On the optimal feedback control of linear quantum systems in the presence of thermal noise

We study the possibility of taking bosonic systems subject to quadratic Hamiltonians and a noisy thermal environment to non-classical stationary states by feedback loops based on weak measurements and conditioned linear driving. We derive general analytical upper bounds for the single mode squeezing and multimode entanglement at steady state, depending only on the Hamiltonian parameters and on the number of thermal excitations of the bath. Our findings show that, rather surprisingly, larger number of thermal excitations in the bath allow for larger steady-state squeezing and entanglement if the efficiency of the optimal continuous measurements conditioning the feedback loop is high enough. We also consider the performance of feedback strategies based on homodyne detection and show that, at variance with the optimal measurements, it degrades with increasing temperature.Comment: 10 pages, 2 figures. v2: minor changes to the letter; better explanation of the necessary and sufficient conditions to achieve the bounds (in the supplemental material); v3: title changed; comparison between optimal general-dyne strategy and homodyne strategy is discussed; supplemental material included in the manuscript and few references added. v4: published versio

Large-Mass Ultra-Low Noise Germanium Detectors: Performance and Applications in Neutrino and Astroparticle Physics

A new type of radiation detector, a p-type modified electrode germanium diode, is presented. The prototype displays, for the first time, a combination of features (mass, energy threshold and background expectation) required for a measurement of coherent neutrino-nucleus scattering in a nuclear reactor experiment. The device hybridizes the mass and energy resolution of a conventional HPGe coaxial gamma spectrometer with the low electronic noise and threshold of a small x-ray semiconductor detector, also displaying an intrinsic ability to distinguish multiple from single-site particle interactions. The present performance of the prototype and possible further improvements are discussed, as well as other applications for this new type of device in neutrino and astroparticle physics (double-beta decay, neutrino magnetic moment and WIMP searches).Comment: submitted to Phys. Rev.

Postpartum maternal morbidity requiring hospital admission in Lusaka, Zambia – a descriptive study

BACKGROUND: Information on the extent of postpartum maternal morbidity in developing countries is extremely limited. In many settings, data from hospital-based studies is hard to interpret because of the small proportion of women that have access to medical care. However, in those areas with good uptake of health care, the measurement of the type and incidence of complications severe enough to require hospitalisation may provide useful baseline information on the acute and severe morbidity that women experience in the early weeks following childbirth. An analysis of health services data from Lusaka, Zambia, is presented. METHODS: Six-month retrospective review of hospital registers and 4-week cross-sectional study with prospective identification of postpartum admissions. RESULTS: Both parts of the study identified puerperal sepsis and malaria as, respectively, the leading direct and indirect causes of postpartum morbidity requiring hospital admission. Puerperal sepsis accounted for 34.8% of 365 postpartum admissions in the 6-month period. Malaria and pneumonia together accounted for one-fifth of all postpartum admissions (14.5% & 6% respectively). At least 1.7% of the postpartum population in Lusaka will require hospital-level care for a maternal morbidity. CONCLUSIONS: In developing country urban settings with high public health care usage, meticulous review of hospital registers can provide baseline information on the burden of moderate-to-severe postpartum morbidity

Social Transmission and the Spread of Modern Contraception in Rural Ethiopia

Socio-economic development has proven to be insufficient to explain the time and pace of the human demographic transition. Shifts to low fertility norms have thus been thought to result from social diffusion, yet to date, micro-level studies are limited and are often unable to disentangle the effect of social transmission from that of extrinsic factors. We used data which included the first ever use of modern contraception among a population of over 900 women in four villages in rural Ethiopia, where contraceptive prevalence is still low (<20%). We investigated whether the time of adoption of modern contraception is predicted by (i) the proportion of ever-users/non ever-users within both women and their husbands' friendships networks and (ii) the geographic distance to contraceptive ever-users. Using a model comparison approach, we found that individual socio-demographic characteristics (e.g. parity, education) and a religious norm are the most likely explanatory factors of temporal and spatial patterns of contraceptive uptake, while the role of person-to-person contact through either friendship or spatial networks remains marginal. Our study has broad implications for understanding the processes that initiate transitions to low fertility and the uptake of birth control technologies in the developing world

Structure of high-lying levels populated in the Y-96 -> Zr-96 beta decay

The nature of $J^{\pi}=1^-$ levels of $^{96}$Zr below the $\beta$-decay $Q_{\beta}$ value of $^{96}$Y has been investigated in high-resolution $\gamma$-ray spectroscopy following the $\beta$ decay as well as in a campaign of inelastic photon scattering experiments. Branching ratios extracted from $\beta$ decay allow the absolute $E1$ excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of $1^-$ levels below the $Q_{\beta}$ value, which are investigated in the theoretical approach of the Quasiparticle Phonon Model. This study clarifies the nuclear structure properties associated with the enhanced population of high-lying levels in the $^{96}$Y$_{gs}$ $\beta$ decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum

Modeling and forecasting daily electricity load curves: a hybrid approach

We propose a hybrid approach for the modeling and the short-term forecasting of electricity loads. Two building blocks of our approach are (1) modeling the overall trend and seasonality by fitting a generalized additive model to the weekly averages of the load and (2) modeling the dependence structure across consecutive daily loads via curve linear regression. For the latter, a new methodology is proposed for linear regression with both curve response and curve regressors. The key idea behind the proposed methodology is dimension reduction based on a singular value decomposition in a Hilbert space, which reduces the curve regression problem to several ordinary (i.e., scalar) linear regression problems. We illustrate the hybrid method using French electricity loads between 1996 and 2009, on which we also compare our method with other available models including the Électricité de France operational model. Supplementary materials for this article are available online