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Outline

Clocks have been a tool for sharing time based on universal periodic phenomena; humankind has relied upon the earth's rotation since antiquity. The radiation from an atom provides us with far more accurate periodicity. State-of-the-art atomic clocks sense the relativistic space-time curved by gravity, which reveals the difficulty of sharing time with others. Moreover, such clocks may be used to investigate the constancy of fundamental constants upon which their operation is based.
Optical lattice clocks proposed in 2001 made ultra-stable and accurate clocks possible by applying the "magic wavelength" protocol. Their precision now surpasses the current definition of the SI second, positioning them as strong candidates for its future redefinition.
Our team leverages advanced atomic physics and quantum optics techniques to develop highly precise, compact, and long-term-operable optical lattice clocks. This enables us to explore novel applications of “space-time engineering” that fully use these new time resources. For instance, a transportable optical lattice clock deployed in the field can function as a gravitational potential sensor. Through such experiments, we are investigating the scientific and practical impact of relativistic geodesy—and the new roles that clocks may play in the future.

Fields

Interdisciplinary Science and Engineering, Engineering

Keywords

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

Subjects

1. Exploration of practical applications of optical lattice clocks
2. Development of the next-generation transportable optical lattice clocks
3. Establishment of relativistic geodetic technology

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. Photonics 14, 411-415 (2020).
2. Ushijima, I., Takamoto, M., and Katori, H.: "Operational magic intensity for Sr optical lattice clocks", Phys. Rev. Lett. 121, 263202 (2018).
3. 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. Photonics 10, 662-666 (2016).
4. Yamanaka, K., Ohmae, N., Ushijima, I., Takamoto, M., and Katori, H.: "Frequency ratio of 199Hg and 87Sr optical lattice clocks beyond the SI limit", Phys. Rev. Lett. 114, 230801 (2015).
5. Ushijima, I., Takamoto, M., Das, M., Ohkubo, T., and Katori, H.: "Cryogenic optical lattice clocks", Nat. Photonics 9, 185-189 (2015).

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