Atom detection in a two-mode optical cavity with intermediate coupling: Autocorrelation studies

We use an optical cavity in the regime of intermediate coupling between atom and cavity mode to detect single moving atoms. Degenerate polarization modes allow excitation of the atoms in one mode and collection of spontaneous emission in the other, while keeping separate the two sources of light; we obtain a higher confidence and efficiency of detection by adding cavity-enhanced Faraday rotation. Both methods greatly benefit from coincidence detection of photons, attaining fidelities in excess of 99% in less than 1 microsecond. Detailed studies of the second-order intensity autocorrelation function of light from the signal mode reveal evidence of antibunched photon emissions and the dynamics of single-atom transits.Comment: 10 pages, 10 figures, to be published in Phys. Rev.

Comment on "Self-Purification in Semiconductor Nanocrystals"

In a recent Letter [PRL 96, 226802 (2006)], Dalpian and Chelikowsky claimed that formation energies of Mn impurities in CdSe nanocrystals increase as the size of the nanocrystal decreases, and argued that this size dependence leads to "self-purification" of small nanocrystals. They presented density-functional-theory (DFT) calculations showing a strong size dependence for Mn impurity formation energies, and proposed a general explanation. In this Comment we show that several different DFT codes, pseudopotentials, and exchange-correlation functionals give a markedly different result: We find no such size dependence. More generally, we argue that formation energies are not relevant to substitutional doping in most colloidally grown nanocrystals.Comment: 1 page, 1 figur

The life and health challenges of young Malaysian couples: results from a stakeholder consensus and engagement study to support non-communicable disease prevention

BACKGROUND: Malaysia faces burgeoning obesity and diabetes epidemics with a 250% and 88% increase respectively between 1996 and 2006. Identifying the health challenges of young adults in Malaysia, who constitute 27.5 % of the population, is critical for NCD prevention. The aim of the study was two-fold: (1) to achieve consensus amongst stakeholders on the most important challenge impacting the health of young adults, and (2) to engage with stakeholders to formulate a NCD prevention framework.METHODS: The Delphi Technique was utilised to achieve group consensus around the most important life and health challenges that young adults face in Malaysia. Subsequently, the results of the consensus component were shared with the stakeholders in an engagement workshop to obtain input on a NCD prevention framework.RESULTS: We found that life stress was a significant concern. It would seem that the apathy towards pursuing or maintaining a healthy lifestyle among young adults may be significantly influenced by the broader distal determinant of life stress. The high cost of living is suggested to be the main push factor for young working adults towards attaining better financial security to improve their livelihood. In turn, this leads to a more stressful lifestyle with less time to focus on healthier lifestyle choices.CONCLUSIONS: The findings highlight a pivotal barrier to healthier lifestyles. By assisting young adults to cope with daily living coupled with realistic opportunities to make healthier dietary choices, be more active, and less sedentary could assist in the development of NCD health promotion strategies<br/

From quantum feedback to probabilistic error correction: Manipulation of quantum beats in cavity QED

It is shown how to implement quantum feedback and probabilistic error correction in an open quantum system consisting of a single atom, with ground- and excited-state Zeeman structure, in a driven two-mode optical cavity. The ground state superposition is manipulated and controlled through conditional measurements and external fields, which shield the coherence and correct quantum errors. Modeling of an experimentally realistic situation demonstrates the robustness of the proposal for realization in the laboratory

Topographic hub maps of the human structural neocortical network

Hubs within the neocortical structural network determined by graph theoretical analysis play a crucial role in brain function. We mapped neocortical hubs topographically, using a sample population of 63 young adults. Subjects were imaged with high resolution structural and diffusion weighted magnetic resonance imaging techniques. Multiple network configurations were then constructed per subject, using random parcellations to define the nodes and using fibre tractography to determine the connectivity between the nodes. The networks were analysed with graph theoretical measures. Our results give reference maps of hub distribution measured with betweenness centrality and node degree. The loci of the hubs correspond with key areas from known overlapping cognitive networks. Several hubs were asymmetrically organized across hemispheres. Furthermore, females have hubs with higher betweenness centrality and males have hubs with higher node degree. Female networks have higher small-world indices

Radio galaxies and their magnetic fields out to z <= 3

We present polarisation properties at $1.4\,$GHz of two separate extragalactic source populations: passive quiescent galaxies and luminous quasar-like galaxies. We use data from the {\it Wide-Field Infrared Survey Explorer} data to determine the host galaxy population of the polarised extragalactic radio sources. The quiescent galaxies have higher percentage polarisation, smaller radio linear size, and $1.4\,$GHz luminosity of $6\times10^{21}<L_{\rm 1.4}<7\times10^{25}\,$W Hz$^{-1}$, while the quasar-like galaxies have smaller percentage polarisation, larger radio linear size at radio wavelengths, and a $1.4\,$GHz luminosity of $9\times10^{23}<L_{\rm 1.4}<7\times10^{28}\,$W Hz$^{-1}$, suggesting that the environment of the quasar-like galaxies is responsible for the lower percentage polarisation. Our results confirm previous studies that found an inverse correlation between percentage polarisation and total flux density at $1.4\,$GHz. We suggest that the population change between the polarised extragalactic radio sources is the origin of this inverse correlation and suggest a cosmic evolution of the space density of quiescent galaxies. Finally, we find that the extragalactic contributions to the rotation measures (RMs) of the nearby passive galaxies and the distant quasar-like galaxies are different. After accounting for the RM contributions by cosmological large-scale structure and intervening Mg\,{II} absorbers we show that the distribution of intrinsic RMs of the distant quasar-like sources is at most four times as wide as the RM distribution of the nearby quiescent galaxies, if the distribution of intrinsic RMs of the WISE-Star sources itself is at least several rad m$^{-2}$ wide.Comment: 12 pages, 8 figures, accepted for publication into MNRA

Observation of ground-state quantum beats in atomic spontaneous emission

We report ground-state quantum beats in spontaneous emission from a continuously driven atomic ensemble. Beats are visible only in an intensity autocorrelation and evidence spontaneously generated coherence in radiative decay. Our measurement realizes a quantum eraser where a first photon detection prepares a superposition and a second erases the "which-path" information in the intermediate state.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Letter