Superinductor-based ultrastrong coupling in a superconducting circuit

2025/07/12 by Alba Torras-Coloma, Torras-Coloma, Alba, Cozzolino, Luca +6 · 1 citation
Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Quantum Physics (quant-ph) #Quantum, superfluid, helium dynamics

paper · pdf · doi:10.48550/arxiv.2507.09339

openalex publication_date 2025/07/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We present an ultrastrong superinductor-based coupling consisting of a flux qubit galvanically coupled to a resonator. The coupling inductor is fabricated in granular Aluminum, a superinductor material able to provide large surface inductances. Spectroscopy measurements on the qubit-resonator system reveal a Bloch-Siegert shift of \SI23\mega\hertz and a coupling fraction of g/ω_r ≃ 0.13, entering the perturbative ultrastrong coupling (USC) regime. We estimate the inductance of the coupler independently by low-temperature resistance measurements providing L_c = (0.74±0.14) nH, which is compatible with g/ω\gtrsim 0.1. Our results show that superinductors are a promising tool to study USC physics in high-coherence circuits using flux qubits with small loop areas and low persistent currents.

Citations

• Engineering decoherence in Josephson persistent-current qubits

Cited by

• Non-Hermitian Quantum Nonlinear Optics with Single Photons

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