“Algebraic Bethe Ansatz, Yang-Baxter Equation and All That” by Prof. Yunfeng JIANG on Tuesday, February 24 – 26, 2026, HOC117/CYM522, HKU

This lecture series provides a systematic introduction to the Algebraic Bethe Ansatz (ABA), also known as the Quantum Inverse Scattering Method (QISM): a powerful framework for solving quantum integrable models exactly. We will begin with its basic construction, demonstrating how to obtain the exact spectra of paradigmatic models such as the Heisenberg spin chain, the Lieb-Liniger model, and the 6-vertex model. We will then explore the rich mathematical structure underlying the method, focusing on the central role of the Yang-Baxter equation and its profound connection to quantum group theory. If time permits, we will discuss extensions of the formalism to compute dynamical quantities, such as form factors and correlation functions, illustrating the full power of ABA as a tool for non-perturbative analysis in quantum theory.

CTCP Seminar: “Recognizing gapless phases in quantum many-body physics” by Prof. Yuan YAO on Wednesday, February 11, 2026, 4:00pm CYM522, HKU

The spectral gap of quantum many-body Hamiltonians is an important but difficult concept in condensed matter. Its identification is complicated and, quite often, controversial because the gap, together with the ground-state degeneracy is a thermdynamic limit notion rather than any finite-size energy splitting.
In this talk, we will discuss a gaplessness indicator. Specifically, we prove that the ground state(s) of an SO(3)-symmetric gapped spin chain must be spin singlet(s), and the expectation value of a twisting operator asymptotically approaches unity in the thermodynamic limit, where finite-size corrections are inversely proportional to the system size. This theorem provides (i) supporting evidence for various conjectured gapped phases, and, contrapositively, (ii) a sufficient criterion for identifying gapless spin chains. We test the efficiency of our theorem by numerical simulations for a variety of spin models and show that it indeed offers a novel efficient way to identify gapless phases in spin chains with spin-rotation symmetry.

CTCP Seminar: “Mesoscopic Non-Hermitian Physics and Theory of Non-Hermitian Symmetry Breaking” by Prof. Wei CHEN on Tuesday, February 3, 2026, 4:00pm CYM522, HKU

Transforming the concept of band topology fostered in electron systems to electromagnetic waves opens a completely new direction for harnessing propagation of light. It is observed that electromagnetic modes in honeycomb photonic crystals exhibit Dirac-type frequency dispersions, which are accompanied by emergent spin degree of freedom, and that deforming the honeycomb structure in a designed way gives birth to a photonic analogue of quantum spin Hall effect. In this talk I will first show that the main physics can be captured phenomenologically by the k∙p theory, and discuss that the photonic topology can be characterized in terms of the Wilson loops based on the C_2 T symmetry. Then I will introduce examples to demonstrate how the recipe can be exploited for harnessing light and deriving advanced optic properties.

HKIQST Co-Hosts the APS Global Physics Summit 2026 in Hong Kong| Monday, 23-27 March 2026 | HKPC Building, HK

HKIQST is proud to co-host the APS Global Physics Summit 2026 Hong Kong Meeting, offering researchers across the Asia-Pacific region the most accessible pathway to participate in this premier international physics gathering.

Dual Access: Registration for the Hong Kong meeting includes full online access to the APS Global Physics Summit (15–20 March 2026), at a significantly reduced cost compared to direct APS registration. Participants can attend live-streamed talks, revisit recordings for 90 days, and explore e-posters without additional fees.
Abstract Submission: Oral abstracts submitted by 5 January 2026 may be selected for inclusion in the official APS Virtual Session.
On-Site Programme: The Hong Kong meeting (23–27 March 2026) will feature a dynamic in-person academic environment, with oral and poster presentations, networking opportunities, and engagement with a diverse community of physicists from across the region.
📍 Venue: Hong Kong Productivity Council, Kowloon Tong 🤝 Organised jointly with PSHK, and supported by APS, HKIQST, and Qebula Mind Ltd.

For registration and more information, please access: https://www.qebulamind.com/aps-conference2026

“Towards Semiconductor Topological Photonics” by Prof. Xiao HU on Monday, January 12, 2026, 2:00pm CYM522, HKU

Transforming the concept of band topology fostered in electron systems to electromagnetic waves opens a completely new direction for harnessing propagation of light. It is observed that electromagnetic modes in honeycomb photonic crystals exhibit Dirac-type frequency dispersions, which are accompanied by emergent spin degree of freedom, and that deforming the honeycomb structure in a designed way gives birth to a photonic analogue of quantum spin Hall effect. In this talk I will first show that the main physics can be captured phenomenologically by the k∙p theory, and discuss that the photonic topology can be characterized in terms of the Wilson loops based on the C_2 T symmetry. Then I will introduce examples to demonstrate how the recipe can be exploited for harnessing light and deriving advanced optic properties.

HK Institute of Quantum Science & Technology
The University of Hong Kong
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