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.

6 pages, 3 figures