PeopleofSuperintelligence

Researcher

Kunihiko Sadakane

Also known as 定兼 邦彦

Kunihiko Sadakane is a computer scientist at the University of Tokyo who builds algorithms and data structures for compressing, indexing and searching very large data. After finishing doctoral studies at Tokyo in 2000, they held posts at Tohoku University, Kyushu University and the National Institute of Informatics before returning to Tokyo as a professor in 2014. Among their works are the 1999 Larsson–Sadakane algorithm behind qsufsort, a 2009 arXiv paper with Gonzalo Navarro on succinct trees, and a 2018 textbook on succinct data structures; the JSPS Prize in fiscal 2015, the Okawa Publications Prize in fiscal 2019 and the MEXT Award for Science and Technology in fiscal 2021 followed. A research project that ran from 2021 to 2025 and a 2025 ACNS paper on oblivious suffix sorting extend the same ideas to secure multi-party computation, with federated learning in bioinformatics among the motivating settings. Sadakane is a professor in the Department of Mathematical Informatics at the University of Tokyo's Graduate School of Information Science and Technology.

Badges

Timeline

  1. 1995–2000

    Degrees at the University of Tokyo

    Sadakane graduates from the Department of Information Science in the Faculty of Science at the University of Tokyo in 1995. They complete the doctoral course in information science at the university's Graduate School of Science in 2000.

  2. 1999

    The qsufsort suffix-sorting algorithm

    The Larsson–Sadakane algorithm of 1999, written with N. Jesper Larsson, becomes the basis of qsufsort, a commonly used routine for building suffix arrays in open-source software.

  3. 2000–2009

    Tohoku and Kyushu University posts

    In April 2000, they start as an assistant at the Graduate School of Information Sciences of Tohoku University. In April 2003, they move to Kyushu University as an associate professor at the Graduate School of Information Science and Electrical Engineering.

  4. 2009–2014

    From NII to the University of Tokyo

    They become an associate professor at the National Institute of Informatics in April 2009 and a professor there in March 2014. With Gonzalo Navarro, they propose the range min-max tree for succinct ordinal trees in an arXiv paper of May 2009. In April 2014, they join the University of Tokyo as a professor in the Department of Mathematical Informatics.

  5. 2015–2021

    JSPS, Okawa and MEXT prizes

    The JSPS Prize comes in fiscal 2015, the Okawa Publications Prize from the Okawa Foundation for Information and Telecommunications in fiscal 2019, and the MEXT Award for Science and Technology in fiscal 2021.

  6. 2018

    A textbook on succinct data structures

    Kyoritsu Shuppan publishes Sadakane's 230-page Japanese textbook Kanketsu-Data Kozo (Succinct Data Structures) in February 2018, as volume 8 of its Algorithm Science Series. The book covers bit vectors, the wavelet tree and the Burrows–Wheeler transform, structures that let searches run on compressed data.

  7. 2021–2025

    Compressed secure computation

    A Grant-in-Aid for Scientific Research (S) project, Big Data Processing with Compressed Secure Computation, runs from 2021 to 2025 with Sadakane as principal investigator. At ACNS 2025 in Munich, in June 2025, they and four coauthors present Oblivious Suffix Sorting, a multi-party computation scheme that cuts the communication for building suffix arrays and FM-indexes from O(n²) to O(n log² n) and targets private string search, for example in federated learning applications in bioinformatics.

  8. As of October 2026

    Professor at the University of Tokyo

    As of October 2026, they are a professor in the Department of Mathematical Informatics at the University of Tokyo's Graduate School of Information Science and Technology. Their Discrete Informatics Laboratory studies succinct data structures that process compressed big data without decompression, with applications such as genome informatics and geographical information systems.

Career

  1. Since 2014University of TokyoProfessor
  2. 2009–2014Research Organization of Information and SystemsAssociate Professor, Professor
  3. 2003–2009Kyushu UniversityAssociate Professor
  4. 2000–2003Tohoku UniversityAssistant

Education

  1. 2000University of TokyoPhD
  2. 1995University of Tokyo

From the biography.

  1. People shaping AI work at a median of 3 organizations over a career: 3 for university starters and institute and lab starters, versus 2 for company startersIncludes University of Tokyo. Across 6,853 people shaping AI with a dated work role, we estimate a median of 3 parent organizations over a career (mean 3.6), comparing role groups, starting sectors and starting decades from the 1950s to 2020–2026.
  2. Universities keep AI researchers for a median of 6 years, compared with 2 years at frontier labsIncludes University of Tokyo. Across 15,811 dated work stays (6,529 people), median role tenure runs from 6 years at universities to 2 years at frontier labs. We compare all five organization types, starting decades from the 1970s to the 2020s, and the organizations that keep people longest.
  3. The Massachusetts Institute of Technology trained or employed 44 of the 187 AI major-prize winners, more than any other universityIncludes University of Tokyo. The Massachusetts Institute of Technology trained or employed 44 of the 187 AI major-prize winners, more than any other university. We compare doctorate and 5+ year employment links, career timing and current workplaces for 187 major-prize and 1,111 best-paper winners.
  4. The United States employs an estimated 48% of people shaping AIIncludes University of Tokyo. We estimate where the people shaping AI work today, how universities, companies and research institutes split across countries, and how country shares have changed since the 1960s.

Colleagues

People named in this biography, and people with dated positions at the same organization in the same years.

Sources and credits

Photo: We have no published photo of Kunihiko Sadakane yet. Send us a free-licensed photo.

  1. 数理2-定兼 | 投稿 | 東京大学工学部計数工学科 keisu.t.u-tokyo.ac.jp. Checked 21 October 2026.
  2. Suffix array - Wikipedia en.wikipedia.org. Checked 21 October 2026.
  3. KAKEN — Researchers | SADAKANE Kunihiko (20323090) nrid.nii.ac.jp. Checked 21 October 2026.
  4. [0905.0768] Fully-Functional Static and Dynamic Succinct Trees arxiv.org. Checked 21 October 2026.
  5. Awards Received | Research | Graduate School of Information Science and Technology, The University of Tokyo i.u-tokyo.ac.jp. Checked 21 October 2026.
  6. UTokyo BiblioPlaza - Kanketsu-Data Kozo u-tokyo.ac.jp. Checked 21 October 2026.
  7. Oblivious Suffix Sorting: A Multi-Party Computation Scheme for Secure and Efficient Suffix Sorting - 東京理科大学 tus.elsevierpure.com. Checked 21 October 2026.
  8. SADAKANE Kunihiko | The University of Tokyo u-tokyo.ac.jp. Checked 21 October 2026.
  9. Discrete Informatics Laboratory (Mathematical Informatics Lab. 2) | Posts | Deptartment of Mathematical Engineering and Information Physics keisu.t.u-tokyo.ac.jp. Checked 21 October 2026.