ABSTRACT
Spin states are long-lived because the spin degree of freedom is often decoupled from the orbital degree of freedom. Spin states in matter are strongly connected to polarization states of light when there is sufficiently strong spin-orbit interaction for one of the optically active states. The addition of a transverse magnetic field leads to a very effective method to initialize the spin of the ground-state electrons. Long spin lifetimes are required for any of the applications envisioned for the area and are desirable also for the experimental research itself. Work on electron spins in modulation-doped GaAs quantum wells has demonstrated the importance of performing Raman rotations with the light off-resonance. Electron spin states have been initialized to a high fidelity by pulses of light and pulse trains. Materials and structures have been prepared for which the spin lifetimes approach limits expected from theory.
