The Study Of Controlled Teleportation Using Cluster States And Cluster-type States As A Quantum Channel

Combined with quantum mechanics and information science, quantum informatics is a a newly-sprung cross discipline, it is the starting point of the quantum state as a information carrier, so relevant information of all questions must be adopted to deal with the laws of quantum mechanics. Quantum communication is an important branch of quantum informatics, mainly including quantum teleportation, quantum dense coding, quantum key distribution etc, Most conspicuous is controlled quantum teleportation, which is the tangible proof of quantum nonlocality and plays an important role in the areas of quantum mechanics. This thesis expounds several schemes for controlled teleportation using cluster states and cluster-type states as quantum channel:Scheme 1: A new scheme for controlled teleportation of an arbitrary two-particle pure or mixed state with the help of a five-qubit cluster state is proposed in detail. In this scheme, a five-particle cluster state is shared by a sender, a controller and a receiver. At first, the sender performs a four-qubit von-Neumann measurement on the qubits at hand, and the controller performs a Hadamard measurement on his qubit. Then the receiver can reconstruct the arbitrary two-particle pure or mixed state by performing some appropriate unitary transformations on his particles after he knows the measure results of the sender and the controller. This controlled teleportation scheme is deterministic.Scheme 2: A new scheme for controlled teleportation of an arbitrary two-particle state is proposed in detail, using a four-particle cluster state as quantum channel and EPR state to achieve control. First of all, the sender applies to the controller, and then the controller performs the Bell-based measurement on the two particles of his own. And the controller notifies the sender to achieve entanglement swapping. Then, the sender makes the appropriate unitary transformation and performs a Newman measurements on the four particles of his own. And the results inform the receiver. According to the sender's measurement results, the receiver can reconstruct the arbitrary two-particle state after he makes the appropriate unitary transformation on his own particles. The probability of success of the program is 100%.Scheme 3: A new scheme for controlled teleportation of an entangled coherent state (ECS) with the help of a four-mode cluster-type entangled coherent state (CTECS) is proposed in detail. In this scheme, a four-mode CTECS is shared by a sender, a controller and a receiver. At first, the sender performs photon number measurement on the modes at hand, and the controller also performs photon number measurement on his modes. Then the receiver can reconstruct the ECS by performing an appropriate unitary transformation on his mode after he knows the measured results of the sender and the controller. And the probability of successful controlled teleportation is approaching 1/2.