The world is full of computation - School of Science, the University of Tokyo
Oct 19, 2015

The world is full of computation

07. Department of Information Sciences — Hagiya Laboratory

Professor Masami Hagiya
Graduate School of Information Science and Technology
Department of Computer Science


Professor Hagiya graduated from the Department of Information Sciences at the University of Tokyo in 1980, then the Master’s Program in Information Sciences in 1982. He received his Ph.D. from Kyoto University in 1988. In 1992 he became an associate professor at the University of Tokyo’s Department of Information Sciences, and then a full professor in computer science in 2001.

Computers are not the only thing to perform computation. “Nature is full of computation,” says Professor Masami Hagiya. This concept is called “natural computing.”

We can observe natural phenomena as computation and describe what we see using precise mathematical definitions, resulting in a computational model. After such models are analyzed and generalized, they can once again be implemented by possibly other kinds of natural phenomena.

What we refer to as “computation” here is a process in which a system changes its state in response to an input. Since a human’s brain and a living cell change their state in response to an input, they are all performing computation.

“The computers we use every day are one form of natural computing,” Professor Hagiya says. “What we’re doing is observing computational features in the movement of electrons and modeling them as “Boolean logic.” We then artificially implement the model by the physical phenomenon called “digital circuits,” and combine those circuits into the form of a computer. The basis of this process is a computational model called Turing machine.”

The idea of Turing machine, which forms the root of our present-day computers, was developed in the first half of the twentieth century by the mathematician Alan Turing. Turing machine was proposed as a model of a mathematician performing computation as a natural phenomenon.

“Lambda calculus and parallel calculi are other examples of computational models,” says Professor Hagiya. “Those are well-established models in a sense, but we are more interested in constructing new models. Doing so requires focusing on natural phenomena that have not been dealt with in the past.”

One of the new phenomena that Professor Hagiya is interested in is quantum effects. A strange phenomenon of the quantum world is “entanglement,” in which systems separated by distance retain a connected relationship. There are now attempts to find computational features of this phenomenon, to model them, and to implement the resulting model in the form of a quantum computer. Professor Hagiya is highly interested in what kinds of computational models can be constructed.

Another major theme is “molecules.” Currently, it is possible to create artificial membranes, into which DNA molecules are inserted, or to use DNA molecules to create a slime-like gel, into which devices made from molecules are inserted. DNA and other molecular devices work as “molecular computers,” which can respond to external stimuli. Going further to create robots has resulted in the research area called “molecular robotics.” Professor Hagiya is currently conducting an interdisciplinary research project pursued by researchers in fields such as chemistry, biology, and systems engineering.

The Hagiya Laboratory researches a wide variety of areas related to natural phenomena. It has welcomed research students from many countries, including China, France, and Algeria. These students pursue research on a wide variety of themes, including quantum computing, molecular computing, the application of computational models to software security analysis (model checking), and verification of the security of quantum encryption. “Our research is quite broad, from fields related to the safety and security of society, to enigmatic areas like quantum and molecular computing that carry a bit of risk,” says Professor Hagiya.

Computational models are quite abstract, but that is what makes them so easy to adapt to various phenomena. “That’s one of the strongest aspects of this research,” says Professor Hagiya. “It’s a wonderful feeling to construct a new model that has universality. Even better is when you can use it to find a relationship between phenomena that seem completely unrelated.”

Increasing the level of abstract thinking opens doors to new, unexplored worlds.

Student Evaluations

“He’s a very interesting professor, the kind I hope to become someday.” (Ibuki Kawamata, D3)
“He’s willing to stick with students, however far they want to go.” (Takahiro Kubota, D3)
“He’s a good combination of nice and strict. And he has such cute handwriting!” (Kentaro Honda, D1)
“I’ve never seen him not smiling.” (Shaoyu Wang, research student)



A model of a DNA state transition machine based on a graph rewriting system. Uppercase and lowercase letters indicate complementary DNA sequences, and chemical reactions are shown as graph rewrites. (Graph by Ibuki Kawamata.)

― Office of Communication ―

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