Nanoscale observation and control of quasiparticle induced magnetic noise in a superconducting resonator

TL;DR

This study uses quantum sensing to observe and control magnetic noise caused by quasiparticles in superconducting resonators, revealing how external factors influence noise levels and demonstrating the potential of quantum sensors in superconducting device analysis.

Contribution

It provides the first direct nanoscale observation of quasiparticle-induced magnetic noise in superconducting resonators using NV centers, highlighting the impact of microwave driving and off-resonant coupling.

Findings

Quasiparticle magnetic noise peaks near the superconducting transition.

Microwave driving increases quasiparticle density and magnetic noise.

Detection of the Hebel-Slichter peak signature outside the superconductor.

Abstract

Superconducting circuits are arguably taking a leading role in driving the ongoing quantum technological revolution. A detailed knowledge of the microscopic fluctuating electromagnetic properties plays an important role in advancing the circuitry design, testing, and material integration of cutting-edge superconducting quantum electronics. Here we report scanning nitrogen-vacancy (NV) quantum sensing of local magnetic noise environment of an on- chip superconducting resonator. We find that quasiparticle-induced fluctuating magnetic fields can drive NV spin relaxation, which shows a peak value around the superconducting transition point of niobium at the thermal equilibrium state. External microwave driving at the resonator mode frequency significantly increases the quasiparticle density, leading to enhancement of magnetic noise. We further perform optically detected magnetic resonance measurements to demonstrate quasiparticle magnetic noise mediated off-resonant dipole coupling between the NV center and niobium resonator. Our work reports experimental observation of the Hebel-Slichter peak signature by an external sensor outside of a superconductor. The presented study also highlights the advantages of quantum sensors in investigating miniaturized superconducting devices, providing insights into their future performance improvements.