Controlled deterministic secure quantum communication using five-qubit entangled states and two-step security test

A five-qubit entangled state is constructed with the four-qubit genuine entangled state. As one of its applications, a controlled deterministic secure quantum communication scheme is proposed. Firstly, the supervisor prepares the five-qubit entangled state and distributes uniformly the four qubits to two users and keeps the rest one for control function. Then the receiver can perform jointly projective measurement on the encoded qubits from the sender to decrypt the secret information. The two-step security test ensures the security of the communication. Moreover, quantum dense coding is applied to enhance the capacity of quantum channel. The communication is realized under the control of the supervisor.