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Ph. Laurent

Bio: Ph. Laurent is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Atomic clock & Atomic fountain. The author has an hindex of 23, co-authored 90 publications receiving 2899 citations. Previous affiliations of Ph. Laurent include University of Montpellier & Pierre-and-Marie-Curie University.


Papers
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Journal ArticleDOI
TL;DR: In this article, an ultrastable cryogenic sapphire oscillator is used to measure the short-term frequency stability of the fountain as a function of the number of detected atoms.
Abstract: We describe the operation of a laser cooled cesium fountain clock in the quantum limited regime. An ultrastable cryogenic sapphire oscillator is used to measure the short-term frequency stability of the fountain as a function of the number of detected atoms ${N}_{\mathrm{at}}$. For ${N}_{\mathrm{at}}$ varying from $4\ifmmode\times\else\texttimes\fi{}{10}^{4}$ to $6\ifmmode\times\else\texttimes\fi{}{10}^{5}$ the Allan standard deviation of the frequency fluctuations is in excellent agreement with the ${N}_{\mathrm{at}}^{\ensuremath{-}1/2}$ law of atomic projection noise. With $6\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms, the relative frequency stability is $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$, where \ensuremath{\tau} is the integration time in seconds. This is the best short-term stability ever reported for primary frequency standards, a factor of 5 improvement over previous results.

513 citations

Journal ArticleDOI
TL;DR: A physical analysis of the response of a two-level atom to the interrogation oscillator phase noise in Ramsey and multi-Rabi interrogation schemes using a standard quantum mechanical approach helps to calculate the degradation of the frequency stability of a pulsed atomic frequency standard.
Abstract: Atomic frequency standards using trapped ions or cold atoms work intrinsically in a pulsed mode. Theoretically and experimentally, this mode of operation has been shown to lead to a degradation of the frequency stability due to the frequency noise of the interrogation oscillator. In this paper a physical analysis of this effect has been made by evaluating the response of a two-level atom to the interrogation oscillator phase noise in Ramsey and multi-Rabi interrogation schemes using a standard quantum mechanical approach. This response is then used to calculate the degradation of the frequency stability of a pulsed atomic frequency standard such as an atomic fountain or an ion trap standard. Comparison is made to an experimental evaluation of this effect in the LPTF Cs fountain frequency standard, showing excellent agreement.

274 citations

Journal ArticleDOI
TL;DR: An overview of the work done with the Laboratoire National de Metrologie et d'Essais-Systemes de Reference Temps-Espace (LNE-SYRTE) fountain ensemble during the last five years is given, and recent studies of several systematic frequency shifts are reviewed.
Abstract: We give an overview of the work done with the Laboratoire National de Metrologie et d'Essais-Systemes de Reference Temps-Espace (LNE-SYRTE) fountain ensemble during the last five years. After a description of the clock ensemble, comprising three fountains, FO1, FO2, and FOM, and the newest developments, we review recent studies of several systematic frequency shifts. This includes the distributed cavity phase shift, which we evaluate for the FO1 and FOM fountains, applying the techniques of our recent work on FO2. We also report calculations of the microwave lensing frequency shift for the three fountains, review the status of the blackbody radiation shift, and summarize recent experimental work to control microwave leakage and spurious phase perturbations. We give current accuracy budgets. We also describe several applications in time and frequency metrology: fountain comparisons, calibrations of the international atomic time, secondary representation of the SI second based on the 87Rb hyperfine frequency, absolute measurements of optical frequencies, tests of the T2L2 satellite laser link, and review fundamental physics applications of the LNE-SYRTE fountain ensemble. Finally, we give a summary of the tests of the PHARAO cold atom space clock performed using the FOM transportable fountain.

259 citations

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TL;DR: These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies: d/dt ln([(nu(Rb))/(nu(Cs))]=(0.2+/-7.0)x 10(-16) yr(-1) (1sigma uncertainty).
Abstract: Over five years, we have compared the hyperfine frequencies of 1 3 3 Cs and 8 7 Rb atoms in their electronic ground state using several laser-cooled 1 3 3 Cs and 8 7 Rb atomic fountains with an accuracy of ∼ 10 - 1 5 . These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies: d/dIn[(v R b )/(v C s )] = (0.2 ′ 7.0) X 10 - 1 6 yr - 1 (1σ uncertainty). The same limit applies to a possible variation of the quantity (μ R b /μ C s )α - 0 . 4 4 , which involves the ratio of nuclear magnetic moments and the fine structure constant.

254 citations

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TL;DR: In this article, it is inferred that the Coimbra-Cordoba lineament could have been a suture zone which evolved into an intracontinental left-lateral shear zone during the Variscan orogeny of the Ibero-Armorican arc.

197 citations


Cited by
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TL;DR: In this article, the authors review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence and tachyon.
Abstract: We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

5,954 citations

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TL;DR: Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging.
Abstract: The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

3,394 citations

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TL;DR: The 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use is presented in this article.
Abstract: This paper gives the 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. The 2010 adjustment takes into account the data considered in the 2006 adjustment as well as the data that became available from 1 January 2007, after the closing date of that adjustment, until 31 December 2010, the closing date of the new adjustment. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2010 set replaces the previously recommended 2006 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.

2,770 citations

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TL;DR: In this article, the deformation of two granitic massifs along a dextral wrench fault zone (the South Armorican Shear Zone) is examined at the sample and grain scales.

1,200 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the application of atomic physics to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics and test the principles of general relativity.
Abstract: Advances in atomic physics, such as cooling and trapping of atoms and molecules and developments in frequency metrology, have added orders of magnitude to the precision of atom-based clocks and sensors. Applications extend beyond atomic physics and this article reviews using these new techniques to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics, and test the principles of general relativity.

1,077 citations