arXiv subjects

Kensuke Matsubara

Publications and source records attributed to Kensuke Matsubara.

3 recordsLinked to original sources

arXiv2020

Frequency ratio of an $^{115}$In$^+$ ion clock and a $^{87}$Sr optical lattice clock

We report on the first frequency ratio measurement of an $^{115}$In+ single ion clock and a $^{87}$Sr optical lattice clock. A hydrogen maser serves as a reference oscillator to measure the ratio by independent optical combs. Over more than 90 000 seconds of measurement time, the frequency ratio $f_{\rm{In^+}}/f_{\rm{Sr}}$ is determined to be 2.952 748 749 874 863 4(21) with relative uncertainty of $7.0 \times 10^{-16}$. The measurement creates a new connection in the network of frequency ratios of optical clocks.

physics.atom-ph↗

arXiv2017

Frequency measurement of the clock transition of an indium ion sympathetically-cooled in a linear trap

We report frequency measurement of the clock transition in an 115In+ ion sympathetically-cooled with Ca+ ions in a linear rf trap. The Ca+ ions are used as a probe of the external electromagnetic field and as the coolant for preparing the cold In+. The frequency is determined to be 1 267 402 452 901 049.9 (6.9) Hz by averaging 36 measurements using an optical frequency comb referenced to the frequency standards located in the same site.

physics.atom-ph↗

arXiv2012

Direct comparison of a Ca+ single ion clock against a Sr optical lattice clock

Optical frequency comparison of the 40Ca+ clock transition ν_{Ca} (2S1/2-2D5/2, 729nm) against the 87Sr optical lattice clock transition ν_{Sr}(1S0-3P0, 698nm) has resulted in a frequency ratio ν_{Ca} / ν_{Sr} = 0.957 631 202 358 049 9(2 3). The rapid nature of optical comparison allowed the statistical uncertainty of frequency ratio ν_{Ca} / ν_{Sr} to reach 1x10-15 in only 1000s and yielded a value consistent with that calculated from separate absolute frequency measurements of ν_{Ca} using the International Atomic Time (TAI) link. The total uncertainty of the frequency ratio using optical comparison (free from microwave link uncertainties) is smaller than that obtained using absolute frequency measurement, demonstrating the advantage of optical frequency evaluation. We report the absolute frequency of ^{40}Ca+ with a systematic uncertainty 14 times smaller than our previous measurement [1].

physics.atom-ph↗