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

OverviewOptical controlling of spin in quantum-dots at 4 K

High fidelity spin state preparation due to Pauli blockade

Self-assembled InAs/GaAs QD

Four-Level System for B=0 , EF EF

,

Laser absorbtion

EF EFHyperfine induced spin-flip

Spontaneous spin-flip Raman scattering

Four-Level System for B>0 , EF EF

,

Laser absorbtion

EF EFHyperfine induced spin-flip

Spontaneous spin-flip Raman scattering

Four-Level System for B>0 with Repump Laser

, EF EF ,

Laser absorbtion

EF EFHyperfine induced spin-flip

Laser absorbtion

How It Works

EF

Blocked!

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-

Results: High FidelityTheoretical model

Exponential fit

Repump Laser

Experimental data

electrons of Number Absorbtion

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

EF EF