From particles to cosmology,
a quest for undiscovered principles of Nature.

The aim of physics is to study various phenomena in Nature. From ancient time, people have been interested in such phenomena in the earth and the sky, and have discovered the mechanisms and the law. However, we still have lots of phenomena that are veiled in mystery. Researchers have devoted themselves day and night to solving such mysteries in Nature. In our physics department, various kinds of researches have been carried out, such as astrophysics and cosmology, -challenging to mysteries in cosmos-, the elementary particles and quantum field theory, -exploring the origin of matter-, and condensed/soft matter physics, -studying the structure and the nature of matter-.

staff table Kaiki Taro Inoue Akihiro Ishibashi Nobuyoshi Ohta Michiyuki Chikawa Mikio Nakahara Toshio Kusakabe Yukihiro Kato Tetsuo Matsui Tomonari Dotera Yasushi Kondo Yohko F. yano Kenichi Kasamatsu Takahiko Masui

Areas of Research
(Click on the figures below for more information.)

Elemental Particle and Gravity Theory Laboratory: Nobuyoshi Ohta [Professor Dr.]
Study of unified quantum theory of particle interactions including gravity

My research studies important problems in particle physics by quantum field theory. In particular, the quantum theory of gravity, one of the greatest problems in modern theoretical physics, is the focus of my research. The leading candidate for such a theory is the superstrings, and I am trying to unravel the underlying principle of the theories, formulation of unified M-theory of superstrings, spontaneous breaking of symmetries, quantum theory of the black holes, nonperturbative analysis of usual and noncommutative field theories and also application to early cosmology within the framework of superstrings.

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Atomic and molecular physics: Toshio Kusakabe [Professor Dr.]
Experimental research for slow ion collision processes relevant to space and fusion edge plasmas

The charge transfer processes in collisions of slow ions with various atoms and molecules are experimentally studied for understanding the character of space plasmas such as solar winds and artificial plasmas such as nuclear fusions.

In the figure, rescent results of the cross-section ratios of the charge transfer for H+ + HD and D2 to H+ + H2 collisions are shown as a function of the collision energy per nucleon together with the theoretical calculations. As apparent, the cross section ratio of D2/H2 decreases to smaller value than unity below 1 keV/u, and reaches a value of 0.57 at the collision energy of 0.18 keV/u. It is understood that the isotope effect in the charge transfer of ion-molecule collisions originates from the combination of a small offset in binding and vibrational energies and the different spaces occupied by the wave functions of the target hydrogen isotope molecules.

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Quantum Control Laboratory: Yasushi Kondo [Professor Dr.]
Controlling of a quantum system

I have been studying superfluid He-3 under rotation, magnetism below 1mK, Si surfaces with SQUID, NMR, STM, and so on at Kyoto University, Low temperature laboratory (Helsinki University of Technology in Finland), Experimental Physik V (Bayreuth University in Germany), and Joint Research Center for Atom Technology - Angstrom-Technology Partnership (dissolved in 2002/3), c/o National Institute for Advanced Interdisciplinary Research in Japan). What I have studied so far were phenomena governed by quantum mechanics. I am now interested in quantum computing, or controlling of a quantum system. I have succeeded to implement several quantum algorithms, such as quantum teleportation without irreversible detection, as shown in the figure I. Recently, I have also started developing an NMR equipment that can be employed for implementing simple quantum algorithms.

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Elementary particle and astrophysics: Michiyuki Chikawa [Professor Dr.]
What does it mean the observation fact of super GZK particles?

Themes of the reserch in Astroparticle Physics Laboratory are to investigate the existence of the ultra-high energy cosmic rays(UHECRs), to study the transparency property of the atmospere of the earth, etc. UHECRs induce a huge extensive air showers(EASs) in the atmosphere through the unknown interaction of quarks and gluons. We are interested in the high energy interaction feature with theoretical framework.

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Soft and complex condensed matter physics: Tomonari Dotera [Professor Dr.]
Beyond fabrics: star-polymers weave a quasiperiodic pattern

Tiling and patterns are known not only to mathematicians and crystallographers, but also to designers and visual artists as the basis of decorative art appearing on furniture, curtains, wall papers, kilts, ceramics, ties, etc. But, nowadays, a cutting-edge art could be self-organized patterning made up of star-polymers designed by scientists. Without fabrication technique, star-polymers can produce elegant self-assembled periodic and quasiperiodic patterns. We have been creating several complex but periodic patterns known as antique Archimedean tiling patterns, and finally, we have shown the evidence of a "polymeric quasicrystals" tiling for the first time.

Quasicrystals are the avant-garde structures that have noncrystallographic symmetry, and initiated a revolution of crystallography and solid-state physics in 1980's. Remarkably, our polymeric dodecagonal quasicrystal has a hundred times length-scale compared to metallic systems, and thus it approaches the scale of visible light, where a promising photonic application has been considered. Our result indicates the universality of quasicrystalline order from atoms to polymers.

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Theoretical physics: Mikio Nakahara [Professor Dr.]
Qauntum computer, quantum information and mathematical physics

Current research interest in our group is primarily on quantum information and quantum computing, where such quantum characteristics as superpoistion principle and entengled states are fully utilized. We are working toward a physical realization of a quantum computer by employing strategies from mathematics, physics, chemistry and information science. We are also working on ultar-cold atoms and contemporary mathematics from physicist's point of view.

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Laboratory for Condensed Matter Theory: Tetsuo Matsui [Professor Dr.]
Matter, Brain, and the Universe: Interesting collective behaviors that are quite different from the behaviors of individual elements

A metal, a set of huge number of molecules, may exhibit magnetism or superconductivity at low temperatures. The brain, a network of neurons connected via synapses, supports consciousness and has functions of learning and recalling. The universe, supposed to be a patchwork of space-time elements at Plank scale, may be curved and folded in various ways; With a tiny probability it form a four-dimensional manifold like our space-time.

Our group studies these collective properties and behaviors of a whole system that are unexpected and are far from the properties of the individual components. The above three systems are quite different each other, but our models for them look surprisingly the same.

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General Relativistic and Cosmology: Akihiro Ishibashi [Associate professor Dr.]
General Relativity and Cosmology

“What was the origin of our universe?” This is perhaps the simplest but one of the most profound questions in physics. And it is related also to other questions such as “Why does our universe look like 4-dimensional?”

Aiming at ultimately addressing such fundamental questions, we have been working in the areas of cosmology and gravitation, concerning especially theoretical aspects of (1) higher dimensional gravity and black holes (2) cosmological dynamics and branes (3) global structure and spacetime singularities, as these play a key role to build bridges between observational cosmology and fundamental theories, such as string theory, that attempt to unify the forces in nature.

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Cosmology: Kaiki Taro Inoue [Associate professor Dr.]
Unraveling the nature of dark matter and dark energy in the universe

Although the dark energy/matter constitute most of energy/matter in the present universe, the nature has been a big mystery. In order to unravel it, I try to determine the fundamental theory of gravity that governs largest-scale structures (superstructures) in the universe. In order to do so, I use data of cosmic microwave background and 3D-distribution of galaxies in the sky. Developing observational tests of the Copernican Principle is another interesting subject. I also investigate distrubution of dark matter on sub-galactic scales (substructures) using QSO-galaxy lensing systems collaborating with astronomers.

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Theory of condensed matter physics: Kenichi Kasamatsu [Associate Professor Dr.]
Theoretical study of ultracold quantum gases and Bose-Einstein condensation

The Bose-Einstein condensation, a new state of matter predicted by Einstein in 1925, is caused by condensation of a macroscopically large number of bosons into a single-particle quantum state below a Bose-Einstein transition temperature. A remarkable consequence caused by the condensation is an expansion of microscopic quantum phenomena into macroscopic scales.

This is an essential origin of superfluidity and superconductivity, in which macroscopically extended phase coherence allows the dissipationless current to flow. Ultracold atoms at nK temperature are simple and controllable systems to address fundamental questions of quantum mechanics and quantum many-body physics, e.g. quantum phase transitions, superfluidity, and efficient quantum information processing, etc. Our current research is to understand theoretically the structure, stability and dynamics of Bose-Einstein Condensates (BECs) of ultracold atomic gases in confining potentials.

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Experimental particle physics: Yukihiro Kato [Professor Dr.]
High energy particle accelerator approaches the origin of the universe.

The universe is born of the high temperature and high density situation, so called Big Bang, and has been inflated with the time passage. How should we research of the birth of the universe? The Collisions of high energy proton and anti-proton, electron and positron using the particle accelerator can make the similar state of the birth of universe during the moment. Observation of the various particles and interactions come from this state can make us predict what happened when the universe was born. Now, we have been developing the detector on International Linear Collider (ILC) project in cooperation with many researchers all over the world.

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Solid State Physics Laboratory: Takahiko Masui [Associate professor Dr.]
Experimental study of Superconductivity and Magnetism

In our laboratory, the targets of the study are exotic properties in solids, such as superconductivity in cuprates, magnetism with frustrated structure. We are interested in contribution of electron-phonon interaction and pseudogap phenomenon in high temperature superconductivity.

In the research various experimental methods are used, such as crystal growth in a furnace, measurements of transport and optical properties.

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Biophysics Laboratory: Yohko F. Yano [Associate professor Dr.]
Towards understanding life phenomena at the atomic level

Our lab is interested in the structural biophysics of proteins especially at interfaces. Since proteins fold their hydrophobic regions within hydrophilic regions in water, conformational changes are expected when they adsorb at water interfaces. One approach towards understanding the mechanisms of protein folding is to study the procedures and conditions that lead to protein unfolding.

X-ray reflectivity technique is a powerful tool for exploring surface phenomena.We are developing an x-ray liquid interface reflection system at SPring-8 to investigate the protein unfolding at interfaces.

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Mikio Nakahara

Lectures on Quantum Computing, Thermodynamics and Statistical Physics [2012/12]

Mikio Nakahara and Shu Tanaka

(200 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4425-18-6 , 978-981-4425-19-3

Interface Between Quantum Information and Statistical Physics [2012/12]

Mikio Nakahara and Shu Tanaka

(280 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4425-27-8 , 978-981-4425-28-5

Quantum Information and Quantum Computing [2012/12]

Mikio Nakahara and Yoshitaka Sasaki

(196 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4425-21-6 , 978-981-4425-22-3

Diversities in Quantum Computation and Quantum Information [2012/12]

Mikio Nakahara and Yidun Wan and Yoshitaka Sasaki

(228 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4425-97-1 , 978-981-4425-98-8

Frontiers in Quantum Information Research [2012/8]

Mikio Nakahara and Shu Tanaka

(360 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4407-18-2 , 978-981-4407-19-9

Decoherence Suppression in Quantum Systems 2008 [2009/11]

Mikio Nakahara and Robabeh Rahimi and Akira SaiToh

(204 pages) World Scientific Pub Co Inc.

ISBN: 978-981-4295-83-3 , 978-981-4295-84-0

Molecular Realizations of Quantum Computing 2007 [2009/6]

Mikio Nakahara and Yukihiro Ota and Robabeh Rahimi and Yasushi Kondo and Masahito Tada-Umezaki

(284 pages) World Scientific Pub Co Inc.

ISBN: 978-981-283-867-4 , 978-981-283-868-1

Mathematical Aspects Of Quantum Computing 2007 [2008/4]

Mikio Nakahara and Robabeh Rahimi and Akira SaiToh

(240 pages) World Scientific Pub Co Inc.

ISBN: 978-981-281-447-0 , 978-981-281-448-7

Quantum Computing: From Linear Algebra To Physical Realizations [2008/3]

Mikio Nakahara and Tetsuo Ohmi

(440 pages) CRC Press, Taylor & Francis

ISBN-10: 0750309830, ISBN-13: 978-0750309837

Physical Realizations of Quantum Computing: Are the DiVincenzo Criteria Fulfilled in 2004? [2006/4]

Mikio Nakahara, Shigeru Kanemitsu, MarttiM. Salomaa, and Shin Takagi

(234 pages) World Scientific Pub Co Inc.

ISBN-10: 981256473X , ISBN-13: 978-9812564733

Zeta Functions, Topology and Quantum Physics [2005/6]

Takashi Aoki, Shigeru Kanemitsu, Mikio Nakahara, and Yasuo Ohno

(235 pages) Springer

ISBN-10: 0387249729 , ISBN-13: 9780387249728

Geometry, Topology and Physics (2nd ed) [2003/10]

Mikio Nakahara

(596 pages) CRC Press, Taylor & Francis

ISBN-10: 0750306068, ISBN-13: 978-0750306065

Superconductivity and Superfluidity (translation) [1998/12]

Mikio Nakahara

(88 pages) Cambridge University Press

ISBN-10: 0521570735
ISBN-13: 978-0521570732 (Hard Cover)
ISBN-10: 052102093X
ISBN-13: 978-0521020930 (Soft Cover)