声子库对量子点系统中量子特性的影响

发布时间：2018-08-22 17:11

【摘要】：量子点是适用于用量子力学原理来研究的足够小的人造微结构体系。由于量子点的大小、形状、耦合强度以及其中电子的数目都能受实验调控,故容易测量其传输性质,因而具有广泛的应用前景。将半导体量子点嵌在微腔中能够形成新的腔量子电动力学系统。近年来,由于半导体腔量子电动力学系统的设计与制造工艺都取得的巨大进步,腔量子电动力学系统在量子信息处理等领域引起了人们的广泛关注。将发射器嵌在固态体系中时,固态腔量子电动力学系统会不可避免地与环境发生相互作用。声子库作为低频热库与腔量子电动力学系统产生耦合作用时,会导致系统的辐射性质发生改变而产生新奇的物理现象。包括受声子调控的拉比震荡衰、量子点共振荧光谱的线宽依赖于驱动光强以及在二能级量子点体系裸态中产生稳态布居反转等。在本文中,我们研究了声子库环境对量子点-腔量子电动力学系统的影响。声子库与不同系统的相互作用能产生光子阻塞,量子干涉以及共振荧光谱压缩等一系列非经典现象。首先,我们研究了声子库对一个同时受两束激光场驱动的量子点-腔系统中光子阻塞效应的影响。通过调节两个驱动场的强度与相位差,我们找到了系统实现光子阻塞的最优化条件,并讨论了反映光场量子统计性质的二阶关联函数和平均光子数。当不考虑声子库参与作用时,在受驱动量子点-腔系统形成的修饰态中由于不同跃迁通道之间发生的相消干涉,量子点-腔系统能够在中等耦合强度范围内实现很强的光子阻塞效应。当考虑声子库参与作用时,在量子点-腔系统修饰态中会产生新的跃迁通道,其效果体现为对之前形成的相消干涉起到破坏作用。因此,当考虑声子库与量子点-腔系统的电-声耦合作用时,系统的光子阻塞效应会受到抑制。我们同时发现,考虑声子库的温度效应同样也不利于系统产生光子阻塞效应。其次,我们揭示了一个在双色激光场的共同作用下与量子点相耦合的声子库如何形成一个等效量子压缩真空库,且该等效库能够实现任意程度的压缩。当双色场拉比频率取不同值时,等效库可以形成正常或者反转谐振子形式的量子压缩场。当双色场两个分量取相同拉比频率时,等效库表现为一个理想压缩库且量子点偶极矩的一个极化分量的衰减会受到抑制,量子点衰变到稳态的过程也依赖于系统初始时刻的相干性。此外,我们还具体讨论了系统初始时刻相干性对稳态下修饰态的布居分布及荧光谱的影响。在共振激发条件下,系统能够实现修饰态布居的完全极化并得到由单个拉比边峰组成的非对称荧光谱。最后,我们讨论了声子库对受双色场驱动的二能级量子点系统辐射性质的影响。通过推导系统主方程发现,在固态声子库环境中,系统动力学演化特征与受宽频带压缩真空库阻尼的二能级原子系统的演化特性相似。通过调节声子库诱导衰变率的相对强度能够实现系统的布居反转。由电-声相互作用引起的声子调控过程能导致弱的探测光被量子点系统吸收或者放大。此外,我们还研究了量子点系统共振荧光的同相正交压缩谱。
[Abstract]:Quantum dots are small enough artificial microstructures for quantum mechanics. Because the size, shape, coupling strength and the number of electrons in the quantum dots can be controlled experimentally, it is easy to measure their transmission properties and therefore has a broad application prospect. Cavity quantum electrodynamics system. In recent years, the design and fabrication of semiconductor cavity quantum electrodynamics system have made great progress. Cavity quantum electrodynamics system has attracted wide attention in the field of quantum information processing. When the emitter is embedded in solid state system, solid state cavity quantum electrodynamics system will be indispensable. When the phonon library acts as a low-frequency heat reservoir coupled with the cavity quantum electrodynamics system, the radiation properties of the system will be changed and novel physical phenomena will occur. In this paper, we study the influence of phonon library environment on quantum dot-cavity quantum electrodynamics system. The interaction between phonon library and different systems can produce a series of non-classical phenomena, such as photon blocking, quantum interference and resonance fluorescence spectrum compression. The phonon library affects the photon blocking effect in a quantum dot-cavity system driven by two laser fields at the same time. By adjusting the intensity and phase difference of the two driving fields, we find the optimum conditions for the system to realize the photon blocking, and discuss the second-order correlation function and the average photon number reflecting the quantum statistical properties of the light field. Considering the interaction of phonon libraries, the quantum dot-cavity system can achieve a strong photon blocking effect in the moderate coupling strength range due to the cancellation interference between different transition channels in the modified state formed by the driven quantum dot-cavity system. When the interaction of phonon libraries is considered, the modified state of the quantum dot-cavity system will be generated. Therefore, the photon blocking effect is suppressed when the electro-acoustic coupling between the phonon library and the quantum dot-cavity system is considered. Secondly, we reveal how a phonon library coupled to a quantum dot under the combined action of a two-color laser field can form an equivalent quantum squeezing vacuum library, which can achieve arbitrary degree of compression. When the Rabi frequency of a two-color field is different, the equivalent library can form a normal or inverted quantum pressure in the form of a harmonic oscillator. When two components of a two-color field have the same Rabi frequency, the equivalent library is an ideal compression library and the attenuation of one polarization component of the dipole moment of a quantum dot is suppressed. The decay to steady state of a quantum dot also depends on the coherence of the initial time of the system. The effect of the phonon library on the radiation properties of the two-level quantum dot system driven by a two-color field is discussed. The master equation of the system shows that the dynamical evolution of the system is similar to that of a two-level atomic system damped by a wide-band squeezed vacuum Library in a solid-state phonon library. The weak probe light is absorbed or amplified by the quantum dot system. In addition, the in-phase orthogonal compression spectra of resonance fluorescence in the quantum dot system are studied.
【学位授予单位】：华中师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O471.1;O413.2

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