Department of Physics, Hong Kong Baptist University
Non-Abelian theories are one of the foundations of modern physics. Operations defined by non-Abelian groups are non-commutative in character, meaning that the outcomes of sequential operations depend on the order of execution. Some non-Abelian processes can be mathematically captured by unitary matrices, which can manifest as a Berry-phase matrix that connects holonomic adiabatic evolutions of multiple states in parameter space. Because the Berry phase is pervasive in a wide variety of systems, non-Abelian operations are realizable in classical waves such as sound and light. In this talk, I will present our recent works that realize non-Abelian braiding in acoustics  and in photonics . Here, the braiding operations are implemented using coupled waveguide arrays, which are adiabatically modulated along the guiding direction to enforce a multi-state Berry-phase matrix that swaps the modal dwell sites. The evolution of the guiding modes maps to the generators of braid groups. The non-Abelian characteristics are revealed by switching the order of two distinct braiding operations involving at least three modes.
Z.-G. Chen, R.-Y. Zhang, C. T. Chan, and G. Ma, Classical Non-Abelian Braiding of Acoustic Modes, Nat. Phys. 18, 179 (2022).
X.-L. Zhang, F. Yu, Z.-G. Chen, Z.-N. Tian, Q.-D. Chen, H.-B. Sun, and G. Ma, Non-Abelian Braiding on Photonic Chips, Nat. Photon. 16, 390 (2022).
Brief CV of Prof. Guancong Ma:
Dr. Guancong Ma is currently a professor of physics at Hong Kong Baptist University. He received B.Sc. in applied physics at the South China University of Technology in 2007 and then Ph.D. in physics at the Hong Kong University of Science and Technology in 2012. After that, he became a postdoc fellow at the Institute for Advanced Study and the Department of Physics at the same institution until 2017, when he joined the Department of Physics at Hong Kong Baptist University. He now serves as a member of the Executive Committee of the Physics Society of Hong Kong. Dr. Ma was awarded the “Young Investigator Award 2021” by the International Phononics Society, and was selected as one of the “Top 10 Rising Stars in Science and Technology 2021” by the China Association for Science and Technology. He is the recipient of the “C. N. Yang Award” in 2022 – a prize from the Association of Asia Pacific Physical Societies and the Asia Pacific Center for Theoretical Physics. Dr. Ma has obtained the support from the National Natural Science Foundation of China’s Excellent Young Scientists Scheme (Hong Kong & Macao).
Dr. Ma's research currently focuses on studying topological physics and non-Hermitian physics in using acoustic-wave and mechanical platforms. He is also interested in metamaterials and complex waves. He has published over 50 papers in peer-reviewed journals, including Science, Nature, Nature Materials, Nature Physics, Physical Review X, Physical Review Letters. His papers have received over 7000 citations, which, according to Charivate, makes him one of the “World’s Top 2% Scientists.” Dr. Ma also holds 11 patents from the United States and China.
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