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Pierre-Francois Cohadon

Publications and source records attributed to Pierre-Francois Cohadon.

3 recordsLinked to original sources

Addressing the problem of the LIGO-Virgo-KAGRA visibility in the scientific literature

As members of the Virgo Collaboration -- one of the large scientific collaborations that explore the universe of gravitational waves together with the LIGO Scientific Collaboration and the KAGRA Collaboration -- we became aware of biased citation practices that exclude Virgo, as well as KAGRA, from achievements that collectively belong to the wider LIGO/Virgo/KAGRA Collaboration. Here, we frame these practices in the context of Merton's Matthew effect, extending the reach of this well studied cognitive bias to include large international scientific collaborations. We provide qualitative evidence of its occurrence, displaying the network of links among published papers in the scientific literature related to Gravitational Wave science. We note how the keyword LIGO is linked to a much larger number of papers and variety of subjects than the keyword Virgo. We support these qualitative observations with a quantitative study based on a year-long monitoring of the relevant literature, where we scan all new preprints appearing in the arXiv electronic preprint database. Over the course of one year we identified all preprints failing to assign due credits to Virgo. As a further step, we undertook positive actions by asking the authors of problematic papers to correct them. We also report on a more in-depth investigation which we performed on problematic preprints that appeared in the first three months of the period under consideration, checking how frequently their authors reacted positively to our request and corrected their papers. Finally, we measure the global impact of papers classified as problematic and observe that, thanks to the changes implemented in response to our requests, the global impact (measured as the number of citations of papers which still contain Virgo visibility issues) was halved. We conclude the paper with general considerations for future work in a wider perspective.

physics.soc-ph

Laser cooling of a Planck mass object close to the quantum ground state

Quantum mechanics has so far not been tested for mechanical objects at the scale of the Planck mass $\sqrt{\hbar c/ G} \simeq 22\,μ\mathrm{g}$. We present an experiment where a 1 mm quartz micropillar resonating at 3.6 MHz with an effective mass of 30 $μ$g is cooled to 500 mK with a dilution refrigerator, and further optomechanically sideband-cooled to an effective temperature of 3 mK, corresponding to a mode thermal occupancy of 20 phonons. This nearly 1000-fold increase in the mass of an optomechanical system with respect to previous experiments near the quantum ground state opens new perspectives in the exploration of the quantum/classical border.

quant-ph

High-finesse Fabry-Perot cavities with bidimensional Si$_3$N$_4$ photonic-crystal slabs

Light scattering by a two-dimensional photonic crystal slab (PCS) can result in dramatic interference effects associated with Fano resonances. Such devices offer appealing alternatives to distributed Bragg reflectors or filters for various applications such as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors, or non-linear optical components. Suspended PCSs also find natural applications in the field of optomechanics, where the mechanical modes of a suspended slab interact via radiation pressure with the optical field of a high finesse cavity. The reflectivity and transmission properties of a defect-free suspended PCS around normal incidence can be used to couple out-of-plane mechanical modes to an optical field by integrating it in a free space cavity. Here, we demonstrate the successful implementation of a PCS reflector on a high-tensile stress Si$_3$N$_4$ nanomembrane. We illustrate the physical process underlying the high reflectivity by measuring the photonic crystal band diagram. Moreover, we introduce a clear theoretical description of the membrane scattering properties in the presence of optical losses. By embedding the PCS inside a high-finesse cavity, we fully characterize its optical properties. The spectrally, angular, and polarization resolved measurements demonstrate the wide tunability of the membrane's reflectivity, from nearly 0 to 99.9470~$\pm$ 0.0025 \%, and show that material absorption is not the main source of optical loss. Moreover, the cavity storage time demonstrated in this work exceeds the mechanical period of low-order mechanical drum modes. This so-called resolved sideband condition is a prerequisite to achieve quantum control of the mechanical resonator with light.

quant-ph