Physical Limits of Non-Hermitian and Non-Reciprocal Devices

Explore the physical limits of non-Hermitian and non-reciprocal devices in this comprehensive lecture by Henning Schomerus from the PCS Institute for Basic Science. Delve into the critical role of active elements in experimental realizations of non-Hermitian phenomena, such as the non-Hermitian skin effect and squared-Lorentzian line shape at exceptional points. Examine the fundamental constraints on passive realizations, linking causality to experimental protocols for determining the density of states. Discover how the non-Hermitian skin effect is hidden in the density of states, while the squared Lorentzian appears as a limited contrast background effect. Gain insights into the generalized time-delay operator, connecting causality constraints with experimental protocols. Investigate the practical formulation of constraints in microscopic models and explore the conceptual link between fundamental concepts and key experimental observables. Study analogous constraints on spectral features and responses in both active and passive non-Hermitian systems through various research examples provided throughout the lecture.