提出一个基于四粒子GHZ纠缠态实现未知单粒子态的可控量子双向传态方案.通信双方Alice和Bob以及控制方事先密享两对四粒子GHZ纠缠态以构建量子信道, 根据纠缠粒子的不同分发方式, 以及测量时所选择的不同测量基, 可以分别实现三方和四方参与的可控量子双向传态.通信开始后, Alice和Bob分别对自己拥有的部分粒子作量子投影测量, 若控制方同意双方通信, 则对自己拥有的粒子作测量并通过经典信道公布测量结果.通信双方根据控制方公布的测量结果对各自的某个粒子作相应的幺正变换, 即可在己方的粒子上重建对方待传的量子态.由于第三方Charlie以及第四方Dennis的加入, 整个双向传态的安全性大为提高.

A scheme for controlled two-way quantum teleportation of unknown one-qubit state via GHZ quadripartite entangled state was proposed.Two sides of communication (Alice and Bob) and the controller,secretly share two pairs of GHZ quadripartite entangled state in advance to construct quantum channel.According to the different ways of distribution along with different measuring vectors choosed to use,two-way quantum teleportation controlled by a third party and a fouth party were realized.After communication,Alice and Bob perform quantum projection measurement on parts of their qubits respectively.If the controller agrees to intercommunication,he should measure his qubits and announce the results via classical channel.Then the both sides of communication can make appropriate unitary transformations on their own certain qubit on the basis of the controller′s results,thus they are able to reconstruct each other′s unknown state on their own qubit.The security of the whole two-way communication is greatly impoved owing to the join of the third party Charlie and the fourth party Dennis.