Research: Short-lived quanta of light topologically knotted

From the effective description of dissipative systems in terms of so called non-Hermitian Hamiltonians, novel metallic phases featuring nodal lines in the form of topological knots have recently been predicted. Using an experimental technique based on the lossy time evolution of single light quanta and their subsequent interferometric measurement, researchers from Beijing, Hefei, and Dresden have now observed key aspects of the aforementioned exotic non-Hermitian phases. In particular, various knotted nodal lines have been directly mapped out and their robustness with respect to imperfections in the simulation protocol corresponding to defects in a host material has been experimentally studied.

K. Wang, L. Xiao, J. C. Budich, W. Yi, P. Xue,
Simulating Exceptional Non-Hermitian Metals with Single-Photon Interferometry,
Phys. Rev. Lett. 127, 026404 (2021) (arXiv)