Tunable inductive coupler with >99.9% two-qubit gate fidelity between fluxonia
ORAL
Abstract
The fluxonium qubit is a promising candidate for quantum computation due to its long coherence times and large anharmonicity. We present a tunable coupler that realizes strong inductive coupling between two heavy-fluxonium qubits, each with ∼ 50MHz frequencies and ∼ 5 GHz anharmonicities. The coupler enables the qubits to have a large tuning range of XX coupling strengths (−35 to 75 MHz). The ZZ coupling strength is < 3kHz across the entire coupler bias range, and < 100Hz at the coupler off-position. These qualities lead to fast, high-fidelity single- and two-qubit gates. By driving at the difference frequency of the two qubits, we realize a √iSWAP gate in 258ns with fidelity 99.72%, and by driving at the sum frequency of the two qubits, we achieve a √bSWAP gate in 102ns with fidelity 99.91%. This latter gate is only 5 qubit Larmor periods in length. We run cross-entropy benchmarking for over 20 consecutive hours and measure stable gate fidelities, with √bSWAP drift (2σ) < 0.02% and √iSWAP drift < 0.08%.
*This work was supported by the Army Research Office under Grant No. W911NF1910016. This work is funded in part by EPiQC, an NSF Expedition in Computing, under grant CCF1730449. This work was partially supported by the University of Chicago Materials Research Science and Engineering Center, which is funded by the National Science Foundation under award number DMR-1420709. Devices were fabricated in the Pritzker Nanofabrication Facility at the University of Chicago, which receives support from Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), a node of the National Science Foundation's National Nanotechnology Coordinated Infrastructure.
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Publication:Tunable inductive coupler for high fidelity gates between fluxonium qubits, arXiv preprint arXiv:2309.05720
