895 research outputs found
Laser phase modulation approaches towards ensemble quantum computing
Selective control of decoherence is demonstrated for a multilevel system by
generalizing the instantaneous phase of any chirped pulse as individual terms
of a Taylor series expansion. In the case of a simple two-level system, all odd
terms in the series lead to population inversion while the even terms lead to
self-induced transparency. These results also hold for multiphoton transitions
that do not have any lower-order photon resonance or any intermediate virtual
state dynamics within the laser pulse-width. Such results form the basis of a
robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted
The Effect of the Federal Reserve Rediscount Policy on Credit Expansion
History and Purpose of the Federal Reserve Act -- In order to make the subject of this thesis more clear it is deemed necessary to give a brief history of the Federal Reserve Act and System
Performance and loads data from a hover test of a full-scale XV-15 rotor
A hover test of a full-scale XV-15 rotor was conducted at the Outdoor Aerodynamic Research Facility at Ames Research Center. The primary objective of the test was to obtain accurate measurements of the hover performance of the original, metal-blade XV-15 rotor system. Data were acquired for rotor tip Mach numbers ranging from 0.60 to 0.73. This report presents data on rotor performance, rotor wake downwash velocities, and rotor loads
Performance and loads data from a hover test of a 0.658-scale V-22 rotor and wing
A hover test of a 0.658-scale model of a V-22 rotor and wing was conducted at the Outdoor Aerodynamic Research Facility at Ames Research Center. The primary objectives of the test were to obtain accurate measurements of the hover performance of the rotor system, and to measure the aerodynamic interactions between the rotor and wing. Data were acquired for rotor tip Mach numbers ranging from 0.1 to 0.73. This report presents data on rotor performance, rotor-wake downwash velocities, rotor system loads, wing forces and moments, and wing surface pressures
Localization of Two-dimensional Electron Gas in LaAlO3/SrTiO3 Heterostructures
We report strong localization of 2D electron gas in LaAlO3 / SrTiO3 epitaxial
thin-film heterostructures grown on (LaAlO3)0.3-(Sr2AlTaO3)0.7 substrates by
using pulsed laser deposition with in-situ reflection high-energy electron
diffraction. Using longitudinal and transverse magnetotransport measurements,
we have determined that disorder at the interface influences the conduction
behavior, and that increasing the carrier concentration by growing at lower
oxygen partial pressure changes the conduction from strongly localized at low
carrier concentration to metallic at higher carrier concentration, with
indications of weak localization. We interpret this behavior in terms of a
changing occupation of Ti 3d bands near the interface, each with a different
spatial extent and susceptibility to localization by disorder, and differences
in carrier confinement due to misfit strain and point defects.Comment: 12 pages, 4 figure
High-Precision Entropy Values for Spanning Trees in Lattices
Shrock and Wu have given numerical values for the exponential growth rate of
the number of spanning trees in Euclidean lattices. We give a new technique for
numerical evaluation that gives much more precise values, together with
rigorous bounds on the accuracy. In particular, the new values resolve one of
their questions.Comment: 7 pages. Revision mentions alternative approach. Title changed
slightly. 2nd revision corrects first displayed equatio
Picosecond excitation and selective intramolecular rates in supersonic molecular beams. IV. Alkylanthracenes
To assess the role of alkylation on IVR, the dynamics of jet cooled 9-methyl and 9-hexylanthracene excited to single vibronic levels (SVL) in S1 are investigated and compared with the parent molecule, anthracene, whose picosecond IVR dynamics are now well characterized. Vibrations in S1 and S0 are analyzed. Decay rates and SVL fluorescence spectra are also presented. The decay rates as a function of excess vibrational energy increase rapidly at low energy but become relatively constant at high energy. The approximate energy threshold at which the decay rate "saturates" is dependent on the substitutent; anthracene ([approximately-equal-to]1800 cm^−1), 9-methylanthracene ([approximately-equal-to]1000 cm^−1), 9-hexylanthracene ([approximately-equal-to]400 cm^−1), and A–(CH2)3–[cursive phi] (<=400 cm^−1). These identified thresholds are discussed and related to IVR processes. Finally, some comments on the importance of low frequency modes to IVR are given
Tailoring a two-dimensional electron gas at the LaAlO3/SrTiO3 (001) interface by epitaxial strain
Recently a metallic state was discovered at the interface between insulating
oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional
electron gas (2DEG) have attracted significant interest due to its potential
applications in nanoelectronics. Control over this carrier density and mobility
of the 2DEG is essential for applications of these novel systems, and may be
achieved by epitaxial strain. However, despite the rich nature of strain
effects on oxide materials properties, such as ferroelectricity, magnetism, and
superconductivity, the relationship between the strain and electrical
properties of the 2DEG at the LaAlO3/SrTiO3 heterointerface remains largely
unexplored. Here, we use different lattice constant single crystal substrates
to produce LaAlO3/SrTiO3 interfaces with controlled levels of biaxial epitaxial
strain. We have found that tensile strained SrTiO3 destroys the conducting
2DEG, while compressively strained SrTiO3 retains the 2DEG, but with a carrier
concentration reduced in comparison to the unstrained LaAlO3/SrTiO3 interface.
We have also found that the critical LaAlO3 overlayer thickness for 2DEG
formation increases with SrTiO3 compressive strain. Our first-principles
calculations suggest that a strain-induced electric polarization in the SrTiO3
layer is responsible for this behavior. It is directed away from the interface
and hence creates a negative polarization charge opposing that of the polar
LaAlO3 layer. This both increases the critical thickness of the LaAlO3 layer,
and reduces carrier concentration above the critical thickness, in agreement
with our experimental results. Our findings suggest that epitaxial strain can
be used to tailor 2DEGs properties of the LaAlO3/SrTiO3 heterointerface
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