Quantum Communication Network Utilizing Quadripartite Entangled States Of Optical Field

Classical capacity of some noisy quantum channels can be increased to a higher level relative to the best known classical capacity achievable without entanglement, which is named the entanglement-assisted classical capacity. Applying multipartite entanglement and dense coding in quantum communication networks we can realize a variety of entanglement-assisted network communications with channel capacities higher than their classical limitsWe presented two types of quantum communication networks in which the TTPC entangled states of light are exploited. Due to the existence of TTPC quantum correlations the signal transmission between two participants can be controlled by others who share the quantum entanglement with the communication participants. Owing to the asymmetric distribution of the quantum correlations among the four submodes of the TTPC entangled state, the communication schemes and results between two users on a neighbor line and a diagonal line are not exactly the same. To achieve the controlled dense coding communication between two user, the electronic feedback from two controllers are added onto the measurement results in the receiver station, while under the help of single controller we have to implement the direct optical coupling between the controller's submode and the receiver's submode. However, in all designed systems the channel capacities can be controlled and the signal-to-noise ratios can surpass the SNL of the classical optical communication. The flexibility and the versatility of the presented communication systems are especially convenient for practical applications.