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Exceptional points, with simultaneous coalescence of eigen-values and eigen-vectors, can be realized with non-Hermitian photonic systems. With the enhanced response, exceptional points have been proposed to improve the performance of…

Optics · Physics 2022-07-22 Dalton Anderson , Manav Shah , Linran Fan

Exceptional points (EPs) are special singularities of non-Hermitian Hamiltonians. At an EP, two or more eigenvalues and the corresponding eigenstates coalesce. Recently, EP-based optical gyroscope near an EP was extensively investigated to…

A theoretical model based on two-point scatterers is suggested to investigate scattering of partially coherent radiation by a non-Hermitian localized structure, invariant under the simultaneous symmetry operations of parity inversion and…

Optics · Physics 2019-10-23 Paulo. A. Brandão , Solange B. Cavalcanti

We reveal a novel topological property of the exceptional points in a two-level parity-time symmetric system and then propose a scheme to detect the topological exceptional points in the system, which is embedded in a larger Hilbert space…

Quantum Physics · Physics 2017-08-02 Jian Xu , Yan-Xiong Du , Wei Huang , Dan-Wei Zhang

We consider a parity-time ($\mathcal{PT}$-) symmetric waveguide consisting of a localized gain and loss elements separated by a variable distance. The situation is modelled by a Schr\"odiner operator with localized complex…

Mathematical Physics · Physics 2019-10-10 D. I. Borisov , D. A. Zezyulin

We show that a composite quantum system described by the tensor product of multiple systems each with a leading-order exceptional point (a non-Hermitian degeneracy at which not only eigenvalues but also eigenstates coalesce) exhibits a…

Quantum Physics · Physics 2025-07-28 Jan Wiersig , Weijian Chen

We investigate the properties of multidimensional parity-time symmetric periodic systems whose non-Hermitian periodicity is an integer multiple of the underlying Hermitian system's periodicity. This creates a natural set of degeneracies…

Optics · Physics 2016-05-25 Alexander Cerjan , Aaswath Raman , Shanhui Fan

Exceptional points (EPs) are singularities in the parameter space of a non-Hermitian system where eigenenergies and eigenstates coincide. They hold promise for enhancing sensing applications, but this is limited by the divergence of shot…

Optics · Physics 2025-04-07 Xu Zheng , Y. D. Chong

Non-Hermitian singularities known as exceptional-points (EPs) have been shown to exhibit increased sensitivities but the observation of EPs has so far been limited to wavelength scaled systems subject to diffraction limit. We propose a…

Optics · Physics 2019-04-03 J. -H. Park , A. Ndao , W. Cai , L. -Y. Hsu , A. Kodigala , T. Lepetit , Y. -H. Lo , B. Kanté

We investigate experimentally and analytically the coalescence of reflectionless (RL) states in symmetric complex wave-scattering systems. We observe RL-exceptional points (EPs), first, with a conventional Fabry-Perot system for which the…

Classical Physics · Physics 2022-06-01 Clément Ferise , Philipp del Hougne , Simon Félix , Vincent Pagneux , Matthieu Davy

Open systems with non-Hermitian degeneracies called exceptional points show a significantly enhanced response to perturbations in terms of large energy splittings induced by a small perturbation. This reaction can be quantified by the…

Quantum Physics · Physics 2023-09-08 Jan Wiersig

Unique and highly tunable optical properties of PT-symmetric systems and metamaterials enable a plenty of entirely new linear and nonlinear optical phenomena with numerous applications, e.g., for designing subdiffraction lenses,…

Optics · Physics 2019-04-15 Denis Novitsky , Alexander Shalin , Andrey Novitsky

Using transfer-matrix methods, we investigate the response of a multilayered metamaterial system containing defects to an incident acoustic plane wave at normal or oblique incidence. The transmission response is composed of pass-bands with…

Materials Science · Physics 2018-06-28 D. Psiachos , M. M. Sigalas

Non-Hermitian systems have recently shown new possibilities to manipulate wave scattering by exploiting loss, yet coherent perfect absorption at an exceptional point (CPA EP) remains elusive in acoustics. Here we demonstrate it based on a…

Applied Physics · Physics 2025-06-06 Yi-Fei Xia , Zi-Xiang Xu , Yu-Ting Yan , An Chen , Jing Yang , Bin Liang , Jian-Chun Cheng , Johan Christensen

Superscattering, i.e., a phenomenon of the scattering cross section from a subwavelength object exceeding the single-channel limit, has important prospects in enhanced sensing/spectroscopy, solar cells, and biomedical imaging.…

We demonstrate that a periodic waveguide comprising of uniform lossless segments together with discrete gain and radiating elements supports exceptional points of degeneracy (EPDs). We provide analytical expressions for all possible…

Applied Physics · Physics 2021-06-16 Ahmed F. Abdelshafy , Tarek Mealy , Ehsan Hafezi , Alireza Nikzamir , Filippo Capolino

Exceptional points are singularities in the spectrum of non-Hermitian systems in which several eigenvectors are linearly dependent and their eigenvalues are equal to each other. Usually it is assumed that the order of the exceptional point…

Quantum Physics · Physics 2025-12-11 Timofey T. Sergeev , Evgeny S. Andrianov , Alexander A. Zyablovsky

We examine the physical manifestations of exceptional points and passage times in a two-level system which is subjected to quantum measurements and which admits a non-Hermitian description. Using an effective Hamiltonian acting in the…

Quantum Physics · Physics 2015-06-12 A. Thilagam

Scattering experiments with microwave cavities were performed and the effects of broken time-reversal invariance (TRI), induced by means of a magnetized ferrite placed inside the cavity, on an isolated doublet of nearly degenerate…

Chaotic Dynamics · Physics 2014-05-07 S. Bittner , B. Dietz , H. L. Harney , M. Miski-Oglu , A. Richter , F. Schäfer

We review some recent work on the occurrence of coalescing eigenstates at exceptional points in non-Hermitian systems and their influence on physical quantities. We particularly focus on quantum dynamics near exceptional points in open…

Quantum Physics · Physics 2021-10-27 Savannah Garmon , Takafumi Sawada , Kenichi Noba , Gonzalo Ordonez