Quantum limits of cold damping with optomechanical coupling

Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms and we show that the optomechanical system allows to reach these limits. Displacement noise can be arbitrarily reduced in a narrow frequency band. In a wide-band analysis we show that thermal fluctuations are reduced as with classical damping whereas quantum zero-point fluctuations are left unchanged. The only limit of cold damping is then due to zero-point energy of the mirrorComment: 10 pages, 3 figures, RevTe

Quantum theory of fluctuations in a cold damped accelerometer

We present a quantum network approach to real high sensitivity measurements. Thermal and quantum fluctuations due to active as well as passive elements are taken into account. The method is applied to the analysis of the capacitive accelerometer using the cold damping technique, developed for fundamental physics in space by ONERA and the ultimate limits of this instrument are discussed. It is confirmed in this quantum analysis that the cold damping technique allows one to control efficiently the test mass motion without degrading the noise level.Comment: 10 pages, 6 figures, RevTeX; Minor change

Terrestrial Carbonaceous Debris Tracing Atmospheric Hypervelocity-Shock Aeroplasma Processes

International audienceAtmospheric hypervelocity impacts are widely viewed to produce the meteoric smoke layer by the shock-less interactions of the impinging air molecules with the vaporized meteoroid. In contrast here, we intend to show how gas and solid aerosols when captured in the Mach cone of a bolide while entering the Earth atmosphere are transformed into a new range of polymeric nanomaterials. Carbonaceous materials from natural situations are studied from collect in a pilot region of Southern France in the following days of a high altitude meteor atmospheric airburst on 2011 August 2 nd and since the 2013 February 15 th Chelyabinsk meteoritic event in Ural. These materials are compared to the ones obtained by hypervelocity shock with the CEA Persephone light-gas gun. A numerical simulation with the Tycho software is performed to model the evolution of the increase of density directly in the rear front of the shockwave with the increase of velocity around an obstacle for high velocity inflow. The multidisciplinary approach reveals the production carbon-based nanosolids from terrestrial precursors by hypervelocity plasma particle deposition (HPPD) processes. The Tycho simulation helps to establish the lack of mixing between the ablation smoke and the surrounding atmosphere. The correlation between the simulation, the hypervelocity experiments and the natural situations shows the distinctive characteristics of visco-elastic filamentary nanosolids formed in the laminar domain of low pressure, the ones of nanoparticle-rich stiff film specific to the thin domain of high shear stress and the ones of dense glassy carbon with nanocarbon crystallites (graphite and graphene-like) only formed in the frontal high temperature and pressure domain. Data on the natural carbon-based nanosolids indicate that the atmospheric shock-dissociation occurred from a carbon pool dominated by dead atmospheric carbon. Diagnostic keys are provided to distinguish natural carbon-based nanosolids synthesized by HPPD just at the time of the hypervelocity atmospheric entry from their subsequent transformations during atmospheric transport by other aeroplasma processes

Prediction of laminar/turbulent transition in an unstructured finite element Navier Stokes solver using a boundary layer code with emphasis on cross flow transition

International audienceThis paper presents some developments performed to achieve an accurate and efficient prediction tool for laminar/turbulent transition. These developments involve industrial codes used at Dassault Aviation for the aerodynamics design of military aircraft and business jets. The process is based on a flexible sequence of simulation tools. The issues concerning influence of the numerical solvers, transition onset criteria and the coupling process are described. The influence of intermittency function is also discussed. Results demonstrate the accuracy of the method with emphasis on transition induced by crossflow instabilities

Beating quantum limits in interferometers with quantum locking of mirrors

The sensitivity in interferometric measurements such as gravitational-wave detectors is ultimately limited by quantum noise of light. We discuss the use of feedback mechanisms to reduce the quantum effects of radiation pressure. Recent experiments have shown that it is possible to reduce the thermal motion of a mirror by cold damping. The mirror motion is measured with an optomechanical sensor based on a high-finesse cavity, and reduced by a feedback loop. We show that this technique can be extended to lock the mirror at the quantum level. In gravitational-waves interferometers with Fabry-Perot cavities in each arms, it is even possible to use a single feedback mechanism to lock one cavity mirror on the other. This quantum locking greatly improves the sensitivity of the interferometric measurement. It is furthermore insensitive to imperfections such as losses in the interferometer

Quantum fluctuations for drag free geodesic motion

The drag free technique is used to force a proof mass to follow a geodesic motion. The mass is protected from perturbations by a cage, and the motion of the latter is actively controlled to follow the motion of the proof mass. We present a theoretical analysis of the effects of quantum fluctuations for this technique. We show that a perfect drag free operation is in principle possible at the quantum level, in spite of the back action exerted on the mass by the position sensor.Comment: 4 pages, 1 figure, RevTeX, minor change

Odyssey 2 : A mission toward Neptune and Triton to test General Relativity

Odyssey 2 will be proposed in December 2010 for the next call of M3 missions for Cosmic Vision 2015-2025. This mission, under a Phase 0 study performed by CNES, will aim at Neptune and Triton. Two sets of objectives will be pursued. The first one is to perform a set of gravitation experiments at the Solar System scale. Experimental tests of gravitation have always shown good agreement with General Relativity. There are however drivers to continue testing General Relativity, and to do so at the largest possible scales. From a theoretical point of view, Einstein's theory of gravitation shows inconsistencies with a quantum description of Nature and unified theories predict deviations from General Relativity. From an observational point of view, as long as dark matter and dark energy are not observed through other means than their gravitational effects, they can be considered as a manifestation of a modification of General Relativity at cosmic scales. The scientific objectives are to: (i) test the gravitation law at the Solar System scale; (ii) measure the Eddington parameter; and (iii) investigate the navigation anomalies during fly-bys. To fulfil these objectives, the following components are to be on board the spacecraft: (i) the Gravity Advanced Package (GAP), which is an electrostatic accelerometer to which a rotating stage is added; (ii) radio-science; (iii) laser ranging, to improve significantly the measure of the Eddington parameter. The second set of objectives is to enhance our knowledge of Neptune and Triton. Several instruments dedicated to planetology are foreseen: camera, spectrometer, dust and particle detectors, and magnetometer. Depending on the ones kept, the mission could provide information on the gravity field, the atmosphere and the magnetosphere of the two bodies as well as on the surface geology of Triton and on the nature of the planetary rings around Neptune.Comment: 61st International Astronautical Congress (Prague, Czech Republic - September 2010), 7 page

Transverse-mode coupling in a Kerr medium

We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be particularly robust with respect to mode coupling, while quadrature squeezing is more sensitive. However, it is possible to find a mode the quadrature squeezing of which is not affected by the coupling.Comment: 11 pages, 6 figures, LaTe