Selective readout and back-action reduction for wideband acoustic gravitational wave detectors

We present the concept of selective readout for broadband resonant mass gravitational wave detectors. This detection scheme is capable of specifically selecting the signal from the contributions of the vibrational modes sensitive to the gravitational waves, and efficiently rejecting the contribution from non gravitationally sensitive modes. Moreover this readout, applied to a dual detector, is capable to give an effective reduction of the back-action noise within the frequency band of interest. The overall effect is a significant enhancement in the predicted sensitivity, evaluated at the standard quantum limit for a dual torus detector. A molybdenum detector, 1 m in diameter and equipped with a wide area selective readout, would reach spectral strain sensitivities 2x10^{-23}/sqrt{Hz} between 2-6 kHz.Comment: 9 pages, 4 figure

High-sensitivity optical monitoring of a micro-mechanical resonator with a quantum-limited optomechanical sensor

We experimentally demonstrate the high-sensitivity optical monitoring of a micro-mechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10^-19 m/rootHz level, and cooled the resonator down to 5K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator.Comment: 4 pages, 5 figure

Stationary entanglement between two movable mirrors in a classically driven Fabry-Perot cavity

We consider a Fabry-Perot cavity made by two moving mirrors and driven by an intense classical laser field. We show that stationary entanglement between two vibrational modes of the mirrors, with effective mass of the order of micrograms, can be generated by means of radiation pressure. The resulting entanglement is however quite fragile with respect to temperature.Comment: 15 pages, 3 figure

Optomechanical characterization of acoustic modes in a mirror

We present an experimental study of the internal mechanical vibration modes of a mirror. We determine the frequency repartition of acoustic resonances via a spectral analysis of the Brownian motion of the mirror, and the spatial profile of the acoustic modes by monitoring their mechanical response to a resonant radiation pressure force swept across the mirror surface. We have applied this technique to mirrors with cylindrical and plano-convex geometries, and compared the experimental results to theoretical predictions. We have in particular observed the gaussian modes predicted for plano-convex mirrors.Comment: 8 pages, 8 figures, RevTe

Thermal and back-action noises in dual-sphere gravitational-waves detectors

We study the sensitivity limits of a broadband gravitational-waves detector based on dual resonators such as nested spheres. We determine both the thermal and back-action noises when the resonators displacements are read-out with an optomechanical sensor. We analyze the contributions of all mechanical modes, using a new method to deal with the force-displacement transfer functions in the intermediate frequency domain between the two gravitational-waves sensitive modes associated with each resonator. This method gives an accurate estimate of the mechanical response, together with an evaluation of the estimate error. We show that very high sensitivities can be reached on a wide frequency band for realistic parameters in the case of a dual-sphere detector.Comment: 10 pages, 7 figure

A micropillar for cavity optomechanics

We present a new micromechanical resonator designed for cavity optomechanics. We have used a micropillar geometry to obtain a high-frequency mechanical resonance with a low effective mass and a very high quality factor. We have coated a 60-$\mu$m diameter low-loss dielectric mirror on top of the pillar and are planning to use this micromirror as part of a high-finesse Fabry-Perot cavity, to laser cool the resonator down to its quantum ground state and to monitor its quantum position fluctuations by quantum-limited optical interferometry

A Cross-Sectional Exploration of Food Security, Depression, and CHAOS in Low-Income Households with Children

Depression has been linked to food security, particularly among low-income mothers. However, less is known about the relationship between CHAOS (Confusion, Hubbub, and Order Scale), a measure of family functioning such as timeliness and order, and varying levels food security. The purpose of this paper was to evaluate the relationship between depression, CHAOS, and sociodemographics on the level of food insecurity in a cross-sectional sample of low-income households with children, ages 0-18 years. Participants were recruited from low-income communities in a medium sized Midwestern city in the United States. Eligible participants were ≥19 years of age, a parent or primary caregiver to at least one child, and English- or Spanish- speaking. Survey items included participation in the Supplemental Nutrition Assistance Program (SNAP), food security, depression, CHAOS, and sociodemographics/family characteristics. Descriptives and Chi-square tests were conducted for all variables. Potential covariates were assessed (e.g., age, income, education, race/ethnicity, sex, SNAP participation, number of children and adults in the household, and marital status) and included in the final logistic regression model through backward elimination. All statistics were conducted using SAS (version 9.4, SAS Institute Inc., Cary, NC). Participants (N=252) were 75% female, 42% Non-Hispanic Black, 31% Non-Hispanic White, 12% Hispanic, and 15% other race categories. The mean number of children in households was 2.33 (SD=1.58), and half of the respondents reported earning ≤$10,000/year. Chi-Square tests showed univariate relationships between study variables and varying household food security levels. Those in the “high” and “medium” groups for depression and CHAOS were both more likely than the “low” groups to experience low or very low food security. Income and education were also related to food security, with low levels of education and low income being associated with low or very low food security. Age, sex, race/ethnicity, and marital status were not associated with food security status. The fully adjusted logistic regression models of depression and CHAOS accounted for 10% and 14% of the variance in food security, respectively (depression: (OR=0.31, CI=0.15-0.65; pp In the current study, CHAOS demonstrated a stronger relationship with food security than depression, when controlling for sociodemographics. CHAOS is a measurement that has not been tested widely among food insecure populations, but has been shown to be an influencing factor on child development, and might help explain some of the stress experienced by low-income families. Understanding more about the psychological aspects of food insecurity may help inform the development of tailored interventions to alleviate food insecurity in low-income households, and ultimately improve health, achievement and related outcomes in children

A Head Start Farm to Family Pilot Program Increased Fruit and Vegetable Intake among Families

Fresh Produce, Fresh Start was a pilot farm to family study which tested the effectiveness of a local produce delivery program on dietary intake of Head Start participants. Utilizing a pre-test/post-test design, measures collected from Head Start parents included 24-hour recall of dietary intake, height and weight, and a food security questionnaire. Intent-to-treat analysis was conducted using paired t-tests. Significant increases were found in intake of vitamin A, vitamin C, fiber, vegetable, and fruit and vegetable servings combined (p \u3c .05) for participants (N = 51). In particular, fruit and vegetable intake increased by 1.4 servings per day. Food security status and weight status did not significantly change. Results indicate that a produce delivery program has potential to improve dietary intake of Head Start families and, possibly, other populations, impacting lifelong consumption habit

Creating and Verifying a Quantum Superposition in a Micro-optomechanical System

Micro-optomechanical systems are central to a number of recent proposals for realizing quantum mechanical effects in relatively massive systems. Here we focus on a particular class of experiments which aim to demonstrate massive quantum superpositions, although the obtained results should be generalizable to similar experiments. We analyze in detail the effects of finite temperature on the interpretation of the experiment, and obtain a lower bound on the degree of non-classicality of the cantilever. Although it is possible to measure the quantum decoherence time when starting from finite temperature, an unambiguous demonstration of a quantum superposition requires the mechanical resonator to be in or near the ground state. This can be achieved by optical cooling of the fundamental mode, which also provides a method to measure the mean phonon number in that mode. We also calculate the rate of environmentally induced decoherence and estimate the timescale for gravitational collapse mechanisms as proposed by Penrose and Diosi. In view of recent experimental advances, practical considerations for the realization of the described experiment are discussed.Comment: 19 pages, 8 figures, published in New J. Phys. 10 095020 (2008); minor revisions to improve clarity; fixed possibly corrupted figure