Electrically driven spin resonance in quantum dots
Time: Tue Apr 1 13:00:00 2014
Location: Building 1, Room 114, Auditorium
The usual way to coherently control the spin of a single electron is to use electron spin resonance (ESR), i.e., to put the electron in a dc magnetic field, and apply a transversal ac magnetic field pulse. Under certain conditions, the ac magnetic field pulse can be substituted by an ac electric field pulse: the latter couples to the charge of the electron and thereby induces an oscillatory motion of the wave function. In turn, this oscillatory motion results in spin Rabi oscillations, provided that a sufficiently strong interaction between the orbital and spin degrees of freedom (e.g., spin-orbit interaction, inhomogeneous B-field, hyperfine interaction, etc) is present in the system.
In the talk, I will review the basic mechanisms and the experimental state-of-the-art of electrically driven spin resonance (EDSR) in semiconductor quantum dots. I will introduce a simple model of EDSR, in which the coupled orbital-spin dynamics arises due to a static, but spatially disordered magnetic field. I will describe single- and multi-photon resonances in this model, and show that for any of these resonances, the spin Rabi frequency is a non-monotonic function of the amplitude of the ac electric field. Furthermore, for strong driving, the multi-photon Rabi frequencies become comparable to the single-photon Rabi frequency. In the context of practical quantum information processing, these findings highlight the availability of multi-photon resonances for qubit control with effectivity close to that of the single-photon resonance, and the possibility that increasing the drive strength might lead to a decreasing qubit-flip speed. I will argue that our simple model might bear relevance for recent experiments in carbon nanotube quantum dots.