Fast High-Fidelity Gates for Galvanically-Coupled Fluxonium Qubits Using Strong Flux Modulation

Long coherence times, large anharmonicity, and robust charge-noise insensitivity render fluxonium qubits an interesting alternative to transmons. Recent experiments have demonstrated record coherence times for low-frequency fluxonium qubits. Here, we propose a galvanic coupling scheme with flux-tuna...

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Bibliographic Details
Published in:PRX quantum 2022-12, Vol.3 (4), p.040336, Article 040336
Main Authors: Weiss, D.K., Zhang, Helin, Ding, Chunyang, Ma, Yuwei, Schuster, David I., Koch, Jens
Format: Article
Language:English
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Summary:Long coherence times, large anharmonicity, and robust charge-noise insensitivity render fluxonium qubits an interesting alternative to transmons. Recent experiments have demonstrated record coherence times for low-frequency fluxonium qubits. Here, we propose a galvanic coupling scheme with flux-tunable XX coupling. To implement a high-fidelity entangling sqrt[iSWAP] gate, we modulate the strength of this coupling and devise variable-time identity gates to synchronize required single-qubit operations. Both types of gates are implemented using strong ac flux drives, lasting for only a few drive periods. We employ a theoretical framework capable of capturing qubit dynamics beyond the rotating-wave approximation as required for such strong drives. We predict an open-system fidelity of F>0.999 for the sqrt[iSWAP] gate under realistic conditions.
ISSN:2691-3399
2691-3399
DOI:10.1103/PRXQuantum.3.040336