量子点cQED系统中的声子效应研究
发布时间：2018-10-31 09:33
【摘要】：空腔量子电动力学(cavity Quantum Electrodynamics,c QED)是量子光学研究领域的一个重要分支。近年来,固态的c QED系统,即量子点-微腔系统引起了人们的研究兴趣。新的系统在量子信息处理中同样具有广泛的应用,范围包含量子位的实现到单光子源的建立。固态系统中的一个重要问题是会受到声子库的影响。这些影响主要表现在三个方面,即声子引起的重整化、纯退相和失谐声子散射。本文首先是介绍了基本的光与原子相互作用模型:J-C模型,以及声子库对量子点c QED系统的影响。声子库的影响主要来自于电子与声子的耦合,这种耦合包含两种机制:压电耦合和形变势耦合。由粒子的波函数出发来计算相应的声子谱函数,从得到的结果中发现压电耦合作用对系统的影响至少比形变势耦合小了一个数量级,这个结果支持了声子库对系统的影响主要来源于LA声子的结论。量子点的形状受到制造技术的影响会有所不同,这意味着在实际系统中量子点形状的影响是一个重要的问题。由波函数出发通过计算得到了三种典型形状:球形、椭球形和圆盘形的量子点的声子谱函数和相应的声子效应曲线。这些结果表明了声子效应与量子点形状有较强的依赖关系。在三种形状量子点中,圆盘形量子点具有最强的电声子耦合和最宽的声子谱分布,相应地,其声子效应也是最明显的。声子库对系统的影响与温度是直接相关的,由于存在耦合重整化,随着温度升高,系统将会从强耦合转变到弱耦合状态。从约化密度矩阵主方程出发,通过计算可以得到这种转变的判定条件。受声子库的影响,量子点的衰减率与温度直接相关,当温度在40-50K时,衰减率会随着温度升高迅速上升。本文的计算表明在这种温度依赖关系下,系统状态的变化在某些情况下会出现反常,如随着温度升高,系统会出现强耦合→弱耦合→强耦合→弱耦合的变化情况。这表明声子库所带来的影响会使量子点c QED系统出现一些新的与原子c QED系统不同的现象。文章最后计算了发射谱随温度的变化曲线,对一些相关问题进行了讨论。
[Abstract]:Cavity quantum electrodynamics (cavity Quantum Electrodynamics,c QED) is an important branch of quantum optics. In recent years, the solid-state c QED system, called quantum dot-microcavity system, has attracted much attention. The new system also has a wide range of applications in quantum information processing, ranging from the realization of quantum bits to the establishment of single photon sources. An important problem in solid state systems is the influence of phonon libraries. These effects are mainly reflected in three aspects: phonon induced renormalization pure dephase and detuning phonon scattering. In this paper, we first introduce the basic model of the interaction between light and atom: J-C model, and the effect of phonon library on the c QED system of quantum dots. The effect of phonon library mainly comes from the coupling of electrons and phonons, which consists of two mechanisms: piezoelectric coupling and deformation potential coupling. The corresponding phonon spectrum function is calculated from the wave function of the particle. It is found that the effect of piezoelectric coupling on the system is at least one order of magnitude less than that of the deformation potential coupling. This result supports the conclusion that the effect of phonon library on the system is mainly derived from LA phonon. The shape of quantum dots will be affected differently by manufacturing technology, which means that the shape of quantum dots is an important problem in practical systems. The phonon spectral functions and the corresponding phonon effect curves of spherical ellipsoid and disk quantum dots are obtained from the wave function. These results indicate that the phonon effect is strongly dependent on the shape of quantum dots. Among the three kinds of quantum dots, the disk quantum dots have the strongest phonon coupling and the widest phonon spectrum distribution, and the phonon effect is also the most obvious. The effect of phonon library on the system is directly related to temperature. Due to the existence of coupling renormalization, the system will change from strong coupling to weak coupling state with the increase of temperature. Based on the main equation of reduced density matrix, the decision conditions of this transformation can be obtained by calculation. Under the influence of phonon pool, the decay rate of quantum dots is directly related to temperature. When the temperature is 40-50K, the attenuation rate will rise rapidly with the increase of temperature. The calculation in this paper shows that under this temperature dependence, the variation of system state will be abnormal in some cases, for example, with the increase of temperature, there will be strong coupling and weak coupling and strong coupling and weak coupling in the system. It is suggested that the effect of phonon library will lead to some new phenomena in the quantum dot c QED system which are different from those in the atomic c QED system. Finally, the curve of emission spectrum with temperature is calculated, and some related problems are discussed.
【学位授予单位】：暨南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O471.1
本文编号：2301685
[Abstract]:Cavity quantum electrodynamics (cavity Quantum Electrodynamics,c QED) is an important branch of quantum optics. In recent years, the solid-state c QED system, called quantum dot-microcavity system, has attracted much attention. The new system also has a wide range of applications in quantum information processing, ranging from the realization of quantum bits to the establishment of single photon sources. An important problem in solid state systems is the influence of phonon libraries. These effects are mainly reflected in three aspects: phonon induced renormalization pure dephase and detuning phonon scattering. In this paper, we first introduce the basic model of the interaction between light and atom: J-C model, and the effect of phonon library on the c QED system of quantum dots. The effect of phonon library mainly comes from the coupling of electrons and phonons, which consists of two mechanisms: piezoelectric coupling and deformation potential coupling. The corresponding phonon spectrum function is calculated from the wave function of the particle. It is found that the effect of piezoelectric coupling on the system is at least one order of magnitude less than that of the deformation potential coupling. This result supports the conclusion that the effect of phonon library on the system is mainly derived from LA phonon. The shape of quantum dots will be affected differently by manufacturing technology, which means that the shape of quantum dots is an important problem in practical systems. The phonon spectral functions and the corresponding phonon effect curves of spherical ellipsoid and disk quantum dots are obtained from the wave function. These results indicate that the phonon effect is strongly dependent on the shape of quantum dots. Among the three kinds of quantum dots, the disk quantum dots have the strongest phonon coupling and the widest phonon spectrum distribution, and the phonon effect is also the most obvious. The effect of phonon library on the system is directly related to temperature. Due to the existence of coupling renormalization, the system will change from strong coupling to weak coupling state with the increase of temperature. Based on the main equation of reduced density matrix, the decision conditions of this transformation can be obtained by calculation. Under the influence of phonon pool, the decay rate of quantum dots is directly related to temperature. When the temperature is 40-50K, the attenuation rate will rise rapidly with the increase of temperature. The calculation in this paper shows that under this temperature dependence, the variation of system state will be abnormal in some cases, for example, with the increase of temperature, there will be strong coupling and weak coupling and strong coupling and weak coupling in the system. It is suggested that the effect of phonon library will lead to some new phenomena in the quantum dot c QED system which are different from those in the atomic c QED system. Finally, the curve of emission spectrum with temperature is calculated, and some related problems are discussed.
【学位授予单位】：暨南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O471.1
【参考文献】
相关期刊论文 前3条
1 赵凤瑷,张春玲,王占国;半导体量子点及其应用(Ⅰ)[J];物理;2004年04期
2 王伟胜;张明亮;陈芝得;;Influence of a phonon bath in a quantum dot cavity QED system:Dependence of the shape[J];Chinese Physics B;2014年09期
3 谢友兰;陈芝得;;Coherent incoherent transition in the spin boson model with a super-ohmic bath[J];Chinese Physics B;2009年11期
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