173 research outputs found
Nonlinear coupling of continuous variables at the single quantum level
We experimentally investigate nonlinear couplings between vibrational modes
of strings of cold ions stored in linear ion traps. The nonlinearity is caused
by the ions' Coulomb interaction and gives rise to a Kerr-type interaction
Hamiltonian H = n_r*n_s, where n_r,n_s are phonon number operators of two
interacting vibrational modes. We precisely measure the resulting oscillation
frequency shift and observe a collapse and revival of the contrast in a Ramsey
experiment. Implications for ion trap experiments aiming at high-fidelity
quantum gate operations are discussed
A 4-unit-cell superstructure in optimally doped YBa2Cu3O6.92 superconductor
Using high-energy diffraction we show that a 4-unit-cell superstructure,
q0=(1/4,0,0), along the shorter Cu-Cu bonds coexists with superconductivity in
optimally doped YBCO. A complex set of anisotropic atomic displacements on
neighboring CuO chain planes, BaO planes, and CuO2 planes, respectively,
correlated over ~3-6 unit cells gives rise to diffuse superlattice peaks. Our
observations are consistent with the presence of Ortho-IV nanodomains
containing these displacements.Comment: Corrected typo in abstrac
ОБЩИННАЯ ТЕОРИЯ Н.Г.ЧЕРНЫШЕВСКОГО В ИСТОРИОГРАФИИ
Розглядається общинна теорія М.Г.Чернишевского та шляхи її вивчення у дореволюційній
та радянській історіоргафії. Вказано на досягнення та вади, які були властиві достідникам
цього питання.There is investigated a community theory of N.Cheryshevsky and ways of its studying in
prerevolutional and revolutional historiography. There are pointed out faults and achievements of this
problem researchers
Depth-dependent critical behavior in V2H
Using X-ray diffuse scattering, we investigate the critical behavior of an
order-disorder phase transition in a defective "skin-layer" of V2H. In the
skin-layer, there exist walls of dislocation lines oriented normal to the
surface. The density of dislocation lines within a wall decreases continuously
with depth. We find that, because of this inhomogeneous distribution of
defects, the transition effectively occurs at a depth-dependent local critical
temperature. A depth-dependent scaling law is proposed to describe the
corresponding critical ordering behavior.Comment: 5 pages, 4 figure
Highly non-Gaussian states created via cross-Kerr nonlinearity
We propose a feasible scheme for generation of strongly non-Gaussian states
using the cross-Kerr nonlinearity. The resultant states are highly
non-classical states of electromagnetic field and exhibit negativity of their
Wigner function, sub-Poissonian photon statistics, and amplitude squeezing.
Furthermore, the Wigner function has a distinctly pronounced ``banana'' or
``crescent'' shape specific for the Kerr-type interactions, which so far was
not demonstrated experimentally. We show that creating and detecting such
states should be possible with the present technology using electromagnetically
induced transparency in a four-level atomic system in N-configuration.Comment: 12 pages, 7 figure
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Non-destructive metallurgical analysis of astrolabes utilizing synchrotron radiation.
From the experiments performed it is possible to determine a wide range of information about the metallurgy of the astrolabes studied. It was found that different brass alloys were used for components that were cast and those that were mechanically deformed. Chemical composition, forming history, and thickness measurements are all determined non-destructively, illustrating that this technique could be useful for many applications with metal artifact analysis where non-intrusive methods are required
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A high energy phase retarder for the simultaneous production of right- and left-handed circularly polarized x-rays
The authors have fabricated and characterized the performance of a monolithic Ge Bragg-Laue phase retarder capable of simultaneously producing both right- and left-handed circularly polarized x rays. The energy range of operation of the phase retarder is between 50 and 100 keV making it well suited to the measurement of spin-dependent Compton profiles within the impulse approximation, primarily because of the increased momentum resolution and larger Compton scattering cross section available at these higher incident energies. Although the phase retarder was optimized for operation at 86 keV, it can produce highly circularly polarized x rays over a substantial energy range. The performance of the phase retarder was tested via magnetic Compton scattering measurements on an Fe sample at the undulator A of the Advanced Photon Source. It was found to perform well in terms of flux and degree of circular polarization thereby greatly reducing the data collection times required for this inherently weak scattering process
Plantas medicinais utilizadas por agricultores ecológicos no tratamento complementar de hipertensão arterial sistêmica e colesterol elevado.
X-Ray-Diffraction Study of Charge-Density-Waves and Oxygen-Ordering in YBa2Cu3O6+x Superconductor
We report a temperature-dependent increase below 300 K of diffuse
superlattice peaks corresponding to q_0 =(~2/5,0,0) in an under-doped
YBa_2Cu_3O_6+x superconductor (x~0.63). These peaks reveal strong c-axis
correlations involving the CuO_2 bilayers, show a non-uniform increase below
\~220 K with a plateau for ~100-160 K, and appear to saturate in the
superconducting phase. We interpret this unconventional T-dependence of the
``oxygen-ordering'' peaks as a manifestation of a charge density wave in the
CuO_2 planes coupled to the oxygen-vacancy ordering.Comment: 4 pages, 4 figure
Fabrication and heating rate study of microscopic surface electrode ion traps
We report heating rate measurements in a microfabricated gold-on-sapphire
surface electrode ion trap with trapping height of approximately 240 micron.
Using the Doppler recooling method, we characterize the trap heating rates over
an extended region of the trap. The noise spectral density of the trap falls in
the range of noise spectra reported in ion traps at room temperature. We find
that during the first months of operation the heating rates increase by
approximately one order of magnitude. The increase in heating rates is largest
in the ion loading region of the trap, providing a strong hint that surface
contamination plays a major role for excessive heating rates. We discuss data
found in the literature and possible relation of anomalous heating to sources
of noise and dissipation in other systems, namely impurity atoms adsorbed on
metal surfaces and amorphous dielectrics.Comment: 17 pages, 5 figure
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