Bidirectional Quantum Transmission with Different Levels of Control

We propose a protocol of bidirectional quantum teleportation with different levels of control using a maximally six-qubit entangled state as the quantum channel. In the scheme, Both Alice and Bob want to transmit an arbitrary unknown single qubit state to each other. The state that Alice wants to transmit to Bob is a lesser important task which can be controlled by supervisor Charlie alone. While the state that Bob wants to transmit to Alice is a more important task which must be under the joint control of supervisor Charlie and David. By selecting suitable measuring base for four agents, the bidirectional quantum transmission with different levels controlling can be realized.