腔QED和超导量子比特系统中的几何量子关联的控制

发布时间：2018-06-30 20:57

本文选题：几何量子关联 + 腔QED系统　；参考：《浙江大学》2016年博士论文

【摘要】：量子信息学是一门方兴未艾的交叉科学,其涵盖的理论基础有量子电动力学、量子光学、电子学、数学和信息学,融合各种现代化的科学与技术,如通信和计算机技术、固体物理和半导体、光电子和激光技术、原子光学与原子制版术等,研究内容包括量子信息的多个学科分支,如量子密码、量子隐形传态、量子算法、量子网络等。该学科诞生以来取得了令人瞩目的成就,如实验上实现了量子远程通信等。其应用有着诱人的前景。在量子信息处理任务中,量子纠缠作为一种有效的资源起着重要的作用。与此同时,人们还发现它有着极其脆弱的一面,容易受环境的干扰发生退相干,甚至在某些量子系统中会发生量子纠缠的突然死亡。Ollivier和Zurek等人提出了另一种量子关联,称为量子谐错,它被认为是一种强壮的物理资源。量子谐错有一些奇特的性质,如分离态的量子纠缠为零,但量子谐错却不为零。人们发现量子谐错能用于完成某些量子计算。此外,在耗散环境中量子系统的量子谐错演化会出现突然转变或突然变化现象。然而用于实际计算时,Ollivier和Zurek等人提出的基于熵的量子谐错定义是一个不便于操作的度量方式,仅有少数量子系统能有量子谐错的解析解。为此,Dakic等人首先提出了基于二范数的几何方法度量量子谐错的思想。他们提出的几何度量方法是在一定情形下简化了量子谐错的计算,优点是能计算任意两比特的量子系统的几何量子谐错。近来,有研究者提出了基于一范数的几何量子谐错的度量。该度量不仅保持了二范数几何量子谐错的优点,而且揭示量子系统存在的突然转交现象。在本文中,我们主要研究了选择性测量和脉冲如何增强和保护超导量子比特系统的几何量子关联,以及应用含时电磁场控制腔QED系统的几何量子关联和量子突然转变现象等。本文的前面部分,我们研究了选择性测量和退耦合脉冲对超导量子比特系统几何量子关联以及量子信息流的影响。首先研究了选择性测量对两个相同的超导量子比特分别与各自数据总线耦合的系统的几何量子谐错和纠缠的影响,得到了在选择性测量下的几何量子谐错和量子纠缠时间演化的表达式。通过理论分析和计算机模拟研究了单次和多次选择性测量对几何量子谐错和量子纠缠的时间演化,结果显示一系列选择性测量对几何量子谐错和量子纠缠的有保护和增强作用,并且选择性测量仅一次同样会产生的增强作用。我们讨论了最佳实施测量的时间函数,探讨了最佳时间测量对两超导量子比特的几何量子关联的影响。发现测量一次或数次不但会增强量子关联,而且能使超导量子比特系统获得最大纠缠态。还进一步研究了选择量子测量是如何影响超导量子比特系统与数据总线之间量子信息的交换,发现选择性测量可以用来控制超导量子比特和数据总线之间的信息流向。对超导量子电路数据总线实施选择性测量,能起到保护超导量子比特的量子信息,使量子信息从数据总线中回流到超导量子比特中。还研究了两量子超导比特间的积距离,通过测量导致瞬间量子信息流增加,验证了选择性测量能保护和增强系统的几何量子关联,发现增强效果与非马尔科夫过程有关。另外,还提出了利用一系列退耦合脉冲控制和保护超导量子比特系统几何量子关联的方案,并用积距离研究其对系统量子信息流向的控制。结果表明,退耦合脉冲能够保护系统的几何量子关联,发现脉冲作用瞬间,量子信息流瞬时从数据总线重新流回超导量子比特中。本文的后面部分,我们研究了如何用含时电磁场以及选择性测量来控制和保护耗散腔QED系统的几何量子关联,讨论了如何用含时电磁场对量子突然转变现象进行操控。首先考虑了两个耗散的Jaynes-Cummings模型组成的系统的几何量子关联,发现对某些初态,一范数的几何量子谐错展现了双量子突然转变现象,并发现应用含时电磁场能有效的延迟两原子的几何量子关联的退化,即延长几何量子关联双量子突然转变的时间间隔。同时研究了Tavis-Cummings模型,发现了存在突然转变现象,还研究了选择性测量对Tavis-Cummings模型系统量子关联动力学的影响。发现通过选择性测量导致瞬间原子积距离增大,迫使量子信息从腔中回流到原子中。以此能更有效的控制和保护原子的几何量子关联和量子信息流,其增强效果与非马尔科夫过程有关。
[Abstract]:Quantum informatics is an emerging cross science which covers the theoretical basis of quantum electrodynamics, quantum optics, electronics, mathematics and Informatics, and the integration of modern science and technology, such as communications and computer technology, solid and semiconductor, photoelectron and laser technology, atomic optics and atomic plate making, and so on. The content includes many branches of quantum information, such as quantum cryptography, quantum teleportation, quantum algorithm, quantum network and so on. Since the birth of this subject, remarkable achievements have been achieved, such as the realization of quantum telecommunication in experiment. Its application has an attractive prospect. Quantum entanglement is a kind of effective in the quantum information processing task. Resources play an important role. At the same time, it is found that it has an extremely fragile side, easy to be decohered by the interference of the environment, and even the sudden death of quantum entanglement in some quantum systems,.Ollivier and Zurek et al. Put forward another kind of quantum correlation, called quantum error, which is considered to be a strong one. The quantum harmonic error has some peculiar properties, such as the quantum entanglement of the separated state, but the quantum harmonic error is not zero. The quantum harmonic energy is found to be used to complete some quantum calculations. In addition, the quantum harmonic evolution of quantum systems in the dissipative environment will appear abrupt or sudden change. The entropy based definition of the quantum harmonic error proposed by Ollivier and Zurek is an inconvenient measure. Only a few quantum systems can have an analytic solution of the quantum harmonic error. For this reason, Dakic et al. First proposed the idea of measuring the quantum harmonic error based on the geometric method based on two norm. The calculation of quantum harmonic error is simplified. The advantage is that the geometric quantum harmonic error of a quantum system with any two bits can be calculated. Recently, some researchers have proposed a metric based geometric quantum error measure. This measure not only maintains the advantages of the quantum harmonic error of the two norm geometry, but also reveals the sudden transition of the quantum system. In this paper, we mainly study the geometric quantum correlation of selective measurement and pulse enhancement and protection of superconducting qubit systems, as well as the application of geometric quantum correlation and quantum abrupt transformation in QED systems with time-dependent electromagnetic field control. The geometric quantum correlation of the subbit system and the influence of the quantum information flow. First, the effects of selective measurement on the geometric quantum error and entanglement of two same superconducting qubits coupled with their respective data bus are studied. The expression of the geometric quantum harmonic error and the quantum entanglement time evolution under the selective measurement are obtained. By theoretical analysis and computer simulation, the time evolution of single and multiple selective measurements for geometric quantum errors and quantum entanglement is studied. The results show that a series of selective measurements have protective and enhanced effects on geometric quantum errors and quantum entanglement, and the enhanced effect of selective measurements only once. The time function of the best measurement is discussed, and the effect of the best time measurement on the geometric quantum correlation of two superconducting qubits is discussed. It is found that the quantum correlation can be enhanced not only once or several times, but also the maximum entanglement state of the superconducting qubit system. The exchange of quantum information between the qubit system and the data bus shows that the selective measurement can be used to control the flow of information between the superconducting qubit and the data bus. In the superconducting qubits, the product distance of two quantum superconducting bits is also studied. By measuring the increase of instantaneous quantum information flow, it is proved that the selective measurement can protect and enhance the geometric quantum correlation of the system. It is found that the enhancement effect is related to the non Markoff process. In addition, a series of decoupling pulse control and the control are also proposed. In order to protect the geometric quantum correlation of the superconducting qubit system, we use the product distance to study the control of the flow direction of the system's quantum information. The results show that the decoupling pulse can protect the geometric quantum correlation of the system. It is found that the quantum information flow instantaneously reflows into the superconducting qubits from the data line. In part, we study how to use time-dependent electromagnetic field and selective measurement to control and protect the geometric quantum correlation of a dissipative cavity QED system. We discuss how to manipulate the quantum sudden change with time-dependent electromagnetic field. First, we consider the geometric quantum correlation of the system composed of two dissipative Jaynes-Cummings models. Some initial states, the geometric quantum harmonic error of one norm shows the phenomenon of double quantum sudden change, and it is found that the application of time-dependent electromagnetic field can effectively delay the geometric quantum correlation of two atoms, that is to extend the time interval of the double quantum sudden transformation of geometric quantum correlation, and study the Tavis-Cummings model, and find the existence of sudden transformation. The effect of selective measurement on the quantum correlation dynamics of the Tavis-Cummings model system is also studied. It is found that the increase of the instantaneous atomic distance by selective measurement forces the quantum information to return from the cavity to the atom. In order to more effectively control and protect the geometric quantum correlation and the quantum information flow of the atom, the enhancement effect and the non effect of the quantum information flow can be enhanced. The Markoff process is related.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O413

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