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The classical wave system has demonstrated itself as an excellent platform to realize and investigate novel phenomena and physics. The bedrock principle is to utilize the macroscopic quantities obtained from the homogenization or mean-field treatment. However, it usually deals with Hermitian problems and averages out fluctuations. Therefore, the presentation will cover two topics: non-Hermitian physics and Casimir effect. The first part focuses on the impact of non Hermitian ingredients on soliton formation and dynamics. By constructing a soliton phase diagram, two distinct soliton phases and their transitions are identified. A Wannier-function-based nonlinear Hamiltonian shows that soliton formation critically depends on how skin-mode localization and band nonreciprocity suppress or enhance wave dispersion. Both soliton phases have been demonstrated to be dynamically accessible from bulk and edge excitations. The second part discusses the influence of the metal’s surface electrons on Casimir forces. A three-dimensional frame transformation method has been established by embedding mesoscopic boundary conditions of electromagnetic fields. We find that mesoscopic Casimir forces are sensitive to the surface electron behavior, including spill-in and spill-out, as verified by the multiple scattering method and proximity force approximation. The mechanism has finally been revealed as Casimir softening distances rooted in quantum surface responses of electrons.

There is a holographic correspondence between (1) nD quantum systems with symmetry C and (2) nD boundaries of the n+1D topological order Z(C), where Z(C) is mathematically the Drinfeld center of C. Such mysterious topological holography has numerous applications and consequences, especially in the recent emerging field of generalized symmetry. By a rigorous construction and proof in 1+1D, we show that the Drinfeld center Z(C) naturally arise as the category of fixed-point local tensors with symmetry C, thus revealing the origin of topological holography. This talk is based on arXiv:2412.07198.

Quantum Key Distribution (QKD) offers information-theoretic security but relies critically on authenticated classical channels for post-processing steps (e.g., basis sifting and key reconciliation). Without authentication, these channels are vulnerable to man-in-the-middle attacks. Traditional methods require Alice and Bob to pre-share symmetric keys via physical meetings—a solution incompatible with multi-user QKD networks. We experimentally demonstrate a practical solution using post-quantum signature algorithms to authenticate QKD classical channels. This approach was validated under multiple QKD network topologies in laboratory environments and a real-world metropolitan QKD network operating continuously for 36 days. Our implementation provides quantum-resistant security while uniquely requiring only short-term security (e.g., ~1 second during authentication), contrasting with long-term security assumptions for post-quantum encryption. Additionally, we propose a quantum-teleportation-based protocol for message authentication that simultaneously ensures confidentiality—enabling secure key reconciliation in QKD.