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/γ-Al2O3/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 γ-Al2O3, for which we find a low intrinsic two-level system loss, δTLS0=(2.8±0.1)×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.
@article{arxiv.2603.29065,
title = {Oxide-nitride heteroepitaxy for low-loss dielectrics in superconducting quantum circuits},
author = {David A. Garcia-Wetten and Mitchell J. Walker and Peter G. Lim and André Vallières and Maria G. Jimenez-Guillermo and Miguel A. Alvarado and Dominic P. Goronzy and Anna Grassellino and Jens Koch and Vinayak P. Dravid and Mark C. Hersam and Michael J. Bedzyk},
journal= {arXiv preprint arXiv:2603.29065},
year = {2026}
}