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| Main Authors: | , , , |
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| Format: | Preprint |
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2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2407.17407 |
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| _version_ | 1866912345500942336 |
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| author | Wang, Z. Parker, R. W. Champion, E. Blok, M. S. |
| author_facet | Wang, Z. Parker, R. W. Champion, E. Blok, M. S. |
| contents | Qudits provide a resource-efficient alternative to qubits for quantum information processing. The multilevel nature of the transmon, with its individually resolvable transition frequencies, makes it an attractive platform for superconducting circuit-based qudits. In this work, we systematically analyze the trade-offs associated with encoding high-dimensional quantum information in fixed-frequency transmons. Designing high $E_J/E_C$ ratios of up to 325, we observe up to 12 levels ($d=12$) on a single transmon. Despite the decreased anharmonicity, we demonstrate process infidelities $e_f < 3 \times 10^{-3}$ for qubit-like operations in each adjacent-level qubit subspace in the lowest 10 levels. Furthermore, we achieve a 10-state readout assignment fidelity of 93.8% with the assistance of deep neural network classification of a multi-tone dispersive measurement. We find that the Hahn echo time $T_{2E}$ for the higher levels is close to the limit of $T_1$ decay, primarily limited by bosonic enhancement. We verify the recently introduced Josephson harmonics model, finding that it yields better predictions for the transition frequencies and charge dispersion. Finally, we show strong $ZZ$-like coupling between the higher energy levels in a two-transmon system. Our high-fidelity control and readout methods, in combination with our comprehensive characterization of the transmon model, suggest that the high-$E_J/E_C$ transmon is a powerful tool for exploring excited states in circuit quantum electrodynamics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_17407 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Systematic study of High $E_J/E_C$ transmon qudits up to $d = 12$ Wang, Z. Parker, R. W. Champion, E. Blok, M. S. Quantum Physics Qudits provide a resource-efficient alternative to qubits for quantum information processing. The multilevel nature of the transmon, with its individually resolvable transition frequencies, makes it an attractive platform for superconducting circuit-based qudits. In this work, we systematically analyze the trade-offs associated with encoding high-dimensional quantum information in fixed-frequency transmons. Designing high $E_J/E_C$ ratios of up to 325, we observe up to 12 levels ($d=12$) on a single transmon. Despite the decreased anharmonicity, we demonstrate process infidelities $e_f < 3 \times 10^{-3}$ for qubit-like operations in each adjacent-level qubit subspace in the lowest 10 levels. Furthermore, we achieve a 10-state readout assignment fidelity of 93.8% with the assistance of deep neural network classification of a multi-tone dispersive measurement. We find that the Hahn echo time $T_{2E}$ for the higher levels is close to the limit of $T_1$ decay, primarily limited by bosonic enhancement. We verify the recently introduced Josephson harmonics model, finding that it yields better predictions for the transition frequencies and charge dispersion. Finally, we show strong $ZZ$-like coupling between the higher energy levels in a two-transmon system. Our high-fidelity control and readout methods, in combination with our comprehensive characterization of the transmon model, suggest that the high-$E_J/E_C$ transmon is a powerful tool for exploring excited states in circuit quantum electrodynamics. |
| title | Systematic study of High $E_J/E_C$ transmon qudits up to $d = 12$ |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2407.17407 |