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 $ω_r = 2π\times 34.7$ GHz and a transmon qubit at $ω_q = 2π\times 3.1$ GHz coupled at rate $g = 2π\times 1.3$ . With such a large detuning between cavity and qubit, $ω_r/ω_q > 10$ , 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.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 $ω_r = 2π\times 34.7$ GHz and a transmon qubit at $ω_q = 2π\times 3.1$ GHz coupled at rate $g = 2π\times 1.3$. With such a large detuning between cavity and qubit, $ω_r/ω_q > 10$, 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.

quant-pharXiv:2603.13837Mar 17, 20260 citations

Superconducting quantum-well device as a millimeter-wave detector

Hiroshi Ota, 太田浩

Jul 1, 19931 citation

ω_r = 2π\times 34.7

GHz and a transmon qubit at

ω_q = 2π\times 3.1

GHz coupled at rate

g = 2π\times 1.3

. With such a large detuning between cavity and qubit,

ω_r/ω_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.