Submicrometer tunnel ferromagnetic Josephson junctions with transmon energy scale

TL;DR

This paper reports the development of submicron ferromagnetic Josephson junctions with energies suitable for transmon qubits, demonstrating high-quality devices operating in the quantum phase diffusion limit, advancing superconducting quantum circuits.

Contribution

The authors fabricated and characterized submicron ferromagnetic Josephson junctions with transmon-scale energies, a novel step toward integrating ferromagnetism into superconducting qubits.

Findings

Junctions operate in the quantum phase diffusion limit

High-quality junctions comparable to standard transmons

Potential for mitigating quantum phase fluctuations

Abstract

We have realized submicron tunnel ferromagnetic Al/AlO$_x$/Al/Ni$_{80}$Fe$_{20}$/Al Josephson junctions (JJs) in Manhattan-style configuration for qubit applications. These junctions have been designed to lie within the energy range of transmons. The current-voltage characteristics of these junctions are comparable with those of standard JJs implemented in state-of-the-art transmons, thus confirming the high quality of the devices and marking a significant step toward the realization of the ferrotransmon. Low-frequency characterization confirms that our junctions operate in the quantum phase diffusion limit, as tunnel JJs in conventional transmons with similar characteristic energies. Ultimately, mitigation of quantum phase fluctuations will represent a key for advancing the entire field of superconducting quantum circuit architectures.