Millimeter Wave Readout of a Superconducting Qubit

Quantum Physics [Submitted on 14 Mar 2026] Millimeter Wave Readout of a Superconducting Qubit Akash V. Dixit, Zachary L. Parrott, Dennis Chunikhin, Bradley Hauer, Trevyn F. Q. Larson, John D. Teufel Millimeter waves are emerging as an enabling technology for connecting and enhancing different quantum platforms such as Rydberg atoms, optomechanics, and superconducting qubits. In this work, we focus on the interaction between millimeter wave photons and conventional transmon qubits, specifically for qubit readout. We study a circuit quantum electrodynamic (cQED) system consisting of a millimeter-wave cavity at \omega_r = 2\pi \times 34.7 GHz and a transmon qubit at \omega_q = 2\pi \times 3.1 GHz coupled at rate g = 2\pi \times 1.3 GHz. With such a large detuning between cavity and qubit, \omega_r/\omega_q > 10, we are able to suppress drive induced unwanted state transitions, enabling strong drives for qubit readout. We measure no resonant state transitions up to 1,000 drive photons and readout the qubit state with more than 100 photons to achieve a measurement fidelity greater than 99% without the aid of a quantum limited amplifier. Comments: 5 pages, 4 figures in main text. 9 pages, 10 figures, 1 table in supplemental materials Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.13837 [quant-ph]   (or arXiv:2603.13837v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.13837 Focus to learn more Submission history From: Akash Dixit [view email] [v1] Sat, 14 Mar 2026 08:45:33 UTC (6,790 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 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?)