Microwave-activated high-fidelity three-qubit gate scheme for fixed-frequency superconducting qubits

• URL: http://arxiv.org/abs/2504.21346v2
• Date: Thu, 16 Oct 2025 13:09:03 GMT
• Title: Microwave-activated high-fidelity three-qubit gate scheme for fixed-frequency superconducting qubits
• Authors: Kui Zhao, Wei-Guo Ma, Ziting Wang, Hao Li, Kaixuan Huang, Yun-Hao Shi, Kai Xu, Heng Fan,
• Abstract summary: We propose a microwave-activated three-qubit gate protocol for fixed-frequency transmon qubits in the large-detuning regime.<n>The protocol maintains process fidelities exceeding $98%$ under decoherence.<n>This strategy advances scalable quantum computing systems by improving coherence properties, reducing spectral congestion, and expanding the experimental toolkit for error-resilient quantum operations.
• Score: 19.88291799199791
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Scalable superconducting quantum processors require balancing critical constraints in coherence, control complexity, and spectral crowding. Fixed-frequency architectures suppress flux noise and simplify control via all-microwave operations but remain limited by residual ZZ crosstalk. Here we propose a microwave-activated three-qubit gate protocol for fixed-frequency transmon qubits in the large-detuning regime ($|\Delta| \gg g$), leveraging the third-order nonlinear interaction to coherently exchange $\ket{001} \leftrightarrow \ket{110}$ states. By incorporating a phase-compensated optimization protocol, numerical simulations demonstrate a high average gate fidelity exceeding $99.9\%$. Systematic error analysis identifies static long-range ZZ coupling as the dominant error source in multi-qubit systems, which can be suppressed via operations in the large-detuning regime ($\sim 1$ GHz). The protocol maintains process fidelities exceeding $98\%$ under decoherence, while demonstrating intrinsic robustness to fabrication-induced parameter variations and compatibility with existing all-microwave two-qubit gate architectures. This hardware-efficient strategy advances scalable quantum computing systems by improving coherence properties, reducing spectral congestion, and expanding the experimental toolkit for error-resilient quantum operations in the noisy intermediate-scale quantum era.

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