Fast logic with slow qubits: microwave-activated controlled-Z gate on low-frequency fluxoniums

• URL: http://arxiv.org/abs/2011.02634v1
• Date: Thu, 5 Nov 2020 03:25:08 GMT
• Title: Fast logic with slow qubits: microwave-activated controlled-Z gate on low-frequency fluxoniums
• Authors: Quentin Ficheux, Long B. Nguyen, Aaron Somoroff, Haonan Xiong, Konstantin N. Nesterov, Maxim G. Vavilov, and Vladimir E. Manucharyan
• Abstract summary: Gate is activated by a $61.6textrmns$ long pulse at the frequency between non-computational transitions. The measured gate error of $(8pm1)times 10-3$ is limited by decoherence in the non-computational subspace.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We demonstrate a controlled-Z gate between capacitively coupled fluxonium qubits with transition frequencies $72.3~\textrm{MHz}$ and $136.3~\textrm{MHz}$. The gate is activated by a $61.6~\textrm{ns}$ long pulse at the frequency between non-computational transitions $|10\rangle - |20\rangle$ and $|11\rangle - |21\rangle$, during which the qubits complete only $4$ and $8$ Larmor periods, respectively. The measured gate error of $(8\pm1)\times 10^{-3}$ is limited by decoherence in the non-computational subspace, which will likely improve in the next generation devices. Although our qubits are about fifty times slower than transmons, the two-qubit gate is faster than microwave-activated gates on transmons, and the gate error is on par with the lowest reported. Architectural advantages of low-frequency fluxoniums include long qubit coherence time, weak hybridization in the computational subspace, suppressed residual $ZZ$-coupling rate (here $46~\mathrm{kHz}$), and absence of either excessive parameter matching or complex pulse shaping requirements.

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