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Updated: Dec 12, 2025

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform
Published on: August 2, 2019
π phase shifter based on NbN-based ferromagnetic Josephson junction on a silicon substrate
Taro Yamashita1, Sunmi Kim2, Haruki Kato3
1Graduate School of Engineering, Nagoya University, Nagoya, Japan. yamashita@nuee.nagoya-u.ac.jp.
Abstract:
In the field of superconducting electronics, a π phase shifter based on a ferromagnetic Josephson junction is expected to provide various advantages to classical and quantum superconducting devices. Here we report niobium nitride (NbN)-based ferromagnetic π junctions on a silicon (Si) substrate with a titanium nitride (TiN) buffer layer, which have applications to flux-bias-free flux quantum bits (qubits) and classical digital logic elements. We fabricated and characterized NbN/aluminum nitride (AlN)/NbN Josephson junctions, NbN/copper nickel (CuNi)/NbN ferromagnetic Josephson junctions, and superconducting quantum interference devices (SQUIDs) consisting of these junctions on the Si substrate. The fabricated NbN/AlN/NbN junctions showed a high junction quality suitable for qubit applications. Furthermore, the magnetic field dependence of the SQUID's critical current indicated that the NbN/CuNi/NbN junction worked as a π phase shifter on the Si substrate.
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