Abstract
A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC) can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external a.c. electric field, an effect called electric-dipole spin resonance. Here we develop a theory that can be applied in the strong SOC regime. We find that there is an optimal SOC strength, where the Rabi frequency induced by the a.c. electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire. In addition, our study is extended to a semiconductor nanowire double quantum dot with strong SOC. We show that both spin-conserved and spin-flipped tunnelings exist and they can compete with each other when increasing the SOC. Moreover, strong Coulomb repulsion in the nanowire double quantum dot can be combined with the SOC-dependent tunnelings to yield an anisotropic exchange coupling between the two spin-orbit qubits. Furthermore, we give an explicit physical picture for this anisotropic exchange coupling.
Coffee and tea will be served 20 minutes prior to the seminar.