arXiv subjects

J. Guéna

Publications and source records attributed to J. Guéna.

12 recordsLinked to original sources

arXiv2017

First international comparison of fountain primary frequency standards via a long distance optical fiber link

We report on the first comparison of distant caesium fountain primary frequency standards (PFSs) via an optical fiber link. The 1415 km long optical link connects two PFSs at LNE-SYRTE (Laboratoire National de métrologie et d'Essais - SYstème de Références Temps-Espace) in Paris (France) with two at PTB (Physikalisch-Technische Bundesanstalt) in Braunschweig (Germany). For a long time, these PFSs have been major contributors to accuracy of the International Atomic Time (TAI), with stated accuracies of around $3\times 10^{-16}$. They have also been the references for a number of absolute measurements of clock transition frequencies in various optical frequency standards in view of a future redefinition of the second. The phase coherent optical frequency transfer via a stabilized telecom fiber link enables far better resolution than any other means of frequency transfer based on satellite links. The agreement for each pair of distant fountains compared is well within the combined uncertainty of a few 10$^{-16}$ for all the comparisons, which fully supports the stated PFSs' uncertainties. The comparison also includes a rubidium fountain frequency standard participating in the steering of TAI and enables a new absolute determination of the $^{87}$Rb ground state hyperfine transition frequency with an uncertainty of $3.1\times 10^{-16}$. This paper is dedicated to the memory of André Clairon, who passed away on the 24$^{th}$ of December 2015, for his pioneering and long-lasting efforts in atomic fountains. He also pioneered optical links from as early as 1997.

physics.atom-ph↗

arXiv2016

Searching for an oscillating massive scalar field as a dark matter candidate using atomic hyperfine frequency comparisons

We use six years of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant, and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.

gr-qc↗

arXiv2015

Atomic fountains and optical clocks at SYRTE: status and perspectives

In this article, we report on the work done with the LNE-SYRTE atomic clock ensemble during the last 10 years. We cover progress made in atomic fountains and in their application to timekeeping. We also cover the development of optical lattice clocks based on strontium and on mercury. We report on tests of fundamental physical laws made with these highly accurate atomic clocks. We also report on work relevant to a future possible redefinition of the SI second.

physics.atom-ph↗

arXiv2013

Experimenting an optical second with strontium lattice clocks

Progress in realizing the SI second had multiple technological impacts and enabled to further constraint theoretical models in fundamental physics. Caesium microwave fountains, realizing best the second according to its current definition with a relative uncertainty of 2-4x10^(-16), have already been superseded by atomic clocks referenced to an optical transition, both more stable and more accurate. Are we ready for a new definition of the second? Here we present an important step in this direction: our system of five clocks connects with an unprecedented consistency the optical and the microwave worlds. For the first time, two state-of-the-art strontium optical lattice clocks are proven to agree within their accuracy budget, with a total uncertainty of 1.6x10^(-16). Their comparison with three independent caesium fountains shows a degree of reproducibility henceforth solely limited at the level of 3.1x10^(-16) by the best realizations of the microwave-defined second.

physics.atom-ph↗

arXiv2013

Testing local position and fundamental constant invariance due to periodic gravitation and boost using long-term comparison of the SYRTE atomic fountains and H-masers

The frequencies of three separate Cs fountain clocks and one Rb fountain clock have been compared to various hydrogen masers to search for periodic changes correlated with the changing solar gravitational potential at the Earth and boost with respect to the Cosmic Microwave Background (CMB) rest frame. The data sets span over more than eight years. The main sources of long-term noise in such experiments are the offsets and linear drifts associated with the various H-masers. The drift can vary from nearly immeasurable to as high as 1.3*10^-15 per day. To circumvent these effects we apply a numerical derivative to the data, which significantly reduces the standard error when searching for periodic signals. We determine a standard error for the putative Local Position Invariance (LPI) coefficient with respect to gravity for a Cs-Fountain H-maser comparison of 4.8*10^-6 and 10^-5 for a Rb-Fountain H-maser comparison. From the same data the putative boost LPI coefficients were measured to a precision of up to parts in 10^11 with respect to the CMB rest frame. By combining these boost invariance experiments to a Cryogenic Sapphire Oscillator versus H-maser comparison, independent limits on all nine coefficients of the boost violation vector with respect to fundamental constant invariance (fine structure constant, electron mass and quark mass respectively), were determined to a precision of parts up to 10^10.

gr-qc↗

arXiv2013

Demonstration of a Dual Alkali Rb/Cs Atomic Fountain Clock

We report the operation of a dual Rb/Cs atomic fountain clock. 133Cs and 87Rb atoms are cooled, launched, and detected simultaneously in LNE-SYRTE's FO2 double fountain. The dual clock operation occurs with no degradation of either the stability or the accuracy. We describe the key features for achieving such a simultaneous operation. We also report on the results of the first Rb/Cs frequency measurement campaign performed with FO2 in this dual atom clock configuration, including a new determination of the absolute 87Rb hyperfine frequency.

physics.atom-ph↗

arXiv2012

A neutral atom frequency reference in the deep UV with 10^(-15) range uncertainty

We present an assessment of the (6s^{2})1S0 -> (6s7s)3P0 clock transition frequency in 199Hg with an uncertainty reduction of nearly three orders of magnitude and demonstrate an atomic quality factor, Q, of ~10^(14). The 199Hg atoms are confined in a vertical lattice trap with light at the newly determined magic wavelength of 362.5697 +/-0.0011 nm and at a lattice depth of 20Er. The atoms are loaded from a single stage magneto-optical trap with cooling light at 253.7 nm. The high Q factor is obtained with an 80 ms Rabi pulse at 265.6 nm. The frequency of the clock transition is found to be 1 128 575 290 808 162.0 +/-6.4 (sys.) +/-0.3 (stat.) Hz (fractional uncertainty = 5.7x10^(-15)). Neither an atom number nor second order Zeeman dependence have yet to be detected. Only three laser wavelengths are used for the cooling, lattice trapping, probing and detection.

physics.atom-ph↗

arXiv2005

Measurement of the parity violating 6S-7S transition amplitude in cesium achieved within 2 \times 10^{-13} atomic-unit accuracy by stimulated-emission detection

We exploit the process of asymmetry amplification by stimulated emission which provides an original method for parity violation (PV) measurements in a highly forbidden atomic transition. The method involves measurements of a chiral, transient, optical gain of a cesium vapor on the 7S-6P_{3/2} transition, probed after it is excited by an intense, linearly polarized, collinear laser, tuned to resonance for one hyperfine line of the forbidden 6S-7S transition in a longitudinal electric field. We report here a 3.5 fold increase, of the one-second-measurement sensitivity, and subsequent reduction by a factor of 3.5 of the statistical accuracy compared with our previous result [J. Guéna et al., Phys. Rev. Lett. 90, 143001 (2003)]. Decisive improvements to the set-up include an increased repetition rate, better extinction of the probe beam at the end of the probe pulse and, for the first time to our knowledge, the following: a polarization-tilt magnifier, quasi-suppression of beam reflections at the cell windows, and a Cs cell with electrically conductive windows. We also present real-time tests of systematic effects, consistency checks on the data, as well as a 1% accurate measurement of the electric field seen by the atoms, from atomic signals. PV measurements performed in seven different vapor cells agree within the statistical error. Our present result is compatible with the more precise Boulder result within our present relative statistical accuracy of 2.6%, corresponding to a 2 \times 10^{-13} atomic-unit uncertainty in E_1^{pv}. Theoretical motivations for further measurements are emphasized and we give a brief overview of a recent proposal that would allow the uncertainty to be reduced to the 0.1% level by creating conditions where asymmetry amplification is much greater.

physics.atom-ph↗

arXiv2004

Proposal for high-precision Atomic Parity Violation measurements using amplification of the asymmetry by stimulated emission in a transverse E and B field pump-probe experiment

Amplification by stimulated emission of radiation provides an intriguing means for increasing the sensitivity of Atomic Parity Violation (APV) measurements in a pump-probe configuration well adapted to the 6S-7S cesium transition. It takes advantage of the large number of atoms excited along the path of the pump beam. In the longitudinal E-field configuration currently exploited in an ongoing APV measurement, this number is limited only by the total voltage sustainable by the Cs vapor. In order to overcome this limit, we consider, both theoretically and experimentally, the possibility of performing the measurements in a transverse E-field configuration requiring a much lower voltage. We discuss the necessarily different nature of the observable and the magnetoelectric optical effects entering into play. They condition modifications of the experimental configuration with, in particular, the application of a transverse magnetic field. We suggest the possibility of rotating the transverse direction of the fields so as to suppress systematic effects. With a long interaction length, a precision reaching 0.1 percent in a quantum noise limited measurement can be expected, now limited only by the necessity of operating below the threshold of spontaneous superradiant emission of the excited medium. If we approached this limit, however, we could greatly amplify the asymmetry using triggered superradiance.

physics.atom-ph↗

arXiv2003

Cylindrical Symmetry Discrimination of Magnetoelectric Optical Systematic Effects in a Pump-probe Atomic Parity Violation Experiment

A pump-probe atomic parity violation (APV) experiment performed in a longitudinal electric field, provides a signal breaking mirror symmetry while preserving the cylindrical symmetry of the set-up. The excited vapor acts on the probe beam as a linear dichroic amplifier, imprinting a very specific signature on the detected signal. Our differential polarimeter is oriented to yield a null result unless the excited atoms are endowed with a chirality of some kind. Ideally, only the APV (E-odd) and the calibration (E-even) signals contribute to a chiral atomic response, a situation highly favourable to the detection of a tiny effect. In the present work we give a thorough analysis of possible unwanted defects like stray transverse fields or misalignments which would spoil the ideal set-up and lead to chiral systematics. A possible way to suppress such effects is to perform global rotations of the experiment by incremental steps of 45 degrees, leaving both stray fields and misalignments unaltered. The conspiration of at least two defects is necessary to affect the E-odd polarimeter signal. The transverse nature of the defects manifests itself by an azimuthal cosine square modulation. The harmful systematics are those which survive the averaging over four successive configurations. They require the presence of a stray transverse electric field, which can be determined and eventually minimized by auxiliary measurements of the systematic effects, amplified by applying a known external magnetic field. Transverse stray magnetic fields must be compensated by a similar procedure. We also propose statistical correlation tests as diagnoses of the aforementioned systematic effects.

physics.atom-ph↗

arXiv2003

Prospects for Forbidden-Transition Spectroscopy and Parity Violation Measurements using a Beam of Cold Stable or Radioactive Atoms

Laser cooling and trapping offers the possibility of confining a sample of radioactive atoms in free space. Here, we address the question of how best to take advantage of cold atom properties to perform the observation of as highly forbidden a line as the 6S-7S Cs transition for achieving, in the longer term, Atomic Parity Violation measurements in radioactive alkali isotopes. Another point at issue is whether one might do better with stable, cold atoms than with thermal atoms. To compensate for the large drawback of the small number of atoms available in a trap, one must take advantage of their low velocity. To lengthen the time of interaction with the excitation laser, we suggest choosing a geometry where the laser beam exciting the transition is colinear to a slow, cold atomic beam, either extracted from a trap or prepared by Zeeman slowing. We also suggest a new observable physical quantity manifesting APV, which presents several advantages:specificity, efficiency of detection, possibility of direct calibration by a parity conserving quantity of a similar nature. It is well adapted to a configuration where the cold atomic beam passes through two regions of transverse, crossed electric fields, leading both to differential measurements and to strong reduction of the contributions from the M_1-Stark interference signals, potential sources of systematics in APV measurements. Our evaluation of signal to noise ratios shows that with available techniques, measurements of transition amplitudes, important as required tests of Atomic Theory should be possible in cesium 133 with a statistical precision of 1/1000 and probably also in Fr isotopes for production rates of 10^6 Fr atoms/s.

physics.atom-ph↗

arXiv2002

A new Manifestation of Atomic Parity Violation in Cesium: a Chiral Optical Gain induced by linearly polarized 6S-7S Excitation

We have detected, by using stimulated emission, an Atomic Parity Violation (APV) in the form of a chiral optical gain of a cesium vapor on the 7S - 6P$_{3/2}$ transition,consecutive to linearly polarized 6S-7S excitation. We demonstrate the validity of this detection method of APV, by presenting a 9% accurate measurement of expected sign and magnitude. We underline several advantages of this entirely new approach in which the cylindrical symmetry of the set-up can be fully exploited. Future measurements at the percent level will provide an important cross-check of an existing more precise result obtained by a different method.

physics.atom-ph↗