Phononic Bragg Reflectors for Thermal Insulation of Scalable Cryogenic Control Electronics from Qubits

Quantum Physics [Submitted on 14 Mar 2026] Phononic Bragg Reflectors for Thermal Insulation of Scalable Cryogenic Control Electronics from Qubits Isabelle V. Sprave, Denny Dütz, Sebastian Kock, René Otten, Tobias Hangleiter, Felix Mende, Marcus Wislicenus, Hendrik Bluhm Scaling solid-state architectures to the millions of qubits required for utility-scale quantum computing could benefit from the integration of control electronics in the immediate vicinity of the quantum layer. However, lithographically fabricated solid-state qubits perform best at temperatures well below 1 K, where available cooling power is limited, whereas the control electronics dissipate substantial power and therefore require the higher cooling power available at elevated temperatures. To address this challenge, we propose a cryopackaging concept that uses broadband phononic Distributed Bragg Reflectors (DBRs) as a thermal barrier between cryoelectronics and the qubit chip. As an experimental realization of this concept, we fabricate and characterize Ta/SiO_2 DBR structures. In this architecture, the DBR is intended to provide mechanical support for superconducting vias while offering substantially better thermal insulation than typical bulk materials. For a 600-nm-thick DBR consisting of 10 Ta/SiO_2 bilayers, we obtain a thermal conduction below 1 mW/cm^2 from 1.5 K to 100 mK. In a centimeter-scale architecture, this level of isolation is compatible with Watt-level cooling power for nearby electronics while maintaining a qubit temperature around 100 mK in commercially available dilution refrigerators. Comments: 10 figures Subjects: Quantum Physics (quant-ph); Applied Physics (physics.app-ph) Cite as: arXiv:2603.13726 [quant-ph]   (or arXiv:2603.13726v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.13726 Focus to learn more Submission history From: Isabelle Victoria Sprave [view email] [v1] Sat, 14 Mar 2026 03:02:34 UTC (4,063 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 Change to browse by: physics physics.app-ph References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)