Interacting Few Level Systems at the Atomic Scale

扫描隧道显微镜（STM）以其在毫开尔文（mK）温度下的原子精度和优异的能量分辨率，在传感和材料科学领域发挥着重要的支撑技术作用。然而，到目前为止，还不能直接访问目标低能级系统中的量子相干性，这些特性可以以不同的方式表现出来。我们将描述，理论上描述，并进一步开发一个STM尖端功能化的单量子态保护在超导隙内，这是非常尖锐的能量。更具体地说，在STM尖端的顶端添加磁性杂质，以诱导间隙内结合的Yu-Shiba-Rusinov （YSR）态。这种状态是关联多体系统中的一种集体状态，其寿命仅受与剩余环境自由度的相互作用的限制。我们的总体目标是了解这种STM尖端状态耦合到目标低能级系统，超导宿主及其周围环境。我们希望直接获得所得到的多体量子系统的相干特性，并实现相干操作方案。此外，我们想要探索YSR-STM作为感知外来量子态的手段的独特特征。我们的团队在实验和理论之间建立了良好的合作关系，并有广泛的联合出版物记录。它汇集了mK-STM的物理和实验技术方面的大量专业知识，以及介观器件中超导量子输运的理论专业知识。

The scanning tunneling microscope (STM) has played an important role as a supporting technology in the context of sensing and material science with its atomic precision and excellent resolution in energy when operated at milli-Kelvin (mK) temperatures. However, it has until now not been able to directly access the properties of quantum coherence in target few level systems, which can manifest in different ways. We will characterize, theoretically describe, and further develop an STM tip functionalized with a single quantum state well-protected inside a superconducting gap, which is extremely sharp in energy. More specifically, a magnetic impurity is added to the apex of the STM tip to induce a bound in-gap Yu-Shiba-Rusinov (YSR) state. This state is a collective state in a correlated many-body system with a lifetime only limited by interactions with residual environmental degrees of freedom. Our general goal is to understand such an STM tip state coupled to target few level systems, to the superconducting hosts, and their surrounding environment. We want to directly access coherence properties of the resulting many-body quantum system and implement coherent manipulation schemes. Furthermore, we want to explore the unique features of the YSR-STM as means for sensing exotic quantum states. Our team is a well-established collaboration between experiment and theory, with an extensive record of joint publications. It brings together vast expertise in the physics and experimental techniques of mK-STM and theoretical expertise in superconducting quantum transport in mesoscopic devices.