Fast compression of a cold atomic cloud using a blue detuned crossed dipole trap

We present the experimental realization of a compressible blue detuned crossed dipole trap for cold atoms allowing for fast dynamical compression (~ 5 - 10 ms) of 5x10^7 Rubidium atoms up to densities of ~ 10^13 cm^-3. The dipole trap consists of two intersecting tubes of blue-detuned laser light. These tubes are formed using a single, rapidly rotating laser beam which, for sufficiently fast rotation frequencies, can be accurately described by a quasi-static potential. The atomic cloud is compressed by dynamically reducing the trap volume leading to densities close to the Ioffe-Reggel criterion for light localization.Comment: 14 pages, 15 figures, 2 table

Realization of Directional Amplification in a Microwave Optomechanical Device

| openaire: EC/FP7/615755/EU//CAVITYQPD | openaire: EC/H2020/732894/EU//HOTDirectional transmission or amplification of microwave signals is indispensable in various applications involving sensitive measurements. In this work we show experimentally how to use a generic cavity optomechanical setup to nonreciprocally amplify microwave signals above 3 GHz in one direction by 9 dB and simultaneously attenuate the transmission in the opposite direction by 21 dB. We use a device including two on-chip superconducting resonators and two metallic drumhead mechanical oscillators. Application of four microwave pump-tone frequencies allows the design of constructive or destructive interference for a signal tone depending on the propagation direction. The device can also be configured as an isolator with lossless nonreciprocal transmission and 18 dB of isolation.Peer reviewe

Localized Deformation along an Inverted Rifted Margin: Example of the Northern Ligurian Margin, Western Mediterranean.

Along rifted margins, continental edges are heterogeneous systems that juxtapose lithospheres with different nature, mechanical behavior and structural inheritance. In this study, we focus on the northern Ligurian margin to examine how such complex systems might deform when they are submitted to a compressive stress field. The northern Ligurian margin, of Oligo-Miocene age, has been undergoing contraction over at least the past ~ 6 Ma. Active thrust faults and folds responsible for the regional uplift of the continental edge have previously been identified below the margin. Although seismicity extends as far as the axis of the basin, no recent or active crustal compressional structure has been identified so far in the oceanic domain. We used new 12-channel high-resolution seismic data (FABLES cruise, 2012) and other seismic reflexion lines from the last decades to image the sedimentary cover in the Ligurian oceanic basin, down to the bottom of the Messinian salt layer ~ 3 km below the seafloor. Because the Messinian event is well dated over the Mediterranean (5.96-5.32 Ma) and well identified in the seismic data, it forms a clear marker characterizing the recent deformation related to both salt and crustal tectonics. Noticeable deformation within the oceanic domain is restricted to large, SW-NE elongated salt walls located 10 to 40 km from the margin toe, over a 70-km length. The salt walls have a specific structure and arrangement that cannot result from salt tectonics only. We thus interpret them as resulting from combined deep-seated crustal and thin-skinned deformations. However, although the salt walls are well expressed in the seafloor morphology, their seismic images do not reveal any significant vertical throw across their trace, and they gradually disappear toward the SW. We thus interpret the salt walls as strike-slip structures with possibly very moderate compression. Overall, the post-Messinian deformation taken along these features is likely moderate as well. Thus, most of the contractional deformation would be focused along the margin since ~5 Ma. The synchronicity of the crustal deformation in the oceanic and the continental domains supports the idea that the lower deformation rates observed within the deep basin are related to somewhat different mechanical behaviors within the continental margin and the adjacent oceanic domain, rather than resulting from a recent basinward propagation of the deformation. Thermo-mechanical models suggest that mainly two factors could control the focused deformation along the margin: (1) the locus of highest topographic gradient of the main crustal interfaces, (2) the thermal contrast between the cooling subsiding oceanic domain and the warming uplifting margin. According to these models, the continental versus oceanic nature of the lithospheres would be of second order in the localization of the deformation

Giant seabed polygons and underlying polygonal faults in the Caribbean Sea as markers of the sedimentary cover extension in the Grenada Basin

Based on an extensive seismic and multibeam dataset, 1-5 km wide giant polygons were identified at the bottom of the Grenada basin, covering a total area of ~55000 km². They represent the top part of an active underlying polygonal fault system due to the volumetric contraction of clay- and smectite-rich sediments during burial. To date, this is the widest area of outcropping polygonal faults ever found on Earth. The seabed polygons are bounded by rectilinear ~1000-1500 m wide and ~10-60 m deep furrows, depending on the ESSOAr | https://doi.org/10.1002/essoar.10506638.1 | CC_BY_NC_4.0 | First posted online: Thu, 1 Apr 2021 00:40:54 | This content has not been peer reviewed location in the basin. They are relatively regular in the north Grenada Basin, whereas they are getting longer and more elongated in the south Grenada Basin. The polygonal faults consist in a set of discrete normal faults affecting a 700 to 1200 m thick interval, initiated in the shallow sub-surface at the transition between Early to Middle Pliocene and then having propagated both upward and downward during sedimentation. The centre43 to-centre method has been applied to determine the local ellipse of strains, providing a major orientation for extension needed for polygons to initiate. In the north, the minor axes are oriented N40°, indicating a general NE-SW extension of the upper part of the sedimentary cover consistent with the forearc/backarc regional extension. In the south Grenada Basin, minor axes are progressively turning towards the south, pointing out the actual maximum subsidence point. This implies that seabed polygonal faults could thus be indicative of the present-day (or recent) strain state within the upper sedimentary column