Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector.

The quantum radiation pressure and the quantum shot noise in laser-interferometric gravitational wave detectors constitute a macroscopic manifestation of the Heisenberg inequality. If quantum shot noise can be easily observed, the observation of quantum radiation pressure noise has been elusive, so far, due to the technical noise competing with quantum effects. Here, we discuss the evidence of quantum radiation pressure noise in the Advanced Virgo gravitational wave detector. In our experiment, we inject squeezed vacuum states of light into the interferometer in order to manipulate the quantum backaction on the 42 kg mirrors and observe the corresponding quantum noise driven displacement at frequencies between 30 and 70 Hz. The experimental data, obtained in various interferometer configurations, is tested against the Advanced Virgo detector quantum noise model which confirmed the measured magnitude of quantum radiation pressure noise.

Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light.

Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of squeezed vacuum states of light into the interferometer's dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to 3.2±0.1 dB beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%-8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded.

Beat note stabilization in dual-polarization DFB fiber lasers by an optical phase-locked loop.

A fully fibered microwave-optical source at 1.5 µm is studied experimentally. It is shown that the beat note between two orthogonally polarized modes of a distributed-feedback fiber laser can be efficiently stabilized using an optical phase-locked loop. The pump-power-induced birefringence serves as the actuator. Beat notes at 1 GHz and 10 GHz are successfully stabilized to a reference synthesizer, passing from the 3 kHz free-running linewidth to a stabilized sub-Hz linewidth, with a phase noise as low as -75 dBc/Hz at 100 Hz offset from the carrier. Such dual-frequency stabilized lasers could provide compact integrated components for RF and microwave photonics applications.

A state observer for the Virgo inverted pendulum.

We report an application of Kalman filtering to the inverted pendulum (IP) of the Virgo gravitational wave interferometer. Using subspace method system identification techniques, we calculated a linear mechanical model of Virgo IP from experimental transfer functions. We then developed a Kalman filter, based on the obtained state space representation, that estimates from open loop time domain data, the state variables of the system. This allows the observation (and eventually control) of every resonance mode of the IP mechanical structure independently.

In-vacuum Faraday isolation remote tuning.

In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment (Virgo), has a 20 mm clear aperture and is illuminated by an almost 20 W incoming beam, having a diameter of about 5 mm. When going in vacuum at 10(-6) mbar, a degradation of the isolation exceeding 10 dB was observed. A remotely controlled system using a motorized lambda=2 waveplate inserted between the first polarizer and the Faraday rotator has proven its capability to restore the optical isolation to a value close to the one set up in air.

[Cholestasis in pregnancy. A pure cytolytic form]. / Cholestase gravidique. Une forme cytolytique pure.

BACKGROUND: Intrahepatic cholestatic disease in pregnancy is the second most frequent cause of jaundice after viral hepatitis. Elevated serum alkaline phosphatase is always found but is of little aid for diagnosis. CASE REPORT: A 32-year-old woman (third gestation, second parturition) consulted at 31 weeks gestation after progressive development of pruritus then jaundice. Transaminase levels were elevated. The diagnosis of intrahepatic cholestasis was retained despite normal alkaline phosphatase levels throughout the disease course. DISCUSSION: Intrahepatic cholestasis of pregnancy is rare in France compared with its frequency in Latin America and in Scandinavia. The pathogenesis remains uncertain. Diagnosis is based on clinical and laboratory findings as well as morphological arguments. Nevertheless, the results of liver tests vary widely. Transaminase levels may rise greatly but no prior case with normal alkaline phosphatase levels has been reported. Most importantly, clinical course is spontaneously regressive; pruritus and jaundice disappear within a few days after delivery allowing the diagnosis of intrahepatic cholestasis of pregnancy.

Ultrahigh-spectral-purity laser for the VIRGO experiment.

We report on the frequency stabilization and on the measurement of the spectral density of frequency fluctuations (range 20 Hz to 20 kHz) and of the Allan variance (0.02 ms to 10(5) s) of a Nd:YAG laser for the VIRGO interferometric detector of gravitational waves. The short-term frequency fluctuations presented here compare favorably with those of other known oscillators. The Allan variance is better than 10(-14) for all measurement times below 0.1 s.