Magnetic flux distribution, quasiparticle spectroscopy, and quality factors in Nb films for superconducting qubits
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866917360056664064 |
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| author | Datta, Amlan Moirangthem, Bicky S. Joshi, Kamal R. Mcfadden, Anthony P. Lecocq, Florent Simmonds, Raymond W. Tanatar, Makariy A. Kramer, Matthew J. Prozorov, Ruslan |
| author_facet | Datta, Amlan Moirangthem, Bicky S. Joshi, Kamal R. Mcfadden, Anthony P. Lecocq, Florent Simmonds, Raymond W. Tanatar, Makariy A. Kramer, Matthew J. Prozorov, Ruslan |
| contents | Niobium is a practical material platform for superconducting microwave circuits; however, device-level performance can vary significantly depending on film growth and processing conditions. We compare three epitaxial Nb films grown on $c-$plane sapphire substrates under nominally identical conditions, except for the deposition temperature. To correlate internal quality factors, $Q_{\mathrm {i}}$, with material properties, we combine magneto-optical imaging of magnetic flux distribution with quasiparticle spectroscopy via measurements of the London penetration depth, $λ(T)$. In the low-$Q_{\mathrm i}$ film, there is a lesser ability to screen the magnetic field and an irregular temperature variation of $λ(T)$, implying the existence of localized in-gap states. High $Q_{\mathrm i}$ films show the opposite trend. We conclude that our measurements provide an efficient method for characterizing and optimizing superconducting films for quantum informatics applications. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_23402 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Magnetic flux distribution, quasiparticle spectroscopy, and quality factors in Nb films for superconducting qubits Datta, Amlan Moirangthem, Bicky S. Joshi, Kamal R. Mcfadden, Anthony P. Lecocq, Florent Simmonds, Raymond W. Tanatar, Makariy A. Kramer, Matthew J. Prozorov, Ruslan Superconductivity Materials Science Niobium is a practical material platform for superconducting microwave circuits; however, device-level performance can vary significantly depending on film growth and processing conditions. We compare three epitaxial Nb films grown on $c-$plane sapphire substrates under nominally identical conditions, except for the deposition temperature. To correlate internal quality factors, $Q_{\mathrm {i}}$, with material properties, we combine magneto-optical imaging of magnetic flux distribution with quasiparticle spectroscopy via measurements of the London penetration depth, $λ(T)$. In the low-$Q_{\mathrm i}$ film, there is a lesser ability to screen the magnetic field and an irregular temperature variation of $λ(T)$, implying the existence of localized in-gap states. High $Q_{\mathrm i}$ films show the opposite trend. We conclude that our measurements provide an efficient method for characterizing and optimizing superconducting films for quantum informatics applications. |
| title | Magnetic flux distribution, quasiparticle spectroscopy, and quality factors in Nb films for superconducting qubits |
| topic | Superconductivity Materials Science |
| url | https://arxiv.org/abs/2603.23402 |