Quantum Information Theory Research Team

Principal Investigator

PI Name Keisuke Fujii
Degree Ph. D. (Eng)
Title Team Leader
Brief Resume
2011Postdoctoral Researcher, Graduate School of Engineering Science, Osaka University
2013Project Assistant Professor, The Hakubi Center for Advanced Research, Kyoto University
2016Assistant Professor, Photon Science Center, The University of Tokyo
2017Project Associate Professor, Graduate School of Science, Kyoto University
2019Professor, Graduate School of Engineering Science, Osaka University (-present)
2020Deputy Director, Center for Quantum Information and Quantum Biology, Institute for Open and Transdisciplinary Research Initiative, Osaka University (-present)
2020Team Leader, Quantum Information Theory Research Team, RIKEN Center for Emergent Matter Science (-present)



Our team focuses on quantum software engineering science, which is necessary for the realization of quantum computers. In the near future, we will develop basic technologies to exploit the performance of quantum computers on a scale that is now being realized or will be realized in the next few years, as well as applications of them to fundamental physics, quantum chemistry, and quantum machine learning. In the long term, we will work on quantum computer architectures, quantum error correction, and optimization of quantum circuits to realize large scale fault-tolerant quantum computers. We are also interested in interdisciplinary fields between quantum information science and fundamental physics, quantum chemistry, machine learning, and high-performance computing.

Research Fields

Physics, Computer Science, Multidisciplinary


Quantum computing
Quantum computer
Quantum information devices
Quantum information
Quantum Technology


Toward realization of a fault-tolerant quantum computer

In recent years, not only universities and governmental institutes but also giant IT companies and startup companies have been actively developing quantum computers. A quantum computer with more than 50 qubits, which would have been a scientific fiction a decade ago, is now being realized, and its performance has been verified by using a supercomputer. However, the number of qubits required for a fault-tolerant quantum computer, which is a holy grail in the field, is estimated to be 1 million or 100 million qubits, and there are many engineering problems to overcome in achieving this goal. The biggest bottleneck is quantum error correction, which is necessary to protect quantum information beyond the physical coherence time, i.e., lifetime of a physical qubit. Our group is working on quantum error correction including the design of the architecture at device level and researches on quantum software and algorithms running on fault-tolerant quantum computers.

A quantum circuit for quantum error correction (Left), fault-tolerant quantum computing using the surface code (Right).


Keisuke Fujii

Team Leader


2-1 Hirosawa, Wako, Saitama 351-0198 Japan