2025/12/24 by Andrei A. Kugut, Kugut, Andrei A., Grigoriy S. Mazhorin +3
Physics and Astronomy · Computer Science · #Mechanical and Optical Resonators #Quantum Information and Cryptography #Quantum and electron transport phenomena
paper · doi:10.48550/arxiv.2512.21189
Fluxonium qubits demonstrate exceptional potential for quantum processing; yet, realizing scalable architectures using them remains challenging. We propose a fluxonium-based square-grid design with fast ∼63~ns controlled-Z (CZ) gates, achieving coherent errors below 10-4, activated via microwave-driven transmon couplers. A central difficulty in such large-scale systems with all-microwave gates and, therefore, strong static couplings, is suppressing parasitic interactions that extend beyond nearest neighbors to include next-nearest elements. We address this issue by introducing several design strategies: the frequency allocation of both qubits and couplers, the localization of coupler wavefunctions, and a differential oscillator that suppresses residual long-range interactions. In addition, the architecture natively supports fast ∼70~ns CZZ gates -- three-qubit operations composed of two CZ gates sharing a common qubit -- which reduce the incoherent error by ∼ 35% compared to performing the corresponding CZs sequentially. Together, these advances establish an interaction-resilient platform for large-scale fluxonium processors and can be adapted to a variety of fluxonium layouts.