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SUMMARY:Coherent laser spectroscopy of quantum dots - Dr Brain Gerardot\, 
 Dept of Physics\, Heriot-Watt University
DTSTART:20071029T153000Z
DTEND:20071029T163000Z
UID:TALK8717@talks.cam.ac.uk
CONTACT:6270
DESCRIPTION:Coherent laser spectroscopy of quantum dots\n\nBrian Gerardot\
 n\nSchool of Engineering and Physical Sciences\, Heriot-Watt University\, 
 Edinburgh EH14 4AS UK\n\nStrong quantum confinement has led to the observa
 tion of discrete\, atom-like energy levels in solid-state quantum dots (QD
 s). However\, for a typical self-assembled QD the confinement potential of
  a particle spans more than 104 atoms. A natural expectation for such a me
 soscopic system is that many-body interactions will dominate and lead to u
 nwanted decoherence. In this talk I will present two experiments which con
 firm that the quantum coherence is in fact maintained for particles in a Q
 D\, both for two and three level systems\, even with intense optical excit
 ation. In the first example\, a single valence-band hole is trapped in the
  QD. Using a resonant laser\, optical pumping of the hole-spin is achieved
 . Due to a very long spin-relaxation time\, high fidelity (~99%) hole-spin
  preparation is realized. Furthermore\, the spin preparation is achieved e
 ven when the spin states are degenerate at zero external magnetic field. T
 his verifies that hole spins not only have reduced interactions with phono
 ns but also negligible hyperfine interaction with the nuclear spins of the
  QD’s constituent atoms. Secondly\, I will discuss a two-color pump-prob
 e experiment on the exciton and bi-exciton states in a QD. In the strong-f
 ield excitation regime\, the dressed-transition states (Autler-Townes spli
 tting) are observed. These results confirm that solid-state mesoscopic sys
 tems are a suitable for quantum optical techniques and promising for appli
 cations in quantum information processing.  \n\n\n
LOCATION:HEP Seminar Room (980) Rutherford Building\, Cavendish Laboratory
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