295 research outputs found
Gap solitons in spatiotemporal photonic crystals
We generalize the concept of nonlinear periodic structures to systems that
show arbitrary spacetime variations of the refractive index. Nonlinear pulse
propagation through these spatiotemporal photonic crystals can be described,
for shallow nonstationary gratings, by coupled mode equations which are a
generalization of the traditional equations used for stationary photonic
crystals. Novel gap soliton solutions are found by solving a modified massive
Thirring model. They represent the missing link between the gap solitons in
static photonic crystals and resonance solitons found in dynamic gratings.Comment: 3 figures, submitte
Conditional large Fock state preparation and field state reconstruction in Cavity QED
We propose a scheme for producing large Fock states in Cavity QED via the
implementation of a highly selective atom-field interaction. It is based on
Raman excitation of a three-level atom by a classical field and a quantized
field mode. Selectivity appears when one tunes to resonance a specific
transition inside a chosen atom-field subspace, while other transitions remain
dispersive, as a consequence of the field dependent electronic energy shifts.
We show that this scheme can be also employed for reconstructing, in a new and
efficient way, the Wigner function of the cavity field state.Comment: 4 Revtex pages with 3 postscript figures. Submitted for publicatio
Extent and Distribution of Soils in Depressional Areas in the Clarion-Nicollet-Webster Soil Association in lowa
The extent and distribution of soils that occur in depressional areas in the Clarion-Nicollet-Webster soil association have been estimated for Iowa counties from a randomly selected sample. The sample consisted of detailed soil maps of approximately 1000 quarter-section (each about 160 acres), or about 2 percent of the total land area. The data from the soil maps of the samples were projected to give estimates of soil conditions by counties and for the area as a whole. The acreage of depressional soils is estimated to be 4.8 percent of the total soil association area with significant variation between counties. The following data are reported by counties for mineral and organic soils: (1) percentage of quarter-sections with depressional soil areas, (2) average number and acreage of depressional areas per quarter-section, and (3) size class distribution of depressional areas
Editorial: Evidenced based medical care of hospitalized children with local adaptations in low-resource settings
Langevin equation for the squeezing of light by means of a parametric oscillator
We show that the Langevin equation for a nonlinear-optical system may be obtained directly from the Heisenberg equation of motion for the annihilation operators, provided a certain linearization procedure is valid. We apply the technique to the parametric oscillator used to generate squeezed light and compare our results to those obtained from Fokker-Planck-type equations. We argue that, only when the Wigner, as opposed to the P or Q, representation of quantum optics is used, do we get a correct description of the underlying stochastic process. We show how the linearization procedure may be carried out to describe the operation of the parametric oscillator both below threshold, where a squeezed vacuum state results, and above threshold, where we find a squeezed coherent state. In the region of the threshold a heuristic extension of the method leads to a possible description of the system by means of a nonlinear Langevin equation
In-loop squeezing is real squeezing to an in-loop atom
Electro-optical feedback can produce an in-loop photocurrent with arbitrarily
low noise. This is not regarded as evidence of `real' squeezing because
squeezed light cannot be extracted from the loop using a linear beam splitter.
Here I show that illuminating an atom (which is a nonlinear optical element)
with `in-loop' squeezed light causes line-narrowing of one quadrature of the
atom's fluorescence. This has long been regarded as an effect which can only be
produced by squeezing. Experiments on atoms using in-loop squeezing should be
much easier than those with conventional sources of squeezed light.Comment: 4 pages, 2 figures, submitted to PR
Demonstration of integrated microscale optics in surface-electrode ion traps
In ion trap quantum information processing, efficient fluorescence collection
is critical for fast, high-fidelity qubit detection and ion-photon
entanglement. The expected size of future many-ion processors require scalable
light collection systems. We report on the development and testing of a
microfabricated surface-electrode ion trap with an integrated high numerical
aperture (NA) micromirror for fluorescence collection. When coupled to a low NA
lens, the optical system is inherently scalable to large arrays of mirrors in a
single device. We demonstrate stable trapping and transport of 40Ca+ ions over
a 0.63 NA micromirror and observe a factor of 1.9 enhancement in photon
collection compared to the planar region of the trap.Comment: 15 pages, 8 figure
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An overview of ISCAT 2000
The Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT) took place over the timer period of 15 November to 31 December in the year 2000. The study location was the Amundsen Scott Station in Antarctica. ISCAT 2000 defines the second phase of a program designed to explore tropospheric chemistry in Antarctica. As in 1998, the 2000 ISCAT study revealed a strong oxidizing environment at South Pole (SP). During the 2000 investigation, however, the suite of measurements was greatly expanded. These new measurements established the recycling of reactive nitrogen as a critical component of this unique environment. This paper first presents the historical background leading up to the ISCAT 2000 observations; then it focuses on providing a summary of the year 2000 results and contrasts these with those recorded during 1998. Important developments made during the 2000 study included the recording of SP data for several species being emitted from the snowpack. These included NO, H 2O2 and CH2O. In this context, eddy-diffusion flux measurements provided the first quantitative estimates of the SP NO and NOx snow-to-atmosphere fluxes. This study also revealed that HNO 3 and HO2NO2 were major sink species for HOx and NOx radicals. And, it identified the critical factors responsible for SP NO levels exceeding those at other polar sites by nearly an order of magnitude. Finally, it reports on the levels of gas phase sulfur species and provides evidence indicating that the absence of DMS at SP is most likely due to its greatly shorten chemical lifetime in the near vicinity of the plateau. It is proposed that this is due to the influence of NO on the distribution of OH in the lower free troposphere over a region that extends well beyond the plateau itself. Details related to each of the above findings plus others can be found in the 11 accompanying Special Issue papers. © 2004 Elsevier Ltd. All rights reserved
Quantum cryptography using balanced homodyne detection
We report an experimental quantum key distribution that utilizes balanced
homodyne detection, instead of photon counting, to detect weak pulses of
coherent light. Although our scheme inherently has a finite error rate, it
allows high-efficiency detection and quantum state measurement of the
transmitted light using only conventional devices at room temperature. When the
average photon number was 0.1, an error rate of 0.08 and "effective" quantum
efficiency of 0.76 were obtained.Comment: Errors in the sentence citing ref.[20] are correcte
Quantum Langevin equations for semiconductor light-emitting devices and the photon statistics at a low-injection level
From the microscopic quantum Langevin equations (QLEs) we derive the
effective semiconductor QLEs and the associated noise correlations which are
valid at a low-injection level and in real devices. Applying the semiconductor
QLEs to semiconductor light-emitting devices (LEDs), we obtain a new formula
for the Fano factor of photons which gives the photon-number statistics as a
function of the pump statistics and several parameters of LEDs. Key ingredients
are non-radiative processes, carrier-number dependence of the radiative and
non-radiative lifetimes, and multimodeness of LEDs. The formula is applicable
to the actual cases where the quantum efficiency differs from the
differential quantum efficiency , whereas previous theories
implicitly assumed . It is also applicable to the cases when
photons in each mode of the cavity are emitted and/or detected inhomogeneously.
When at a running point, in particular, our formula predicts
that even a Poissonian pump can produce sub-Poissonian light. This mechanism
for generation of sub-Poissonian light is completely different from those of
previous theories, which assumed sub-Poissonian statistics for the current
injected into the active layers of LEDs. Our results agree with recent
experiments. We also discuss frequency dependence of the photon statistics.Comment: 10 pages, 8 figure
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