1. Quantum-Dot Spin-State Preparation with Near-Unity Fidelity M. Atatüre, J. Dreiser, A. Badolato, A. Högele, K. Karrai, A. Imamoglou Science 312, 551 (2006) 30.01.07

2. Overview Optical controlling of spin in quantum-dots at 4 K High fidelity spin state preparation due to Pauli blockade Self-assembled InAs/GaAs QD

3. Four-Level System for B=0 EFEF EFEF    Laser absorbtion EFEF EFEF  Hyperfine induced spin-flip    Spontaneous spin- flip Raman scattering

4. Four-Level System for B>0 EFEF EFEF    Laser absorbtion EFEF EFEF  Hyperfine induced spin-flip    Spontaneous spin- flip Raman scattering

5. Four-Level System for B>0 with Repump Laser EFEF EFEF    Laser absorbtion EFEF EFEF  Hyperfine induced spin-flip       Laser absorbtion   

6. How It Works EFEF    Blocked!

7. Results: Laser Absorption Absorbtion due to cotunneling Repump Laser detuned by 6 GHz (Zeeman splitting) Absorbtion suppressed due to Pauli blockade Linewidth of the transition X -

8. Results: High Fidelity Theoretical model Exponential fit Repump Laser Experimental data

9. Conclusions and Outlook High-fidelity spin preparation (99.8 %) Spin cooling down to 20 mK (T=4 K) Works for both spins Prepare arbitrary superpostition of spin states Tune  by changing the magnetic field orientation with respect to the confinement axis EFEF EFEF 