Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Quantum Dots and Wires, Optical Properties IV: Spin

HL 55.2: Talk

Thursday, March 25, 2010, 14:15–14:30, H14

Ultrafast optical rotations of electron spins in an InGaAs/GaAs quantum dot ensemble — •Stefan Spatzek¹, Alex Greilich¹, Sophia E. Economou², Dmitri R. Yakovlev^1,3, Dirk Reuter⁴, Andreas D. Wieck⁴, Thomas L. Reinecke², and Manfred Bayer¹ — ¹Experimentelle Physik 2, TU Dortmund, 44221 Dortmund, Germany — ²Naval Research Laboratory, Washington, DC 20375, USA — ³3A. F. Ioffe Physico-Technical Institute, RAS, 194021 St. Petersburg — ⁴Angewandte Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany

We report on fast optical rotation operations on electron spins in a quantum dots ensemble [1]. The spins are initialized in the z direction (quantum dot growth and light propagation direction). The spin vector oscillates about a transversal magnetic field B till a ultrafast 2π-"control" laser pulse induces rotations of the spins about the z axis. The 2π-control pulse rotates the spin without generating a new spin polarization. The rotation angle is determined by the photon energy detuning of the control pulse from the optical resonance. For the first time for optically controlled spins, spin echoes and extension of the dephasing time were seen. By combining the rotation about the two axis a spin rotations about arbitrary axis has been realized. This robust optically controlled single spin rotation gate provides the basis for single-qubit logic operations.

[1] A. Greilich, S. E. Economou, S. Spatzek, D. R. Yakovlev, D. Reuter, A. D. Wieck, T. L. Reinecke and M. Bayer, Nature Physics 5, 262