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arXiv · 2603.29065

Oxide-nitride heteroepitaxy for low-loss dielectrics in superconducting quantum circuits

David A. Garcia-Wetten·Mitchell J. Walker·Peter G. Lim·André Vallières·Maria G. Jimenez-Guillermo·Miguel A. Alvarado·Dominic P. Goronzy·Anna Grassellino·Jens Koch·Vinayak P. Dravid·Mark C. Hersam·Michael J. Bedzyk
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Abstract

Superconducting qubits show great promise for the realization of fault-tolerant quantum computing, but lossy, amorphous dielectrics limit current technology. Identifying highly crystalline and stoichiometric dielectrics with intrinsically low microwave loss is therefore a central materials challenge, yet experimentally validated platforms remain scarce. In this work, we integrate a crystalline dielectric into a heteroepitaxial TiN/$\gamma$-Al$_2$O$_3$/TiN trilayer grown via pulsed laser deposition. Correlative high-resolution imaging, diffraction, and spectroscopy measurements confirm the single-crystal quality and chemical integrity of all layers, with minimal defects and limited anion interdiffusion across the oxide-nitride interfaces. Using microwave lumped-element resonators with parallel-plate capacitors, we report the first direct measurement of the dielectric loss of epitaxial $\gamma$-Al$_2$O$_3$, for which we find a low intrinsic two-level system loss, $\delta_{\text{TLS}}^0 = (2.8 \pm 0.1) \times 10^{-5}$. These results establish heteroepitaxial oxides on transition metal nitrides as an attractive materials platform for superconducting quantum circuits, particularly for integration into compact device architectures such as merged-element transmons and microwave kinetic inductance detectors.

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David A. Garcia-Wetten, Mitchell J. Walker, Peter G. Lim, André Vallières, Maria G. Jimenez-Guillermo, Miguel A. Alvarado, Dominic P. Goronzy, Anna Grassellino, Jens Koch, Vinayak P. Dravid, Mark C. Hersam, Michael J. Bedzyk. 2026-03-30. Oxide-nitride heteroepitaxy for low-loss dielectrics in superconducting quantum circuits. https://arxiv.org/abs/2603.29065

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