High fidelity two-qubit gates on fluxoniums using a tunable coupler

TL;DR

This paper demonstrates high-fidelity two-qubit gates on fluxonium qubits using a tunable coupler, achieving fidelities over 99% and suppressing residual interactions, advancing scalable superconducting quantum computing.

Contribution

It experimentally realizes a fluxonium-based quantum processor with tunable coupler, demonstrating high-fidelity gates and low residual interactions, confirming theoretical proposals.

Findings

fSim and controlled-Z gates with over 99% fidelity

Residual ZZ interaction suppressed to a few kHz

High fidelity single-qubit gates and state initialization achieved

Abstract

Superconducting fluxonium qubits provide a promising alternative to transmons on the path toward large-scale superconductor-based quantum computing due to their better coherence and larger anharmonicity. A major challenge for multi-qubit fluxonium devices is the experimental demonstration of a scalable crosstalk-free multi-qubit architecture with high fidelity single-qubit and two-qubit gates, single-shot readout and state initialization. Here, we present a two-qubit fluxonium-based quantum processor with a tunable coupler element following our theoretical proposal [DOI: 10.1063/5.0064800]. We experimentally demonstrate fSim-type and controlled-Z gates with $99.55\%$ and $99.23\%$ fidelities, respectively. The residual ZZ interaction is suppressed down to the few kHz level. Using a galvanically coupled flux control line, we implement high fidelity single-qubit gates and ground state initialization with a single arbitrary waveform generator channel per qubit.