| Geometric discord is a representative measurement of quantum correlations,and it can measure nonclassical correlation in the system,so it plays a key role in quantum information processing tasks.In this thesis,geometric discord of two entangled states in different noise channels are studied.The main contents are listed as follows:1.Geometric discord of Bell states in the memory Pauli channels is studied.By introducing the memory parameter,the Pauli noises are memorized.According to the different noise parameters of memory Pauli channels,geometric discord of Bell states are discussed under dephasing noise,depolarizing noise,double Pauli noise and three kinds of flip noises.It is significant to obtain the relationship between geometric discord of Bell states and the noise parameters.It shows that geometric discord of Bell states under the influence of noise is less in the memory Pauli channels,that is,the memory Pauli channels can effectively enhance the stability of geometric discord of Bell states under the influence of noise.2.Geometric discord of GHZ state under decoherence channels is studied.Firstly,it is interesting to discuss the influence of the Kraus operators acting on different qubits of GHZ state.Secondly,geometric discord of GHZ state is explored under decoherence channels.Finally,the conclusion can be obtained through comparing the variation trends of its geometric discord under three decoherence channels.It indicates that geometric discord of GHZ state decreases with time and gradually approaches to a stable value under decoherence channels.Especially under bit flip and bit-phase flip channels,their change trends of geometric discord are exactly the same.Comparing change trends of GHZ state under three decoherence channels,it is found that the influence of geometric discord is greatest under phase flip channel,that is,GHZ state has stronger decoherence resistance to bit flip and bit-phase flip channels. |
