Tunable inductive coupler for high fidelity gates between fluxonium qubits

• URL: http://arxiv.org/abs/2309.05720v2
• Date: Mon, 25 Sep 2023 22:10:20 GMT
• Title: Tunable inductive coupler for high fidelity gates between fluxonium qubits
• Authors: Helin Zhang, Chunyang Ding, D. K. Weiss, Ziwen Huang, Yuwei Ma, Charles Guinn, Sara Sussman, Sai Pavan Chitta, Danyang Chen, Andrew A. Houck, Jens Koch, David I. Schuster
• Abstract summary: We present a tunable coupler that realizes strong inductive coupling between two heavy-fluxonium qubits. These qualities lead to fast, high-fidelity single- and two-qubit gates.
• Score: 0.27638147714466216
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• 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 $\sim50$MHz frequencies and $\sim5$ GHz anharmonicities. The coupler enables the qubits to have a large tuning range of $\textit{XX}$ coupling strengths ($-35$ to $75$ MHz). The $\textit{ZZ}$ coupling strength is $<3$kHz across the entire coupler bias range, and $<100$Hz 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 $\sqrt{i\mathrm{SWAP}}$ gate in $258$ns with fidelity $99.72\%$, and by driving at the sum frequency of the two qubits, we achieve a $\sqrt{b\mathrm{SWAP}}$ gate in $102$ns 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 $\sqrt{b\mathrm{SWAP}}$ drift ($2 \sigma$) $< 0.02\%$ and $\sqrt{i\mathrm{SWAP}}$ drift $< 0.08\%$.

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