Quantum coherence, control, and information in mesoscopic systems

拟议的理论研究目标是理解和控制量子态及其在凝聚态系统中的相干性，如超导纳米电路和半导体量子点。它直接旨在理解和提出实验。它探讨了在低温下，当物理相关性具有很长的寿命时，对退相干（经典动力学和量子动力学之间的边界）的精细理解。一个具体的重点是研究噪声源，如低频噪声，这是迄今为止非标准的理论，但在实验中无处不在。在同样的背景下，将沿着实际超导器件的模型研究使用有效的非线性探测器和强耦合器件的量子测量物理。这种类型的研究允许在量子测量的一般主题的新见解，并允许设计测量理论的概念具体的测试实验。量子逻辑门将使用最优控制理论进行优化。最佳的解决方案将考虑到退相干，并探索退相干下的控制边界。来自量子光学和原子物理学的想法将被调查，特别是从电路腔量子电动力学使用线性腔以及超导量子干涉器件（SQUID）作为非线性腔。这些工具的潜力，创造非经典状态的微波场，如猫态，压缩态，纠缠对将被调查。拟议的研究将扩展到介观器件的一般高频特性，如超导单光子探测器的量子动力学。这些高频特性是纳米器件电子应用的关键。理论工具联合收割机结合了凝聚态理论、非平衡统计力学、量子光学和核磁共振理论的最新方法。

The proposed theoretical research targets the understanding and control of quantum states and their coherence in condensed matter systems such as superconducting nanocircuits and semiconductor quantum dots. It is directly aimed at understanding and proposing experiments. It explores a refined understanding of decoherence - the boundary between classical and quantum dynamics - at low temperatures, when physical correlations have a long lifetime. A specific focus is the study of noise sources such as low frequency noise, which are so far non-standard to theory but ubiquitous in experimentation. In the same context, the physics of quantum measurement using efficient nonlinear detectors and strongly coupled devices will be investigated along models for actual superconducting devices. This type of research allows novel insights in the general topic of quantum measurement and allows to design specific test experiments for the concepts of measurement theory. Quantum logic gates will be optimized using optimum control theory. The optimum solutions will take decoherence into account and explore the boundaries of control under decoherence. Ideas originating from quantum optics and atomic physics will be investigated, specifically from circuit-cavity quantum electrodynamics using linear cavities as well as superconducting quantum interference devices (SQUIDs) as nonlinear cavities. The potential of these tools to creating nonclassical states of microwave fields such as cat states, squeezed states, and entagled pairs will be investigated. The proposed research will extend towards general high-frequency properties of mesosocopic devices such as the quantum kinetics of superconducting single-photon detectors. These high-freuqency properties are key to electronics applications of nanodevices. The theoretical tools combine up-to-date methods of condensed-matter theory, nonequilibrium statistical mechanics, quantum optics, and theory of nuclear magentic resonance.