makino
超导量子电路中微波相干效应的研究
摘要
量子相干和干涉效应是量子光学和激光物理中非常重要的课题之一，基于相干效应的许多新颖的量子现象已经得到了研究学者的深入研究。另一方面，超导量子电路，又称人工原子，近年来在量子信息和计算方面得到了广泛的应用。超导量子比特是一种固态装置，不仅易于设计性，而且有很好的参数可控性和实验制备性。因此，各种各样的超导比特已得到了精确制备和广泛应用，而且，许多量子光学现象可以在超导量子电路系统中得以验证，在量子光学领域有着重要的研究和应用价值。
本文中，我们主要研究微波驱动的三能级∆型超导fluxonium 比特电路系统的量子相干效应。通过选择合适的参数展现系统的量子光学特性，进而分析系统的特征和量子现象的物理机制。研究内容如下：
(1) 我们研究了三能级∆型超导fluxonium电路系统中的色散转换特性。当用三个微波场分别耦合于三能级超导fluxonium电路的三个不同的跃迁时，超导电路系统的吸收和色散谱强烈依赖于外场的相对相位和强度。当相对相位π/2 改变到3π/2时，正负色散发生转换，此时，吸收为零。正负色散转换对光的超慢与超快传播方面有着重要的应用。而且，当我们固定相对相位时，通过通过调节经典场的相对强度也可以获得无吸收的色散开关。
(2) 我们研究了三能级∆型超导fluxonium电路系统中的相干布居捕获现象。考虑三个外加场应用于不同跃迁的物理模型，结果表明系统的相干布居捕获效应强烈地依赖外加场的相对相位和强度。当相对相位为0或π时，最大的原子相干获得，相干布居捕获发生。但是当相对相位为π/2时，原子的相干性减弱。此外，当固定相对相位为π/2并增强两个低能级间的Rabi频率时，相干性减小。我们利用缀饰态方法解释相对相位及强度对布居捕获调制的物理机制。
say goodbye什么意思
总之，利用外加微波场与超导fluxonium电路系统的相互作用，依赖于外加场相位和强度的色散开关和相干布居捕获效应发生。这里我们应用了超导量子电路这个易操控的固态系统，而且采用的是可行性的实验参数。因此系统的量子光学特性在实验中可以观测。我们的研究不仅有助于加深对量子相干效应的理解，而且对固态系统的特征及其光学特性有着更加深入的了解，为量子信息处理提供了理论帮助。
关键词：超导量子电路，相位控制，色散转换，相干布居捕获
STUDIES ON MICROWAVE COHERENCE EFFECT IN SUPERCONDUCTING QUANTUM CIRCUITS
ABSTRACT
Quantum coherence and interference effects have been one of the very important topics in quantum optics and lar physics, and many novel quantum phenomena bad on coherent effects have been widely studied by the rearchers. On the other hand, the superconducting quantum circuits, which are also named as artificial atoms, have the crucial applications in quantum information and quantum computation in recent years. Superconducting qubit is a solid-state device, which not only is easy to be designed, but also has the properties of controllable parameters and experimental fabrication. As a conquence, the various superconducting qubits have been accurately prepared and extensively applied, and many quantum optical phenomena could be demonstrated in superconducting quantum circuit system, which have the very important values of rearch and application in the field of quantum optics.
In this paper, we discuss quantum coherence effects in the microwave-driven three-level ∆-type superconducting fluxonium qubit. With a good choice of the experimental parameters, the quantum-optics features of the system have been shown and the discussions of the system characters and the inherent physical mechanisms have been done. The main contents are listed as follows:
(1) We have studied the switching of dispersion in the three-level ∆-type superconducting fluxonium circuit. When three microwave fields are applied to three transitions of the conducting fluxonium circmba报考要求
uit, respectively, the absorption and dispersion spectra of the superconducting circuit system are strongly dependent on the relative pha and the intensity of the external field. When the relative pha is changed from π/2 to 3π/2, the switching from positive to negative dispersion aris and at the same time the absorption is nearly equal to zero. Switching from positive to negative dispersion has important applications in the subluminal and superluminal light propagation. In addition, for the f ixed relative pha π/2, the dispersion switching with vanishing absorption could be obtained by adjusting the relative intensity of classical fields.
(2) We have investigated the behavior of coherent population trapping in the Δ-type three-level superconducting fluxonium circuit. In the physical model of three transitions respectively driven by three externally electromagnetic field, the coherent population trapping of the system strongly depends on the applied-field relative pha and intensities. When the relative pha is tuned to 0 or π, the maximal atomic coherence is prent and coherent population trapping occurs. While for the choice of π/2, the atomic coherence becomes weak. Meanwhile, for the fixed relative pha π/2, the value of coherence had d ecreas as the increa of Rabi frequency of the external field coupled with two lower levels. We have
utilized the dresd-state method to explain the physical mechanism of coherent population trapping,
which is controlled by the relative pha and intensities of the applied fields.
In conclusion, bad on the interaction between the microwave field and the superconducting fluxonium circuit system, the dispersion switching and coherent population trapping effects occur, which are dependent on the relative pha and intensities of the applied fields. Here we u the easily-manipulated superconducting quantum circuit system, and consider the feasible physical parameters. Thus, the quantum-optics properties of the system could be obrved experimentally. Our rearch can not only be helpful for the deep understanding of quantum coherence effects, but also have a understanding for the system features and optical properties of solid state systems, which may offer the help for quantum information processing.
Key Words:Superconducting quantum circuit，Pha control，Dispersion switching，Coherent population trapping
目录
nicolas主要符号说明 (1)
第一章绪论 (2)
wireless是什么意思
1.1 引言 (2)
1.2 超导量子电路研究概况 (3)
1.2.1 超导电荷量子比特 (4)
1.2.2 超导磁通量子比特 (5)
1.2.3 超导相位量子比特 (6)
1.3 超导量子电路中光学现象的研究 (7)
第二章基本理论工具 (9)
周思成讲课视频2.1 量子力学中的三种绘景 (9)
2.2 光与物质相互作用系统 (10)
2.2.1两能级原子系统 (10)
2.2.1.1概率幅求解法 (12)
2.2.1.2密度矩阵求解法 (13)
2.2.2 三能级原子系统 (14)
2.2.2.1 相干布居捕获 (14)
2.2.2.2 电磁诱导透明 (15)
2. 3 哈密顿量的旋转 (18)
2.3.1 原子场频率 (18)
2.3.2 光场频率 (19)
星期一英文
第三章超导量子电路 (20)
3.1 超导电路量子化 (20)
3.1.1 LC电路量子化 (20)
3.1.2 固态超导电路量子化 (23)
朴相民
3.1.2.1 Jophson 系统 (23)
3.1.2.2 Cooper-Pair Box系统 (23)
3.2. 超导Fluxonium电路 (25)
join in第四章在超导量子电路中利用相位和振幅控制转换正负色散 (28)
4.1 引言 (28)
4.2 物理模型与方程 (28)
晚安英语怎么说4.3 结果和讨论 (30)
4.3 小结 (33)
