What’s New

We are pleased to announce the HK Forum on Quantumology香港量子學論壇 , held in celebration of the International Year of Quantum Science and Technology (IYQ). The event is organized by the HK Institute of Quantum Science and Technology in collaboration with the HK Branch of the Quantum Science Centre of the Guangdong-Hong Kong-Macau Greater Bay Area. Scheduled for 23 November 2025 at the Rysan Huang Theatre, of HKU, this event offers a distinguished platform for academic exchange, collaboration, and innovation in quantum science and technology. You are cordially invited to participate in a series of engaging activities, including keynote and invited talks, as well as roundtable discussions featuring leading quantum scientists. The event program includes: Please find tentative program: 09:00 – 09:20: Welcome Address 09:20 – 09:30: Inauguration Ceremony (HK Branch for QSC) 09:30 – 12:20: Key-note Presentations 14:00 – 16:30: Invited Talks 16:50 – 17:50: Round Table Discussion (An interactive forum for knowledge exchange and collaboration) Please register at no cost using the link below to secure your participation and receive additional event details. Kindly note that, due to the HKU visitor registration system, you will need to bring and present the confirmation email upon entry. We look forward to your valuable contribution to this landmark celebration of quantum science and technology. [Registration] For HKU members (HKU Portal login is required): https://hkuems1.hku.hk/hkuems/ec_hdetail.aspx?ueid=103117 For non-HKU members: https://hkuems1.hku.hk/hkuems/ec_hdetail.aspx?guest=Y&ueid=103117

In this talk I will discuss a non-dissipative, parity-odd transport of (2+1)-dimensional relativistic fermions generated by torsion, namely the torsional Hall viscosity. After introducing the torsional Hall viscosity of massive Dirac fermions, I will discuss two experimentally relevant deformations of this phenomenon. Firstly, in the presence of a constant electromagnetic field, we find that the magnetic field induces a contribution to the torsional Hall viscosity that competes with the one originating from the Dirac mass. Then, we consider the band structure deformation quadratic in momentum terms that was proposed by Bernevig–Hughes–Zhang (BHZ). We find that the BHZ deformation enhances the torsional Hall viscosity in magnitude, but reverses its sign as compared to the standard massive Dirac fermion, indicating a Hall response in opposite direction to the typical Hall viscous force. Nevertheless, the torsional Hall viscosity still discriminates between topologically trivial and nontrivial regimes. These results pave the way for a deeper understanding of the topological response due to torsion and its possible verification in experiments.

Shaping and controlling electromagnetic waves have wide-ranging scientific and practical implications. In this talk, I will present a few theoretical proposals to generate novel topological structures in light. In particular, I show that the transmission nodal lines are general topological responses from non-local metasurfaces and can be used to generate spatiotemporal optical vortices. Additionally, I discuss the possible topological structures that can occur in electromagnetic waves. I show that three-dimensional topological structures, known as hopfions and Shankar skyrmions can be created in free-space electromagnetic waves. Such complex shaping of light may be used for optical emulation of new topological physics, or be used in optical trapping and manipulation applications.