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Q: Fachverband Quantenoptik und Photonik
Q 60: Quanteneffekte: Dekohärenz
Q 60.4: Vortrag
Freitag, 6. März 2009, 11:15–11:30, VMP 6 HS-D
Qubit protection in nuclear-spin quantum dot memory — •Zoltan Kurucz1,2, Jakob M. Taylor3, Mikhail D. Lukin4, and Michael Fleischhauer1 — 1Fachbereich Physik, Univ. of Kaiserslautern, 67663 Kaiserslautern, Germany — 2Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus — 3Dept. of Physics, MIT, Cambridge, MA 02139, USA — 4Dept. of Physics, Harvard Univ. Cambridge, MA 02138, USA
Nuclear spins in semiconductor nanostructures are excellent candidates for storing quantum information. While they are largely decoupled from their environment and have long intrinsic lifetimes, the hyperfine interaction with electron spins allows one to access ensembles of nuclear spins in a controlled way. In particular, the quantum state of an electron spin can be coherently mapped onto the nuclear spins constituting a quantum dot, thus giving rise to a collective quantum memory [1]. Nevertheless, memory lifetimes are limited, e.g., by dipole-dipole interactions among the nuclei. In the talk we demonstrate that the presence of the electron can substantially reduce the decoherence of this collective memory. The hyperfine-induced dynamic Stark shift energetically isolates the storage states from the rest of the Hilbert space and protects them against nuclear spin flips and spin diffusion. We show that our scheme is robust against the deleterious effects of inhomogeneous Knight shift and we also analyze the case when the nuclear spins are not perfectly polarized.
[1] J. M. Taylor, C. M. Marcus, M. D. Lukin, Phys. Rev. Lett. 90, 206803 (2003); J. M. Taylor, A. Imamoglu, M. D. Lukin, Phys. Rev. Lett. 91, 246802 (2003)