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URSI General Assembly and Scientific Symposium

Improved measurement of the40Ca+clock transition frequency towards an uncertainty of 10−15level

Kensuke Matsubara, Kazuhiro Hayasaka, Ying Li, Shigeo Nagano, Hiroyuki Ito, Reiko Kojima, Masatoshi Kajita, Yuko Hanado, Yasuhiro Koyama, Mizuhiko Hosokawa

Published Aug 1, 2011• 0 citations
Publisher

Abstract

We report improved frequency measurement of a single40Ca+optical clock towards the 10-15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by the magnetic field fluctuation, the use of a magnetic shield significantly reduced the observed linewidth of its2S1/2-2D5/2clock transition. From frequency comparison between the40Ca+clock and an87Sr lattice clock, an Allan deviation of 7 × 10-16at an averaging time of one thousand seconds was measured. We now measure the absolute frequency of the40Ca+clock transition with respect to the SI definition of the second.

DOI
10.1109/ursigass.2011.6050324

Related papers

Improvement in accuracy of a single40Ca+optical clock towards the 10−15level using a magnetic shield

Kensuke Matsubara, Ying Li, Shigeo Nagano +6 more

We report a frequency measurement of a single40Ca+optical clock towards the 10−15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by line broadening due to the magnetic field fluctuation, the use of a magnetic shield significantly reduced the spectrum linewidth of the clock transition. By a frequency comparison to an87Sr lattice clock, an Allan deviation of 7 × 10−16was observed at an averaging time of 103seconds. We preliminarily measured the clock transition frequency to be 411 042 129 776 397 (3) Hz with respect to the SI definition of the second. Further measurements are executed aiming at an accuracy of low parts in the 10−15level.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•May 1, 2011•0 citations

Frequency measurement of the40Ca+clock transition using a LD-based clock laser and UTC(NICT)

K. Matsubara, Y. Li, Shigeo Nagano +6 more

We developed an optical frequency standard with the 4 2S1/2-3 2D5/2 electric quadrupole transition of 40Ca+ ions. Its absolute transition frequency is 411 042 129 776 390(±7) Hz. The accuracy is limited by the electric quadrupole shift and the ambient magnetic field fluctuation. To determine the absolute transition frequency with a better accuracy, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency corrected for the electric quadrupole shift. In addition, we are developing a magnetic-shielded ion-trap chamber to suppress the transition-line broadening caused by the magnetic field fluctuation.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Aug 20, 2009•0 citations

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We developed an optical frequency standard using40Ca+with the 42S1/2-32D5/2electric quadrupole transition. Its absolute transition frequency is 411 042 129 776 390(7) Hz. The uncertainty is limited by the electric quadrupole shift and ambient magnetic field fluctuation. To determine the absolute transition frequency with a better uncertainty, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency which is corrected for the electric quadrupole shift. It will be used to determine the absolute transition frequency with respect to the SI base units of time and length. In addition, we are developing a magnetic-shielded ion-trap chamber to reduce the transition-line broadening caused by the magnetic field fluctuation.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Apr 1, 2009•2 citations

Hertz-level measurement of the 40 Ca + 4s 2S1/2 – 3d 2D5/2 clock transition frequency with respect to the SI second through the Global Positioning System

Yao Huang, Jian Zhong Cao, P. Liu +6 more

We have measured the absolute frequency of a clock transition at the 10${}^{\ensuremath{-}15}$ level with a single, trapped, laser-cooled ${}^{40}$Ca${}^{+}$ ion in a miniature Paul trap. In our measurement, an optical frequency comb is referenced to a hydrogen maser, which is calibrated to the SI second through the Global Positioning System (GPS). By analyzing the experimental data obtained within 32 days of a total averaging time $>$2 $\ifmmode\times\else\texttimes\fi{}$ 10${}^{6}$ s, the absolute frequency of the ${}^{40}$Ca${}^{+}$ 4$s$ ${}^{2}\phantom{\rule{-0.16em}{0ex}}{S}_{1/2}$--3$d$ ${}^{2}\phantom{\rule{-0.16em}{0ex}}{D}_{5/2}$ clock transition is measured as 411 042 129 776 393.0 (1.6) Hz with a fractional uncertainty of 3.9 $\ifmmode\times\else\texttimes\fi{}$ 10${}^{\ensuremath{-}15}$.

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Absolute frequency measurement of the $^{40}$Ca$^{+}$ clock transition using a GNSS link to the SI second

M. Guevara-Bertsch, M. K. Joshi, M. I Hussain +2 more

We report the absolute frequency measurement of the $4s$ $ ^{2}S_{1/2}\leftrightarrow 3d$ $^{2}D_{5/2}$ $^{40}$Ca$^{+}$ clock transition with respect to the SI second. To perform this measurement, a link between our laboratory in Innsbruck and the clocks realizing the Coordinated Universal Time at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig was installed and characterized using the Global Navigation Satellite System GNSS. The comparison between our clock and the ones at PTB was done using the Precise Point Positioning technique. After the evaluation of the systematic shifts, the measured transition frequency is 411 042 129 776 401.2$\pm$0.6 Hz with a fractional uncertainty of 1.5 $\times$ 10$^{-15}$. The stability of the clock measurements was also corroborated by comparing two different calcium ion clock experiments, which share the clock laser source at our institute. Furthermore, after careful evaluation of the trap-drive induced ac magnetic fields, we estimate ac Zeeman shifts on the $D_{5/2}$ sublevels and reevaluate the Landé g-factor of the $3d$ $^{2}D_{5/2}$ level to be g$_{5/2}= 1.200329(1)$.

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Progress towards a 40Ca+ optical clock with a fractional uncertainty at the 10−18 level

Yao Huang, Hua Guan, Kelin Gao

We recently reported a 5×10-17level frequency comparison of two40Ca+optical clocks, one of which has fractional frequency uncertainty of 3.4×10-17, limited by the BBR effect. Here we present progress towards a40Ca+optical clock with uncertainty at the 10-18level. The differential static scalar polarizability Δα0 of the40Ca+ion clock transition is obtained by precisely measuring the “magic” rf drive frequency. Δα0 is measured as -7.2653(44)x10-40J m2/V2, the blackbody radiation shift is then calculated to be 0.3790(2) Hz at 300 K. The contribution of the blackbody shift coefficient to the uncertainty of the optical clock at room temperature is reduced to 5.6×10-19, the excess micromotion induced clock uncertainty is also reduced to the 10-19level by choosing the appropriate trap drive frequency. With a suppression of the BBR field temperature uncertainty to the sub-Kelvin level and improved clock stability, a robust, relatively low-cost40Ca+ion clock with uncertainty at 10-18level can be made.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jul 1, 2017•0 citations
We report improved frequency measurement of a single40Ca+optical clock towards the 10-15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by the magnetic field fluctuation, the use of a magnetic shield significantly reduced the observed linewidth of its2S1/2-2D5/2clock transition. From frequency comparison between the40Ca+clock and an87Sr lattice clock, an Allan deviation of 7 × 10-16at an averaging time of one thousand seconds was measured. We now measure the absolute frequency of the40Ca+clock transition with respect to the SI definition of the second.
We report a frequency measurement of a single40Ca+optical clock towards the 10−15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by line broadening due to the magnetic field fluctuation, the use of a magnetic shield significantly reduced the spectrum linewidth of the clock transition. By a frequency comparison to an87Sr lattice clock, an Allan deviation of 7 × 10−16was observed at an averaging time of 103seconds. We preliminarily measured the clock transition frequency to be 411 042 129 776 397 (3) Hz with respect to the SI definition of the second. Further measurements are executed aiming at an accuracy of low parts in the 10−15level.
We developed an optical frequency standard with the 4 2S1/2-3 2D5/2 electric quadrupole transition of 40Ca+ ions. Its absolute transition frequency is 411 042 129 776 390(±7) Hz. The accuracy is limited by the electric quadrupole shift and the ambient magnetic field fluctuation. To determine the absolute transition frequency with a better accuracy, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency corrected for the electric quadrupole shift. In addition, we are developing a magnetic-shielded ion-trap chamber to suppress the transition-line broadening caused by the magnetic field fluctuation.
We developed an optical frequency standard using40Ca+with the 42S1/2-32D5/2electric quadrupole transition. Its absolute transition frequency is 411 042 129 776 390(7) Hz. The uncertainty is limited by the electric quadrupole shift and ambient magnetic field fluctuation. To determine the absolute transition frequency with a better uncertainty, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency which is corrected for the electric quadrupole shift. It will be used to determine the absolute transition frequency with respect to the SI base units of time and length. In addition, we are developing a magnetic-shielded ion-trap chamber to reduce the transition-line broadening caused by the magnetic field fluctuation.
We have measured the absolute frequency of a clock transition at the 10${}^{\ensuremath{-}15}$ level with a single, trapped, laser-cooled 40{}^{40}40Ca+{}^{+}+ ion in a miniature Paul trap. In our measurement, an optical frequency comb is referenced to a hydrogen maser, which is calibrated to the SI second through the Global Positioning System (GPS). By analyzing the experimental data obtained within 32 days of a total averaging time $>$2 $\ifmmode\times\else\texttimes\fi{}$ 106{}^{6}6 s, the absolute frequency of the 40{}^{40}40Ca+{}^{+}+ 4sss 2S1/2{}^{2}\phantom{\rule{-0.16em}{0ex}}{S}_{1/2}2S1/2​--3ddd 2D5/2{}^{2}\phantom{\rule{-0.16em}{0ex}}{D}_{5/2}2D5/2​ clock transition is measured as 411 042 129 776 393.0 (1.6) Hz with a fractional uncertainty of 3.9 $\ifmmode\times\else\texttimes\fi{}$ 10${}^{\ensuremath{-}15}$.
Absolute frequency measurement of the 40^{40}40Ca+^{+}+ clock transition using a GNSS link to the SI second
We report the absolute frequency measurement of the 4s4s4s $ ^{2}S_{1/2}\leftrightarrow 3d$ 2D5/2^{2}D_{5/2}2D5/2​ 40^{40}40Ca+^{+}+ clock transition with respect to the SI second. To perform this measurement, a link between our laboratory in Innsbruck and the clocks realizing the Coordinated Universal Time at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig was installed and characterized using the Global Navigation Satellite System GNSS. The comparison between our clock and the ones at PTB was done using the Precise Point Positioning technique. After the evaluation of the systematic shifts, the measured transition frequency is 411 042 129 776 401.2$\pm$0.6 Hz with a fractional uncertainty of 1.5 ×\times× 10−15^{-15}−15. The stability of the clock measurements was also corroborated by comparing two different calcium ion clock experiments, which share the clock laser source at our institute. Furthermore, after careful evaluation of the trap-drive induced ac magnetic fields, we estimate ac Zeeman shifts on the D5/2D_{5/2}D5/2​ sublevels and reevaluate the Landé g-factor of the 3d3d3d 2D5/2^{2}D_{5/2}2D5/2​ level to be g5/2=1.200329(1)_{5/2}= 1.200329(1)5/2​=1.200329(1).
We recently reported a 5×10-17level frequency comparison of two40Ca+optical clocks, one of which has fractional frequency uncertainty of 3.4×10-17, limited by the BBR effect. Here we present progress towards a40Ca+optical clock with uncertainty at the 10-18level. The differential static scalar polarizability Δα0 of the40Ca+ion clock transition is obtained by precisely measuring the “magic” rf drive frequency. Δα0 is measured as -7.2653(44)x10-40J m2/V2, the blackbody radiation shift is then calculated to be 0.3790(2) Hz at 300 K. The contribution of the blackbody shift coefficient to the uncertainty of the optical clock at room temperature is reduced to 5.6×10-19, the excess micromotion induced clock uncertainty is also reduced to the 10-19level by choosing the appropriate trap drive frequency. With a suppression of the BBR field temperature uncertainty to the sub-Kelvin level and improved clock stability, a robust, relatively low-cost40Ca+ion clock with uncertainty at 10-18level can be made.