Superconductor-ferromagnet-junction Phase Qubit

Abstract

We propose a scheme for a phase qubit in an SIFIS junction, consisting of bulk superconductors (S), a proximity-induced ferromagnet (F), and insulating barriers (I). The qubit state is constituted by the 0 and the pi phase states of the junction, in which the charging energy of the junction leads to a superposition of the two states. The qubit is operated by the gate voltage applied to the ferromagnet and is insensitive to the decoherence sources existing in other superconducting qubits. We discuss a scalable scheme for qubit measurement and tunable two-qubit coupling, and a possible experimental realization.