JQI Special Seminar: Kenji Ohmori

Speaker: Kenji Ohmori  (Institute for Molecular Science (IMS), National Institutes of Natural Sciences, Japan / Yaqumo Inc., Japan)

Title: Ultrafast quantum computing with ultracold atom arrays at quantum speed limit

Abstract: Neutral-atom quantum computers use the arrays of ultracold atoms assembled with optical tweezers, in which each single atom serves as a high-quality qubit, whereas the whole system operates at room temperatures. We use rubidium (Rb) atoms as qubits and have various core competences including ultrafast laser technologies that allow for an ultrafast two-qubit gate operating in nanoseconds, faster than any other two-qubit gates with neutral atoms by two orders of magnitude [1]. This has been made possible with two nearby ultracold Rb atoms excited with an ultrashort laser pulse to a Rydberg state far beyond the Rydberg blockade regime [2-5]. We have also been developing underlying technologies that would improve the fidelity of this ultrafast gate, such as a stable gate-operation laser and an automated system for ultraprecise initialization of many qubits [6, 7].

In another direction of our R&D, we are currently developing a full-stack quantum computer with 500 qubits. This would be Japan’s first full-stack quantum computer with neutral-atoms, and one of only a few in the world, scheduled to start its full operation in this year 2025.

References
[1] Y. Chew et al., Nat. Photonics. 16, 724 (2022). (Front Cover Highlight)
[2] N. Takei et al., Nature Commun. 7, 13449 (2016).
Highlighted by Science 354, 1388 (2016); IOP PhyscisWorld.com (2016).
[3] M. Mizoguchi et al., Phys. Rev. Lett. 124, 253201 (2020).
[4] V. Bharti et al., Phys. Rev. Lett. 131, 123201 (2023).
[5] V. Bharti et al., Phys. Rev. Lett. 133, 093405 (2024).
[6] Y. T. Chew et al., Phys. Rev. A 110, 053518 (2024).
[7] T. P. Mahesh et al., Opt. Lett. 50, 403 (2025).

Short bio:
Kenji Ohmori is a Chair Professor at the Institute for Molecular Science (IMS), National Institutes of Natural Sciences, Japan. After receiving his Ph.D. from The University of Tokyo in 1992, he was a Research Associate and an Associate Professor at Tohoku University. In 2003 he was appointed a Full Professor at IMS. Professor Ohmori is currently leading large-scale / long-term national projects on the development of ultrafast quantum simulators and quantum computers (2018-2031) generously supported with priority by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) and Cabinet Office of the government of Japan. He has been celebrated with many honors. Highlights include the Japan Academy Medal (2007), Fellow of the American Physical Society (2009), Humboldt Research Award from the government of Germany (2012), Commendation for Science and Technology by the Minister of MEXT (2018), and the National Medal with Purple Ribbon from His Majesty the Emperor of Japan for his achievements on quantum physics (2021). The Medal with Purple Ribbon is awarded for inventions and discoveries in science and technology, and for outstanding achievements in the fields of science, sports, art and culture.  He has served as the Chair of the “Committee for Quantum Science and Technology Policy” of MEXT from 2023-2025, after serving as the Vice Chair from 2015-2022. He is the Co-founder of Japan’s first neutral atom quantum computing startup “Yaqumo Inc.” launched on 1st April 2025.