Characterization and Comparison of Energy Relaxation in Fluxonium Qubits

• URL: http://arxiv.org/abs/2603.23636v1
• Date: Tue, 24 Mar 2026 18:21:42 GMT
• Title: Characterization and Comparison of Energy Relaxation in Fluxonium Qubits
• Abstract summary: Fluxonium superconducting qubits have demonstrated long coherence times and high single- and two-qubit gate fidelities.<n>We investigate the dominant limitations to fluxonium qubit energy relaxation time $T_$ using a set of eight planar, aluminum-on-silicon qubits.
• Score: 0.3735138621055794
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Fluxonium superconducting qubits have demonstrated long coherence times and high single- and two-qubit gate fidelities, making them a favorable building block for superconducting quantum processors. We investigate the dominant limitations to fluxonium qubit energy relaxation time $T_1$ using a set of eight planar, aluminum-on-silicon qubits. We find that a circuit-based model for capacitive dielectric loss best captures the frequency dependence of $T_1$, which we analyze within both a two-level and a six-level energy relaxation model. We convert the measured $T_1$ into an effective capacitive quality factor $Q_\mathrm{C}^{\mathrm{eff}}$ to compare qubits on equal footing, accounting for independently estimated contributions from $1/f$ flux noise and radiative loss to the control and readout circuitry. We apply this methodology to compare qubits from two fabrication processes: a baseline process and one that applies a fluorine-based wet treatment prior to Josephson junction deposition. We resolve a small improvement of (13.8 $\pm$ 8.4$)\%$ in the process mean $Q_\mathrm{C}^{\mathrm{eff}}$, indicating that the fluorine treatment may have reduced loss from the metal-substrate interface, but did not address the primary source of loss in these fluxonium qubits.

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