Improvement on cyclic controlled teleportation by using a seven-qubit entangled state (Englisch)

Abstract Recently, Sang [Int. J. Theor. Phys. 57, 3835–3838 (2018)] proposed a scheme for cyclic controlled quantum teleportation (CYCQT) of three arbitrary single-qubit states by utilizing a seven-qubit entangled state as the quantum channel shared by the four parties Alice, Bob, Charlie and David. In this scheme, single-qubit state is teleported by Alice to Bob, Bob teleports his single-qubit state to Charlie and Charlie teleports his single-qubit state to Alice. It is claimed that all the three participants Alice, Bob and Charlie cannot reconstruct the desired teleported state without the help of the controller David. Contrary to this, we show that the two involved participants Alice and Charlie can reconstruct the desired teleported state without the permission of controller. The controller David has no control over the teleportation processes Bob to Charlie and Charlie to Alice. To resolve this issue, we propose a modification to Sang’s scheme for CYCQT. Our scheme may play an important for secure quantum communication among the quantum nodes of a quantum network.