Optimizing single-photon-source heralding efficiency at 1550 nm using periodically poled lithium niobate

We explore the feasibility of using high conversion-efficiency periodically-poled crystals to produce photon pairs for photon-counting detector calibrations at 1550 nm. The goal is the development of an appropriate parametric down-conversion (PDC) source at telecom wavelengths meeting the requirements of high-efficiency pair production and collection in single spectral and spatial modes (single-mode fibers). We propose a protocol to optimize the photon collection, noise levels and the uncertainty evaluation. This study ties together the results of our efforts to model the single-mode heralding efficiency of a two-photon PDC source and to estimate the heralding uncertainty of such a source.Comment: 14 pages, 2 tables and 3 figures, final version accepted by Metrologi

Seroprevalence of ehrlichia spp., anaplasma spp., borrelia burgdorferi sensu lato, and dirofilaria immitis in stray dogs, from 2016 to 2019, in southern Italy

Canine vector-borne diseases (CVBD) are an important and emerging health concern for humans and animals worldwide. The purpose of the presented study was to assess, from 2016 to 2019, the seroprevalence of CVBD agents and clarify the epidemiology of tick-borne disease in stray dogs living in the Campania Region, Southern Italy. For this purpose, blood samples were collected from January 2016 to December 2019 from 1023 dogs in authorized kennels located in the five municipalities of the Campania Region. SNAP® 4DX® from IDEXX® Laboratories was used for detection of Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi sensu lato (s.l.), and Dirofilaria immitis antibodies. The overall seroprevalence of CVBD in stray dogs was 19.6% (95% Confidence Intervals (CI): 17.2–22.8%; 201/1023). The most common pathogen was Ehrlichia spp., with a percentage of positivity of 16.03%, followed by Anaplasma spp. with 7.8%. B. burgdorferi s.l. and D. immitis were detected in only 0.2% of dogs; co-infection was detected in 4.5% of stray dogs tested. No link was detected between the gender, age, location, and CVBD seropositivity, except for Ehrlichia spp. for which location (Avellino Province; p = 0.007) and gender (male, p = 0.002) were risk factors for seropositivity. Our results demonstrated that animals are exposed to at least one of the four etiological agents (Ehrlichia spp., Anaplasma spp. Borrelia burgdorferi s.l., and Dirofilaria immitis) transmitted by vectors. Finally, this study highlighted the utility of serological monitoring in stray dogs, housed in kennels, given the threat posed by CVBD to animals and the zoonotic implications of these etiological agents and their vectors on human health

Reduced Deadtime and Higher Rate Photon-Counting Detection using a Multiplexed Detector Array

We present a scheme for a photon-counting detection system that can be operated at incident photon rates higher than otherwise possible by suppressing the effects of detector deadtime. The method uses an array of N detectors and a 1-by-N optical switch with a control circuit to direct input light to live detectors. Our calculations and models highlight the advantages of the technique. In particular, using this scheme, a group of N detectors provides an improvement in operation rate that can exceed the improvement that would be obtained by a single detector with deadtime reduced by 1/N, even if it were feasible to produce a single detector with such a large improvement in deadtime. We model the system for continuous and pulsed light sources, both of which are important for quantum metrology and quantum key distribution applications.Comment: 6 figure

Avalanche Photo-Detection for High Data Rate Applications

Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers due to multiphoton events. Assuming Poissonian input light statistics we ascertain the effective mean photon-number of the incident light with high accuracy. Time multiplexed detectors (TMD) allow to accomplish photon- number resolution by photon chopping. This detection setup extends the linear response function to higher photon-numbers and statistical methods may be used to compensate for non-linearity. We investigated this effect, compare it to the single APD case and show the validity of the convolution treatment in the TMD data analysis.Comment: 16 pages, 5 figure

Has VZV epidemiology changed in Italy? Results of a seroprevalence study

The aim of the study was to evaluate if and how varicella prevalence has changed in Italy. In particular a seroprevalence study was performed, comparing it to similar surveys conducted in pre-immunization era. During 2013–2014, sera obtained from blood samples taken for diagnostic purposes or routine investigations were collected in collaboration with at least one laboratory/center for each region, following the approval of the Ethics Committee. Data were stratified by sex and age. All samples were processed in a national reference laboratory by an immunoassay with high sensitivity and specificity. Statutory notifications, national hospital discharge database and mortality data related to VZV infection were analyzed as well. A total of 3707 sera were collected and tested. In the studied period both incidence and hospitalization rates decreased and about 5 deaths per year have been registered. The seroprevalence decreased in the first year of life in subjects passively protected by their mother, followed by an increase in the following age classes. The overall antibody prevalence was 84%. The comparison with surveys conducted with the same methodology in 1996–1997 and 2003–2004 showed significant differences in age groups 1–19 y. The study confirms that in Italy VZV infection typically occurs in children. The impact of varicella on Italian population is changing. The comparison between studies performed in different periods shows a significant increase of seropositivity in age class 1–4 years, expression of vaccine interventions already adopted in some regions

Modelling the Dynamics of an Aedes albopictus Population

We present a methodology for modelling population dynamics with formal means of computer science. This allows unambiguous description of systems and application of analysis tools such as simulators and model checkers. In particular, the dynamics of a population of Aedes albopictus (a species of mosquito) and its modelling with the Stochastic Calculus of Looping Sequences (Stochastic CLS) are considered. The use of Stochastic CLS to model population dynamics requires an extension which allows environmental events (such as changes in the temperature and rainfalls) to be taken into account. A simulator for the constructed model is developed via translation into the specification language Maude, and used to compare the dynamics obtained from the model with real data.Comment: In Proceedings AMCA-POP 2010, arXiv:1008.314