Collaborative Research: Design and modeling of novel superconducting circuits with coherent phase slips

超导是一种量子现象，表现为当温度降至临界温度以下时，某些材料的电阻率突然消失。纳米制造、材料科学和高精度测量的最新进展使研究各种新颖的超导纳米系统成为可能，而这在几年前还几乎是不可想象的。具体地说，纳米超导导线及其电路中的量子输运现象的研究正迅速成为现代物理和工程的中心主题之一。随着导线变得更窄，各种有趣的量子效应变得明显起来。强烈的空间限制导致复杂的电子关联，从而影响结构的超导性质。最终，超导电性可能会逐渐消失，一些导线可能会表现出明显的绝缘行为，导致所谓的超导体-绝缘体转变。从未来应用的角度来看，超导体是非常有吸引力的系统，因为它们可以成为量子计算机和其他运行在相干量子隧道事件上的设备的存储位的基本构建块。这个联合项目的主要目的是利用量子相干的力量，解决当前研究前沿的纳米级电路超导的紧迫问题，并在这个令人兴奋的领域发现新的物理。我们的方法将是结合凝聚态理论家和实验者的专业知识，这两人都在相关领域拥有丰富的经验。研究的协作结构将为培训学生在广泛的实验纳米科学和理论凝聚态物理方面提供丰富的环境。教育方面将通过开发与拟议研究直接相关的课程，以及通过与研究有关的研讨会、科学奥林匹克竞赛和针对高中教师的会议来进一步整合。该项目的目标是研究现代纳米级超导电路中新出现的量子输运现象，这些电路被驱动远离平衡，并填充了相干相移，以揭示超导关联在外部条件和环境的新领域中的最终命运。所提出的研究的很大一部分致力于超导纳米线、纳米线桥谐振器和干涉仪中相干相位滑移的随机动力学。重点讨论了微波偏置和磁场对重入超导电性的相互作用，超导开关、双稳性和电流-电压特性的统计，以及相移隧道事件的奇偶宇称效应的研究。建议对超额散粒噪声的研究，跨越超导转变，将提供对驰豫和波动的微观机制的额外洞察。该项目还深入到探索超导和半导体异质结构之间的邻近诱导超导电性的新领域，这些异质结构拥有拓扑秩序。这一研究方向旨在回答拓扑保护对相互作用、无序和其他相关扰动的影响的稳健性和稳定性的关键问题。该项目的长期目标是开发用于量子电路电动力学应用的具有相干相位滑移的新型超导量子比特。所提出的结构设计基于相位滑移结、相位滑移振荡器和基于具有可调非线性的超流载流电感的替代器件。这一方案的成功和完成将对信息处理和光子探测的技术进步具有重要意义。作为这一提议的一部分，将开发的技术和理论方法与多体系统量子物理中更广泛的一类问题有关。拟议工作的结果将在出版物、研讨会、座谈会和会议发言中广泛传播。在该项目下工作的学生将接受广泛的培训，学习凝聚态物理的现代方面，开发非平衡超导系统的新概念方法，并从事原创性研究。作为多样性和教育倡议的一部分，PIS将为代表不足的群体的本科生扩大研究机会，并为科学奥林匹克校际竞赛计划做出贡献。

Superconductivity is a quantum phenomenon that manifests itself as an abrupt disappearance of resistivity in certain materials as temperature is lowered below their critical temperature. Recent advances in the nanometer size fabrication, materials science and high precision measurements made it possible to investigate a variety of novel superconducting nanosystems, which were almost unthinkable only a few years ago. Specifically the studies of quantum transport phenomena in nanoscale superconducting wires and circuits made of them are rapidly emerging as one of the central themes of modern physics and engineering. As wire is made narrower, a variety of intriguing quantum effects becomes apparent. Strong spatial confinement leads to intricate electron correlations that influence superconducting properties of the structure. Ultimately superconductivity could be gradually extinguished and some wires may display pronounced insulating behavior, leading to the so-called superconductor-insulator transition. Superconductors are extremely attractive systems from the point of view of future applications as they could become elementary building blocks for memory bits of quantum computers and other devices operating on coherent quantum tunneling events. The main aim of this joint project is to harness the power of quantum coherence, address the urgent problems of nanoscale-circuit-superconductivity at the frontier of current research, and discover new physics in this exciting field. Our approach will be to combine the expertise of a condensed matter theorist and an experimentalist both having extended experience in related fields. The collaborative structure of the research will provide a rich environment for training students in a broad spectrum of experimental nanoscience and theoretical condensed matter physics. Educational aspects will be further integrated through the development of courses directly related to the proposed research and through research-related seminars, science olympiads, and meetings that target high-school teachers.The goal of the project is to study emergent quantum transport phenomena in the modern nanoscale superconducting circuits driven far from equilibrium and populated with coherent phase slips to reveal the ultimate fate of superconducting correlations in the new domain of external conditions and environments. A substantial part of the proposed research is devoted to stochastic kinetics of the coherent phase slips in superconducting nanowires, nanowire-bridged resonators, and interferometers. The focus in on the mutual role of microwave bias and a magnetic field on the reentrant superconductivity, statistics of the supercurrent switching, bi-stability and current-voltage characteristics, and a study of even-odd parity effects for the phase slip tunneling events. Suggested studies of the excess shot noise, carried across the superconducting transition, will provide additional insights into the microscopic mechanisms of the relaxation and fluctuations. The project also dwells into the new area of exploring proximity-induced superconductivity between superconducting and semiconducting heterostructures that host topological order. This research direction aims to answer the key questions concerning robustness and stability of the topological protection to effects of interactions, disorder and other relevant perturbations. The long-term goal of this project is to develop novel superconducting qubits with coherent phase slips for quantum circuit electrodynamics applications. The proposed architecture designs are based on the phase-slip-junction, the phase-slip-oscillator and an alternative device based on the supercurrent carrying inductor with tunable nonlinearity. The success and completion of this proposal will be of value for the technological advances in the information processing and the photon detection. The technical and theoretical methods that will be developed as a part of this proposal are relevant to a much wider class of problems in the quantum physics of many-body systems. The results of the proposed work will be widely disseminated in publications, seminars, colloquia and conference presentations. Students working under this project will receive extensive training by studying modern aspects of the condensed matter physics, developing new conceptual approaches to nonequilibrium superconducting systems and pursuing original research. As a part of the diversity and educational initiatives PIs will expand research opportunities for the undergraduate students of underrepresented groups and contribute to the science olympiad interscholastic competition program.