Magnetic field robust high quality factor NbTiN superconducting microwave resonators

TL;DR

This study demonstrates that NbTiN superconducting microwave resonators maintain high quality factors under strong magnetic fields and across a broad temperature range, making them promising for quantum technologies.

Contribution

We systematically analyze NbTiN resonators' performance under magnetic fields and temperature variations, highlighting their robustness and substrate-dependent loss characteristics.

Findings

High internal Q-factors (~2x10^5) on pristine Si substrates at 2.2 K and millikelvin temperatures.

Reduced Q-factors (~1x10^4) on thermally oxidized substrates, indicating additional loss channels.

Resonators retain high Q-factors (~5x10^5) at 7 mK in high power regimes.

Abstract

We systematically study the performance of compact lumped element planar microwave $\mathrm{Nb_{70}Ti_{30}N}$ (NbTiN) resonators operating at 5 GHz in external in-plane magnetic fields up to 440 mT, a broad temperature regime from 2.2 K up to 13 K, as well as mK temperatures. For comparison, the resonators have been fabricated on thermally oxidized and pristine, (001) oriented silicon substrates. When operating the resonators in the multi-photon regime at $T=2.2$ K, we find internal quality factors $Q_{\mathrm{int}}\simeq$ $2\cdot10^5$ for NbTiN resonators grown on pristine Si substrates, while resonators grown on thermally oxidized substrates show a reduced value of $Q_{\mathrm{int}}\simeq$ $1\cdot10^4$, providing evidence for additional loss channels for the latter substrate. In addition, we investigate the $Q$-factors of the resonators on pristine Si substrates at millikelvin temperatures to asses their applicability for quantum applications. We find $Q_{\mathrm{int}}\simeq$ $2\cdot10^5$ in the single photon regime and $Q_{\mathrm{int}}\simeq$ $5\cdot10^5$ in the high power regime at $T=7$ mK.