Introducing disorder in the superconducting materials has been considered promising to enhance the electromagnetic impedance and realize noise-resilient superconducting qubits. Despite a number of pioneering implementations, the understanding of the correlation between the material disorder and the qubit coherence is still developing. Here, we demonstrate a systematic characterization of fluxonium qubits with the superinductors made by spinodal titanium-aluminum-nitride with varied disorder. From qubit noise spectroscopy, the flux noise and the dielectric loss are extracted as a measure of the coherence properties. Our results reveal that the 1/f α flux noise dominates the qubit decoherence around the flux-frustration point, strongly correlated with the material disorder; while the dielectric loss are largely similar under a wide range of material properties. From the flux-noise amplitudes, the areal density (σ) of the phenomenological spin defects and material disorder are found to be approximately correlated by <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41467_2025_58745_Article_IEq1.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="58" /> </InlineMediaObject> <EquationSource Format="TEX">$\sigma \propto {\rho }_{xx}^{3}$</EquationSource> <EquationSource Format="MATHML"><math> <mi>σ</mi> <mo>∝</mo> <msubsup> <mrow> <mi>ρ</mi> </mrow> <mrow> <mi>x</mi> <mi>x</mi> </mrow> <mrow> <mn>3</mn> </mrow> </msubsup> </math></EquationSource> </InlineEquation>, or effectively <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41467_2025_58745_Article_IEq2.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="TEX">${({k}_{F}l)}^{-3}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mrow> <mo>(</mo> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>F</mi> </mrow> </msub> <mi>l</mi> </mrow> <mo>)</mo> </mrow> </mrow> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </math></EquationSource> </InlineEquation>. This work has provided new insights on the origin of decoherence channels beyond surface defects and within the superconductors, and could serve as a useful guideline for material design and optimization.

The effects of disorder in superconducting materials on qubit coherence

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2025年4月16日

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Ran Gao,
Feng Wu,
Hantao Sun,
Jianjun Chen,
Hao Deng,
Xizheng Ma,
Xiaohe Miao,
Zhijun Song,
Xin Wan,
Fei Wang,
Tian Xia,
Make Ying,
Chao Zhang,
Yaoyun Shi,
Hui-Hai Zhao,
Chunqing Deng

摘要

Introducing disorder in the superconducting materials has been considered promising to enhance the electromagnetic impedance and realize noise-resilient superconducting qubits. Despite a number of pioneering implementations, the understanding of the correlation between the material disorder and the qubit coherence is still developing. Here, we demonstrate a systematic characterization of fluxonium qubits with the superinductors made by spinodal titanium-aluminum-nitride with varied disorder. From qubit noise spectroscopy, the flux noise and the dielectric loss are extracted as a measure of the coherence properties. Our results reveal that the 1/f ^α flux noise dominates the qubit decoherence around the flux-frustration point, strongly correlated with the material disorder; while the dielectric loss are largely similar under a wide range of material properties. From the flux-noise amplitudes, the areal density (σ) of the phenomenological spin defects and material disorder are found to be approximately correlated by $\sigma \propto {\rho }_{xx}^{3}$ $σ \propto ρ_{x x}^{3}$ , or effectively ${({k}_{F}l)}^{-3}$ ${(k_{F} l)}^{- 3}$ . This work has provided new insights on the origin of decoherence channels beyond surface defects and within the superconductors, and could serve as a useful guideline for material design and optimization.