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arXiv · 2410.00431

Residual-$ZZ$-coupling suppression and fast two-qubit gate for Kerr-cat qubits based on level-degeneracy engineering

Takaaki Aoki·Akiyoshi Tomonaga·Kosuke Mizuno·Shumpei Masuda
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Abstract

Building large-scale quantum computers requires an interqubit-coupling scheme with a high on-off ratio to avoid unwanted crosstalk coming from residual coupling and to enable fast multi-qubit operations. We propose a $ZZ$-coupling scheme for two Kerr-cat qubits with a frequency-tunable coupler. By making four relevant states of the two Kerr-cat qubits quadruply degenerate, we can switch off the $ZZ$ coupling. By partially lifting the level degeneracy, we can switch it on. We theoretically show that an experimentally feasible circuit model suppresses the residual $ZZ$ coupling. Moreover, our circuit can realize $R_{ZZ}(-\pi/2)$-gate fidelity higher than $99.9\%$ within $18$ ns when decoherence is ignored. Our model includes the first-order terms in expansion beyond the rotating-wave approximation.

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Takaaki Aoki, Akiyoshi Tomonaga, Kosuke Mizuno, Shumpei Masuda. 2024-10-01. Residual-$ZZ$-coupling suppression and fast two-qubit gate for Kerr-cat qubits based on level-degeneracy engineering. https://doi.org/10.1063/5.0241315

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