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arXiv · 2308.16040

Native approach to controlled-Z gates in inductively coupled fluxonium qubits

Xizheng Ma·Gengyan Zhang·Feng Wu·Feng Bao·Xu Chang·Jianjun Chen·Hao Deng·Ran Gao·Xun Gao·Lijuan Hu·Honghong Ji·Hsiang-Sheng Ku·Kannan Lu·Lu Ma·Liyong Mao·Zhijun Song·Hantao Sun·Chengchun Tang·Fei Wang·Hongcheng Wang·Tenghui Wang·Tian Xia·Make Ying·Huijuan Zhan·Tao Zhou·Mengyu Zhu·Qingbin Zhu·Yaoyun Shi·Hui-Hai Zhao·Chunqing Deng
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Abstract

The fluxonium qubits have emerged as a promising platform for gate-based quantum information processing. However, their extraordinary protection against charge fluctuations comes at a cost: when coupled capacitively, the qubit-qubit interactions are restricted to XX-interactions. Consequently, effective XX- or XZ-interactions are only constructed either by temporarily populating higher-energy states, or by exploiting perturbative effects under microwave driving. Instead, we propose and demonstrate an inductive coupling scheme, which offers a wide selection of native qubit-qubit interactions for fluxonium. In particular, we leverage a built-in, flux-controlled ZZ-interaction to perform qubit entanglement. To combat the increased flux-noise-induced dephasing away from the flux-insensitive position, we use a continuous version of the dynamical decoupling scheme to perform noise filtering. Combining these, we demonstrate a 20 ns controlled-Z (CZ) gate with a mean fidelity of 99.53%. More than confirming the efficacy of our gate scheme, this high-fidelity result also reveals a promising but rarely explored parameter space uniquely suitable for gate operations between fluxonium qubits.

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Xizheng Ma, Gengyan Zhang, Feng Wu, Feng Bao, Xu Chang, Jianjun Chen, Hao Deng, Ran Gao, Xun Gao, Lijuan Hu, Honghong Ji, Hsiang-Sheng Ku, Kannan Lu, Lu Ma, Liyong Mao, Zhijun Song, Hantao Sun, Chengchun Tang, Fei Wang, Hongcheng Wang, Tenghui Wang, Tian Xia, Make Ying, Huijuan Zhan, Tao Zhou, Mengyu Zhu, Qingbin Zhu, Yaoyun Shi, Hui-Hai Zhao, Chunqing Deng. 2023-08-30. Native approach to controlled-Z gates in inductively coupled fluxonium qubits. https://doi.org/10.1103/physrevlett.132.060602

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