The first detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015 launched the era of gravitational-wave astronomy. The quest for gravitational-wave ...signals from objects that are fainter or farther away impels technological advances to realize ever more sensitive detectors. Since 2019, one advanced technique, the injection of squeezed states of light, is being used to improve the shot-noise limit to the sensitivity of the Advanced LIGO detectors, at frequencies above ∼50 Hz. Below this frequency, quantum backaction, in the form of radiation pressure induced motion of the mirrors, degrades the sensitivity. To simultaneously reduce shot noise at high frequencies and quantum radiation pressure noise at low frequencies requires a quantum noise filter cavity with low optical losses to rotate the squeezed quadrature as a function of frequency. We report on the observation of frequency-dependent squeezed quadrature rotation with rotation frequency of 30 Hz, using a 16-m-long filter cavity. A novel control scheme is developed for this frequency-dependent squeezed vacuum source, and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as "A+."
Recent experiments have demonstrated that squeezed vacuum states can be injected into gravitational wave detectors to improve their sensitivity at detection frequencies where they are quantum noise ...limited. Squeezed states could be employed in the next generation of more sensitive advanced detectors currently under construction, such as Advanced LIGO, to further push the limits of the observable gravitational wave Universe. To maximize the benefit from squeezing, environmentally induced disturbances such as back scattering and angular jitter need to be mitigated. We discuss the limitations of current squeezed vacuum sources in relation to the requirements imposed by future gravitational wave detectors, and show a design for squeezed light injection which overcomes these limitations.
Loss in long-storage-time optical cavities Isogai, T; Miller, J; Kwee, P ...
Optics express,
2013-Dec-02, 2013-12-02, 20131202, Letnik:
21, Številka:
24
Journal Article
Recenzirano
Odprti dostop
Long-storage-time Fabry-Perot cavities are a core component of many precision measurement experiments. Optical loss in such cavities is a critical parameter in determining their performance; however, ...it is very difficult to determine a priori from independent characterisation of the individual cavity mirrors. Here, we summarise three techniques for directly measuring this loss in situ and apply them to a high-finesse, near-concentric, 2 m system. Through small modifications of the cavity's length, we explore optical loss as a function of beam spot size over the 1-3 mm range. In this regime we find that optical loss is relatively constant at around 5 ppm per mirror and shows greater dependence on the positions of the beam spots on the cavity optics than on their size. These results have immediate consequences for the application of squeezed light to advanced gravitational-wave interferometers.
We present a simple feedback description of parametric instabilities which can be applied to a variety of optical systems. Parametric instabilities are of particular interest to the field of ...gravitational-wave interferometry where high mechanical quality factors and a large amount of stored optical power have the potential for instability. In our use of Advanced LIGO as an example application, we find that parametric instabilities, if left unaddressed, present a potential threat to the stability of high-power operation.
Squeezed states of light are an important tool for optical measurements below the shot noise limit and for optical realizations of quantum information systems. Recently, squeezed vacuum states were ...deployed to enhance the shot noise limited performance of gravitational wave detectors. In most practical implementations of squeezing enhancement, relative fluctuations between the squeezed quadrature angle and the measured quadrature (sometimes called squeezing angle jitter or phase noise) are one limit to the noise reduction that can be achieved. We present calculations of several effects that lead to quadrature fluctuations, and use these estimates to account for the observed quadrature fluctuations in a LIGO gravitational wave detector. We discuss the implications of this work for quantum enhanced advanced detectors and even more sensitive third generation detectors.
Investigations on the biological effects of high voltage electric pulses primarily concern membrane permeabilization and microbial inacti-vation. Electroporation resulting from increased ...transmembrane potential is probably the main cause for membrane permeabilization. Equations are presented for this phenomenon. Results from several studies on the inactivation of microorganisms by pulsed electric fields are summarized in tables that relate the rate of inactivation to process conditions. The influence of three sets of parameters is discussed: 1) type and physiological state of the microorganism; 2) chemical composition and electrical resistivity of the microorganism-containing food or medium; 3) process conditions such as field intensity, duration and number of pulses, dissipated energy, final temperature, type of pulse and of treatment chamber. Data can be used to select conditions which produce a 5-6 log cycle inactivation for many yeasts or vegetative bacteria. Bacterial spores generally resist inactivation. Pulsed electric fields of relatively low intensity may be used to permeabilize larger cells from plant or animal tissues in order to facilitate theextraction of specific constituents or to increase the drying rate. Little is known concerning the possible chemical or physico-chemical modifications of food constituents by high voltage electric pulses. Some enzymes appear to be inactivated, even at low temperatures, while others are more resistant. The sensorial characteristics of a number of foods subjected to electric fields do not appear to be significantly altered. Potential food applications are numerous and mainly related to liquid foods (fruit juices, milk, sauces, liquid egg) or to pumpable food pastes (fruit or vegetable purées, minced meat, etc.). Both neutral and acidic foods are likely candidates. The main objectives of microbial inactivation by electric pulses are food sanitation and/or extension of chilled storage. The process should be nonthermal (maximum ?T of ∼30°C) to preserve food freshness and quality. A low operating cost, estimated at 0.4-0.8 US cents per liter of food (capital investment not included) and continuous operation at high flow rate (>1000 L/h) represent significant industrial advantages for this new technology.
Little information is available about management practice effects on the net global warming potential (GWP) and greenhouse gas intensity (GHGI) under dryland cropping systems. We evaluated the ...effects of cropping sequences (conventional-tillage malt barley Hordeum vulgaris L.–fallow CTB-F, no-till malt barley–pea Pisum sativum L. NTB-P, and no-till continuous malt barley NTCB) and N fertilization rates (0 and 80 kg N ha−1) on net GWP and GHGI from 2008 to 2011 in eastern Montana. Carbon dioxide sources from farm operations were greater under CTB-F than NTB-P and NTCB and greater with N fertilization than without, but the sources from soil greenhouse gases (GHGs) varied among treatments and years. Carbon dioxide sinks from crop residue and soil organic C (SOC) sequestration were greater under NTB-P or NTCB with 80 kg N ha−1 than other treatments. Net GWP and GHGI based on soil respiration (GWPR and GHGIR, respectively) and SOC (GWPC and GHGIC, respectively) were greater under CTB-F with 0 kg N ha−1 than other treatments, suggesting that alternate-year fallow and the absence of N fertilization to crops can increase net GHG emissions. Because of greater grain yield but lower GWP and GHGI, NTB-P with N rates between 0 and 80 kg N ha−1 may be used as management options to mitigate global warming potential while sustaining dryland malt barley and pea yields compared with CTB-F with 0 kg N ha−1 in the northern Great Plains. The results can be applied to other semiarid regions with similar soil and climatic conditions. Abbreviations: CTB-F, conventional-tillage malt barley–fallow; GHG, greenhouse gas; GHGI, greenhouse gas intensity; GHGIC, greenhouse gas intensity based on soil organic carbon; GHGIR, greenhouse gas intensity based on soil respiration; GWP, global warming potential; GWPC, global warming potential based on soil organic carbon; GWPR, global warming potential based on soil respiration; NTB-P, no-till malt barley–pea; NTCB, no-till continuous malt barley; SOC, soil organic carbon.
Malt barley (Hordeum vulgare L.) yield and quality have been evaluated using various cultivars and N rates but little is known about the effects of tillage and cropping sequence. We evaluated the ...effects of tillage, cropping sequence, and N fertilization on dryland malt barley yield, grain characteristics, N uptake, and N use‐efficiency from 2006 to 2011 in eastern Montana. Treatments were no‐till continuous malt barley (NTCB), no‐till malt barley–pea (Pisum sativum L.) (NTB–P), no‐till malt barley–fallow (NTB–F), and conventional till malt barley–fallow (CTB–F), with split application of N rates (0,40, 80, and 120 kg N ha–1) in randomized complete block with three replications. As N rates increased, malt barley grain yield, protein concentration, and N uptake increased in NTB–F, NTB–P, and NTCB, but test weight, plumpness, and N‐use efficiency decreased in all tillage and cropping sequence treatments. Similarly, plant stand, biomass (stems and leaves) yield, and N uptake increased with increased N rates. Grain and biomass yields, N uptake, and N‐use efficiency were greater in CTB–F than in NTB–P and NTCB but tillage had no effect on these parameters. Malt barley yield and N uptake varied with cropping sequences and N rates among years. Although grain yield increased with increased N rates, NTB–P with N rates between 40 and 80 kg N ha−1 may be used to sustain dryland malt barley yield and quality (protein concentration < 135 g kg−1, plumpness > 800 g kg−1), thereby helping to reduce the potentials for soil erosion and N leaching and increase soil organic matter in the northern Great Plains.
PDF
