Testing Lorentz Invariance using Zeeman Transitions in Atomic Fountains

Lorentz Invariance (LI) is the founding postulate of Einstein's 1905 theory of relativity, and therefore at the heart of all accepted theories of physics. It characterizes the invariance of the laws of physics in inertial frames under changes of velocity or orientation. This central role, and indications from unification theories hinting toward a possible LI violation, have motivated tremendous experimental efforts to test LI. A comprehensive theoretical framework to describe violations of LI has been developed over the last decade: the Lorentz violating Standard Model Extension (SME). It allows a characterization of LI violations in all fields of present day physics using a large (but finite) set of parameters which are all zero when LI is satisfied. All classical tests (e.g. Michelson-Morley or Kennedy-Thorndike experiments) can be analyzed in the SME, but it also allows the conception of new types of experiments, not thought of previously. We have carried out such a conceptually new LI test, by comparing particular atomic transitions (particular orientations of the involved nuclear spins) in the $^{133}$Cs atom using a cold atomic fountain clock. This allows us to test LI in a previously largely unexplored region of the SME parameter space, corresponding to first measurements of four proton parameters and an improvement by 11 and 12 orders of magnitude on the determination of four others. In spite of the attained accuracies, and of having extended the search into a new region of the SME, we still find no indication of LI violation.Comment: 5 pages, in proceedings of the IEEE-FCS, (2005). New version with typo in Tab. III correcte

Horloges atomiques et applications

Maste

Towards an optical lattice clock based on neutral mercury

We are investigating the possibilities of using neutral mercury as a new species to realize a highly accurate atomic clock using the non-perturbing dipole lattice trapping scheme. Typically, accuracy below 10-17 is targeted, which would make neutral mercury an interesting candidate for a redefinition of the SI second. This paper presents our on-going work towards the realization of an optical lattice clock using neutral mercury. We will describe a 254 nm laser source delivering several hundreds of milliWatts at this wavelength with a suitably low frequency noise for laser cooling and magneto-optic trapping. We will describe our vacuum system for magneto-optic trap and report on the status of our work regarding magneto-optic trapping of mercury. We will also describe our clock laser at 266 nm.Institut Francilien de Recherche sur les Atomes Froids (IFRAF)Centre National d'Études Spatiales (CNES

High Resolution Frequency Standard Dissemination via Optical Fibre Metropolitan Network

We present in this paper results on a new dissemination system of ultra-stable reference signal at 100 MHz on a standard fibre network. The 100 MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solution suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100 km, with a relative frequency resolution of 10-14 at one second integration time and 10-17 for one day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks

Accuracy Evaluation of an Optical Lattice Clock with Bosonic Atoms

We report the first accuracy evaluation of an optical lattice clock based on the 1S0 - 3P0 transition of an alkaline earth boson, namely 88Sr atoms. This transition has been enabled using a static coupling magnetic field. The clock frequency is determined to be 429 228 066 418 009(32) Hz. The isotopic shift between 87Sr and 88Sr is 62 188 135 Hz with fractional uncertainty 5.10^{-7}. We discuss the conditions necessary to reach a clock accuracy of 10^{-17} or less using this scheme.Comment: 3 pages, 4 figures, uses ol.sty fil

Delivery of High-Stability Optical and Microwave Frequency Standards over an Optical Fiber Network

Optical and radio frequency standards located in JILA and National Institute of Standards and Technology (NIST) laboratories have been connected through a 3.45-km optical fiber link. An optical frequency standard based on an iodine-stabilized Nd:YAG laser at 1064 nm (with an instability of ∼4×10−14 at 1 s) has been transferred from JILA to NIST and simultaneously measured in both laboratories. In parallel, a hydrogen maser-based radio frequency standard (with an instability of ∼2.4×10−13 at 1 s) is transferred from NIST to JILA. Comparison between these frequency standards is made possible by the use of femtosecond frequency combs in both laboratories. The degradation of the optical and rf standards that are due to the instability in the transmission channel has been measured. Active noise cancellation is demonstrated to improve the transfer stability of the fiber link

L'unité de temps : directions actuelles et futures

International audienceSome 50 years ago, physicists, and after them the entire world, started to found their time reference on atomic properties instead of motions of the Earth that have been in use since the origin. Far from being an arrival point, this decision marked the beginning of an adventure characterized by an improvement by 6 orders of magnitude in the uncertainty of realization of atomic frequency and time references. Ever-progressing atomic frequency standards and time references derived from them are key resources for science and for society. We will describe how the unit of time is realized with a fractional accuracy approaching and how it is delivered to users via the elaboration of the international atomic time. We will describe the tremendous progress of optical frequency metrology over the last 20 years that led to a novel generation of optical frequency standards with fractional uncertainties of . We will describe work toward a possible redefinition of the SI second based on such standards. We will describe existing and emerging applications of atomic frequency standards in science.Il y a une cinquantaine d'années, les physiciens, et après eux le monde entier, ont commencé à fonder leur référence temporelle sur les propriétés atomiques au lieu des mouvements de la Terre, qui étaient utilisés depuis l'origine. Loin d'être un point d'arrivée, cette décision a marqué le début d'une aventure caractérisée par une amélioration par six ordres de grandeur de l'incertitude de la réalisation des références atomiques de fréquence et de temps. Les étalons de fréquence atomique en constante progression et les références de temps qui en découlent sont des ressources essentielles pour la science et pour la société. Nous décrirons comment l'unité de temps est réalisée avec une précision relative approchant et comment elle est mise à la disposition des utilisateurs via l'élaboration du temps atomique international. Nous montrerons les progrès considérables de la métrologie des fréquences optiques au cours des vingt dernières années, qui ont conduit à une nouvelle génération d'étalons de fréquence optique avec des incertitudes relatives de . Nous décrirons les travaux en vue d'une éventuelle redéfinition de la seconde du SI basée sur ces étalons. Nous décrirons les applications scientifiques existantes et émergentes des étalons atomiques de fréquence

Prototype of an ultra-stable optic cavity for space applications

We report the main features and performances of a prototype of an ultra-stable cavity designed and realized by industry for space applications with the aim of space missions. The cavity is a 100 mm long cylinder rigidly held at its midplane by a engineered mechanical interface providing an efficient decoupling from thermal and vibration perturbations. Intensive finite element modeling was performed in order to optimize thermal and vibration sensitivities while getting a high fundamental resonance frequency. The system was designed to be transportable, acceleration tolerant (up to several g) and temperature range compliant [−33◦C;73◦C]. Thermal isolation is ensured by gold coated Aluminum shields inside a stainless steel enclosure for vacuum. The axial vibration sensitivity was evaluated at(4±0.5)×10 −11/(m.s−2), while the transverse one is <1×10−11/(m.s−2). The fractional frequency instability is 1×10−15 from 0.1 to a few seconds and reaches 5−6×10−16at 1s

Design and Control of Femtosecond Lasers for Optical Clocks and the Synthesis of Low-Noise Optical and Microwave Signals

This paper describes recent advances in the design and control of femtosecond laser combs for their use in optical clocks and in the synthesis of low-noise microwave and optical signals. The authors present a compact and technically simple femtosecond laser that directly emits a broad continuum and shows that it can operate continuously on the timescale of days as the phase-coherent "clockwork" of an optical clock. They further demonstrate phase locking of an octave-spanning frequency comb to an optical frequency standard at the millihertz level. As verified through heterodyne measurements with an independent optical frequency standard, this provides a network of narrow optical modes with linewidths at the level of ~ 150 Hz, presently limited by measurement noise. Finally, they summarize their progress in using the femtosecond laser comb to transfer the stability and low phase-noise optical oscillators to the microwave domain