Ultrastrong Coupling and Coherent Dynamics in a Gate-Tunable Transmon Qubit

• URL: http://arxiv.org/abs/2603.19438v1
• Date: Thu, 19 Mar 2026 20:05:32 GMT
• Title: Ultrastrong Coupling and Coherent Dynamics in a Gate-Tunable Transmon Qubit
• Abstract summary: Ultrastrong light-matter coupling (USC) gives access to exotic quantum phenomena and promises faster quantum gates.<n>Here, we realize USC in a hybrid system consisting of an InAs nanowire-based gatemon qubit coupled to a superconducting resonator.<n>We achieve time-resolved coherent control of the qubit and measure coherence times comparable to gatemons operating outside the USC regime.
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• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Ultrastrong light-matter coupling (USC) gives access to exotic quantum phenomena and promises faster quantum gates, yet coherent time-domain control in this regime remains largely unexplored. Here, we realize USC in a hybrid system consisting of an InAs nanowire-based gatemon qubit coupled to a superconducting resonator. Spectroscopy reveals an avoided crossing that cannot be captured by the Jaynes-Cummings (JC) model, as well as photon-number-dependent transitions whose energies deviate markedly from the JC ladder expected in the strong coupling regime. Beyond demonstrating USC, we achieve time-resolved coherent control of the qubit and measure coherence times comparable to gatemons operating outside the USC regime. These results establish that hybrid semiconductor-superconductor qubits can retain coherent control in USC and provide a platform for exploring quantum dynamics and device concepts in this regime.

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