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RIKEN Center for Advanced Photonics Space-Time Engineering Research Team

Team Leader: Hidetoshi Katori (D.Eng.)

Research Summary

Hidetoshi  Katori(D.Eng.)

Clocks have served as a tool to share time, based on universal periodic phenomena; humankind relied upon the rotation of the earth from antiquity. The radiation from an atom provides us with far more accurate periodicity. The state-of-the-art atomic clocks sense the relativistic space-time curved by gravity, which reveal the difficulty of sharing time with others. Moreover, such clocks may be used to investigate the constancy of fundamental constants, where the foundation of the atomic clocks is anchored.

Optical lattice clocks raised the possibility of ultra-stable and accurate timekeeping by applying the "magic wavelength" protocol on optical lattices. Since the proposal of the scheme in 2001, the optical lattice clocks are being developed by more than 20 groups in the world, and the clocks are surpassing the uncertainty of the current SI second, becoming one of the most promising candidates for the future redefinition of the second.

Our team develops highly precise and transportable optical lattice clocks capable of long time operation by introducing advanced techniques in the field of atomic physics and quantum optics; we thus explore applications of "space-time engineering" that fully utilize the novel time resource provided by such clocks. For example, a transportable ultraprecise atomic clock, which may be taken out into the field, will function as a gravitational potential meter. We experimentally investigate the impact of such relativistic geodesy as a newer role for clocks in the future.

Main Research Fields

  • Interdisciplinary Science & Engineering

Related Research Fields

  • Engineering


  • Quantum electronics
  • Atomic clock
  • Quantum metrology
  • Optical lattice clock
  • Relativistic geodesy

Selected Publications

  • 1. Takamoto, M., Ushijima, I., Ohmae, N., Yahagi, T., Kokado, K., Shinkai, H., and Katori, H.:
    "Test of general relativity by a pair of transportable optical lattice clocks"
    Nat. Photon. 14, 411-415 (2020).
  • 2. Yamaguchi, A., Safronova, M. S., Gibble, K., and Katori, H.:
    "Narrow-line Cooling and Determination of the Magic Wavelength of Cd"
    Phys. Rev. Lett. 123, 113201 (2019).
  • 3. Ushijima, I., Takamoto, M., and Katori, H.:
    "Operational magic intensity for Sr optical lattice clocks"
    Phys. Rev. Lett. 121, 263202 (2018).
  • 4. Akatsuka, T., Takahashi, T., and Katori, H.:
    "Optically guided atom interferometer tuned to magic wavelength"
    Appl. Phys. Exp. 10, 112501 (2017)
  • 5. Ohmae, N., Kuse, N., Fermann, M. E., and Katori, H.:
    "All-polarization-maintaining, single-port Er:fiber comb for high-stability comparison of optical lattice clocks"
    Appl. Phys. Exp. 10, 062503 (2017).
  • 6. Takano T., Takamoto M., Ushijima I., Ohmae N., Akatsuka T., Yamaguchi A., Kuroishi Y., Munekane H., Miyahara B., and Katori H.:
    "Geopotential measurements with synchronously linked optical lattice clocks"
    Nat. Photon. 10, 662 (2016)
  • 7. Nemitz N., Ohkubo T., Takamoto M., Ushijima I., Das M., Ohmae N., and Katori H.:
    "Frequency ratio of Yb and Sr clocks with 5x10-17 uncertainty at 150 seconds averaging time"
    Nat. Photon. 10, 258-261(2016).
  • 8. Yamanaka K., Ohmae N, Ushijima I., Takamoto M, and Katori H.:
    "Frequency Ratio of 199 Hg and 87Sr Optical Lattice Clocks beyond the SI Limit"
    Phys. Rev. Lett. 114, 230801(2015).
  • 9. Katori, H., Ovsiannikov, V. D., Marmo, S. I., and Palchikov, V. G.:
    "Strategies for reducing the light shift in atomic clocks,"
    Phys. Rev. A 91, 052503 (2015).
  • 10. Ushijima I., Takamoto M., Das M., Ohkubo T. and Katori H.:
    "Cryogenic Optical Lattice Clocks"
    Nat. photon. 9, 185-189 (2015).

Recent Research Results

Related Links

Lab Members

Principal investigator

Hidetoshi Katori
Team Leader

Core members

Masao Takamoto
Senior Research Scientist
Atsushi Yamaguchi
Senior Research Scientist
Shinji Ito
Technical Staff II

Contact Information

Cooperation Center, W421
2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Email: hkatori [at] riken.jp