A Josephson Junction Microscope for Low-frequency Fluctuators

TL;DR

This paper introduces a Josephson junction-based microwave microscope that uses its resonator mode to investigate low-frequency two-level fluctuators in tunnel barriers, aiding understanding of decoherence in quantum devices.

Contribution

It proposes a novel spectroscopic method utilizing a Josephson junction's resonator mode to study TLS coupling mechanisms under magnetic fields.

Findings

Spectroscopic transmission reveals TLS coupling variation with magnetic field.

The method can distinguish different TLS coupling mechanisms.

Potential to improve superconducting qubit coherence times.

Abstract

The high-Q harmonic oscillator mode of a Josephson junction can be used as a novel probe of spurious two-level systems (TLSs) inside the amorphous oxide tunnel barriers of the junction. In particular, we show that spectroscopic transmission measurements of the junction resonator mode can reveal how the coupling magnitude between the junction and the TLSs varies with an external magnetic field applied in the plane of the tunnel barrier. The proposed experiments offer the possibility of clearly resolving the underlying coupling mechanism for these spurious TLSs, an important decoherence source limiting the quality of superconducting quantum devices.