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Published Online April 6, 2006
Science DOI: 10.1126/science.1126074

Reports

Submitted on February 10, 2006
Accepted on March 28, 2006

Quantum-Dot Spin-State Preparation with Near-Unity Fidelity

Mete Atatüre 1*, Jan Dreiser 1, Antonio Badolato 1, Alexander Högele 2, Khaled Karrai 3, Atac Imamoglu 1*

1 Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland.
2 Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland; Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universität, 80539 Munich, Germany.
3 Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universität, 80539 Munich, Germany.

* To whom correspondence should be addressed.
Mete Atatüre , E-mail: atature{at}phys.ethz.ch
Atac Imamoglu , E-mail: imamoglu{at}phys.ethz.ch

We demonstrate laser cooling of a single electron spin trapped in a semiconductor quantum dot. Optical coupling of electronic spin states is achieved using resonant excitation of the charged quantum dot (trion) transitions along with the heavy-light hole mixing which leads to weak, yet finite, rates for spin-flip Raman scattering. With this mechanism the electron spin can be cooled from 4.2 Kelvin to 0.020 Kelvin, as confirmed by the strength of the induced Pauli blockade of the trion absorption. Within the framework of quantum information processing, this corresponds to a spin-state preparation with a fidelity exceeding 99.8%.


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Science. ISSN 0036-8075 (print), 1095-9203 (online)