Entanglement verification for quantum key distribution systems with an underlying bipartite qubit-mode structure

We consider entanglement detection for quantum key distribution systems that use two signal states and continuous variable measurements. This problem can be formulated as a separability problem in a qubit-mode system. To verify entanglement, we introduce an object that combines the covariance matrix of the mode with the density matrix of the qubit. We derive necessary separability criteria for this scenario. These criteria can be readily evaluated using semidefinite programming and we apply them to the specific quantum key distribution protocol.Comment: 6 pages, 2 figures, v2: final versio

Improvement of continuous-variable quantum key distribution systems by using optical preamplifiers

Continuous-variable quantum key distribution protocols, based on Gaussian modulation of the quadratures of coherent states, have been implemented in recent experiments. A present limitation of such systems is the finite efficiency of the detectors, which can in principle be compensated for by the use of classical optical preamplifiers. Here we study this possibility in detail, by deriving the modified secret key generation rates when an optical parametric amplifier is placed at the output of the quantum channel. After presenting a general set of security proofs, we show that the use of preamplifiers does compensate for all the imperfections of the detectors when the amplifier is optimal in terms of gain and noise. Imperfect amplifiers can also enhance the system performance, under conditions which are generally satisfied in practice.Comment: 11 pages, 7 figures, submitted to J. Phys. B (special issue on Few Atoms Optics

Lung Cancer in a U.S. Population with Low to Moderate Arsenic Exposure

BackgroundLittle is known about the carcinogenic potential of arsenic in areas with low to moderate concentrations of arsenic (< 100 microg/L) in drinking water.ObjectivesWe examined associations between arsenic and lung cancer.MethodsA population-based case-control study of primary incident lung cancer was conducted in 10 counties in two U.S. states, New Hampshire and Vermont. The study included 223 lung cancer cases and 238 controls, each of whom provided toenail clippings for arsenic exposure measurement by inductively coupled-plasma mass spectrometry. We estimated odds ratios (ORs) of the association between arsenic exposure and lung cancer using unconditional logistic regression with adjustment for potential confounders (age, sex, race/ethnicity, smoking pack-years, education, body mass index, fish servings per week, and toenail selenium level).ResultsArsenic exposure was associated with small-cell and squamous-cell carcinoma of the lung [OR = 2.75; 95% confidence interval (CI), 1.00-7.57] for toenail arsenic concentration > or = 0.114 microg/g, versus < 0.05 microg/g. A history of lung disease (bronchitis, chronic obstructive pulmonary disease, or fibrosis) was positively associated with lung cancer (OR = 2.86; 95% CI, 1.39-5.91). We also observed an elevated risk of lung cancer among participants with a history of lung disease and toenail arsenic > or = 0.05 microg/g (OR = 4.78; 95% CI, 1.87-12.2) than among individuals with low toenail arsenic and no history of lung disease.ConclusionAlthough this study supports the possibility of an increased risk of specific lung cancer histologic types at lower levels of arsenic exposure, we recommend large-scale population-based studies

SODAR DATA FROM OYSTER BAY AT WINYAH BAY NATIONAL ESTUARINE RESEARCH RESERVE

The SecondWind Triton® is a SODAR (SOnic Detection And Ranging) sonic wind profiler (Triton® sodar) system capable of profiling the wind characteristics up to 200m above the instrument. SODAR systems transmit acoustic chirps into the atmosphere and measure the backscattered signal returned to the device. The primary source of acoustic scattering is variations in air temperature, which cause changes in the refractive index of sound. By measuring the Doppler‐shifted frequency of these returned signals, the Triton® can calculate the wind’s speed and direction for the volume of air above the instrument, measured at ten fixed heights, known as station heights. The Triton® is specifically designed for the purpose of wind energy resource assessment as it can remotely capture wind data at heights above ground where wind turbine rotors operate. The measurements made include horizontal wind speed and direction, vertical wind speed, and turbulence. Other integrated sensors provide time and location via GPS, barometric pressure, humidity, and the tilt of the instrument. The study area is located east of Georgetown, South Carolina in North Inlet ‐ Winyah Bay National Estuarine Research Reserve. The monitoring period for data in this report begins 5/14/2009 9:30:00 AM EST and ends 8/2/2010 11:40:00 AM EST

Wigner function for twisted photons

A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented, with special emphasis in the implications of rotational periodicity and angular-momentum discreteness.Comment: 6 pages, 4 figure

Deep Eyedentification: Biometric Identification using Micro-Movements of the Eye

We study involuntary micro-movements of the eye for biometric identification. While prior studies extract lower-frequency macro-movements from the output of video-based eye-tracking systems and engineer explicit features of these macro-movements, we develop a deep convolutional architecture that processes the raw eye-tracking signal. Compared to prior work, the network attains a lower error rate by one order of magnitude and is faster by two orders of magnitude: it identifies users accurately within seconds

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

Gaps to bridge: Misalignment between perception, reality and actions in obesity

Aims Despite increased recognition as a chronic disease, obesity remains greatly underdiagnosed and undertreated. We aimed to identify international perceptions, attitudes, behaviours and barriers to effective obesity care in people with obesity (PwO) and healthcare professionals (HCPs). Materials and methods An online survey was conducted in 11 countries. Participants were adults with obesity and HCPs who were primarily concerned with direct patient care. Results A total of 14 502 PwO and 2785 HCPs completed the survey. Most PwO (68%) and HCPs (88%) agreed that obesity is a disease. However, 81% of PwO assumed complete responsibility for their own weight loss and only 44% of HCPs agreed that genetics were a barrier. There was a median of three (mean, six) years between the time PwO began struggling with excess weight or obesity and when they first discussed their weight with an HCP. Many PwO were concerned about the impact of excess weight on health (46%) and were motivated to lose weight (48%). Most PwO (68%) would like their HCP to initiate a conversation about weight and only 3% were offended by such a conversation. Among HCPs, belief that patients have little interest in or motivation for weight management may constitute a barrier for weight management conversations. When discussed, HCPs typically recommended lifestyle changes; however, more referrals and follow‐up appointments are required. Conclusions Our international dataset reveals a need to increase understanding of obesity and improve education concerning its physiological basis and clinical management. Realization that PwO are motivated to lose weight offers an opportunity for HCPs to initiate earlier weight management conversations

A dose-finding and safety study of novel erythropoiesis stimulating protein (NESP) for the treatment of anaemia in patients receiving multicycle chemotherapy

Darbepoetin alfa is a novel erythropoiesis stimulating protein (NESP), which stimulates erythropoiesis by the same mechanism as recombinant human erythropoietin (rHuEPO). NESP has been shown to be safe and efficacious in patients with chronic renal failure. NESP is biochemically distinct from rHuEPO, due to its increased sialic acid content. NESP has an approximately 3-fold greater half-life. rHuEPO has been shown to be safe and effective for the treatment of chemotherapy-induced anaemia. This study assessed the safety and efficacy of NESP administered once per week, under the supervision of a physician, to patients with solid tumours who were receiving multicycle chemotherapy for up to 12 weeks. Three dose cohorts are presented in this sequential, unblinded and dose-escalating study. Thirteen to 59 patients received NESP (0.5, 1.5 or 2.25 mcg kg−1wk−1) in each cohort. Patients were monitored for adverse events, including antibody formation to NESP and for effects on haemoglobin. NESP appeared to be well tolerated. Adverse events were similar across all cohorts and were consistent with the population being studied. No antibody formation was detected over the 16-week study period and follow-up. A dose–response relationship was evident for NESP and multiple measures of efficacy, including proportion of patients responding to NESP and the mean change in haemoglobin by week 4 and end of treatment for NESP 0.5, 1.5 and 2.25 mcg kg−1wk−1cohorts (mean change in haemoglobin at end of treatment was 1.24, 1.73 and 2.15 g dl−1respectively). Controlled studies of this agent at higher doses and less frequent schedules of administration are ongoing. © 2001 Cance Cancer Research Campaig