An alternating electric field, applied to a ``spin 1/2'' quantum dot, couples to the electron spin via the spin-orbit interaction. We analyze different types of spin-orbit couplings known in the literature and find that an electric dipole spin resonance (EDSR) scheme for spin manipulation can be realized with the up-to-date experimental setups. In particular, for the Rashba and Dresselhaus spin-orbit couplings, a fully transverse effective magnetic field arises in the presence of a Zeeman splitting in the lowest order of spin-orbit interaction. Spin manipulation and measurement of the spin decoherence time T_2 are straightforward in lateral GaAs quantum dots through the use of EDSR.
We consider a mechanism of spin decay for an electron spin in a quantum dot due to coupling to a nearby quantum point contact (QPC) with and without an applied bias voltage. The coupling of spin to charge is induced by the spin-orbit interaction in the presence of a magnetic field. We perform a microscopic calculation of the effective Hamiltonian coupling constants to obtain the QPC-induced spin relaxation and decoherence rates in a realistic system. This rate is shown to be proportional to the shot noise of the QPC in the regime of large bias voltage and scales as "a-6" where "a" is the distance between the quantum dot and the QPC. We find that, for some specific orientations of the setup with respect to the crystallographic axes, the QPC-induced spin relaxation and decoherence rates vanish, while the charge sensitivity of the QPC is not changed. This result can be used in experiments to minimize QPC-induced spin decay in read-out schemes.
We show that a special type of entangled states, cluster states, can be created with Heisenberg interactions and local rotations in 2d steps where d is the dimension of the lattice. We find that, by tuning the coupling strengths, anisotropic exchange interactions can also be employed to create cluster states. Finally, we propose electron spins in quantum dots as a possible realization of a one-way quantum computer based on cluster states.
We consider a spherical thick 3-brane immersed in a five-dimensional bulk spacetime. We demonstrate how the thick brane equation of motion expanded in powers of the thickness of the brane can be obtained from the expected junction conditions on the boundaries of thick brane with the two embedding spacetimes. It is shown that the finite thickness leads to a faster collapse of the spherical shell.
ConferencesPASPS V, August 2008, Foz Do Iguacu (Brazil).
Swiss Wokshop on Basic Research in Nanoscience, June 2008, Davos (Switzerland).
Frontiers in Nanoscale Science and Technology, January 2008, Basel (Switzerland).
Quantum Transport and Dynamics in Nanostructures, August 2007, Windsor, London (England).
DPG Meeting, March 2007, Regensburg, Bavaria (Germany).
International Conference on Nanoscience and Technology (ICN+T 2006), July & August 2006, Basel (Switzerland).
Spin and Charge Effects at the Nanoscale, June 2006, Pisa (Italy).
DPG Meeting, March 2006, Dresden (Germany).
International Symposium on Mesoscopic Superconductivity
and Spintronics, February 2006, NTT Lab, Atsugi (Japan).
Swiss Physical Society Meeting, Februaray 2006, EPFL, Lausanne (Switzerland).
NCCR Meeting, September 2005, Gwatt (Switzerland).
Quantum Coherence, August 2005, Monte Verita, Ascona (Switzerland).
DPG Meeting, March 2005, Berlin (Germany).
Solid State Based Quantum Information Processing, September 2004, Herrsching (Germany).
Quantum Information Meeting, March 2004, Flums (Switzerland).
Summer School on String Theory, Astroparticle Physics and Cosmology, June & July 2002, Trieste (Italy).