Accéléromètre à atomes froids aéroporté pour un test du Principe d'Equivalence

Dans ce mémoire, nous présentons l'étude d'un senseur inertiel à ondes de matière embarqué dans un avion effectuant des vols paraboliques.Une source laser bi-fréquence robuste et compacte permettant de refroidir et d'interroger simultanément des atomes de 87Rb et 39K a été développée. Elle est basée sur des lasers télécom asservis sur un peigne de fréquences optique et doublés en fréquence. L'utilisation de composants optiques fibrés permet de rendre le système intrinsèquement résistant aux vibrations et aux fluctuations thermiques. Le dispositif a été validé en vol par l'obtention d'un double piège magnéto-optique.Nous avons utilisé la source laser pour faire fonctionner un interféromètre à atomes froids de 87Rb dans l'avion. Un accéléromètre mécanique auxiliaire permet d'augmenter la dynamique du capteur atomique et d'enregistrer des franges d'interférences malgré le niveau élevé des fluctuations d'accélération. Le senseur hybride ainsi réalisé a une résolution de 4.10-3 m.s-2.Hz-1/2, environ 100 fois plus faible que le niveau des vibrations dans l'avion.Dans la perspective de réaliser un test du principe d'équivalence en microgravité avec des atomes froids, nous étudions enfin de manière théorique le fonctionnement d'un interféromètre différentiel et nous intéressons à l'influence de certains effets systématiques.In this thesis, we report on the study of a matter-wave inertial sensor, operated in an airplane carrying out parabolic flights.We have developped a compact and robust dual-wavelength laser source to cool and interrogate 87Rb and 39K atoms. It is based on frequency-doubled telecom lasers locked on a femtosecond optical frequency comb. The use of fibered optical components makes the setup intrinsically immune to vibrations and thermal fluctuations. The laser source was validated in flight by obtaining a double-species magneto-optical trap.We have used the source to carry out airborne measurements with an atom interferometer operating with cold 87Rb atoms. An auxiliary mechanical accelerometer makes it possible to increase the atomic sensor's dynamic range, and to record interference fringes despite the high level of acceleration fluctuations. This hybrid sensor has a resolution of 4.10-3 m.s-2.Hz-1/2, which is approximately 100 times lower than the typical vibration level in the plane.In the perspective of testing the equivalence principle with cold atoms in microgravity, we finally theoretically study the operation of a differential interferometer and investigate the influence of some systematic effects.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Motor resonance facilitates movement execution: an ERP and kinematic study

International audienceAction observation, simulation and execution share neural mechanisms that allow for a common motor representation. It is known that when these overlapping mechanisms are simultaneously activated by action observation and execution, motor performance is influenced by observation and vice versa. To understand the neural dynamics underlying this influence and to measure how variations in brain activity impact the precise kinematics of motor behavior, we coupled kinematics and electrophysiological recordings of participants while they performed and observed congruent or non-congruent actions or during action execution alone. We found that movement velocities and the trajectory deviations of the executed actions increased during the observation of congruent actions compared to the observation of non-congruent actions or action execution alone. This facilitation was also discernible in the motor-related potentials of the participants; the motor-related potentials were transiently more negative in the congruent condition around the onset of the executed movement, which occurred 300 ms after the onset of the observed movement. This facilitation seemed to depend not only on spatial congruency but also on the optimal temporal relationship of the observation and execution events

Pushing the limits of a Differential Quantum Gravimeter

International audienceMeasuring the acceleration of the Earths gravity g and the gravity gradient simultaneously and at the same location promises to provide enhance information about the distribution of underground masses, especially at shallow depths [1]. Quantum sensors relying on Atom Interferometry with laser cooled-atoms [2,3] is a technology of choice to implement such new sensing capability and an industry-grade demonstrator has been recently developed. We present the performance of the device that has been integrated and discuss its stationary measurement capability, with the demonstration of a resolution below 1E for the measurement of the vertical gravity gradient (1E = 10-9 s-2 = 0.1 Gal/m) and 0.5 Gal for the measurement of g. In order to illustrate the potential for mass balance monitoring and gravity survey we will present a proof-of-principle experiment with realistic masses and measurement durations. The compactness of the instrument and the field-tested technology [4] on which it is based allows to consider the deployment of this new sensor in real environment as a future short-term outcome to investigate both spatial and temporal mass balance in the field. Promising case studies will be discussed, as this type of sensor can sense mass changes that are not detected by gravimeters. [1] G. Pajot, O. de Viron, M. M. Diament, M. F. Lequentrec-Lalancette, V. Mikhailov, Geophysics 73, 123 (2008) [2] R.Geiger, A.Landragin, S.Merlet, F. Pereira Dos Santos, AVS QuantumScience 2, 024702(2020) [3] V. Menoret et al., "Gravity measurements below 109 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018) [4] A.-K. Cooke, C. Champollion, N. Le Moigne, Geoscientific Instrumentation, Methods and Data Systems Discussions 2020, 1 (2020

Pushing the limits of a Differential Quantum Gravimeter

International audienceMeasuring the acceleration of the Earths gravity g and the gravity gradient simultaneously and at the same location promises to provide enhance information about the distribution of underground masses, especially at shallow depths [1]. Quantum sensors relying on Atom Interferometry with laser cooled-atoms [2,3] is a technology of choice to implement such new sensing capability and an industry-grade demonstrator has been recently developed. We present the performance of the device that has been integrated and discuss its stationary measurement capability, with the demonstration of a resolution below 1E for the measurement of the vertical gravity gradient (1E = 10-9 s-2 = 0.1 Gal/m) and 0.5 Gal for the measurement of g. In order to illustrate the potential for mass balance monitoring and gravity survey we will present a proof-of-principle experiment with realistic masses and measurement durations. The compactness of the instrument and the field-tested technology [4] on which it is based allows to consider the deployment of this new sensor in real environment as a future short-term outcome to investigate both spatial and temporal mass balance in the field. Promising case studies will be discussed, as this type of sensor can sense mass changes that are not detected by gravimeters. [1] G. Pajot, O. de Viron, M. M. Diament, M. F. Lequentrec-Lalancette, V. Mikhailov, Geophysics 73, 123 (2008) [2] R.Geiger, A.Landragin, S.Merlet, F. Pereira Dos Santos, AVS QuantumScience 2, 024702(2020) [3] V. Menoret et al., "Gravity measurements below 109 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018) [4] A.-K. Cooke, C. Champollion, N. Le Moigne, Geoscientific Instrumentation, Methods and Data Systems Discussions 2020, 1 (2020

Genome-wide analyses of Shavenbaby target genes reveals distinct features of enhancer organization

International audienceBackground: Developmental programs are implemented by regulatory interactions between Transcription Factors (TFs) and their target genes, which remain poorly understood. While recent studies have focused on regulatory cascades of TFs that govern early development, little is known about how the ultimate effectors of cell differentiation are selected and controlled. We addressed this question during late Drosophila embryogenesis, when the finely tuned expression of the TF Ovo/Shavenbaby (Svb) triggers the morphological differentiation of epidermal trichomes.Results: We defined a sizeable set of genes downstream of Svb and used in vivo assays to delineate 14 enhancers driving their specific expression in trichome cells. Coupling computational modeling to functional dissection, we investigated the regulatory logic of these enhancers. Extending the repertoire of epidermal effectors using genome-wide approaches showed that the regulatory models learned from this first sample are representative of the whole set of trichome enhancers. These enhancers harbor remarkable features with respect to their functional architectures, including a weak or non-existent clustering of Svb binding sites. The in vivo function of each site relies on its intimate context, notably the flanking nucleotides. Two additional cis-regulatory motifs, present in a broad diversity of composition and positioning among trichome enhancers, critically contribute to enhancer activity.Conclusions: Our results show that Svb directly regulates a large set of terminal effectors of the remodeling of epidermal cells. Further, these data reveal that trichome formation is underpinned by unexpectedly diverse modes of regulation, providing fresh insights into the functional architecture of enhancers governing a terminal differentiation program