Hybrid ferromagnetic transmon qubit: Circuit design, feasibility, and detection protocols for magnetic fluctuations

We propose to exploit currently available tunnel ferromagnetic Josephson junctions to realize a hybrid superconducting qubit. We show that the characteristic hysteretic behavior of the ferromagnetic barrier provides an alternative and intrinsically digital tuning of the qubit frequency by means of magnetic field pulses. To illustrate functionalities and limitation of the device, we discuss the coupling to a readout resonator and the effect of magnetic fluctuations. The possibility to use the qubit as a noise detector and its relevance to investigate the subtle interplay of magnetism and superconductivity is envisaged.

Automated summary

This paper proposes a method to realize a hybrid superconducting qubit using currently available tunnel ferromagnetic Josephson junctions, utilizing magnetic field pulses to tune the qubit frequency. It discusses the coupling to a readout resonator and the impact of magnetic fluctuations, and suggests the possibility of using the qubit as a noise detector to investigate the interplay of magnetism and superconductivity.