The measurement of minuscule forces and displacements with ever greater precision is inhibited by the Heisenberg uncertainty principle, which imposes a limit to the precision with which the position ...of an object can be measured continuously, known as the standard quantum limit
. When light is used as the probe, the standard quantum limit arises from the balance between the uncertainties of the photon radiation pressure applied to the object and of the photon number in the photoelectric detection. The only way to surpass the standard quantum limit is by introducing correlations between the position/momentum uncertainty of the object and the photon number/phase uncertainty of the light that it reflects
. Here we confirm experimentally the theoretical prediction
that this type of quantum correlation is naturally produced in the Laser Interferometer Gravitational-wave Observatory (LIGO). We characterize and compare noise spectra taken without squeezing and with squeezed vacuum states injected at varying quadrature angles. After subtracting classical noise, our measurements show that the quantum mechanical uncertainties in the phases of the 200-kilowatt laser beams and in the positions of the 40-kilogram mirrors of the Advanced LIGO detectors yield a joint quantum uncertainty that is a factor of 1.4 (3 decibels) below the standard quantum limit. We anticipate that the use of quantum correlations will improve not only the observation of gravitational waves, but also more broadly future quantum noise-limited measurements.
Tides and freshwater inflow which influence water movement in estuarine areas govern the exposure-regime of pollutants. In this experiment, we examined the in situ impact of double pulses of copper ...and the herbicide Irgarol 1051 on the photosynthesis of the seagrass,
Zostera capricorni. Despite a 4-day recovery period between the two 10
h pulses of toxicant, the effective quantum yield of photosystem II (Δ
F/Fm′) and total chlorophyll concentrations indicated that multiple-pulses had a greater impact than a single pulse. During the first exposure period, samples exposed to Irgarol 1051 had Δ
F/Fm′ values as low as zero while controls remained around 0.6 relative units. After the second exposure period, treated samples recovered to only 0.4 relative units. Samples exposed to copper had Δ
F/Fm′ values around 0.3 relative units during the first exposure period and while these samples recovered before the second dose, they remained below 0.2 relative units after the second exposure period.
Alternate samples were also exposed to one toxicant, allowed to recover and then exposed to the other toxicant. Δ
F/Fm′ values indicated that copper exposure followed by Irgarol 1051 exposure was more toxic than Irgarol 1051 exposure followed by copper exposure.
The goal was to determine whether a signal (e.g., a click) at food availability affects timing behavior in rats. Twenty-four rats were trained on an appetitive lever-press procedure that varied on ...two dimensions: shape of the interreinforcer distribution (i.e., fixed-interval 60
s or random-interval 60
s) and number of signals (i.e., the presence or absence of a click at the time of reinforcer availability). The rats were randomly partitioned into one of four groups (each group had six rats): Fixed, Signaled-Fixed, Random, and Signaled-Random. The shape of the interreinforcer distribution affected the response pattern; the presence of the click affected response rate. These results provide support for a simultaneous temporal processing account of behavior.
Searches are under way in Advanced LIGO and Virgo data for persistent gravitational waves from continuous sources, e.g. rapidly rotating galactic neutron stars, and stochastic sources, e.g. relic ...gravitational waves from the Big Bang or superposition of distant astrophysical events such as mergers of black holes or neutron stars. These searches can be degraded by the presence of narrow spectral artifacts (lines) due to instrumental or environmental disturbances. We describe a variety of methods used for finding, identifying and mitigating these artifacts, illustrated with particular examples. Results are provided in the form of lists of line artifacts that can safely be treated as non-astrophysical. Such lists are used to improve the efficiencies and sensitivities of continuous and stochastic gravitational wave searches by allowing vetoes of false outliers and permitting data cleaning.
The Advanced LIGO detectors have recently completed their second observation run successfully. The run lasted for approximately 10 months and led to multiple new discoveries. The sensitivity to ...gravitational waves was partially limited by laser noise. Here, we utilize auxiliary sensors that witness these correlated noise sources, and use them for noise subtraction in the time domain data. This noise and line removal is particularly significant for the LIGO Hanford Observatory, where the improvement in sensitivity is greater than 20%. Consequently, we were also able to improve the astrophysical estimation for the location, masses, spins, and orbital parameters of the gravitational wave progenitors.
The survival and subsequent growth potential of Anabaena spp. and other filamentous cyanobacteria and the cells of Aulacoseira spp. (diatom) and Ceratium hirundinella (dinoflagellate) following ...passage through the Multi Level Inlet Tower (MLIT) and offtake works at Chaffey Reservoir in New South Wales, Australia was investigated in late summer. The study aimed to test whether the phytoplankton cells were destroyed or otherwise rendered less viable during passage through the outlet works. The reservoir was strongly thermally stratified with a shallow surface mixed layer, which contributed to considerable temporal variability in the numbers of phytoplankton cells present immediately opposite the intake portal of the outlet works. To compensate, considerable replicate sampling was undertaken both upstream and downstream of the MLIT. Results indicate limited destruction of cyanobacteria, with fewer cells present immediately downstream compared to upstream. Greater destruction of cells was indicated at lower mean daily discharge rates compared to higher discharge rates. Filament lengths of both cyanobacteria and Aulacoseira were also reduced during passage. There was no apparent reduction in Ceratium cell number. Laboratory incubation studies on surviving cells collected downstream indicated no impairment on the viability of any taxa. Calculations of rates-of-strain likely to be experienced by the phytoplankton as they transited through the offtake revealed very high stress being applied to the filaments and cells at the valve, and within the spillway sections of the works. These were several orders of magnitude greater than published values shown to disrupt cells and filaments, and to impair viability for subsequent growth in laboratory studies. However, exposure times to the high rates-of-strain at Chaffey Reservoir were brief, which may reduce the impacts of the high turbulence. The conclusions were that unless cyanobacterial cell destruction during passage through an outlet works can be shown to be more effective at larger reservoirs, the withdrawal of warm, cyanobacterial infested waters from close to the surface is unlikely to provide an acceptable management action for the prevention of cold water pollution downstream.
The shifts in wavenumber of the ν3(SiO4) (approximately 1008 cm-1) Raman band of fully crystalline synthetic zircon with changing pressure (P) and temperature (T) were calibrated for application as a ...Raman spectroscopic pressure sensor in optical cells to about 1000 °C and 10 GPa. The relationship between wavenumber (ν) of this band and T from 22 to 950 °C is described by the equation ν (cm-1) = 7.54·10-9·T3 - 1.61·10-5·T2 - 2.89·10-2·T + 1008.9, where T is given in °C. The pressure dependence is nearly linear over the studied range in P. At approximately 25 °C, the θν/θP slope to 6.6 GPa is 5.69 cm-1/GPa, and that to 2 GPa is 5.77 cm-1/GPa. The θν/θP slope does not significantly change with temperature, as determined from experiments conducted along isotherms up to 700 °C. Therefore, this pressure sensor has the advantage that a constant θν/θP slope of 5.8 ± 0.1 cm-1/GPa can be applied in experiments to pressures of at least about 6.6 GPa without introducing a significant error. The pressure sensor was tested to determine isochores in experiments with H2O+Na2Si3O7 and H2O+NaAlSi3O8 fluids to 803 °C and 1.65 GPa. These pressures were compared to pressures calculated from the equation of state (EoS) of H2O based on the measured vapor dissolution or ice melting temperature for the same experiment. Pressures determined from the zircon sensor in runs in which NaAlSi3O8 melt dissolved in aqueous fluid were close to or lower than the pressure calculated from the EoS of H2O using the vapor dissolution or ice melting temperature. In experiments with H2O+Na2O+SiO2 fluids, however, the pressure obtained from the Raman spectrum of zircon was often significantly higher than that estimated from the EoS of H2O. This suggests that the pressures along some critical curves of water-silicate melt pseudobinary systems should be revised.
Gravitational wave interferometers achieve their profound sensitivity by combining a Michelson interferometer with optical cavities, suspended masses, and now, squeezed quantum states of light. These ...states modify the measurement process of the LIGO, VIRGO and GEO600 interferometers to reduce the quantum noise that masks astrophysical signals; thus, improvements to squeezing are essential to further expand our gravitational view of the Universe. Further reducing quantum noise will require both lowering decoherence from losses as well more sophisticated manipulations to counter the quantum back-action from radiation pressure. Both tasks require fully understanding the physical interactions between squeezed light and the many components of km-scale interferometers. To this end, data from both LIGO observatories in observing run three are expressed using frequency-dependent metrics to analyze each detector's quantum response to squeezed states. The response metrics are derived and used to concisely describe physical mechanisms behind squeezing's simultaneous interaction with transverse-mode selective optical cavities and the quantum radiation pressure noise of suspended mirrors. These metrics and related analysis are broadly applicable for cavity-enhanced optomechanics experiments that incorporate external squeezing, and-for the first time-give physical descriptions of every feature so far observed in the quantum noise of the LIGO detectors.
PDF
