Some Research About Transmission Of Quantum Information

Quantum communication is a technology for communicating quantum information with qubit or qudit. As one of the important fields in quantum information, it is a interesting issue which attracts many people to study. In comparison with classical communication, quantum communication not only overcomes the limitations of classical communication, but also is much more securer than them. Based on the former studies by the other researchers, I devote myself into studying transmission of quantum information.The main work is as following.1, Using the entangled GHZ-type states, which are offered by others, two schemes about quantum teleportation are proposed. The first scheme is to split an arbitrary d-level qudit state among three agents, and the second scheme is to teleport an arbitrary d-level qudit state via a set of 2-level partially entangled GHZ-type states. The two schemes are worked in the degree-mismatched quantum system and all the operations are easy to be performed, such as, the receiver only needs to perform few Pauli operations on his particles and the controller need to perform classical measurements on his own particles respectively. Moreover, both of the schemes can be implemented perfectively with probabilities 1.2, By employing the partially entangled states, controlled directional teleportation is studied, which allows two agents to teleport their information to each other at the same time. Recently, more people are studying on the work of bidirectional teleportation and so many schemes are proposed via different entangled states as quantum channel. However,in most of schemes, the particles of quantum channel are maximally entangled, and less schemes are worked via partially entangled states. So that, a scheme of controlled bidirectional teleportation for communicating arbitrary qubit via 2-level partially entangled GHZ-type state is proposed. In the latter, the scheme of controlled bidirectional teleportation is generalized to the case of exchanging two d-level qudits via a set of 2-level partially entangled GHZ-type states. Both types of partially entangled states, which work as quantum channel in schemes, can be prepared from general partially entangled GHZ states by two quantum circuits. Furthermore, the two schemes are performed perfectly with probabilities 1.3, As the reverse process of telecloning, remote quantum information concentration is utilized on some quantum works. However, a great many schemes are worked with probabilities less than 1. Base on several schemes of the former type of schemes, the quantum channel particles in schemes is transformed by quantum circuits to make the schemes implemented deterministically. Firstly, a 2→1 scheme of controlled remote quantum information concentration with maximally entangled GHZ-type state as quantum channel is given in the article. Then, the scheme is extended to the case of 5-qubit partially entangled states as quantum channel. Although the second scheme can be played perfectly with partially entangled states, two particles of quantum channel do not work in the scheme. To reducing the consumption of the entangled states, the former scheme is generalized to the case of controlled remote quantum information concentration via4-qubit partially entangle states. In the end, another 3→1 remote quantum information concentration via 6-qubit partially entangled state is proposed. All of the operations in our schemes are easy to be performed and the entangled states, worked as quantum channel, are transformed from the general maximally or non-maximally entangled GHZ states via four quantum circuits. Furthermore, it is important that all of the schemes are implemented deterministically.