Researches On Dynamics Characteristics And State Control Of Quantum System In Non-markovian Environments

Based on quantum system in non-Markovian environments,the main research includes the following several points.First of all,the coherence dynamics of qubit system in the non-Markovian environment is investigated.The results show that the coherence dynamics of qubit system has a direct relationship with the surrounding non-Markovian environment.The coherence of qubit in ohmic reservoir at low temperature decays gradually to zero and then revives after a period of time,while the coherence of qubit in ohmic reservoir at high temperature decreases to zero without any revive.Meanwhile,the revival amplitude and time of coherence increases with resonance decreasing.Next,quantum correlation dynamics of a mixed three-qubit W-type state in three independent non-Markovian reservoirs with Lorentzian spectral density is investigated.The effects of environment's amount of non-Markovianity ?/ ?,the detuning between the qubit frequency and the cavity centre frequency or parameters in initial states on the three-qubit quantum correlation dynamics are presented in detail.The results show that in the non-Markovian regime quantum correlation exhibits oscillations as time evolves and leads to quantum correlation deaths and survivals.Moreover,quantum correlation can be preserved for a long time if the non-Markovian condition and the detuning condition are satisfied simultaneously.Finally,utilizing the method of optimal control,we investigate the tactics of state transfer in the non-Markovian quantum system.Based on the optimal control theorem,the system control laws used to transfer state are designed.the characteristics of coherence and purity change in non-markovian open system are studied.The numerical simulations indicate that arbitrary state transfer can be realized with a success rate of more than 98 percent under the optimal control function by a proper external control field in non-Markovian system.When the right control field and function is implemented,not only the decoherence is compensated completely but also the purity of quantum states are maintained in the process of state transfer.