الفهرس 
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Abstract
1.1 Thesis outline
The thesis consists of four chapters. Their contents are as follows: Chapter 1
This chapter is an introduction for the thesis in which basic concepts and infor- mation needed for the following chapters are presented. First, basics of quantum mechanics are introduced. Second, Two-level atom and the atomic coherent state are reviewed. Finally, Information functions like the Boltzmann’s entropy and the fidelity are summarized.
Chapter 2
In this chapter, Bloch equations of a single non-dissipative qubit driven by a laser pulse of arbitrary shape are solved. The solution obtained are used to investigate the instantaneous atomic population and polarization for various shapes of laser pulses (namely, rectangular, triangular, sin2-and train of Gaussian pulses).
Chapter 3
In this chapter, we used the exact analytical solutions for the Heisenberg equa- tions for the atomic operators obtained in the previous chapter to study the atomic entropy, variance squeezing and entropy squeezing for a non dissipative resonantly pulsed driven qubit. three different s hapes o f t he l aser p ulse are con- sidered, namely, rectangular, sin2-and the train of Gaussian pulses. Furthermore, two initial states for the qubit are considered, namely, the atomic ground state and the atomic coherent state.
Chapter 4
The transient quantum fidelity, F(τ ), for a pulsed driven non-dissipative qubit is investigated in cases of different pulse shapes, namely, rectangular, triangular, sin2-and n-Gaussian pulses. Specifically, for the qubit initially in the coherent state |θ, ϕ⟩, we search, graphically and analytically, for the contours (isolines) of the maximum fidelity in the respected planes: (θ, ϕ)-, (θ, τ )- and (ϕ, τ )-planes. The temporal behaviour of the maximum average fidelity over the (θ, ϕ) param- eters is investigated. The case of moving atom in a cavity is investigated and compared with the above pulsed-driven cases.
1.2 Basic of quantum mechanics
Newton’s laws and Maxwell equations are the bases of classical mechanics. This mechanics succeeded to explain matter and energy in the macroscopic range, while failed when applied to the microscopic phenomena [1]. Black body radiation, photoelectric effect and Compton scattering [2, 3] are some phenomena which classical mechanics failed to explain. Quantum mechanics emerged as an attempt to explain phenomena in microscopic range [4, 5], such as photon-atom scattering and flow of electrons in semiconductors. Max Planck in 1900 assumed that the energy exchange between matter and radiation occurs in discrete amounts. He was able to give an accurate explanation to the black body radiation by introducing the concept of the quantum of energy [6–9]. In 1905 Albert Eienstein was able to explain the photoelectric effect by assuming that the light is made of discrete bits of energy called photons [6–9].
1.2.1 Postulates
Quantum mechanics is based on a number of postulates which leads to agree- ment with experimental observations in the microscopic range. There are five postulates of quantum mechanics:
Postulate 1. The state of a quantum system is completely specified by a wave function ψ that depends on the coordinate and the time. The square modulus of this function |ψ|2 gives the probability density for finding the system with a specified set of coordinate values [3, 10, 11]. The wave function ψ must be a single valued, finite and continuous