The Effects Of Non-Markovian Environment On The Quantum Information Processing

Due to the fact that the environment inevitably acts on the open quantum system, so if you want to extremely restore the evolution of quantum system, one needs to consider the effect of environment on the quantum system. The core idea of non-Markovian approximation is to quantify the non-Markovianity in trems of the information that flows from environment back to the system. The non-Markovian dynamics successfully explains many phenomena, such as the non-monotonous decreasing of quantum correlations and thus attracts extensive atten-tion of researchers.This thesis mainly involves the influence of non-Markovian environment on the quantum information processing, i.e., the evolution of a specific two-level atom in the non-Markovian environment. We also studied the non-Markovian property of the dynamics of high-dimensional systems. The main contents are as follows:Chapter 1 is the introduction. We introduce the basic concepts in quantum information and open quantum system, mainly the non-Markovian property and its quantification.In Chapter 2, we study the influence of non-Markovian environment to quan-tum logic operations. We choose one-qubit logic gate as the research object, and the environment is assumed to have a Lorentzian structure with zero tempera-ture. The results show that the non-Markovian proprety contributes to weaken the effect of noise environment, and thus effectively protect the operation quality of quantum logic gates. In this chapter, we also discuss the problem of how to control the operation time to improve the precision of logic gates.In chapter 3, we study the entanglement (measured by negativity) evolution and the non-Markovianity for the dynamical process of a spin-S system embed- ded in dephasing environment. Results show that the decoherence function gov-erns the evolutions of coherence, entanglement, and the non-Markovianity of the corresponding dynamical processes. We also give the relationship bteween non-Markovianity and the system dimension.Chapter 4 is the last charpter which is a summary of the work and an outlook of the thesis.