  We propose a spin-orbit qubit in a nanowire quantum dot on the surface of a
multiferroic insulator with a cycloidal spiral magnetic order. The spiral
exchange field from the multiferroic insulator causes an inhomogeneous
Zeeman-like interaction on the electron spin in the quantum dot, producing a
spin-orbit qubit. The absence of an external magnetic field benefits the
integration of such spin-orbit qubit into high-quality superconducting
resonators. By exploiting the Rashba spin-orbit coupling in the quantum dot via
a gate voltage, one can obtain an effective spin-photon coupling with an
efficient on/off switching. This makes the proposed device controllable and
promising for hybrid quantum communications.
