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

• URL: http://arxiv.org/abs/2603.29065v1
• Date: Mon, 30 Mar 2026 23:05:18 GMT
• Title: Oxide-nitride heteroepitaxy for low-loss dielectrics in superconducting quantum circuits
• Abstract summary: Superconducting qubits show great promise for the realization of fault-tolerant quantum computing.<n>But lossy, amorphous dielectrics limit current technology.<n>We identify highly crystalline and stoichiometric dielectrics with intrinsically low microwave loss.<n>These results establish heteroepitaxial on transition metal nitrides as an attractive materials platform for superconducting quantum circuits.
• Score: 0.15494706660649596
• License: http://creativecommons.org/licenses/by/4.0/
• 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/$γ$-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 $γ$-Al$_2$O$_3$, for which we find a low intrinsic two-level system loss, $δ_{\text{TLS}}^0 = (2.8 \pm 0.1) \times 10^{-5}$. 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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