6,250 research outputs found
Real-Time Cavity QED with Single Atoms
The combination of cold atoms and large coherent coupling enables investigations in a new regime in cavity QED with single-atom trajectories monitored in real time with high signal-to-noise ratio. The underlying âvacuum-Rabiâ splitting is clearly reflected in the frequency dependence of atomic transit signals recorded atom by atom, with evidence for mechanical light forces for intracavity photon number <1. The nonlinear optical response of one atom in a cavity is observed to be in accord with the one-atom quantum theory but at variance with semiclassical predictions
Gotcha! Coronavirus, crises and the politics of blame games
Politicians are primarily motivated by avoiding blame for failure. But what happens in a major crisis, when some level of failure is inevitable? Matthew Flinders examines the politics of blame during the COVID-19 pandemic
Discriminating cool-water from warm-water carbonates and their diagenetic environments using element geochemistry: the Oligocene Tikorangi Formation (Taranaki Basin) and the dolomite effect
Fields portrayed within bivariate element plots have been used to distinguish between carbonates formed in warm- (tropical) water and cool- (temperate) water depositional settings. Here, element concentrations (Ca, Mg, Sr, Na, Fe, and Mn) have been determined for the carbonate fraction of bulk samples from the late Oligocene Tikorangi Formation, a subsurface, mixed dolomite-calcite, cool-water limestone sequence in Taranaki Basin, New Zealand. While the occurrence of dolomite is rare in New Zealand Cenozoic carbonates, and in cool-water carbonates more generally, the dolomite in the Tikorangi carbonates is shown to have a dramatic effect on the "traditional" positioning of cool-water limestone fields within bivariate element plots. Rare undolomitised, wholly calcitic carbonate samples in the Tikorangi Formation have the following average composition: Mg 2800 ppm; Ca 319 100 ppm; Na 800 ppm; Fe 6300 ppm; Sr 2400 ppm; and Mn 300 ppm. Tikorangi Formation dolomite-rich samples (>15% dolomite) have average values of: Mg 53 400 ppm; Ca 290 400 ppm; Na 4700 ppm; Fe 28 100 ppm; Sr 5400 ppm; and Mn 500 ppm. Element-element plots for dolomite-bearing samples show elevated Mg, Na, and Sr values compared with most other low-Mg calcite New Zealand Cenozoic limestones. The increased trace element contents are directly attributable to the trace element-enriched nature of the burial-derived dolomites, termed here the "dolomite effect". Fe levels in the Tikorangi Formation carbonates far exceed both modern and ancient cool-water and warm-water analogues, while Sr values are also higher than those in modern Tasmanian cool-water carbonates, and approach modern Bahaman warm-water carbonate values. Trace element data used in conjunction with more traditional petrographic data have aided in the diagenetic interpretation of the carbonate-dominated Tikorangi sequence. The geochemical results have been particularly useful for providing more definitive evidence for deep burial dolomitisation of the deposits under the influence of marine-modified pore fluids
Large-Scale Assessment of Polygon-Edge Boulder Clustering in the Martian Northern Lowlands
Two features evident in many images of the martian northern low-lands are polygonal fractures (especially northwards of 60N) and meter-scale surface boulders. Since their first observation, several attempts have been made to classify and study these polygons as well as how the forces that form these polygons may modify the surface. Surface boulders have been used as a potential indicator of such modification, though current studies find evidence both for and against their association with the underlying polygons. Both these investigations are limited by the same fundamental challenge: map-ping the location of surface boulders manually is not practical at large scales. Here, we use the Martian Boulder Automatic Recognition System (MBARS) to provide image-wide assessments of boulder location and size, enabling large-scale assessment of boulder populations. To compare these boulder locations with the underlying polygons, we modified the 2-D Fourier analysis described by Orloff in 2013 to analyze boulder locations. When compared with Orloffs observations of polygon scales, this provides an avenue for large-scale comparison of boulder-cluster scale and polygon scale
Real-time cavity QED with single atoms
We report the first measurement of the real-time evolution of the complex field amplitude brought on by single atom transits. We show the variation in time of both quadrature amplitudes (simultaneously recorded) of the light transmitted through the cavity, as well the resultant optical phase for a single atom transit event. In this particular measurement, the cavity and laser were both detuned by 10 MHz from the Cs resonance
Institutional isomorphism, negativity bias and performance information use by politicians : a survey experiment
A
On the Optimum Sampling Time for the Measurement of Pollutants in Ambient Air
No measurement
result of any kind is complete without an associated statement of
uncertainty. In general, the aim is to minimise this measurement
uncertainty to the extent that the measurement made is fit for
purpose, or the uncertainty meets an acceptable level such as a
âdata quality objectiveâ. This paper
demonstrates how the sampling time used to measure a pollutant in
ambient air over a given time period, particularly with automatic
instruments, can affect the uncertainty of the measurement result.
It is shown that the uncertainty of the overall result depends
critically on how the precision characteristics of the measuring
instrumentation vary with analyte abundance. An example of the
determination of these characteristics for mercury vapour
measurement and the conclusions that may be drawn about optimum
sampling times to minimise uncertainty are presented. For
situations where uncertainty is minimised by the use of long
sampling periods, the implications of this strategy on the
âinformation richnessâ of the data
and on the detection of short-term episodes, as well as peak
concentrations, are discussed
Superradiance for atoms trapped along a photonic crystal waveguide
We report observations of superradiance for atoms trapped in the near field
of a photonic crystal waveguide (PCW). By fabricating the PCW with a band edge
near the D transition of atomic cesium, strong interaction is achieved
between trapped atoms and guided-mode photons. Following short-pulse
excitation, we record the decay of guided-mode emission and find a superradiant
emission rate scaling as for average atom number atoms, where
is the peak single-atom radiative decay
rate into the PCW guided mode and is the Einstein- coefficient
for free space. These advances provide new tools for investigations of
photon-mediated atom-atom interactions in the many-body regime.Comment: 11 pages, 10 figure
Surface spin-flop phases and bulk discommensurations in antiferromagnets
Phase diagrams as a function of anisotropy D and magnetic field H are
obtained for discommensurations and surface states for a model antiferromagnet
in which is parallel to the easy axis. The surface spin-flop phase exists
for all . We show that there is a region where the penetration length of the
surface spin-flop phase diverges. Introducing a discommensuration of even
length then becomes preferable to reconstructing the surface. The results are
used to clarify and correct previous studies in which discommensurations have
been confused with genuine surface spin-flop states.Comment: 4 pages, RevTeX, 2 Postscript figure
Coherent generation of EPR-entangled light pulses mediated by a single trapped atom
We show that a single, trapped, laser-driven atom in a high-finesse optical
cavity allows for the quantum-coherent generation of entangled light pulses on
demand. Schemes for generating simultaneous and temporally separated pulse
pairs are proposed. The mechanical effect of the laser excitation on the
quantum motion of the cold trapped atom mediates the entangling interaction
between two cavity modes and between the two subsequent pulses, respectively.
The entanglement is of EPR-type, and its degree can be controlled through
external parameters. At the end of the generation process the atom is
decorrelated from the light field. Possible experimental implementations of the
proposals are discussed.Comment: 11 pages, 4 figure
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