Inductive Coupling Scheme in Unimon Qubit Architecture

The unimon qubit [1] is a superconducting qubit consisting of a Josephson junction embedded in the center conductor of a coplanar-waveguide (CPW) resonator. This design enables a compact layout and supports strong circuit nonlinearity and large anharmonicity. Unlike conventional transmons, unimons are fully tolerant against dc charge noise, show reduced sensitivity to flux noise, and benefit from a streamlined fabrication process, making them strong candidates for scalable quantum hardware. In addition, their geometry naturally supports inductive coupling, offering a robust and straightforward mechanism for connecting qubits while preserving design simplicity. Here, we highlight our ongoing work on modeling the coupled modes, optimizing coupling strengths, and understanding the role of circuit parameters in maintaining coherence and high-fidelity one- and two-qubit operations. This study aims to lay the foundation for scalable multi-qubit operations in unimon-based superconducting processors.

[1]  E. Hyyppä, S. Kundu, C. F. Chan, A. Gunyhó, J. Hotari, D. Janzso, K. Juliusson, O. Kiuru, J. Kotilahti, A. Landra, W. Liu, F. Marxer, A. M¨akinen, J.-L. Orgiazzi, M. Palma, M. Savytskyi, F. Tosto, J. Tuorila, V. Vadimov, T. Li, C. Ockeloen-Korppi, J. Heinsoo, K. Y. Tan, J. Hassel, and M. Möttönen, Unimon qubit, Nature Communications 13, 6895 (2022).