First Long-Term Application of Squeezed States of Light in a Gravitational-Wave Observatory

We report on the first long-term application of squeezed vacuum states of light to improve the shot-noise-limited sensitivity of a gravitational-wave observatory. In particular, squeezed vacuum was applied to the German/British detector GEO600 during a period of three months from June to August 2011, when GEO600 was performing an observational run together with the French/Italian Virgo detector. In a second period squeezing application continued for about 11 months from November 2011 to October 2012. During this time, squeezed vacuum was applied for 90.2% (205.2 days total) of the time that science-quality data was acquired with GEO600. Sensitivity increase from squeezed vacuum application was observed broad-band above 400Hz. The time average of gain in sensitivity was 26% (2.0dB), determined in the frequency band from 3.7kHz to 4.0kHz. This corresponds to a factor of two increase in observed volume of the universe, for sources in the kHz region (e.g. supernovae, magnetars). We introduce three new techniques to enable stable long-term application of squeezed light, and show that the glitch-rate of the detector did not increase from squeezing application. Squeezed vacuum states of light have arrived as a permanent application, capable of increasing the astrophysical reach of gravitational-wave detectors.Comment: 4 pages, 4 figure

Apex Exponents for Polymer--Probe Interactions

We consider self-avoiding polymers attached to the tip of an impenetrable probe. The scaling exponents $\gamma_1$ and $\gamma_2$, characterizing the number of configurations for the attachment of the polymer by one end, or at its midpoint, vary continuously with the tip's angle. These apex exponents are calculated analytically by $\epsilon$-expansion, and numerically by simulations in three dimensions. We find that when the polymer can move through the attachment point, it typically slides to one end; the apex exponents quantify the entropic barrier to threading the eye of the probe

Estimates for practical quantum cryptography

In this article I present a protocol for quantum cryptography which is secure against attacks on individual signals. It is based on the Bennett-Brassard protocol of 1984 (BB84). The security proof is complete as far as the use of single photons as signal states is concerned. Emphasis is given to the practicability of the resulting protocol. For each run of the quantum key distribution the security statement gives the probability of a successful key generation and the probability for an eavesdropper's knowledge, measured as change in Shannon entropy, to be below a specified maximal value.Comment: Authentication scheme corrected. Other improvements of presentatio

Cost-benefit analysis for commissioning decisions in GEO600

Gravitational wave interferometers are complex instruments, requiring years of commissioning to achieve the required sensitivities for the detection of gravitational waves, of order 10^-21 in dimensionless detector strain, in the tens of Hz to several kHz frequency band. Investigations carried out by the GEO600 detector characterisation group have shown that detector characterisation techniques are useful when planning for commissioning work. At the time of writing, GEO600 is the only large scale laser interferometer currently in operation running with a high duty factor, 70%, limited chiefly by the time spent commissioning the detector. The number of observable gravitational wave sources scales as the product of the volume of space to which the detector is sensitive and the observation time, so the goal of commissioning is to improve the detector sensitivity with the least possible detector down time. We demonstrate a method for increasing the number of sources observable by such a detector, by assessing the severity of non-astrophysical noise contaminations to efficiently guide commissioning. This method will be particularly useful in the early stages and during the initial science runs of the aLIGO and adVirgo detectors, as they are brought up to design performance.Comment: 17 pages, 17 figures, 2 table

Mechanical ventilation: lessons from the ARDSNet trial

The acute respiratory distress syndrome (ARDS) is an inflammatory disease of the lungs characterized clinically by bilateral pulmonary infiltrates, decreased pulmonary compliance and hypoxemia. Although supportive care for ARDS seems to have improved over the past few decades, few studies have shown that any treatment can decrease mortality for this deadly syndrome. In the 4 May 2000 issue of New England Journal of Medicine, the results of an NIH-sponsored trial were presented; they demonstrated that the use of a ventilatory strategy that minimizes ventilator-induced lung injury leads to a 22% decrease in mortality. The implications of this study with respect to clinical practice, further ARDS studies and clinical research in the critical care setting are discussed

GEO 600 and the GEO-HF upgrade program: successes and challenges

The German-British laser-interferometric gravitational wave detector GEO 600 is in its 14th year of operation since its first lock in 2001. After GEO 600 participated in science runs with other first-generation detectors, a program known as GEO-HF began in 2009. The goal was to improve the detector sensitivity at high frequencies, around 1 kHz and above, with technologically advanced yet minimally invasive upgrades. Simultaneously, the detector would record science quality data in between commissioning activities. As of early 2014, all of the planned upgrades have been carried out and sensitivity improvements of up to a factor of four at the high-frequency end of the observation band have been achieved. Besides science data collection, an experimental program is ongoing with the goal to further improve the sensitivity and evaluate future detector technologies. We summarize the results of the GEO-HF program to date and discuss its successes and challenges

Interplay between geometry and flow distribution in an airway tree

Uniform fluid flow distribution in a symmetric volume can be realized through a symmetric branched tree. It is shown here, however, that the flow partitioning can be highly sensitive to deviations from exact symmetry if inertial effects are present. This is found by direct numerical simulation of the Navier-Stokes equations in a 3D tree geometry. The flow asymmetry is quantified and found to depend on the Reynolds number. Moreover, for a given Reynolds number, we show that the flow distribution depends on the aspect ratio of the branching elements as well as their angular arrangement. Our results indicate that physiological variability should be severely restricted in order to ensure uniform fluid distribution in a tree. This study suggests that any non-uniformity in the air flow distribution in human lungs should be influenced by the respiratory conditions, rest or hard exercise

The influence of attentional focus on balance control over seven days of training

This study examined the training effect of attentional focus (external focus, internal focus, or no focus instructions) on a dynamic balance task. Participants completed baseline balance testing, seven consecutive days of dynamic balance board training, and retention testing 24 hours after the last session. The novel finding of this study was the presence of a training effect on balance control when adopting an external focus relative to an internal focus or no focus instructions. Further, we report the unique observation that more patterned behavior was adopted regardless of the focus instructions. These findings provide insight into how instructions can be altered to enhance human balance control and complement the constrained-action hypothesis

A simple radionuclide-driven single-ion source

We describe a source capable of producing single barium ions through nuclear recoils in radioactive decay. The source is fabricated by electroplating 148Gd onto a silicon {\alpha}-particle detector and vapor depositing a layer of BaF2 over it. 144Sm recoils from the alpha decay of 148Gd are used to dislodge Ba+ ions from the BaF2 layer and emit them in the surrounding environment. The simultaneous detection of an {\alpha} particle in the substrate detector allows for tagging of the nuclear decay and of the Ba+ emission. The source is simple, durable, and can be manipulated and used in different environments. We discuss the fabrication process, which can be easily adapted to emit most other chemical species, and the performance of the source