Millimeter Wave Readout of a Superconducting Qubit

Abstract: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 explore 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 $g = 2\pi \times 1.3$. With such a large detuning between cavity and qubit, $\omega_r/\omega_q > 10$, we are able to suppress drive induced unwanted resonant state transitions, enabling strong drives for qubit readout. We measure no resonant state transitions even when driving with more than $100$ photons and read out the qubit state with more than $100$ photons to achieve a measurement fidelity greater than $99\%$ without the aid of a quantum limited amplifier.

5 pages, 4 figures in main text. 10 pages, 11 figures, 1 table in supplemental materials

arXiv:2603.13837 [quant-ph]

(or arXiv:2603.13837v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2603.13837 Focus to learn more arXiv-issued DOI via DataCite

Phys. Rev. Lett. 137, 180803 (2026)

https://doi.org/10.1103/c84y-ggqs Focus to learn more DOI(s) linking to related resources

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