基于电路理论的超导量子比特消相干机理的研究

项目名称： 基于电路理论的超导量子比特消相干机理的研究

项目编号： No.10864002

项目类型： 地区科学基金项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 嵇英华

作者单位： 江西师范大学

项目金额： 20万元

中文摘要： 含超导量子比特的固态量子电路，由于具有损耗小、可规模化等特点，是实现量子通信与量子计算最有希望的方案之一。目前关于超导量子比特系统研究工作的一个重点是消相干与退纠缠的研究。本项目应用量子物理学与电路理论中的研究方法，对超导量子比特系统的动力学特性进行研究。研究内容包括：超导量子电路的结构、超导量子电路与环境之间的耦合方式、耦合强度等因素对系统动力学演化的影响。在本项目中，我们就超导量子电路的多能级结构、电路的结构及电路元器件参数对消相干的影响进行了比较系统的研究。主要研究结果表明：利用超导量子电路多能级结构是克服量子计算误差并提高量子门速度的一个有效途径。我们也对量子系统的初态、演化路径，系统与环境间的耦合模式等因素对纠缠动力学演化的影响也进行了比较深入的探讨。这方面的主要研究结果表明：通过优化演化路径与耦合模式，能够有效地避免环境引起的消相干并阻止出现完全退纠缠。同时，我们还对三能级量子系统在混合态下的量子几何相位进行了探索性的研究。基于研究工作，我们得到了一些比较有意义的结果，能够为实现超导量子比特的有效操纵提供一定的理论依据与指导。

中文关键词： 超导量子比特；开系统；消相干；量子纠缠

英文摘要： The solid quantum circuit containing superconducting qubits is one of the most promising protocols to realize quantum communication and quantum computation due to small wastage, scalability and other characteristics. Now, the research on superconducting qubit system focuses on the decoherence and disentanglement. Our subjects undertake the study on the dynamic characteristics of superconducting qubit systems by use of the methods in quantum physics and circuit theory. Investigating contents include that the factors, such as structure of superconducting quantum circuits, the coupling way between superconducting quantum circuits and environment, the coupling strength, could influence on the dynamic evolution of system. In this project, we study systematically the effects of superconducting quantum circuits for multi-level structure, the structure of the circuit and the circuit component parameters on decoherence. The main results indicate that making use of the multi-level structure of superconducting quantum circuits is an effective way to overcome quantum calculation error and increase the speed of quantum gate. We also made a relatively in-depth discussion on the influence of the factors such as the initial state of quantum systems, evolution path and the coupling way between the system and environment on the entanglement dynamic evolution. The main results show that we can effectively avoid the environmentally induced decoherence and prevent emergence of complete disentanglement by optimizing the evolution path and coupled modes. Meanwhile, we also made an exploratory study on the geometric phase of three-level quantum systems in mixed states. Based on above research works, we get some meaningful results which provide a theoretical basis and guidance to achieve the effective control of superconducting qubits.

英文关键词： superconducting qubit; open system; decoherence; quantum entanglement