Concepts of Quantum and Spacetime

The workshop “Concepts of Quantum and Spacetime” was held at KEK in Japan from 9 to 12 March 2026, a joint workshop organized by KEK Theory Center and RIKEN iTHEMS.

The two fundamental questions, “What is quantum?” and “What is spacetime?” are deeply intertwined. The workshop discussed the question “How can quantum theory and spacetime be understood in a consistent manner?” from a fundamental and broad perspective and shared various ideas with open minds, to find directions guiding quantum theory over the next 100 years. The topics were diverse: foundations of quantum theory, quantum gravity, emergence of spacetime, formulation of semi-classical gravity, experimental aspects of fundamental properties in nature, and foundations of quantum many-body systems and thermodynamics.

Around 100 researchers from various countries, generations, and fields came together. Around 40% of them were from overseas. The 14 keynote speakers shared their visions on quantum theory and spacetime. The talk slides are available on the website. There were 13 selected discussions; we also held a poster award competition.

Interestingly, the disagreements and confusion arising from differences in their expertise and viewpoints actually gave rise to valuable discussions and new ideas. This was likely due to the open atmosphere of sincere engagement that emerged because the topic was not confined to specific methods or theoretical frameworks. Participants did not merely listen; they truly shaped the workshop. Visit the website to find more photos taken during the event.

These are the result of the deep curiosity shared by all participants regarding fundamental questions, "What is quantum?" and "What is spacetime?". It is precisely such curiosity that will naturally give rise to new ideas and collaborative research and connect the world. I hope that workshops embodying a similar spirit will be held around the world on a variety of themes in the future.