About the Workshop

Concepts of Quantum and Spacetime

March 9 — 12, 2026 @ KEK, Tsukuba, Japan.

The two fundamental questions—“What is quantum?” and “What is spacetime?”—are deeply intertwined. On one hand, the formulation and interpretation of quantum theory depend both implicitly and explicitly on our conceptions of time and space. On the other hand, we believe that fully taking into account the quantum character of nature will force us to revise our understanding of spacetime. These two conceptual problems lie at the heart of the unsolved challenge of how to quantize classical spacetime, and conversely, how (semi-) classical descriptions of spacetime emerge from quantum theory. Furthermore, if the entire matter-spacetime system is a kind of quantum many-body system, thermodynamics—which governs its statistical behaviors—should play a key role in elucidating these problems.

This workshop will discuss the question “How can quantum theory and spacetime be understood in a consistent manner?” from a fundamental and broad perspective. To tackle this challenge, we gather researchers in foundations of quantum theory, quantum gravity, and related fields from around the world, providing a "space and time" to share various ideas with open minds and engage in lively discussions. By exploring new concepts and principles, we hope to uncover directions to guide quantum theory over the next 100 years.

This workshop covers…

Foundations of quantum theory
Quantum gravity and emergence of spacetime
Formulation of semi-classical gravity
Experimental aspects of fundamental properties in nature and quantum gravity
Foundations of quantum many-body systems and thermodynamics
Other related topics are welcome.

This event is a workshop jointly organized by KEK Theory Center and RIKEN iTHEMS, and varieties of workshops are also being held at either KEK or RIKEN: WS1, WS2, WS3.

Invited Speakers

Caslav Brukner (IQOQI Vienna) * Link1, Link2
Bob Coecke (Quantinuum)
Fay Dowker (Imperial College London)
Justin Dressel (Chapman University)
Laurent Freidel (Perimeter Institute) Link
Philipp Höhn (OIST)*
Hidetoshi Katori (University of Tokyo)
Adrian Kent (University of Cambridge)
Akira Matsumura (Kyushu University) Link1, Link2
"Gravity sourced by quantum matter"
Shunji Matsuura (RIKEN) Link
"Quantum State Transfer from Natural Systems via Hamiltonian Learning and Information Scrambling"
Djordje Minic (Virginia Tech) Link
"Quantum gravity, quantum spacetime and gravitized quantum theory"
Takayuki Miyadera (Meiji Gakuin University) Link
"Quantum Incompatibility"
Daniele Oriti (Complutense University of Madrid) Link
"Emergent spacetime and cosmology from quantum gravity"
Tamiaki Yoneya (University of Tokyo) Link
"String Theory, Quantum Gravity and Spacetime"

(*=TBD. The above titles are tentative.)

Registration

Registration Form

Registration fee: ¥20,000
See Registration Form for details.

Contributions
We welcome applications for short talks and poster presentations.

Important Days (Japan Standard Time)

Deadline for requesting visa support: January 05, 2026
Dormitory reservation starting date (see below): January 22, 2026
Deadline for abstract submission: February 02, 2026
Deadline for registration and payment: February 10, 2026
Deadline for cancelation: February 20, 2026

Program

March 9 — 12, 2026

The workshop will start at 10:00 on March 9th and end at 17:00 on March 12th.
The detailed program will be announced later.

Venue and Access

Venue

Seminar Hall on the ground floor at Building 3 (San-Go-Kan), K03,
High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 Japan.

Google Map

KEK Campus Map (Please check ZONE-K in the table.)

Access

Access to KEK

Bus Timetable: Tsukuba Center ⇄ KEK Bus Stop

Accommodation

Please see this link for KEK dormitory reservations and a list of nearby hotels.→Hotel & KEK dormitory

Organizers

Yuta Hamada (KEK), Shoji Hashimoto (KEK), Puttarak Jai-akson (RIKEN), Christy Kelly (RIKEN), Amaury Micheli (RIKEN), Kyohei Mukaida (KEK), Wei-Hsiang Shao (RIKEN), Yutaka Shikano (University of Tsukuba), Yuko Urakawa (KEK), Yuki Yokokura (Chair, KEK/RIKEN)

Inquiries

Ms.Makiko Ohishi, Secretary, Theory Center, IPNS, KEK.
makiko[at]post.kek.jp

Advisory

Satoshi Iso (RIKEN/KEK), Shoji Hashimoto (KEK), Yoshimasa Hidaka (Kyoto University/RIKEN), Shigehiro Nagataki (RIKEN)