Native CCZ Gate with Fluxonium Qubits and a Microwave-Driven Coupler
arXiv:2607.27094
The paper reports an experimental demonstration of a native three-qubit controlled-controlled-phase (CCZ) gate using fluxonium qubits coupled via a microwave-driven transmon coupler, achieving 99.39% fidelity in 65 ns.
Abstract
Native multi-qubit gates could reduce the overhead associated with decompositions into single- and two-qubit operations, but whether they can simultaneously provide high fidelity, simple control and robustness against parasitic interactions in scalable architectures remains unclear. Here we experimentally realize a 65-ns native controlled-controlled-phase operation, locally equivalent to the Toffoli gate, with a fidelity of 99.39(5)% in a three-qubit processor unit based on fluxonium qubits coupled via a microwave-driven transmon coupler. The implemented operation would require CZ fidelities of approximately 99.94% if realized through a conventional decomposition. The gate is implemented with a single control pulse, that relies on a simple calibration procedure yielding coherence-limited performance. This processor unit naturally extends to scalable two-dimensional layouts with low parasitic interactions. Altogether, these results establish native multi-qubit gates as a viable hardware-efficient primitive for scalable superconducting quantum processors.
12 pages, 7 figures, 3 tables