Quantum coherence, control, and information in mesoscopic systems

提出的理论研究目标是理解和控制凝聚态系统中的量子态及其相干性，如超导纳米电路和半导体量子点。它的直接目的是理解和提出实验。它探索了在低温下对退相干（经典动力学和量子动力学之间的边界）的精确理解，此时物理相关性具有很长的寿命。一个特别的重点是噪声源的研究，如低频噪声，这是迄今为止的非标准理论，但在实验中普遍存在。在同样的背景下，利用有效的非线性探测器和强耦合器件进行量子测量的物理学将沿着实际超导器件的模型进行研究。这种类型的研究允许对量子测量的一般主题有新的见解，并允许为测量理论的概念设计特定的测试实验。量子逻辑门将使用最优控制理论进行优化。最优解将考虑退相干并探索退相干下的控制边界。源自量子光学和原子物理学的想法将被研究，特别是使用线性腔的电路腔量子电动力学以及超导量子干涉器件（squid）作为非线性腔。这些工具在创造微波场的非经典态（如猫态、压缩态和纠缠对）方面的潜力将被研究。提出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学应用的关键。理论工具结合了凝聚态理论，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.