Native Approach to Controlled- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi></mml:mrow></mml:math> Gates in Inductively Coupled Fluxonium Qubits

Authors:
raw_author_name: Xizheng Ma
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Gengyan Zhang
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Feng Wu
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Feng Bao
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Xu Chang
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Jianjun Chen
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Hao Deng
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Ran Gao
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Xun Gao
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group USA, Bellevue, Washington 98004, USA.
raw_author_name: Hsiang-Sheng Ku
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Lu Ma
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Liyong Mao
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Zhijun Song
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Hantao Sun
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Fei Wang
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Hongcheng Wang
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Tenghui Wang
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Tian Xia
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Make Ying
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Mengyu Zhu
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Qingbin Zhu
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.
raw_author_name: Yaoyun Shi
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group USA, Bellevue, Washington 98004, USA.
raw_author_name: Hui-Hai Zhao
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Beijing 100102, China.
raw_author_name: Chunqing Deng
raw_affiliation_string: DAMO Quantum Laboratory, Alibaba Group, Hangzhou, Zhejiang 311121, China.

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 ZZ 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 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.Received 12 September 2023Accepted 8 January 2024DOI:https://doi.org/10.1103/PhysRevLett.132.060602© 2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum controlQuantum gatesQuantum information with solid state qubitsPhysical SystemsSuperconducting qubitsQuantum Information, Science & TechnologyCondensed Matter, Materials & Applied Physics