Quantum coherence, control, and information in mesoscopic systems

拟议的理论研究旨在理解和控制超导纳米电路和半导体量子点等凝聚态系统中的量子态及其相干性。它的直接目的是理解和提出实验。它探索了对退相干的精细理解-经典动力学和量子动力学之间的边界-在低温下，物理关联具有很长的寿命。一个特别的焦点是研究噪声源，如低频噪声，到目前为止，这些噪声源在理论上是非标准的，但在实验中普遍存在。在同样的背景下，使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进行新的见解，并允许为测量理论的概念设计特定的测试实验。量子逻辑门将利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。来自量子光学和原子物理的想法将被研究，特别是使用线性腔和超导量子干涉器件(SQUID)作为非线性腔的电路-腔量子电动力学。我们将研究这些工具创造非经典微波场状态的可能性，如猫态、压缩态和纠缠对。拟议的研究将扩展到中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。这些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.