Why Superconducting Ta Qubits Have Fewer Tunneling Two-Level Systems at the Air-Oxide Interface Than Nb Qubits
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| Format: | Preprint |
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2024
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| _version_ | 1866913683626524672 |
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| author | Wang, Zhe Yu, Clare C. Wu, Ruqian |
| author_facet | Wang, Zhe Yu, Clare C. Wu, Ruqian |
| contents | Superconducting qubits are a key contender for quantum computing elements, but they often face challenges like noise and decoherence from two-level systems (TLS). Tantalum (Ta) qubits are notable for their long T$_1$ coherence times nearing milliseconds, mainly due to fewer TLS, though the cause was unclear. Our research explored this by analyzing the air-oxide interface with density functional theory, particularly comparing Nb oxide (Nb$_2$O$_5$) and Ta oxide (Ta$_2$O$_5$). We discovered that Ta$_2$O$_5$ forms a smoother surface with fewer dangling O atoms and TLS than Nb$_2$O$_5$. The greater atomic mass of Ta also lowers the TLS tunnel splittings below the qubit's operating frequency. Furthermore, using external electric fields or SO$_2$ passivation can significantly reduce TLS on Nb surfaces, potentially improving their coherence times. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_09842 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Why Superconducting Ta Qubits Have Fewer Tunneling Two-Level Systems at the Air-Oxide Interface Than Nb Qubits Wang, Zhe Yu, Clare C. Wu, Ruqian Materials Science Superconducting qubits are a key contender for quantum computing elements, but they often face challenges like noise and decoherence from two-level systems (TLS). Tantalum (Ta) qubits are notable for their long T$_1$ coherence times nearing milliseconds, mainly due to fewer TLS, though the cause was unclear. Our research explored this by analyzing the air-oxide interface with density functional theory, particularly comparing Nb oxide (Nb$_2$O$_5$) and Ta oxide (Ta$_2$O$_5$). We discovered that Ta$_2$O$_5$ forms a smoother surface with fewer dangling O atoms and TLS than Nb$_2$O$_5$. The greater atomic mass of Ta also lowers the TLS tunnel splittings below the qubit's operating frequency. Furthermore, using external electric fields or SO$_2$ passivation can significantly reduce TLS on Nb surfaces, potentially improving their coherence times. |
| title | Why Superconducting Ta Qubits Have Fewer Tunneling Two-Level Systems at the Air-Oxide Interface Than Nb Qubits |
| topic | Materials Science |
| url | https://arxiv.org/abs/2405.09842 |