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Ultraviolet and visible integrated photonics enable applications in quantum information, sensing, and spectroscopy, among others. Few materials support low-loss photonics into the UV, and the relatively low refractive index of known depositable materials limits the achievable functionality. Here, we present a high-index integrated photonics platform based on HfO₂and Al₂O₃composites deposited via atomic layer deposition (ALD) with low loss in the visible and near UV. We show that Al₂O₃incorporation dramatically decreases bulk loss compared to pure HfO₂, consistent with inhibited crystallization due to the admixture of Al₂O₃. Composites exhibit refractive indexnfollowing the average of that of HfO₂and Al₂O₃, weighted by the HfO₂fractional compositionx. Atλ = 375 nm, composites withx = 0.67 exhibitn = 2.01, preserving most of HfO₂’s significantly higher index, and 3.8(7) dB/cm material loss. We further present fully etched and cladded waveguides, grating couplers, and ring resonators, realizing a single-mode waveguide loss of 0.25(2) dB/cm inferred from resonators of 2.6 million intrinsic quality factor atλ = 729 nm, 2.6(2) dB/cm atλ = 405 nm, and 7.7(6) dB/cm atλ = 375 nm. We measure the composite’s thermo-optic coefficient (TOC) to be 2.44(3) × 10⁻⁵RIU/°C nearλ = 397 nm. This work establishes (HfO₂)_x(Al₂O₃)_1−xcomposites as a platform amenable to integration for low-loss, high-index photonics spanning the UV to NIR. 

Quantum computing hardware technologies have advanced during the past two decades, with the goal of building systems that can solve problems that are intractable on classical computers. The ability to realize large-scale systems depends on major advances in materials science, materials engineering, and new fabrication techniques. We identify key materials challenges that currently limit progress in five quantum computing hardware platforms, propose how to tackle these problems, and discuss some new areas for exploration. Addressing these materials challenges will require scientists and engineers to work together to create new, interdisciplinary approaches beyond the current boundaries of the quantum computing field.