The Quantum State Transmission In Spin Chains Under Weak Measurement And Quantum Measurement Reversal

Applying quantum physics to information science, we obtain the quantum information science,which is an emerging interdiciplinary. The quantum information science is mainly composed of quantum computing and quantum communication, in which the quantum communication is the first to go into practical application. The process of quantum communication is usually associated with the quantum information transmission, while the applicable information carrier is necessary to realize quantum information transfer. The spin chain is the vital model in solid system. By virtue of the controllability and rich entangle properties, spin chain is considered as the optimal quantum information carrier to realize quantum information transfer. For a long time, the quantum information transfer treating spin chain as carrier is one hot research in the field of quantum information.Therefore, in this thesis, we primarily investigate the transmission of two-qubit entangled state in spin chains under weak measurement and quantum measurement reversal, and the main context can be shown by:1. The effects generated by weak measurement and quantum measurement reversal on the transmission of quantum state)1001(2/1 ? in 1D XX spin chain have been studied. The results show that for different operations’ strengths the scheme of the combination of weak measurement and quantum measurement reversal reveals positive or negative effects to suppress the decoherence of spin chain, while the quantum measurement reversal always improves the input state transfer. The further studies indicate that the weak measurement does hinder the transfer of quantum state, and the larger of the weak measurement’ strength is the stronger of the hinder is. The influence shown by weak measurements in this study is opposite to the previous researches. In addition, in the thermodynamic limit, the input state transfer can still be improved by quantum measurement reversal and for different operations’ strengths the corresponding distribution curves of maximum entanglement transfer and fidelity with lattice m develop independently.2. Under weak measurement and quantum measurement reversal, we have designed a optimal scheme of entanglement transfer and investigated the transmission of quantum state?? ?1100 in two parallel Heisenberg spin chains with DM interaction. The results indicate that based on the scheme more input states can be transferred in this system, and any kinds of input states transfers in this system can all be improved by some probability by this scheme.Moreover, for the small α case, there are two kinds of post operations and the correspondingentanglement transfer has the same analysis formula but with total successful probabilities evolving inversely with time. In the thermodynamic limit, our scheme still works to promote input state transfer in this system. Finally, the effects of DM interaction on input state transfer are also studied. We find that DM interaction can enhance the degree of entanglement transfer for the odd chains but with the loss of the symmetry of the maximal entanglement transfer with m,which is opposite in even chains. In the thermodynamic limit, DM interaction displays no effects on the degree of entanglement transfer but accelerating entanglement transfer.