Spin-Selective Energy Level Modification via the AC Stark Effect in a Quantum Dot*

Applying a strong laser far detuned from the resonance of a charged quantum dot causes an AC Stark shift of the energy levels, where the magnitude and direction of the shift is dependent upon the polarization, detuning, and intensity of the laser. The polarization also determines which spin manifold is shifted with circular polarization shifting only one spin projection. There is also a secondary energy shift, which is very likely caused by dynamic nuclear polarization, or the transfer of spin polarization from electron to nuclei, manifesting itself in the form of the Overhauser effect. In principle, the AC Stark effect in a Voigt geometry magnetic field will allow read out of the spin state of a quantum dot.