4,535 research outputs found
Coherent spectroscopy of rare-earth-ion doped whispering-gallery mode resonators
We perform an investigation into the properties of Pr3+:Y2SiO5 whispering
gallery mode resonators as a first step towards achieving the strong coupling
regime of cavity QED with rare-earth-ion doped crystals. Direct measurement of
cavity QED parameters are made using photon echoes, giving good agreement with
theoretical predictions. By comparing the ions at the surface of the resonator
to those in the center it is determined that the physical process of making the
resonator does not negatively affect the properties of the ions. Coupling
between the ions and resonator is analyzed through the observation of optical
bistability and normal-mode splitting.Comment: 8 pages, 9 figure
Non-classical Photon Statistics For Two-mode Optical Fields
The non-classical property of subpoissonian photon statistics is extended
from one to two-mode electromagnetic fields, incorporating the physically
motivated property of invariance under passive unitary transformations.
Applications to squeezed coherent states, squeezed thermal states, and
superposition of coherent states are given. Dependences of extent of
non-classical behaviour on the independent squeezing parameters are graphically
displayed.Comment: 15 pages, RevTex, 5 figures, available by sending email to
[email protected]
Giant optical Faraday rotation induced by a single electron spin in a quantum dot: Applications to entangling remote spins via a single photon
We propose a quantum non-demolition method - giant Faraday rotation - to
detect a single electron spin in a quantum dot inside a microcavity where
negatively-charged exciton strongly couples to the cavity mode. Left- and
right-circularly polarized light reflected from the cavity feels different
phase shifts due to cavity quantum electrodynamics and the optical spin
selection rule. This yields giant and tunable Faraday rotation which can be
easily detected experimentally. Based on this spin-detection technique, a
scalable scheme to create an arbitrary amount of entanglement between two or
more remote spins via a single photon is proposed.Comment: 5 pages, 3 figure
Efficient engineering of multi-atom entanglement through single-photon detections
We propose an efficient scheme to engineer multi-atom entanglement by
detecting cavity decay through single-photon detectors. In the special case of
two atoms, this scheme is much more efficient than previous probabilistic
schemes, and insensitive to randomness in the atom's position. More generally,
the scheme can be used to prepare arbitrary superpositions of multi-atom Dicke
states without the requirements of high-efficiency detection and separate
addressing of different atoms.Comment: 5 pages, 2 figure
Age at quitting smoking as a predictor of risk of cardiovascular disease incidence independent of smoking status, time since quitting and pack-years
BACKGROUND Risk prediction for CVD events has been shown to vary according to current smoking status, pack-years smoked over a lifetime, time since quitting and age at quitting. The latter two are closely and inversely related. It is not known whether the age at which one quits smoking is an additional important predictor of CVD events. The aim of this study was to determine whether the risk of CVD events varied according to age at quitting after taking into account current smoking status, lifetime pack-years smoked and time since quitting. FINDINGS We used the Cox proportional hazards model to evaluate the risk of developing a first CVD event for a cohort of participants in the Framingham Offspring Heart Study who attended the fourth examination between ages 30 and 74 years and were free of CVD. Those who quit before the median age of 37 years had a risk of CVD incidence similar to those who were never smokers. The incorporation of age at quitting in the smoking variable resulted in better prediction than the model which had a simple current smoker/non-smoker measure and the one that incorporated both time since quitting and pack-years. These models demonstrated good discrimination, calibration and global fit. The risk among those quitting more than 5 years prior to the baseline exam and those whose age at quitting was prior to 44 years was similar to the risk among never smokers. However, the risk among those quitting less than 5 years prior to the baseline exam and those who continued to smoke until 44 years of age (or beyond) was two and a half times higher than that of never smokers. CONCLUSIONS Age at quitting improves the prediction of risk of CVD incidence even after other smoking measures are taken into account. The clinical benefit of adding age at quitting to the model with other smoking measures may be greater than the associated costs. Thus, age at quitting should be considered in addition to smoking status, time since quitting and pack-years when counselling individuals about their cardiovascular risk.This research was supported by an NHMRC health services
research grant (no. 465130), an NHMRC/NHF PhD scholarship and a
Vichealth Fellowship
A field-based analysis of the accuracy of niche models applied to the fossil record
The use of ecological niche modeling (ENM) to estimate the geographic ranges of species is widely employed with modern fauna and is becoming more widespread in paleontology. Herein, field validation is utilized to assess the predictive accuracy of ENM methods for Paleozoic brachiopod species. This study represents the first field validation analysis of ENM methods in the fossil record. Previously published species distributions models for 8 Late Ordovician brachiopod species from the Cincinnati, Ohio region (United States) developed using GARP (Genetic Algorithm using Rule-set Prediction) were assessed for accuracy by comparing species occurrence data from a newly available set of 18 localities with the original species distribution models. Based on this data, the statistical significance of the original model set was assessed; 18 of the 22 original models were demonstrated to be statistically significant, based on field validation. Of the 140 individual species occurrences assessed, 60.8% were accurately predicted, 9.2% exhibited over prediction, and 30% exhibited under prediction. Accurate results were more common for species modeled from the greatest number of species occurrence points. The least accurate species models developed were for eurytopic species or those for which taxonomic affinities are unclear. Results indicate that with ample outcrop, well-defined stratigraphy, and sufficient fossil occurrence data, ENM methods could be successfully applied to many intervals in Earth history
Confinement effects on the stimulated dissociation of molecular BECs
We show that a molecular BEC in a trap is stabilized against stimulated
dissociation if the trap size is smaller than the resonance healing length
. The condensate shape determines the critical
atom-molecule coupling frequency. We discuss an experiment for triggering
dissociation by a sudden change of coupling or trap parameters. This effect
demonstrates one of the unique collective features of 'superchemistry' in that
the yield of a chemical reaction depends critically on the size and shape of
the reaction vessel.Comment: 4 pages, 4 figure
Intensity fluctuations in steady state superradiance
Alkaline-earth like atoms with ultra-narrow optical transitions enable
superradiance in steady state. The emitted light promises to have an
unprecedented stability with a linewidth as narrow as a few millihertz. In
order to evaluate the potential usefulness of this light source as an
ultrastable oscillator in clock and precision metrology applications it is
crucial to understand the noise properties of this device. In this paper we
present a detailed analysis of the intensity fluctuations by means of
Monte-Carlo simulations and semi-classical approximations. We find that the
light exhibits bunching below threshold, is to a good approximation coherent in
the superradiant regime, and is chaotic above the second threshold.Comment: 8 pages, 5 figure
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