19 research outputs found
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 (Sr), ytterbium (Yb) and mercury (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