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arXiv · 2509.26024

Gradiometric, Fully Tunable C-Shunted Flux Qubits

Benedikt Berlitz·Alexander Konstantin Händel·Etienne Daum·Alexey V. Ustinov·Jürgen Lisenfeld
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Abstract

Fully tunable flux qubits offer in-situ and independent controls of their energy potential asymmetry and tunnel barrier, making them versatile tools for quantum computation and the study of decoherence sources. However, only short coherence times have been demonstrated so far with this type of qubit. Here, we present a capacitively shunted flux qubit featuring improved relaxation times up to T1 = 25 $\mu$s and a frequency tunability range of $\sim$ 20 GHz at the flux-insensitive sweet spot. As a model application, we demonstrate detection of two-level tunneling defects in a frequency range spanning one octave.

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Benedikt Berlitz, Alexander Konstantin Händel, Etienne Daum, Alexey V. Ustinov, Jürgen Lisenfeld. 2025-09-30. Gradiometric, Fully Tunable C-Shunted Flux Qubits. https://arxiv.org/abs/2509.26024

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