Tuning Superinductors by Quantum Coherence Effects for Enhancing Quantum Computing

TL;DR

This paper investigates how quantum coherence effects in disordered superconducting thin films can significantly enhance kinetic inductance while maintaining high quality factors, offering insights for optimizing superinductors in quantum technology.

Contribution

It provides a theoretical analysis of kinetic inductance and quality factor in disordered superconductors, revealing quantum coherence effects that enhance superinductor performance near the superconductor-insulator transition.

Findings

Exponential increase of kinetic inductance with disorder at low temperatures.

High quality factors (~10^4) coexist with increased inductance.

Quantum coherence effects cause a broad distribution of quality factors near the transition.

Abstract

Research on spatially inhomogeneous weakly-coupled superconductors has recently received a boost of interest because of the experimental observation of a dramatic enhancement of the kinetic inductance with relatively low losses. Here, we study the kinetic inductance and the quality factor of a strongly-disordered weakly-coupled superconducting thin film. We employ a gauge-invariant random-phase approximation capable of describing collective excitations and other fluctuations. In line with the experimental findings, we have found that in the range of frequencies of interest, and for sufficiently low temperatures, an exponential increase of the kinetic inductance with disorder coexists with a still large quality factor $\sim 10^4$. More interestingly, on the metallic side of the superconductor-insulator transition, we have identified a range of frequencies and temperatures $T \sim 0.1T_c$ where quantum coherence effects induce a broad statistical distribution of the quality factor with an average value that increases with disorder. We expect these findings to further stimulate experimental research on the design and optimization of superinductors for a better performance and miniaturization of quantum devices such as qubit circuits and microwave detectors.