Stable quantum memories with limited measurement

We demonstrate the existence of a finite temperature threshold for a 1D stabilizer code under an error correcting protocol that requires only a fraction of the syndrome measurements. Below the threshold temperature, encoded states have exponentially long lifetimes, as demonstrated by numerical and analytical arguments. We sketch how this algorithm generalizes to higher dimensional stabilizer codes with string-like excitations, like the toric code.Comment: 11 Pages, 7 Figure

Stroboscopic Generation of Topological Protection

Trapped neutral atoms offer a powerful route to robust simulation of complex quantum systems. We present here a stroboscopic scheme for realization of a Hamiltonian with $n$-body interactions on a set of neutral atoms trapped in an addressable optical lattice, using only 1- and 2-body physical operations together with a dissipative mechanism that allows thermalization to finite temperature or cooling to the ground state. We demonstrate this scheme with application to the toric code Hamiltonian, ground states of which can be used to robustly store quantum information when coupled to a low temperature reservoir.Comment: 5 pages, 2 figures. Published versio

Exploration of the Genetic Epidemiology of Asthma: A Review, With a Focus on Prevalence in Children and Adolescents in the Caribbean

Asthma is a chronic disease caused by the inflammation of the main air passages of the lungs. This paper outlines a review of the published literature on asthma. While a few studies show a trend of rising asthma cases in the Caribbean region, even fewer have explored the genetic epidemiological factors of asthma. This is a literature review that seeks to sum the body of knowledge on the epidemiology of asthma. Specifically, the major objective of the literature review is to provide a unified information base on the current state of factors involved in the genetic epidemiology of asthma. The review is a simple, yet detailed summary of the literature sources and their methodology and findings on the genetic epidemiology of asthma. Further, it seeks to direct this effort to the Caribbean region. The paper then reviews a summarized and synthesized collection of the body of previous research. Of specific interest are peer-reviewed sources that have been published in recent times. The paper provides more recent insight and recapitulates on the previous research, while tracing the intellectual progress on the debate. Where possible, reviewing and discussing the results of the previous literature, this review singles out the gaps and potential future research directions for studying the genetic epidemiology of asthma. Overall, we hope to contribute to a more synthesized knowledge and improved understanding of the previous literature and future potential direction of genetic and epidemiological asthma research

GRB000301C with peculiar afterglow emission

The CCD magnitudes in Johnson V and Cousins R and I photometric passbands are determined for GRB 000301C afterglow starting ~ 1.5 day after the gamma-ray burst. In fact we provide the earliest optical observations for this burst. Light curves of the afterglow emissions in U, B, V, R, I, J and K' passbands are obtained by combining the present measurements with the published data. Flux decay shows a very uncommon variation relative to other well observed GRBs. Overall, there is a steepening of the optical and near-infrared flux decay caused by a geometric and sideways expanding jet. This is superimposed by a short term variability especially during early time (Delta t < 8 days). The cause of variability is not well understood, though it has occurred simultaneously with similar amplitude in all the filters. We derive the early and late time flux decay constants using jet model. The late time flux decay is the steepest amongst the GRB OTs observed so far with alpha ~ 3. Steepening in the flux decay seems to have started simultaneously around Delta t ~ 7.6 day in all passbands. The value of spectral index in the optical-near IR region is ~ -1.0. Redshift determination with z=2.0335 indicates cosmological origin of the GRB having a luminosity distance of 16.6 Gpc. Thus it becomes the second farthest amongst the GRBs with known distances. An indirect estimate of the fluence > 20 keV indicates, if isotropic,> =10^53 ergs of release of energy. The enormous amount of released energy will be reduced, if the radiation is beamed which is the case for this event. Using a jet break time of 7.6 days, we infer a jet opening angle of ~ 0.15 radian. This means the energy released is reduced by a factor of ~ 90 relative to the isotropic value.Comment: LaTeX file, 11 pages including 4 figures, uses psfig.sty, Bull. Astron. Society of India(accepted, Sept, 2000 issue

Quantum non-demolition measurements of single donor spins in semiconductors

We propose a technique for measuring the state of a single donor electron spin using a field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is facilitated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outline experimental requirements. Our measurement provides a single-shot, projective, and quantum non-demolition measurement of an electron-encoded qubit state.Comment: 8+ pages. 4 figures. Published versio

Optical observations of the bright long duration peculiar GRB 021004 afterglow

The CCD magnitudes in Johnson $B,V$ and Cousins $R$ and $I$ photometric passbands are determined for the bright long duration GRB 021004 afterglow from 2002 October 4 to 16 starting $\sim$ 3 hours after the $\gamma-$ray burst. Light curves of the afterglow emission in $B$,$V$,$R$ and $I$ passbands are obtained by combining these measurements with other published data. The earliest optical emission appears to originate in a revese shock. Flux decay of the afterglow shows a very uncommon variation relative to other well-observed GRBs. Rapid light variations, especially during early times ($\Delta t < 2$ days) is superposed on an underlying broken power law decay typical of a jetted afterglow. The flux decay constants at early and late times derived from least square fits to the light curve are $0.99\pm0.05$ and $2.0\pm0.2$ respectively, with a jet break at around 7 day. Comparison with a standard fireball model indicates a total extinction of $E(B-V)=0.20$ mag in the direction of the burst. Our low-resolution spectra corrected for this extinction provide a spectral slope $\beta = 0.6\pm0.02$. This value and the flux decay constants agree well with the electron energy index $p\sim 2.27$ used in the model. The derived jet opening angle of about $7^{\circ}$ implies a total emitted gamma-ray energy $E_{\gamma} = 3.5\times10^{50}$ erg at a cosmological distance of about 20 Gpc. Multiwavelength observations indicate association of this GRB with a star forming region, supporting the case for collapsar origin of long duration GRBs.Comment: 19 pages, 3 figures, BASI, 31, 1

The role of infectious disease impact in informing decision-making for animal health management in aquaculture systems in Bangladesh

The aquaculture sector in Bangladesh is an important employer and a significant source of foreign exchange. In addition, it contributes significantly to food security due to the role of fish in peoples’ diets, the most important source of protein and micronutrients. However, infectious diseases represent an important barrier to sector development due to economic losses and vulnerability of smallholders. The aim of this study was to gain an overview of the impact of infectious diseases in the aquaculture sector, and to assess the usefulness and use of impact studies in decision making for animal health management and biosecurity governance in Bangladesh. A review of scientific and grey literature on infectious disease impact in different aquaculture systems was conducted and their methodologies and findings summarised. Subsequently, interviews with 28 stakeholders from the private and public sector were conducted to enquire about decision-making structures in animal health management. The data were analysed using the framework method to allow the development of themes, by using the information, experiences and opinions inductively obtained from interviewees, deductively through the reviewed literature. Results showed a substantial socio-economic impact of infectious diseases. The numerous stakeholders involved in the decision-making process explained that key barriers to effective aquaculture health management were insufficient resources to investigate and tackle infectious aquatic animal diseases, a dearth of legislation and capacity for disease surveillance, a reliance on reactive response, and a lack of impact and evidence-based approaches for prioritising problem-solving, commonly based on anecdotal evidence. Furthermore, communication among the multiple stakeholders involved was reported to be weak. This complex situation requires a multi-level response, which should span from strengthening the knowledge of farmers and professionals in the field to the improvement of surveillance and diagnostic systems. Improved systems along with evidence on disease impact could inform the prioritisation of diseases and resource allocation for disease control in Bangladesh. Further, this evidence needs to be used to advise decisions to have a true value, for which establishing and strengthening communication pathways and processes is critical to make systematic use of the information and improve animal health management. In the light of future threats to Bangladesh such as climate change, increasing population density and demand for animal source foods, it is crucial to strengthen animal health management systems to reduce livelihoods vulnerability, food insecurity and the likelihood of disease emergence