I am a senior research scientist at Time Standards Group, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology.
My research interest lies in exploring fundamental physics with AMO techniques, or in more common words, precision measurements. In this field, researches are mainly performed as precision spectroscopies of atomic and molecular systems including ions. Although the energy scale of such spectroscopy is 1 eV, because its precision is extremely high, it can infer physics of billion times or even larger energy scale due to small perturbative mixing of such high-energy effects into the low energy system. Or, the system is sensitive to a faint coupling with hypothetical fields. This opens a way to investigate high-energy particle physics and other kinds of new physics through low-energy systems. Spectroscopy is utilized for various searches oriented to fundamental physics, such as searches for time variation of fundamental constants and dark matter, spectroscopy of atoms involving anti-particles, highly-charged ions, and nuclear clock, and searches for fifth-force search with isotope shift measurements, parity non-conservation in nuclei and electron EDM. Some of these topics are summarized in my review paper.
Currently, we are performing precision spectroscopy of the 431 nm transition in Yb towards searches for time variation of the fine structure constant, ultralight dark matter, and new interactions between an electron and a neutron. We observed the transition and performed an absolute frequency measurement of this transition for the first time in the world with an uncertainty of 8.2 kHz. With the isotope shift data obtained from absolute frequency measurements for multiple isotopes, we obtained the charge radius difference for ytterbium isotopes, and put constraints on the existence of new forces between an electron and a neutron. We are working on improving the uncertainty to <1 Hz level for the state-of-the-art precision spectroscopy and higher sensitivities for the searches for fundamental physics. See more in Current Research and an article for non-physicists.
A graduate student position is available, and we are searching for a postdoc. Please refer to Available Positions, or contact Akio Kawasaki for details.
Latest update: 2025.9.22 The home page is modified.
Contact Information
Tsukuba Central 3
1-1-1 Umezono
Tsukuba-shi, Ibaraki 305-8563, Japan
E-mail address: akio．kawasaki＠aist．go．jp
Obsolete e-mail addresses akiok@mit.edu and akiok@stanford.edu should be replaced with the e-mail address above.
Last update: September 22, 2025