1,884 research outputs found
Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet
We report the coherent manipulation of electron spins in a double quantum dot
integrated with a micro-magnet. We performed electric dipole spin resonance
experiments in the continuous wave (CW) and pump-and-probe modes. We observed
two resonant CW peaks and two Rabi oscillations of the quantum dot current by
sweeping an external magnetic field at a fixed frequency. Two peaks and
oscillations are measured at different resonant magnetic field, which reflects
the fact that the local magnetic fields at each quantum dot are modulated by
the stray field of a micro-magnet. As predicted with a density matrix approach,
the CW current is quadratic with respect to microwave (MW) voltage while the
Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values
of two Rabi oscillations directly reflects the MW electric field across the two
dots. These results show that the spins on each dot can be manipulated
coherently at will by tuning the micro-magnet alignment and MW electric field.Comment: 5 pages, 3 figure
Continuous-time quantum walks on star graphs
In this paper, we investigate continuous-time quantum walk on star graphs. It
is shown that quantum central limit theorem for a continuous-time quantum walk
on star graphs for -fold star power graph, which are invariant under the
quantum component of adjacency matrix, converges to continuous-time quantum
walk on graphs (Complete graph with two vertices) and the probability of
observing walk tends to the uniform distribution.Comment: 17, page; 4 figur
Localization of the Grover walks on spidernets and free Meixner laws
A spidernet is a graph obtained by adding large cycles to an almost regular
tree and considered as an example having intermediate properties of lattices
and trees in the study of discrete-time quantum walks on graphs. We introduce
the Grover walk on a spidernet and its one-dimensional reduction. We derive an
integral representation of the -step transition amplitude in terms of the
free Meixner law which appears as the spectral distribution. As an application
we determine the class of spidernets which exhibit localization. Our method is
based on quantum probabilistic spectral analysis of graphs.Comment: 32 page
Initial Data for General Relativity with Toroidal Conformal Symmetry
A new class of time-symmetric solutions to the initial value constraints of
vacuum General Relativity is introduced. These data are globally regular,
asymptotically flat (with possibly several asymptotic ends) and in general have
no isometries, but a group of conformal isometries. After
decomposing the Lichnerowicz conformal factor in a double Fourier series on the
group orbits, the solutions are given in terms of a countable family of
uncoupled ODEs on the orbit space.Comment: REVTEX, 9 pages, ESI Preprint 12
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