Hidekazu Hachisu
YOU?
Author Swipe
View article: Incorporation of hydrogen masers into a free ensemble timescale aimed for optically steered UTC(k)
Incorporation of hydrogen masers into a free ensemble timescale aimed for optically steered UTC(k) Open
The combination of a single hydrogen maser and an intermittently operated optical clock can generate a highly accurate timescale, but it is difficult to address a sudden deterioration of the hydrogen maser. This issue can be resolved by th…
View article: Hydrogen maser flywheels for optical clocks
Hydrogen maser flywheels for optical clocks Open
We consider the statistical and systematic uncertainties that arise from using a hydrogen maser as a flywheel oscillator for an intermittently operating optical clock. Diurnal delay variations observed in the distribution and measurement o…
View article: Contributions of the optical lattice clock NICT-Sr1 to TAI calibration and UTC(NICT) steering
Contributions of the optical lattice clock NICT-Sr1 to TAI calibration and UTC(NICT) steering Open
Our efforts with the optical lattice clock NICT-Sr1 are now focused on contribution to both the international and the local timescale. Since 2018, NICT-Sr1 has been recognized as a secondary frequency standard and frequently contributed to…
View article: Geodetic measurements and quantitative evaluation for reduced gravitational redshift uncertainty of NICT optical frequency standards
Geodetic measurements and quantitative evaluation for reduced gravitational redshift uncertainty of NICT optical frequency standards Open
The frequency accuracy of optical atomic clocks has dramatically increased over the past 15 years, improving by more than two orders of magnitude from 16 digits of precision to 18 or even 19 digits of precision. Since around 2015 researche…
View article: A broadband VLBI system using transportable stations for geodesy and metrology: an alternative approach to the VGOS concept
A broadband VLBI system using transportable stations for geodesy and metrology: an alternative approach to the VGOS concept Open
We have developed a broadband VLBI (very long baseline interferometry) system inspired by the concept of the VLBI Global Observing System (VGOS). The new broadband VLBI system was implemented in the Kashima 34 m antenna and in two transpor…
View article: Absolute frequency of <sup>87</sup>Sr at 1.8 × 10<sup>−16</sup> uncertainty by reference to remote primary frequency standards
Absolute frequency of <sup>87</sup>Sr at 1.8 × 10<sup>−16</sup> uncertainty by reference to remote primary frequency standards Open
The optical lattice clock NICT-Sr1 regularly reports calibration measurements of the international timescale TAI. By comparing measurement results to the reports of eight primary frequency standards, we find the absolute frequency of the 8…
View article: Dataset for 'Intercontinental comparison of optical atomic clocks through very long baseline interferometry'
Dataset for 'Intercontinental comparison of optical atomic clocks through very long baseline interferometry' Open
Dataset for the international comparison of optical atomic clocks using Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) precise point positioning solution with integer ambiguity (IPPP) techniques appeared in Na…
View article: Dataset for 'Intercontinental comparison of optical atomic clocks through very long baseline interferometry'
Dataset for 'Intercontinental comparison of optical atomic clocks through very long baseline interferometry' Open
Dataset for the international comparison of optical atomic clocks using Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) precise point positioning solution with integer ambiguity (IPPP) techniques appeared in Na…
View article: Frequency ratio of an <sup>115</sup>In<sup>+</sup> ion clock and a <sup>87</sup>Sr optical lattice clock
Frequency ratio of an <sup>115</sup>In<sup>+</sup> ion clock and a <sup>87</sup>Sr optical lattice clock Open
We report on the first, to the best of our knowledge, frequency ratio measurement of an single-ion clock and a optical lattice clock. A hydrogen maser serves as a flywheel oscillator to measure the ratio by independent optical combs. From …
View article: New bounds on dark matter coupling from a global network of optical atomic clocks
New bounds on dark matter coupling from a global network of optical atomic clocks Open
The first Earth-scale quantum sensor network based on optical atomic clocks is looking for dark matter candidates.
View article: First observation with global network of optical atomic clocks aimed for a dark matter detection
First observation with global network of optical atomic clocks aimed for a dark matter detection Open
We report on the first earth-scale quantum sensor network based on optical atomic clocks aimed at dark matter (DM) detection. Exploiting differences in the susceptibilities to the fine-structure constant of essential parts of an optical at…
View article: Advanced Satellite-Based Frequency Transfer at the 10<sup>−16</sup> Level
Advanced Satellite-Based Frequency Transfer at the 10<sup>−16</sup> Level Open
Advanced satellite-based frequency transfers by two-way carrier-phase (TWCP) and integer precise point positioning have been performed between the National Institute of Information and Communications Technology and Korea Research Institute…
View article: Months-long real-time generation of a time scale based on an optical clock
Months-long real-time generation of a time scale based on an optical clock Open
Time scales consistently provide precise time stamps and time intervals by combining atomic frequency standards with a reliable local oscillator. Optical frequency standards, however, have not been applied to the generation of time scales,…
View article: Advanced Satellite-based Frequency Transfer at the 10^{-16} Level
Advanced Satellite-based Frequency Transfer at the 10^{-16} Level Open
Advanced satellite-based frequency transfers by TWCP and IPPP have been performed between NICT and KRISS. We confirm that the disagreement between them is less than 1x10^{-16} at an averaging time of several days. Additionally, an intercon…
View article: Absolute frequency measurement at 10<sup>-16</sup>level based on the international atomic time
Absolute frequency measurement at 10<sup>-16</sup>level based on the international atomic time Open
Referring to International Atomic Time (TAI), we measured the absolute frequency of the 87Sr lattice clock with its uncertainty of 1.1 x 10-15. Unless an optical clock is continuously operated for the five days of the TAI grid, it is requi…
View article: Rapid evaluation of time scale using an optical clock
Rapid evaluation of time scale using an optical clock Open
Feasibility of steering a time scale using an optical clock is investigated. Since the high stability of optical frequency standards enables rapid evaluation of the scale interval, the requirement for the continuous operation is mitigated.…