230 research outputs found
Single shot cathode transverse momentum imaging in high brightness photoinjectors
In state of the art photoinjector electron sources, thermal emittance from photoemission dominates the final injector emittance. Therefore, low thermal emittance cathode developments and diagnostics are very important. Conventional thermal emittance measurements for the high gradient gun are time-consuming and thus thermal emittance is not measured as frequently as quantum efficiency during the lifetime of photocathodes, although both are important properties for the photoinjector optimizations. In this paper, a single shot measurement of photoemission transverse momentum, i.e., thermal emittance per rms laser spot size, is proposed for photocathode rf guns. By tuning the gun solenoid focusing, the electrons' transverse momenta at the cathode are imaged to a downstream screen, which enables a single shot measurement of both the rms value and the detailed spectra of the photoelectrons' transverse momenta. Both simulations and proof of principle experiments are reported
Beyond the Jaynes-Cummings model: circuit QED in the ultrastrong coupling regime
In cavity quantum electrodynamics (QED), light-matter interaction is probed
at its most fundamental level, where individual atoms are coupled to single
photons stored in three-dimensional cavities. This unique possibility to
experimentally explore the foundations of quantum physics has greatly evolved
with the advent of circuit QED, where on-chip superconducting qubits and
oscillators play the roles of two-level atoms and cavities, respectively. In
the strong coupling limit, atom and cavity can exchange a photon frequently
before coherence is lost. This important regime has been reached both in cavity
and circuit QED, but the design flexibility and engineering potential of the
latter allowed for increasing the ratio between the atom-cavity coupling rate
and the cavity transition frequency above the percent level. While these
experiments are well described by the renowned Jaynes-Cummings model, novel
physics is expected in the ultrastrong coupling limit. Here, we report on the
first experimental realization of a superconducting circuit QED system in the
ultrastrong coupling limit and present direct evidence for the breakdown of the
Jaynes-Cummings model.Comment: 5 pages, 3 figure
Quantum state engineering in hybrid open quantum systems
We investigate a possibility to generate nonclassical states in light-matter coupled noisy quantum systems, namely, the anisotropic Rabi and Dicke models. In these hybrid quantum systems, a competing influence of coherent internal dynamics and environment-induced dissipation drives the system into nonequilibrium steady states (NESSs). Explicitly, for the anisotropic Rabi model, the steady state is given by an incoherent mixture of two states of opposite parities, but as each parity state displays light-matter entanglement, we also find that the full state is entangled. Furthermore, as a natural extension of the anisotropic Rabi model to an infinite spin subsystem, we next explored the NESS of the anisotropic Dicke model. The NESS of this linearized Dicke model is also an inseparable state of light and matter. With an aim to enrich the dynamics beyond the sustainable entanglement found for the NESS of these hybrid quantum systems, we also propose to combine an all-optical feedback strategy for quantum state protection and for establishing quantum control in these systems. Our present work further elucidates the relevance of such hybrid open quantum systems for potential applications in quantum architectures
The coherent interaction between matter and radiation - A tutorial on the Jaynes-Cummings model
The Jaynes-Cummings (JC) model is a milestone in the theory of coherent
interaction between a two-level system and a single bosonic field mode. This
tutorial aims to give a complete description of the model, analyzing the
Hamiltonian of the system, its eigenvalues and eigestates, in order to
characterize the dynamics of system and subsystems. The Rabi oscillations,
together with the collapse and revival effects, are distinguishing features of
the JC model and are important for applications in Quantum Information theory.
The framework of cavity quantum electrodynamics (cQED) is chosen and two
fundamental experiments on the coherent interaction between Rydberg atoms and a
single cavity field mode are described.Comment: 22 pages, 7 figures. Tutorial. Submitted to a special issue of EPJ -
ST devoted to the memory of Federico Casagrand
Quantum Simulation of Spin Chains Coupled to Bosonic Modes with Superconducting Circuits
We propose the implementation of a digital quantum simulation of spin chains
coupled to bosonic field modes in superconducting circuits. Gates with high
fidelities allows one to simulate a variety of Ising magnetic pairing
interactions with transverse field, Tavis-Cummings interaction between spins
and a bosonic mode, and a spin model with three-body terms. We analyze the
feasibility of the implementation in realistic circuit quantum electrodynamics
setups, where the interactions are either realized via capacitive couplings or
mediated by microwave resonators.Comment: Chapter in R. S. Anderssen et al. (eds.), Mathematics for Industry 11
(Springer Japan, 2015
1994 turfgrass research report
Moss control on bentgrass greens evaluation / Jill Taylor -- Preemergent spotted spurge broadleaf weed control evaluation / William Pound and Renee Stewart -- Finale/Roundup herbicide demonstration evaluation / William Pound and Renee Stewart -- Turflon solvent evaluation / William Pound and Renee Stewart -- General turfgrass broadleaf weed control evaluation / William Pound and Renee Stewart -- Postemergence herbicide efficacy on crabgrass / John Street and Renee Stewart -- Preemergence herbicide efficacy on crabgrass / John Street, Jill Taylor and Renee Stewart -- Leaf spot control study / Joe Rimelspach, Karl Danneberger and Jill Taylor -- Dollar spot control study / Karl Danneberger, Joe Rimelspach and Jill Taylor -- Brown patch control study / Karl Danneberger, Joe Rimelspach and Jill Taylor -- Anthracnose control study / Karl Danneberger, Joe Rimelspach and Jill Taylor -- Summer patch control study / Joe Rimelspach, Karl Danneberger and Jill Taylor -- Yellow tuft control study / Karl Danneberger, Joe Rimelspach and Jill Taylor -- Red thread control study, Columbus / Joe Rimelspach, Karl Danneberger and Jill Taylor -- Red thread control study, Delaware / Joe Rimelspach, Bobby Joyner, Joe Green and Jerry Sullivan -- Susceptibility of bentgrass cultivars to Fore+ Aliette combinations / Karl Danneberger and Jill Taylor -- Suppression of turf diseases with biocontrol agent fortified compost-amended topdressings / Marcella Grebus, Carol Musselman, Joe Rimelspach and Harry Hoitink -- Evaluation of fungicides for resistance to dollar spot (Sclerotinia homoecmpa) on creeping bentgrass / Joe Rimelspach, Jill Taylor and Karl Danneberger -- Application of an insect growth regulator and insecticide on baits for control of ant mounds in turfgrass / David Shetlar, Harry Niemczyk and Kevin Power -- Application of insecticides for control of black turfgrass ataenius larvae in turfgrass / David Shetlar, Harry Niemczyk and Kevin Power -- Evaluation of biorationals and biologicals for control of black cutworm (Agrotis ipsilon Hufnagel) and sod webworm (Pyralidae, Crambinae) larvae in bentgrass, 1994 / David Shetlar, Harry Niemczyk and Kevin Power -- Evaluation of pyrethroids and other insecticides for control of black cutworm (Agrotis ipsilon Hufnagel) and sod webworm (Pyralidae, Crambinae) larvae in bentgrass, 1994 / David Shetlar, Harry Niemczyk and Kevin Power -- Surface and subsurface applied insecticides for control of white grubs in turfgrass / David Shetlar, Harry Niemczyk and Kevin Power -- Influence of application time on the efficacy of insect growth regulators for control of white grubs in turfgrass / David Shetlar, Harry Niemczyk and Kevin Power -- Subsurface placement of controlled release chlorpyrifos granules for extended control of Japanese beetle larvae in turfgrass: third report / Harry Niemczyk and David Shetlar -- Evaluation of Turplex 3 % EC for control of black cutworm larvae on the greens of Shadow Creek Golf Course, N. Las Vegas, Nevada / Harry Niemczyk -- Nitrogen Source and Rate effect on Kentucky bluegrass / John Street and Renee Stewart -- Polymer-coated nitrogen source effect on Kentucky bluegrass / John Street and Renee Stewart -- Evaluation of turfgrass species and cultivars for shade / Jill Taylor -- Regional low input sustainable turf study / Jill Taylor -- 1990 NTEP perennial ryegrass test / Jill Taylor -- 1994 NTEP perennial ryegrass test / Jill Taylor -- 1993 NTEP bentgrass test (fairway/tee) / Jill Taylor -- 1993 NTEP fineleaf fescue test / Jill Taylor -- Bermudagrass management study / John Street and Jill Taylor -- Duration of rolling as measured by ball roll / Karl Danneberger, Jill Taylor and Jobin Morrow -- Golf ball roll as influenced by soft spike and traditional metal spike golf shoes / Karl Danneberger and Jobin Morrow -- Primo/Banner interaction study / Bill Pound, Renee Stewart and Joe Rimelspach -- Primo growth regulator evaluation on creeping bentgrass / William Pound and Renee Stewart -- Restriction of arbitrary amplification fragments of Poa annua L. / Patty Sweeney and Karl Danneberge
Josephson Coupling and Fiske Dynamics in Ferromagnetic Tunnel Junctions
We report on the fabrication of Nb/AlO_x/Pd_{0.82}Ni_{0.18}/Nb
superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson
junctions with high critical current densities, large normal resistance times
area products, high quality factors, and very good spatial uniformity. For
these junctions a transition from 0- to \pi-coupling is observed for a
thickness d_F ~ 6 nm of the ferromagnetic Pd_{0.82}Ni_{0.18} interlayer. The
magnetic field dependence of the \pi-coupled junctions demonstrates good
spatial homogeneity of the tunneling barrier and ferromagnetic interlayer.
Magnetic characterization shows that the Pd_{0.82}Ni_{0.18} has an out-of-plane
anisotropy and large saturation magnetization, indicating negligible dead
layers at the interfaces. A careful analysis of Fiske modes provides
information on the junction quality factor and the relevant damping mechanisms
up to about 400 GHz. Whereas losses due to quasiparticle tunneling dominate at
low frequencies, the damping is dominated by the finite surface resistance of
the junction electrodes at high frequencies. High quality factors of up to 30
around 200 GHz have been achieved. Our analysis shows that the fabricated
junctions are promising for applications in superconducting quantum circuits or
quantum tunneling experiments.Comment: 15 pages, 9 figure
Quantum Acoustics with Surface Acoustic Waves
It has recently been demonstrated that surface acoustic waves (SAWs) can
interact with superconducting qubits at the quantum level. SAW resonators in
the GHz frequency range have also been found to have low loss at temperatures
compatible with superconducting quantum circuits. These advances open up new
possibilities to use the phonon degree of freedom to carry quantum information.
In this paper, we give a description of the basic SAW components needed to
develop quantum circuits, where propagating or localized SAW-phonons are used
both to study basic physics and to manipulate quantum information. Using
phonons instead of photons offers new possibilities which make these quantum
acoustic circuits very interesting. We discuss general considerations for SAW
experiments at the quantum level and describe experiments both with SAW
resonators and with interaction between SAWs and a qubit. We also discuss
several potential future developments.Comment: 14 pages, 12 figure
Effects of chemical modifications on photophysics and exciton dynamics of π -conjugation attenuated and metal-chelated photoconducting polymers.
Abstract Effects of two types of chemical modifications on photoconducting polymers consisting of polyphenylenevinylene (PPV) derivatives are studied by static and ultrafast transient optical spectroscopy as well as semi-empirical ZINDO calculations. The first type of modification inserts 2,2'-bipyridyl-5 -vinylene units (bpyV) in the PPV backbone, and the second type involves metal -chelation with the bpy sites. Photohuninescence and exciton dynamics of polymers 1 and 2 with PV:bpyV ratios of 1 and 3 were examined in solution, and compared to those of the homopolymer, poly(2,5-bis(2' -ethylhexyloxy)-l ,4-phenylenevinylene) (BEH-PPV), Similar studies were carried out for several metal-chelated polymers. These results can be explained by changes in n-conjugation throughout the polymer backbone. The attenuation in n-conjugation by the chemical modifications transforms a conducting polymer from one-dimensional semiconductor to molecular aggregates. Keywords poly(phenylene vinylene) derivatives, molecular aggregates, x-conjugation, time-resolved fast spectroscopy, chemical synthesis, semi-empirical and model calculations. Introduction In order to expand applications for conducting polymers, chemical modifications have been carried out by researchers l-s. These modifications may occur at the backbone or at the side groups of the polymers5'7-'0. In this study, the photophysics of two poly(phenylene vinylene) (PPV) derivatives which are chemically modified at the backbon
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