10,481 research outputs found
Matter-wave Tests of the Gravitational Redshift in Space
A recent measurement of the gravitational redshift was based on interference
of matter waves. Operation in microgravity can improve it by a factor of
and, in some models, even .Comment: Talk given at the Fifth Meeting on CPT and Lorentz Symmetry, at
Indiana University, Bloomington, IN. Corrected problem with Figur
Optical conductivity in cluster dynamical mean field theory: formalism and application to high temperature superconductors
The optical conductivity of the one-band Hubbard model is calculated using
the 'Dynamical Cluster Approximation' implementation of dynamical mean field
theory for parameters appropriate to high temperature copper-oxide
superconductors. The calculation includes vertex corrections and the result
demonstrates their importance. At densities of one electron per site, an
insulating state is found with gap value and above-gap absorption consistent
with measurements. As carriers are added the above gap conductivity rapidly
weakens and a three component structure emerges, with a low frequency 'Drude'
peak, a mid-infrared absorption, and a remnant of the insulating gap. The
mid-infrared feature obtained at intermediate dopings is shown to arise from a
pseudogap structure in the density of states. On further doping the
conductivity evolves to the Drude peak plus weakly frequency dependent tail
structure expected for less strongly correlated metals.Comment: 5 pages, 3 figure
Least-squares finite element method for fluid dynamics
An overview is given of new developments of the least squares finite element method (LSFEM) in fluid dynamics. Special emphasis is placed on the universality of LSFEM; the symmetry and positiveness of the algebraic systems obtained from LSFEM; the accommodation of LSFEM to equal order interpolations for incompressible viscous flows; and the natural numerical dissipation of LSFEM for convective transport problems and high speed compressible flows. The performance of LSFEM is illustrated by numerical examples
Optimal least-squares finite element method for elliptic problems
An optimal least squares finite element method is proposed for two dimensional and three dimensional elliptic problems and its advantages are discussed over the mixed Galerkin method and the usual least squares finite element method. In the usual least squares finite element method, the second order equation (-Delta x (Delta u) + u = f) is recast as a first order system (-Delta x p + u = f, Delta u - p = 0). The error analysis and numerical experiment show that, in this usual least squares finite element method, the rate of convergence for flux p is one order lower than optimal. In order to get an optimal least squares method, the irrotationality Delta x p = 0 should be included in the first order system
Quantum Computer Using Coupled Quantum Dot Molecules
We propose a method for implementation of a quantum computer using artificial
molecules. The artificial molecule consists of two coupled quantum dots stacked
along z direction and one single electron. One-qubit and two-qubit gates are
constructed by one molecule and two coupled molecules, respectively.The ground
state and the first excited state of the molecule are used to encode the |0>
and |1> states of a qubit. The qubit is manipulated by a resonant
electromagnetic wave that is applied directly to the qubit through a microstrip
line. The coupling between two qubits in a quantum controlled NOT gate is
switched on (off) by floating (grounding) the metal film electrodes. We study
the operations of the gates by using a box-shaped quantum dot model and
numerically solving a time-dependent Schridinger equation, and demonstrate that
the quantum gates can perform the quantum computation. The operating speed of
the gates is about one operation per 4ps. The reading operation of the output
of the quantum computer can be performed by detecting the polarization of the
qubits.Comment: 18 pages, 7 figures, submitted to Jpn. J. Appl. Phys, please send
your e-mail to Nan-Jian Wu <[email protected]
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