The joint research group of RIKEN, the University of Tokyo, Geospatial Information Authority of Japan, and Osaka Institute of Technology has succeeded for the first time in the world in developing an ultra-high-precision portable optical lattice clock with 18-digit accuracy in collaboration with Shimadzu Corporation.The height of the Tokyo Sky Tree was precisely measured and the general theory of relativity was verified.
According to Einstein's general theory of relativity, the higher the altitude, the faster the clock advances, but with the accuracy of the prior art, it was difficult to measure the difference that the difference in altitude gives to the way the clock advances on the ground.However, by grasping the gravitational field (difference in gravitational potential) using an optical lattice clock and measuring the difference in the way the clock advances according to the altitude, the difference in altitude between two distant points can be measured with high accuracy at the centimeter level. Measurement becomes possible.
The research group has developed a portable strontium optical lattice clock that can achieve 18-digit accuracy (equivalent to a deviation of 1 second in 2 billion years) not only in the laboratory environment but also in the environment outside the laboratory.These two clocks are installed at two locations, the ground floor and the observatory, where there is an altitude difference of about 450 meters in Tokyo Sky Tree, and the difference in the way each clock advances is measured.The results were compared with the elevation difference measured by the Geographical Survey Institute, and a verification experiment of the general theory of relativity was conducted.
As a result, it was measured that the clock on the observatory was ahead of the clock on the ground floor, and the verification was successful with an accuracy approaching that of an experiment using a conventional satellite. Compared to the conventional space experiment that required a height difference of 1 kilometers, the portable optical lattice clock developed this time enables the same experiment with a height difference that is more than 1 times smaller.
Demonstration of high-precision portable optical lattice clocks for outdoor operation will be a major step toward the social implementation of optical lattice clocks.In the future, it is expected that relativistic sensing technology such as monitoring of crustal movements with accuracy of several centimeters due to plate motion and volcanic activity will be put into practical use.
Paper information:[Nature Photonics] Test of General Relativity by a Pair of Transportable Optical Lattice Clocks
