliability of communication.