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| Main Authors: | , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2507.09339 |
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| _version_ | 1866915385998049280 |
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| author | Torras-Coloma, Alba Cozzolino, Luca Gómez-del-Pulgar-Martínez, Ariadna Bertoldo, Elia Forn-Díaz, P. |
| author_facet | Torras-Coloma, Alba Cozzolino, Luca Gómez-del-Pulgar-Martínez, Ariadna Bertoldo, Elia Forn-Díaz, P. |
| contents | We present an ultrastrong superinductor-based coupling consisting of a flux qubit galvanically coupled to a resonator. The coupling inductor is fabricated in granular Aluminum, a superinductor material able to provide large surface inductances. Spectroscopy measurements on the qubit-resonator system reveal a Bloch-Siegert shift of \SI{23}{\mega\hertz} and a coupling fraction of $g/ω_r \simeq 0.13$, entering the perturbative ultrastrong coupling (USC) regime. We estimate the inductance of the coupler independently by low-temperature resistance measurements providing $L_c = (0.74\pm0.14)\,\mathrm{nH}$, which is compatible with $g/ω\gtrsim 0.1$. Our results show that superinductors are a promising tool to study USC physics in high-coherence circuits using flux qubits with small loop areas and low persistent currents. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_09339 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Superinductor-based ultrastrong coupling in a superconducting circuit Torras-Coloma, Alba Cozzolino, Luca Gómez-del-Pulgar-Martínez, Ariadna Bertoldo, Elia Forn-Díaz, P. Quantum Physics We present an ultrastrong superinductor-based coupling consisting of a flux qubit galvanically coupled to a resonator. The coupling inductor is fabricated in granular Aluminum, a superinductor material able to provide large surface inductances. Spectroscopy measurements on the qubit-resonator system reveal a Bloch-Siegert shift of \SI{23}{\mega\hertz} and a coupling fraction of $g/ω_r \simeq 0.13$, entering the perturbative ultrastrong coupling (USC) regime. We estimate the inductance of the coupler independently by low-temperature resistance measurements providing $L_c = (0.74\pm0.14)\,\mathrm{nH}$, which is compatible with $g/ω\gtrsim 0.1$. Our results show that superinductors are a promising tool to study USC physics in high-coherence circuits using flux qubits with small loop areas and low persistent currents. |
| title | Superinductor-based ultrastrong coupling in a superconducting circuit |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2507.09339 |