News and views (1 & 2)

1 Honorary AAPPS fellow conferred to Prof. Jia-er Chen, AAPPS President 1997–1999 by Gui-Lu Long

On the occasion of his 90th birthday this October, Prof. Ja-er Chen, president of AAPPS during 1997–1999 and a world-renowned physicist in accelerator physics, was presented the certificate of AAPPS honorary fellow for his great contributions to the AAPPS, and the decision was made in an AAPPS council meeting in 2019. The certificate was conferred to him by Prof. Jie Zhang, the president of CPS and the president of AAPPS between 2008 and 2010.

Jia-er graduated from the Physics Department of Northeast Renmin University in 1954, the predecessor of Jilin University, and became a lecturer afterwards. In 1955, he was transferred to work in Peking University. From 1963 to 1966, he was a visiting scholar at Oxford University and Rutherford Institute of High Energy. From 1982 to 1984, he worked as a visiting scientist at Lawrence Berkeley Laboratory and the Nuclear Physics Laboratory of the State University of New York at Stony Brook. In 1984, he was appointed as Vice President of Peking University. In 1993, he was elected as an academician of China Academy of Sciences. From August 1996 to December 1999, he served as the President of Peking University (Fig. 1).

Fig. 1

Prof. Jiaer Chen (right) was presented the certificate of honorary AAPPS fellow by Prof. Jie Zhang (left), President of Chinese Physical Society and AAPPS President between 2008 and 2010

2 Honorary AAPPS fellow conferred to Prof. Jie Zhang, AAPPS President 2008–2010 by Gui-Lu Long

Prof Jie Zhang, AAPPS President 2008–2010, was awarded the title of AAPPS Honorary Fellow during the 14th annual workshop on frontiers of optics in Xiong-an in September 2023. The certificate was presented to Jie by Prof. Guozhen Yang, former president of CPS. Prof. Gui-Lu Long, President of AAPPS 2017–2019, chaired the ceremony. In the introduction speech, Gui-Lu summarized the three major contributions of Jie Zhang to AAPPS. First, he made a series of contributions to enhance the profile of AAPPS in various ways; second, he started the Asia-Europe Physics Summit, which has been a regular series and a close link between AAPPS and EPS; third, he restarted the publication of AAPPS Bulletin after a stop of more than 1 year. Prof. Jie Zhang is the current president of CPS (Fig. 2).

Fig. 2

From left to right: Guozhen Yang, Jie Zhang, and Gui-Lu Long

3 Congratulations to Prof. Qikun Xuen, AAPPS Council Secretary 2008–2010 for winning 2024 APS Oliver E. Buckley Prize by Gui-Lu Long

On 24 October 2023, the American Physical Society announced that Prof. Qikun Xue, AAPPS Council Secretary 2008–2010, Professor at Tsinghua University, and President of Southern University of Science and Technology, and Prof. Ashvin Vishwanath, from Harvard University, are winners of the 2024 Oliver E. Buckley Condensed Matter Physics Prize. Oliver Buckley Prize is widely recognized as the highest prize in the fields of condensed matter physics. The 2024 prize is conferred to Qikun Xue from Tsinghua University and Ashvin Vishwanath from Harvard University for their “groundbreaking theoretical and experimental studies on the collective electronic properties of materials that reflect topological aspects of their band structure.”

Prof. Qikun Xue made breakthroughs in topological insulator and the discovered quantum anomalous Hall effect. Congratulations to Qikun! (Fig. 3).

Fig. 3

Prof. Qikun Xue, at Southern University of Science and Technology in Shenzhen

4 Vigyan Pratibha — enhancing science and mathematics learning experiences in Indian high schools by Deepa Chari, Ankush Gupta, and Arnab Bhattacharya (Vigyan Pratibha HBCSE, and Apex coordinator team)

Vigyan Pratibha is a Department of Atomic Energy, India, funded program aimed at increasing high school students’ scientific and mathematics proficiencies through capacity building of their teachers. The program is operational under the leadership of Homi Bhabha Centre for Science Education and TIFR with 11 other national science and mathematics research centers including IMSc, NISER-Bhubneshwar, IoP-Bhubneshwar, IISER-Mohali, IISER-Kolkata, IISER-Bhopal, and SINP that form regional centers, partnering in various educational activities conducted under the program.

Vigyan Pratibha also connects these centers with students and teachers of three major nation-wide school systems (Atomic Energy Commission Schools, Kendriya Vidyalayas, and Jawahar Navodaya Vidyalayas) encompassing a network of approximately 1700 schools across India. Thus, Vigyan Pratibha provides unique channels of communication about science and mathematics across multiple stakeholders, and ideas are exchanged through high-quality teaching and learning resources (called learning units), workshops, online discussion sessions, school visits, exposure visits, and many more roofed under the program. In the first few years, we have reached out to 100 + schools, oriented 600 + teachers about Vigyan Pratibha activities via ~ 150 workshops, and online discussion sessions, a number that is increasing rapidly, as more regional centers join the Vigyan Pratibha network.

Physics learning units are among the most popular within the school community as students explore many known/unknown phenomena, and nothing is taken for granted. Students go beyond the procedures/tasks, challenge their peers, and delve deeper in richer scientific discourse. Learning units such as moon and its shape introduce students to carefully analyze their own observational data and use it to predict rise and set time of moon on another day, and the unit on measurement challenges students to explore the wealth of information a seemingly simple measurement can carry. Figure 4 showcased at the event shows two such learning unit examples where (4A) students explore a pin-hole camera as a measuring device and (4B) students challenge popular tales of thirsty/witty crow through a model design and experimentation.

Fig. 4

Glimpses of A pin-hole camera B measuring volume physics learning unit activities

Similarly, mathematics learning units provide opportunities to engage deeper with practices similar to mathematicians or scientists in their endeavors. For instance, Fig. 5 shows how students during mathematics learning units with dot grids explore relationships of area and perimeters in specific geometries by uncovering mathematical proofing practices.

Fig. 5

Glimpses of exploring dot grids mathematics unit activities

High school teachers across Asia are encouraged to explore, modify, and utilize these openly available science and mathematics learning resources (developed in English) with their students. Many learning units are translated in regional Indian languages including Marathi, Hindi, Tamil, Gujarati, and Punjabi and can be explored for dissemination in local non-English medium schools.

Teachers interested in contributing to the program by means like disciplinary education research, material development, and dissemination at local levels are welcome to reach out to us at vp@hbcse.tifr.res.in or via the Vigyan Pratibha website.

Contact details are as follows: deepa@hbcse.tifr.res.in, ankush@hbcse.tifr.res.in, and arnab@hbcse.tifr.res.in.

5 Indonesia-APCTP workshop on quantum computing and simulation by Ahmad Ridwan Tesna Nugraha

The National Research and Innovation Agency (BRIN), through its Research Center for Quantum Physics, successfully organized a workshop on quantum computing and simulation from December 6 to 8 2023. This workshop was organized jointly with the Department of Physics, University of Indonesia (UI), and sponsored by the Asia Pacific Center for Theoretical Physics (APCTP). The Center for Theoretical Physics of Complex Systems (PCS) at the Institute for Basic Science (IBS), Korea, supported the workshop by sending one of its leading researchers as the invited speaker. The workshop also obtained support from the SpinQ Technology Corporation, which lent its portable quantum computer showcased at the event (Fig. 6).

Fig. 6

Snapshots of the workshop sessions from day 1 (top) and day 2 (bottom)

More than 80 participants registered for this event, and more than 70 of them consistently listened to all the talks every day (see Fig. 6). Several international researchers in quantum information and quantum technologies were invited: Leong-Chuan Kwek from the National University of Singapore (NUS) with a presentation titled, “NISQ Era: Challenges and Alternatives”; Rangga P. Budoyo from NUS (“Development of superconducting quantum technologies”); Dominik Šafránek from PCS-IBS (“Entanglement and its applications in quantum computing”), and Hongyang Zou from SpinQ (“Introduction to superconducting quantum computer and NMR quantum computer”). The workshop also involves local speakers such as Muhammad Aziz Majidi from UI (“Tight-binding Hamiltonians and quantum computing”), Agung Budiyono from BRIN (“Nonclassical aspects of quantum mechanics as resources in quantum technology”), and Muhammad Yusrul Hanna, who gave some hands-on sessions on Qiskit and Pennylane programming (see Fig. 7). It is interesting to note that some cats (fortunately, not the Schrödinger’s Cats) sneak into the workshop room, but it is guaranteed that no cats were harmed during the workshop (Fig. 8).

Fig. 7

Participants enjoying a Qiskit hands-on session

Fig. 8

No cats were harmed during the workshop

One of the purposes of the workshop is to build local expertise and a talent pipeline by encouraging students and young researchers to pursue quantum science and technology. Therefore, it is necessary to provide some informal settings of the workshop to catalyze fluid conversations and fruitful discussions between the participants. A unique feature of this workshop is a total of 2 h of time allocated for a coffee break and lunch break every day. With such quite long hours of free time, participants can blend each other, obtain beneficial insights from the experienced, and discuss necessary actions to catalyze quantum computing research, especially in Indonesia. Laughter and excitement can be heard and seen during the conversations (see Fig. 9).

Fig. 9

Active, informal discussion between participants and speakers in various settings of the workshop

Both during the question–answer session in each talk and during the informal conversation in the workshop, we could see that many participants engaged in various discussions exploring different aspects of quantum computing and simulation. The discussions cover fundamental principles (especially during the talks from Prof. Kwek, Dr. Agung, Dr. Majidi, and Dr. Šafránek), potential applications in industries (Dr. Budoyo and Dr. Zou), and quantum computing influence on shaping our technological future. It is really hoped that the exchange of ideas and the collaborative atmosphere fostered during this gathering will undoubtedly contribute to the progress and improvement of quantum research in Indonesia, which just began its “official” journey in this field since the establishment of the BRIN Research Center for Quantum Physics in 2022.

The workshop also became complete with the presence of SpinQ representatives who generously brought a portable quantum computer sample to Indonesia. Most of the participants, especially young students who had never seen a quantum computer in their life before, were very excited when the SpinQ company persons revealed their two-qubit NMR-based quantum computer (see bottom-left of Fig. 9). Although the number of qubits is very small and of limited use for real quantum computing, the SpinQ portable quantum computer is already useful as a tool of demonstration and education. Indeed, only after attending this workshop, some of the participants commented that they finally believed quantum computers could exist.

It is hoped that such an event will not stop just because of following the quantum hype in the world. Indonesia, with the support of APCTP and collaboration with neighboring countries, should position itself as a potential country in the development of quantum science and technology. The human resources, particularly of young age, are large and need to be encouraged to join the quantum workforce. This workshop is really one of the first crucial steps, and we would like to see its outcomes in the near future becoming the leader of the country in the quantum research fields. Who knows, among the students photographed in Fig. 10, there could be one of them win a Nobel Prize in Physics in the future due to his/her contribution to quantum science and technology.

Fig. 10

Group photo of the workshop

6 Young Scientist Award of the Physical Society of Japan, 2024 by JPS

Every year, the Physical Society of Japan presents its Young Scientist Awards to young researchers to recognize outstanding achievements in their early research careers. This year’s winners were recently decided by the board of directors of the JPS based on the recommendations of the selection committees established in 19 divisions of the JPS. The maximum number of winners from each division has been determined based on the number of talks given at the Annual Meetings in the past 3 years. Each winner is to give an award lecture at the next Annual Meeting of the JPS, which is scheduled for March 2024. Here is the list of winners and their research topics.

• Theoretical particle physics

Kensuke Akita (Institute for Basic Science).

“A precision calculation of relic neutrino decoupling”

Junsei Tokuda (Center for Theoretical Physics of the Universe, Institute for Basic Science).

“Positivity bounds for scattering amplitudes in gravitational theory”

Okuto Morikawa (Osaka University).

“Studies on generalized symmetries in lattice field theory”

• Experimental particle physics

SHIMIZU, Nobuhiro (International Center for Hadron Astrophysics, Chiba University).

“First search for K_L → π⁰γ”.

BRONNER, Christophe (Institute for Cosmic Ray Research, University of Tokyo).

“Improved constraints on neutrino mixing from the T2K experiment with 3.13×10²¹ protons on target”

OTONO, Hidetoshi (Research Center for Advanced Particle Physics, Kyushu University).

“The tracking detector of the FASER experiment”

• Theoretical nuclear physics

Yuuka Kanakubo (University of Jyväskylä).

“Construction of a framework for production of quark-gluon plasma fluid based on core-corona picture”

Hidetoshi Taya (RIKEN iTHEMS).

“Fundamental research on cooperative phenomena in perturbative and nonperturbative particle production processes under electric fields”

Takeru Yokota (RIKEN, Interdisciplinary Theoretical and Mathematical Sciences Program).

“Construction of energy density functional with functional-renormalization-group method”

• Experimental nuclear physics

Masaomi Tanaka (Kyushu University, Faculty of Arts and Science).

“Evolution of neutron skin probed by nuclear fragmentation reactions”

Momo Mukai (Nagoya University).

“Comprehensive nuclear spectroscopy of neutron-rich nuclei toward the N=126 waiting points”

Takuya Nanamura (Japan Atomic Energy Agency).

“Differential cross section measurement and phase shift analysis for Σ⁺p elastic scattering”

• Cosmic ray and astrophysics

Nanami Kawada (Research Center for Neutrino Science, Tohoku University).

“Spectroscopic measurement of geoneutrinos from uranium and thorium with KamLAND”

Tomohiko Oka (Research Organization of Science and Technology, Ritsumeikan University).

“Multiwavelength data analysis of supernova remnants for unraveling of acceleration mechanisms of cosmic rays”

Sho Fujibayashi (Max Planck Institute for Gravitational Physics at Potsdam).

“Comprehensive study on the mass ejection and nucleosynthesis in binary neutron star mergers”

• Beam physics

Masayasu Hata (Kansai Institute for Photon Science, National Institutes for Quantum Science and Technology).

“Research on plasma dynamics for laser-driven ion beam applications”

Takaaki Yamaguchi (Accelerator Laboratory, High Energy Accelerator Research Organization).

“Systematic study on the static Robinson instability in an electron storage ring”

• ◦ Atomic and molecular physics, quantum electronics, and radiation

Ryoichi Saito (School of Science, Tokyo Institute of Technology).

“Matter-wave interference of a trapped single ion for the development of an ion trap gyroscope”

Akinobu Niozu (Graduate School of Advanced Science and Engineering, Hiroshima University).

“Non-equilibrium structural dynamics of rare-gas clusters studied by XFEL”

Yuki Miyazawa (Institute of Innovative Research, Tokyo Institute of Technology).

“Bose–Einstein condensate of europium atoms”.

• Plasma

Kunihiro Ogawa (National Institute for Fusion Science).

“Energetic particle confinement study in helical plasmas”

Masato Ota (National Institute for Fusion Science).

“Study of relativistic Coulomb field by electro-optic sampling”

• Magnetism

Takashi Kikkawa (Department of Applied Physics, Graduate School of Engineering, University of Tokyo).

“An experimental study on magnon, phonon, and nuclear spintronics”

Yuya Haraguchi (Tokyo University of Agriculture and Technology).

“Development of new Kitaev materials”.

Junji Fujimoto (Department of Electrical Engineering, Electronics and Applied Physics, Saitama University).

“Theoretical study of physical phenomena caused by electric current vorticity”

• Semiconductors, mesoscopic systems, and quantum transport

Ryo Okugawa (Department of Applied Physics, Tokyo University of Science).

“Exploration of novel properties in various topological phases through model construction and analysis”

Kenji Yasuda (Department of Physics, Massachusetts Institute of Technology).

“Symmetry control and functionality at the stacking interface of two-dimensional materials”

• Optical properties of condensed matter

Katsumasa Yoshioka (NTT Basic Research Laboratories).

“Pioneering terahertz spectroscopy techniques for investigating ultrafast local and nonlocal responses”

Takayuki Kurihara (Institute of Solid State Physics).

“Spectroscopy and technical advancement of nonlinear magnonics in terahertz to mid-infrared”

• Metal physics (liquid metals, quasicrystals), low-temperature physics (ultralow temperatures, superconductivity, density waves)

Sachio Komori (Department of Physics, School of Science, Nagoya university).

“Research on unconventional proximity effects at superconductor/ferromagnet interfaces”

Shun Maegochi (Hitachi, Ltd.)

“Experimental study of nonequilibrium phase transitions using a superconducting vortex system”

• Molecular solids

Shusaku Imajo (Institute for Solid State Physics, University of Tokyo).

“Study on unconventional superconductivity of molecular charge-transfer salts”

Takuro Sato (Institute for Molecular Science).

“Study of novel non-equilibrium electromagnetic responses in strongly correlated electron/spin systems”

• Strongly correlated electron systems

Naoya Kanazawa (Institute of Industrial Science, University of Tokyo).

“Formation of topological spin textures and emergent electromagnetic properties in chiral crystals”

Maximilian Hirschberger (Department of Applied Physics, University of Tokyo).

“Thermoelectric studies of electronic structure in quantum materials”

Shunsaku Kitagawa (Division of Physics and Astronomy, Graduate School of Science, Kyoto University).

“Study of multiple superconducting phases due to sublattice degrees of freedom”

Akihiko Ikeda (Department of Engineering Science, University of Electro-Communications).

“Uncovering novel electronic phases in LaCoO₃ up to 600 Tesla using original strain gauge for 1000 T”

• Surfaces and interfaces and crystal growth

Naoya Kawakami (Department of Electrophysics, National Yang-Ming Chiao Tung University).

“Research on silicene growth on Ag(111)”.

Naoki Nagatsuka (Department of Chemistry, Graduate School of Science, Kyoto University).

“Electronic properties of surface defects and their effect on the adsorption structure of molecules”

• Dielectrics, ferroelectricity, lattice defects and nanostructures, phononic properties, and X-ray and particle beams

Koji Michishio (National Institute of Advanced Industrial Science and Technology (AIST)).

“Generation of high-quality positron beams using the positron trapping method and its applications”

• Fundamental theory of condensed matter physics, statistical mechanics, fluid dynamics, applied mathematics, and socio- and econophysics

Hiroyasu Tajima (Department of Communication Engineering and Informatics, University of Electro-Communications).

“Study of the effect of coherence on quantum gates and quantum engines”

Jumpei Yamagishi (Department of Basic Science, University of Tokyo).

“Linear response theory of metabolic systems from microeconomic perspective”

Yoshihiko Nishikawa (Graduate School of Information Sciences, Tohoku University).

“Studies on static and dynamic properties of structural glasses based on large scale numerical simulations”

• Soft matter physics, chemical physics, and biophysics

Tetsuro Nagai (Fukuoka University).

“Mass transport in heterogeneous systems studied using new dynamic Monte Carlo simulations and large-scale molecular dynamics simulations”

Yuji Higuchi (Kyushu University).

“Understanding structures and physical properties of soft matter by molecular simulations”

Shunsuke Yabunaka (Japan Atomic Energy Agency).

“Theoretical study of phase transitions and bifurcation phenomena in soft (active) matters”

• Physics education, history of physics, and environmental physics

Hajime Inaba (Meiji University School of Political Science and Economics).

“Historical investigations into the development of statistical mechanics”

7 The Physical Society of Japan: second (2024) AAPPS-JPS Award by JPS

In order to promote research in physics in Japan, the Physical Society of Japan (JPS) and the Association of Asia Pacific Physical Societies (AAPPS) shall jointly award the “AAPPS-JPS Award” for young JPS members who achieve outstanding research results.

The 2024 winners of the second Association of Asia Pacific Physical Society (AAPPS)—the Physics-JPS Award, are listed below.

Tatsuya Kobayashi

National Institute for Fusion Science, National Institutes of Natural Sciences, Associate Professor.

Experimental study on nonlinear emergent phenomena in high-temperature plasmas.

Dr. Tatsuya Kobayashi has made outstanding achievements in experimental research on nonlinear emergent phenomena with structure formation in ultrahigh-temperature plasmas. In magnetic fusion plasmas, heat and particle transport due to turbulence is one of the important issues for fusion development. In addition to the diffusion process due to the Coulomb collision, turbulent electric field fluctuations drive collective motion of charged particles across the magnetic field and enhance transport. Meanwhile, highly symmetric plasma flows are occasionally generated due to nonlinear effects of collective motion that lead to the plasma transition to a “high confinement” state. Dr. Kobayashi and his collaborators have developed a cutting-edge high-resolution measurement and state-of-the-art analysis system to survey ordered structures in turbulence and have achieved many important results by clarifying the relationship between the ordered structure and plasma inhomogeneity (non-equilibrity). He has also uncovered the nonlinearity of self-regulated oscillations between a plasmoid and radiation intensity in the plasma periphery and has successfully modeled it using a predator–prey relationship. These results are expected not only to provide important scientific knowledge for the realization of fusion energy but also to contribute to the elucidation of the dissipative structure formation, which is universally observed in various systems, ranging from astronomical and space plasmas to semiconductor process plasmas.

Akito Sakai

Faculty of Science & Graduate School of Science, The University of Tokyo, Lecturer.

Anomalous metals beyond the conventional magnetic quantum criticality scenario such as quadrupole Kondo lattice systems and geometrical frustrated quantum critical systems.

Dr. Akito Sakai is a young researcher who leads research on quantum matter in strongly correlated electron systems and topological magnetic materials. He has been conducting research on new quantum critical phenomena by extending the conventional framework for understanding magnetic quantum critical points to include quadrupolar order, frustrated magnetic metals, and topological magnetic materials. He received this award in recognition of his discovery of a new compound that will serve as the stage for experimental research on the quadrupole Kondo lattice system and the experimental elucidation of its unconventional physical properties.

Junsei Tokuda

Institute for Basic Science, Center for Theoretical Physics of the Universe, Senior Researcher.

S-matrix consistency between quantum gravity and low-energy physics.

No consistent quantum theory of gravity is known today. The standard model of particle physics must be modified at high energies where the effect of gravity becomes significant and be integrated in the theory including gravity. In that sense, the standard model should be understood as a low-energy effective theory of yet unknown theory, but still some conditions that the standard model must obey can be obtained. Dr. Tokuda et al. derived a condition for particle scattering amplitude and consider the light-by-light scattering to show that non-perturbative effect is important to saturate the condition. This work shed a light on the relation between the standard model and gravity and deserves the AAPPS-JPS Award.

Natsumi Nagata

Graduate School of Science, The University of Tokyo, Assistant Professor.

Theoretical studies on dark matter and astroparticle physics.

Dr. Natsumi Nagata obtained more stringent constraints on the axion decay constant than those given by SN 1987A by analyzing the consistency with observed surface temperatures of a neutron star in Cassiopeia A. He also showed that internal heating effects caused by out-of-β-equilibrium in the cooling process of neutron stars can have a significant impact on the possibility of using surface temperature observations of neutron stars to search for dark matter.

Furthermore, he pointed out that the gravitational acceleration of neutron stars causes dark matter particles to collide with neutron stars at high energies, and thus, electroweak multiplet dark matter can be efficiently searched for through inelastic scattering processes. He is highly expected to continue to play a leading role in this field.

Shuhei Hayakawa

Department of Physics, Tohoku University, Assistant Professor.

Double-strangeness hypernuclear research.

Double-hyper nuclear will make an important contribution to understanding nuclear forces, and this has been an ongoing challenge for many years. Dr. Hayakawa’s highly accurate measurement of the mass (Ξ binding energy) of the Ξ hyper nucleus is very important as a milestone in this research field. Dr. Hayakawa was in charge of the spectrometer system for the high-purity K beam that was the basis of this result, and his contribution was significant. We believe that further progress can be expected based on these results, and Dr. Hayakawa is worthy of the award.

8 2023 Nishina Memorial Prize

Dr. Atsuko Ichikawa

Professor, Department of Physics, Graduate School of Science, Tohoku University.

8.1 Constraining CP violating phase δ in neutrino oscillations

The T2K experiment searches for a violation of the symmetry between particles and antiparticles, called CP violation, in the neutrino oscillation phenomena. In the experiment, the J-PARC 30-GeV, high-power proton accelerator located at Tokai, Ibaraki Prefecture, launches neutrinos and antineutrinos separately toward the Super-Kamiokande at Kamioka, Gifu Prefecture, located 295 km away. The difference between neutrino oscillations and antineutrino oscillations, if observed, is the signature of CP violation.

Matter in the universe was created through the Big Bang. According to particle theory, particles and antiparticles, whose signs of electric charges (or particle numbers in general) are reversed to each other, are always created in pairs and annihilate in pairs. Matter is composed of particles, while antimatter is composed of antiparticles. Therefore, the fact that only matter and no antimatter remains in the current universe is known as the “mystery of the predominance of matter in the universe” and is considered as a big problem in the cosmic and elementary particle theory. Sakharov’s three conditions are known to be necessary for matter to be predominant in the universe; they are baryon number violation, C and CP violation, and nonequilibrium. CP symmetry holds if the laws of physics are invariant under simultaneous transformations of charge (particle to antiparticle) and parity (spatial inversion). Although CP violation has been discovered in quarks, it is considered insufficient to explain the predominance of matter in the universe, and accordingly, CP violation in leptons, including neutrinos, has attracted attention. CP violation in neutrinos is represented by the complex phase δ of the neutrino mixing matrix, and if δ has a value other than 0 or ± π (with a period of 2π), CP symmetry is violated.

A strong neutrino beam is indispensable to the search for CP violation in neutrinos. Dr. Ichikawa has been involved in the conceptualization, design, and fabrication of neutrino beam generators since the beginning of the T2K experiment and played a central role in the realization of a device called an electromagnetic horn to focus the neutrino beam and increase the beam intensity. The electromagnetic horn is a highly technical device that operates in the harshest radiation environment of any neutrino beam facility. In addition to serving as a physics analysis leader, she has been the spokesperson of the T2K experiment from 2019 to 2023 leading an international experimental group consisting of about 500 collaborators. She has led the research in all aspects of the experiment.

Results published in 2020 [1] rejected nearly half of the possible values δ with a confidence level of 3σ or higher. This is the first experimental result in the world that provided a constraint on δ. The results also prefer δ =  − π/2 corresponding to CP violation, and the range of possible values δ at a confidence level of 3σ has been provided to be [− 3.41, − 0.03] for the case of the normal ordering of three neutrino masses (${m}_{1}<{m}_{2}\ll {m}_{3}$) and [− 2.54, − 0.32] for the case of the inverted ordering (${m}_{3}\ll {m}_{1}<{m}_{2}$), respectively. The symmetry-preserving values, 0 or ± πσ, are rejected at 95% confidence level, which means that the results indicate CP violation in neutrinos with 95% confidence.

In the world, the US NOνA experiment of competing performance is following up the T2K experiment, and furthermore, next-generation projects are being prepared in the world. In Japan, Hyper-Kamiokande is under construction, and the measurement of δ-value is one of its main objectives. In addition to the enlargement of the neutrino detector at Hyper-Kamiokande, the further enhancement of neutrino beam intensity is planned to discover CP violation and to measure CP phase with high precision. Another large-scale project, DUNE, is also prepared in the USA for the measurement of δ. The results of T2K will have a significant impact on these large-scale projects as well as on future research in particle physics and astrophysics.