Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 37: Quantum Coherence, Quantum Information Systems 1
TT 37.2: Talk
Wednesday, March 13, 2013, 09:45–10:00, H19
Quantum limit of nuclear spin polarization in semiconductor quantum dots — •Julia Hildmann1, Eleftheria Kavousanaki2, Hugo Ribeiro1, and Guido Burkard1 — 1Department of Physics, University of Konstanz, D-78457 Konstanz, Germany — 2Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology, Graduate University, Okinawa, 904-0412 Japan
Since the original proposal by Loss and DiVincenzo to use single electron spins confined in quantum dots (QDs) as quantum bits (qubits) [1], a lot of effort has been made to perform coherent control of electron spins in QDs. One of the challenges for using electron spins as qubits remains decoherence due to hyperfine interaction with the nuclear spin bath of the host material (III-V semiconductors). Among various proposals to extend coherence times, there is the possibility to polarize the nuclear spins to a high degree (close to 100% [2]). A recent experiment, which relies on spin-forbidden transitions between heavy holes and positive trions, shows the highest until now reported polarization of about 65% [3]. Simple rate equations describing the pumping mechanism fail to describe the observed saturation predicting a fully polarized nuclear state and not constituting an appropriate description of the nuclear spin bath dynamics. We present a full quantum mechanical approach to this particular problem and show that the pumping saturation is a consequence of the collective nuclear spin quantum dynamics. [1] D. Loss and D. P. DiVincenzo, Phys Rev. A 57, 120 (1998). [2] W. A. Coish and D. Loss, Phys. Rev. B 70, 195340 (2004). [3] E. A. Chekhovich et al, Phys. Rev. Lett. 104, 066804 (2010).