SIFIS Josephson junction qubit

Abstract

We propose a voltage-controlled superconducting SIFIS junction qubit consisting of the $0$ and $\pi$ phase states of the junction. Quantum tunneling due to the charging energy of insulating barrier (I) leads to coherent superposition of two states. Controlled by gate voltage on the ferromagnetic layer (F) the qubit can be operated by either non-adiabatic voltage pulses or alternating-voltage-driven Rabi-type oscillation at the degeneracy point. This qubit is robust against the decoherence due to both the magnetic microwave field and charge fluctuations. We introduce a scalable design for measurement of qubit states, switching function, controllable coupling, and Bell state formation.