1,884 research outputs found

    Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet

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    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

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    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 NN-fold star power graph, which are invariant under the quantum component of adjacency matrix, converges to continuous-time quantum walk on K2K_2 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

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    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 nn-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

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    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 U(1)×U(1)U(1)\times U(1) 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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