Scalable Fluxonium Quantum Processors via Tunable-Coupler Architecture

TL;DR

This paper presents a scalable fluxonium quantum processor architecture with high-fidelity gates, validated on a 22-qubit system, demonstrating fluxonium's potential for scalable quantum computing.

Contribution

It introduces a modular fluxonium-coupler design that suppresses errors and enables scalable, high-fidelity multi-qubit operations in superconducting quantum processors.

Findings

Parallel single-qubit gate fidelity ~99.99%

Two-qubit CZ gate fidelity ~99% with 32 ns duration

Successful generation of GHZ states involving up to 10 qubits

Abstract

Superconducting quantum processors have largely converged on transmon-based architectures, while alternative qubit modalities with intrinsic error protection have lacked a demonstrated path to scalable system integration. In particular, although tunable-coupler-mediated interactions have been validated for small fluxonium systems, it remains unclear whether such designs can be scaled to a multi-qubit lattice. Here, we establish a scalable fluxonium processor architecture based on a modular qubit-coupler unit cell engineered to suppress residual interactions and spectator errors in a many-qubit lattice. The system enables parallel single-qubit gate fidelities approaching 99.99% and two-qubit CZ gate fidelities around 99%. With an optimized gate duration of 32 ns, the best CZ gate fidelity reaches 99.9%. We further validate this architecture in a 22-qubit processor based on the same configuration, where parallel operations enable the deterministic generation of Greenberger-Horne-Zeilinger states involving up to 10 qubits. Together, these results demonstrate that the fluxonium-tunable-coupler unit cell composes without emergent interaction pathologies and establish fluxonium as a scalable superconducting qubit platform.