Atomic trajectory characterization in a fountain clock based on the spectrum of a hyperfine transition

We describe a new method to determine the position of the atomic cloud during its interaction with the microwave field in the cavity of a fountain clock. The positional information is extracted from the spectrum of the F=3,mF=0 to F=4,mF=-1 hyperfine transition, which shows a position dependent asymmetry when the magnetic C-field is tilted by a few degrees with respect to the cavity axis. Analysis of this spectral asymmetry provides the horizontal center-of-mass position for the ensemble of atoms contributing to frequency measurements. With an uncertainty on the order of 0.1 mm, the obtained information is useful for putting limits on the systematic uncertainty due to distributed cavity phase gradients. The validity of the new method is demonstrated through experimental evidence.Comment: 6 figures, submitted to PR

Decomposed description of Ramsey spectra under atomic interactions

We introduce a description of Ramsey spectra under atomic interactions as a sum of decomposed components with differing dependence on interaction parameters. This description enables intuitive understanding of the loss of contrast and asymmetry of Ramsey spectra. We derive a quantitative relationship between the asymmetry and atomic interaction parameters, which enables their characterization without changing atom density. The model is confirmed through experiments with a Yb optical lattice clock

Modeling light shifts in optical lattice clocks

We present an extended model for the lattice-induced light shifts of the clock frequency in optical lattice clocks, applicable to a wide range of operating conditions. The model extensions cover radial motional states with sufficient energies to invalidate the harmonic approximation of the confining potential. We reevaluate lattice-induced light shifts in our Yb optical lattice clock with an uncertainty of 6.1E-18 under typical clock operating conditions.Comment: 12 pages, 10 figure

Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications

This article describes the recent progress of optical lattice clocks with neutral strontium ($^{87}$Sr), ytterbium ($^{171}$Yb) and mercury ($^{199}$Hg) atoms. In particular, we present frequency comparison between the clocks locally via an optical frequency comb and between two Sr clocks at remote sites using a phase-stabilized fibre link. We first review cryogenic Sr optical lattice clocks that reduce the room-temperature blackbody radiation shift by two orders of magnitude and serve as a reference in the following clock comparisons. Similar physical properties of Sr and Yb atoms, such as transition wavelengths and vapour pressure, have allowed our development of a compatible clock for both species. A cryogenic Yb clock is evaluated by referencing a Sr clock. We also report on a Hg clock, which shows one order of magnitude less sensitivity to blackbody radiation, while its large nuclear charge makes the clock sensitive to the variation of fine-structure constant. Connecting all three types of clocks by an optical frequency comb, the ratios of the clock frequencies are determined with uncertainties smaller than possible through absolute frequency measurements. Finally, we describe a synchronous frequency comparison between two Sr-based remote clocks over a distance of 15 km between RIKEN and the University of Tokyo, as a step towards relativistic geodesy.Comment: 11 pages, 5 figures, invited review article in Comptes Rendus de Physique 201

Frequency ratio of Yb and Sr clocks with 5 × 10−17 uncertainty at 150 seconds averaging time

Transition frequencies of atoms and ions are among the most accurately accessible quantities in nature, playing important roles in pushing the frontiers of science by testing fundamental laws of physics, in addition to a wide range of applications such as satellite navigation systems. Atomic clocks based on optical transitions approach uncertainties of 10−18 (refs 1–3), where full frequency descriptions are far beyond the reach of the SI second. Direct measurements of the frequency ratios of such super clocks, on the other hand, are not subject to this limitation4, 5, 6, 7, 8. They can verify consistency and overall accuracy for an ensemble of super clocks, an essential step towards a redefinition of the second9. Here we report a measurement that finds the frequency ratio of neutral ytterbium and strontium clocks to be ℛ = 1.207507039343337749(55), with a fractional uncertainty of 4.6 × 10−17 and a measurement instability as low as 4 × 10−16 (τ/s)−1/2.UTokyo Research掲載「異なる原子の光格子時計の短時間精密比較に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/rapid-comparison-of-optical-lattice-clocks.htmlUTokyo Research "Rapid comparison of optical lattice clocks" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/rapid-comparison-of-optical-lattice-clocks.htm

Frequency ratio of Yb and Sr clocks with 5 × 10−17 uncertainty at 150 seconds averaging time

Transition frequencies of atoms and ions are among the most accurately accessible quantities in nature, playing important roles in pushing the frontiers of science by testing fundamental laws of physics, in addition to a wide range of applications such as satellite navigation systems. Atomic clocks based on optical transitions approach uncertainties of 10−18 (refs 1–3), where full frequency descriptions are far beyond the reach of the SI second. Direct measurements of the frequency ratios of such super clocks, on the other hand, are not subject to this limitation4, 5, 6, 7, 8. They can verify consistency and overall accuracy for an ensemble of super clocks, an essential step towards a redefinition of the second9. Here we report a measurement that finds the frequency ratio of neutral ytterbium and strontium clocks to be ℛ = 1.207507039343337749(55), with a fractional uncertainty of 4.6 × 10−17 and a measurement instability as low as 4 × 10−16 (τ/s)−1/2.UTokyo Research掲載「異なる原子の光格子時計の短時間精密比較に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/rapid-comparison-of-optical-lattice-clocks.htmlUTokyo Research "Rapid comparison of optical lattice clocks" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/rapid-comparison-of-optical-lattice-clocks.htm