Phase qubits fabricated with trilayer junctions

TL;DR

This paper introduces a new Josephson junction design with minimal lossy dielectric, leading to higher quality trilayer junctions suitable for qubits, demonstrated by improved relaxation times and low loss.

Contribution

The authors present a novel trilayer Josephson junction geometry with reduced dielectric loss, enhancing qubit performance and coherence.

Findings

Observed few avoided level crossings in spectroscopy

Measured qubit relaxation time of approximately 400 ns

Demonstrated low loss due to minimal dielectric volume

Abstract

We have developed a novel Josephson junction geometry with minimal volume of lossy isolation dielectric, being suitable for higher quality trilayer junctions implemented in qubits. The junctions are based on in-situ deposited trilayers with thermal tunnel oxide, have micron-sized areas and a low subgap current. In qubit spectroscopy only a few avoided level crossings are observed, and the measured relaxation time of $T_1\approx400\;\rm{nsec}$ is in good agreement with the usual phase qubit decay time, indicating low loss due to the additional isolation dielectric.