Enhancing the area of a Raman atom interferometer using a versatile double-diffraction technique

IIn this paper we demonstrate a new scheme for Raman transitions which realize a symmetric momentum-space splitting of $4 \hbar k$, deflecting the atomic wave-packets into the same internal state. Combining the advantages of Raman and Bragg diffraction, we achieve a three pulse state labelled interferometer, intrinsically insensitive to the main systematics and applicable to all kind of atomic sources. This splitting scheme can be extended to $4N \hbar k$ momentum transfer by a multipulse sequence and is implemented on a $8 \hbar k$ interferometer. We demonstrate the area enhancement by measuring inertial forces

Robustness: a New Form of Heredity Motivated by Dynamic Networks

We investigate a special case of hereditary property in graphs, referred to as {\em robustness}. A property (or structure) is called robust in a graph $G$ if it is inherited by all the connected spanning subgraphs of $G$. We motivate this definition using two different settings of dynamic networks. The first corresponds to networks of low dynamicity, where some links may be permanently removed so long as the network remains connected. The second corresponds to highly-dynamic networks, where communication links appear and disappear arbitrarily often, subject only to the requirement that the entities are temporally connected in a recurrent fashion ({\it i.e.} they can always reach each other through temporal paths). Each context induces a different interpretation of the notion of robustness. We start by motivating the definition and discussing the two interpretations, after what we consider the notion independently from its interpretation, taking as our focus the robustness of {\em maximal independent sets} (MIS). A graph may or may not admit a robust MIS. We characterize the set of graphs \forallMIS in which {\em all} MISs are robust. Then, we turn our attention to the graphs that {\em admit} a robust MIS (\existsMIS). This class has a more complex structure; we give a partial characterization in terms of elementary graph properties, then a complete characterization by means of a (polynomial time) decision algorithm that accepts if and only if a robust MIS exists. This algorithm can be adapted to construct such a solution if one exists

Splendors and miseries of expired CO2 measurement in the suspicion of pulmonary embolism

Capnography has been studied for decades as a potential diagnostic tool for suspected pulmonary embolism. Despite technological refinements and its combination with other non-invasive instruments, no evidence to date allows recommending the use of expired carbon dioxide measurement as a rule-out test for pulmonary embolism without additional radiological testing. Further investigations are, however, still warranted

Stability comparison of two absolute gravimeters: optical versus atomic interferometers

We report the direct comparison between the stabilities of two mobile absolute gravimeters of different technology: the LNE-SYRTE Cold Atom Gravimeter and FG5X\#216 of the Universit\'e du Luxembourg. These instruments rely on two different principles of operation: atomic and optical interferometry. The comparison took place in the Walferdange Underground Laboratory for Geodynamics in Luxembourg, at the beginning of the last International Comparison of Absolute Gravimeters, ICAG-2013. We analyse a 2h10 duration common measurement, and find that the CAG shows better immunity with respect to changes in the level of vibration noise, as well as a slightly better short term stability.Comment: 6 page

Accelerometer using atomic waves for space applications

The techniques of laser cooling combined with atom interferometry make possible the realization of very sensitive and accurate inertial sensors like gyroscopes or accelerometers. Besides earth-based developments, the use of these techniques in space should provide extremely high sensitivity for research in fundamental physics, Earth's observation and exploration of the solar system

Effective velocity distribution in an atom gravimeter: effect of the convolution with the response of the detection

We present here a detailed study of the influence of the transverse motion of the atoms in a free-fall gravimeter. By implementing Raman selection in the horizontal directions at the beginning of the atoms free fall, we characterize the effective velocity distribution, ie the velocity distribution of the detected atom, as a function of the laser cooling and trapping parameters. In particular, we show that the response of the detection induces a pronounced asymetry of this effective velocity distribution that depends not only on the imbalance between molasses beams but also on the initial position of the displaced atomic sample. This convolution with the detection has a strong influence on the averaging of the bias due to Coriolis acceleration. The present study allows a fairly good understanding of results previously published in {\it Louchet-Chauvet et al., NJP 13, 065025 (2011)}, where the mean phase shift due to Coriolis acceleration was found to have a sign different from expected

Double diffraction in an atomic gravimeter

We demonstrate the realization of a new scheme for cold atom gravimetry based on the use of double diffraction beamsplitters recently demonstrated in \cite{Leveque}, where the use of two retro-reflected Raman beams allows symmetric diffraction in $\pm \hbar k_{eff}$ momenta. Though in principle restricted to the case of zero Doppler shift, for which the two pairs of Raman beams are simultaneously resonant, we demonstrate that such diffraction pulses can remain efficient on atoms with non zero velocity, such as in a gravimeter, when modulating the frequency of one of the two Raman laser sources. We use such pulses to realize an interferometer insensitive to laser phase noise and some of the dominant systematics. This reduces the technical requirements and would allow the realization of a simple atomic gravimeter. We demonstrate a sensitivity of $1.2\times10^{-7}g$ per shot