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

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

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.