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Encircling an exceptional point (EP) in a parity-time (PT) symmetric system has shown great potential for chiral optical devices, such as chiral mode switching for symmetric and anti-symmetric modes. However, the chiral switching for…

Non-Hermitian systems exhibit a variety of unique features rooted in the presence of exceptional points (EP). The distinct topological structure in the proximity of an EP gives rise to counterintuitive behaviors absent in Hermitian systems,…

Quantum Physics · Physics 2025-05-13 He Zhang , Tong Liu , Zhongcheng Xiang , Kai Xu , Heng Fan , Dongning Zheng

Non-Hermitian systems have attracted significant interest because of their intriguing and useful properties, including exceptional points (EPs), where eigenvalues and the corresponding eigenstates of non-Hermitian operators become…

Quantum Physics · Physics 2025-03-28 Hamed Ghaemi-Dizicheh , Shahram Dehdashti , Andreas Hanke , Ahmed Touhami , Janis Nötzel

The dynamics of spontaneous emission of an atomic system is studied in the framework of an open quantum system. The resulting quantum master equation for the atomic system is non hermitian. The generator $\mathcal{L}$ can possess…

Quantum Physics · Physics 2016-03-23 Morag Am-Shallem , Ronnie Kosloff , Nimrod Moiseyev

Owing to the presence of exceptional points (EPs), non-Hermitian (NH) systems can display intriguing topological phenomena without Hermitian analogs. However, experimental characterizations of exceptional topological invariants have been…

Bound states in the continuum (BICs) and exceptional points (EPs), as two distinct physical singularities represented by complex frequencies in non-Hermitian systems, have garnered significant attention and clear definitions in their…

We classify gapped phases and characteristic nodal points of non-Hermitian band structures on two-dimensional nonorientable parameter spaces. Such spaces arise in a wide range of physical systems in the presence of nonsymmorphic parameter…

Mesoscale and Nanoscale Physics · Physics 2026-03-30 J. Lukas K. König , Kang Yang , André Grossi Fonseca , Sachin Vaidya , Marin Soljačić , Emil J. Bergholtz

Exceptional points (EPs) are singularities of energy levels in non-Hermitian systems. In this Letter, we demonstrate the surface of EPs on a magnon polariton platform composed of coupled magnons and microwave photons. Our experiments show…

Mesoscale and Nanoscale Physics · Physics 2019-12-11 Xufeng Zhang , Kun Ding , Dafei Jin , Xianjing Zhou , Jing Xu

Dynamic encircling a second-order exception point (EP) exhibit chiral state transfer, while there is few research on dynamic encircling multiple and higher-order EPs. Here, we study proximity-encirclement of the EPs in a multimode…

Optics · Physics 2023-05-26 Zheng Fan , Dan Long , Xuan Mao , Guo-Qing Qin , {Min Wang , Gui-Qin Li , Gui-Lu Long

One of the most fascinating and puzzling aspects of non-Hermitian systems is their spectral degeneracies, i.e., exceptional points (EPs), at which both eigenvalues and eigenvectors coalesce to form a defective state space. While coupled…

Mesoscale and Nanoscale Physics · Physics 2023-03-08 Kuangyin Deng , Xin Li , Benedetta Flebus

Exceptional points (EPs), indicative of parity-time (PT) symmetry breaking, play a central role in non-Hermitian physics, yet most studies begin from deliberately engineered effective Hamiltonians whose parameters are tuned to exhibit…

Quantum Physics · Physics 2026-03-12 Eric R. Bittner , Bhavay Tyagi , Kevin E. Bassler

We propose an efficient optomechanical mass sensor operating at exceptional points (EPs), non-hermitian degeneracies where eigenvalues of a system and their corresponding eigenvectors simultaneously coalesce. The benchmark system consists…

Mesoscale and Nanoscale Physics · Physics 2019-08-07 P. Djorwé , Y. Pennec , B. Djafari-Rouhani

Non-Hermitian systems associated with exceptional points (EPs) are expected to demonstrate a giant response enhancement for various sensors. The widely investigated enhancement mechanism based on diverging from an EP should destroy the EP…

Optics · Physics 2023-07-19 Xuan Mao , Guo-Qing Qin , Hao Zhang , Bo-Yang Wang , Dan Long , Gui-Qin Li , Gui-Lu Long

The amplitude of resonant oscillations in a non-Hermitian environment can either decay or grow in time, corresponding to a mode with either loss or gain. When two coupled modes have a specific difference between their loss or gain, a…

Classical Physics · Physics 2025-11-07 N. J. Lambert , A. Schumer , J. J. Longdell , S. Rotter , H. G. L. Schwefel

The fascinating realm of non-Hermitian physics with the interplay of parity (P) and time-reversal (T) symmetry has been witnessing immense attention in exploring unconventional physics at Exceptional Point (EP) singularities. Particularly,…

Optics · Physics 2024-05-20 Dinesh Beniwal , Arnab Laha , Adam Miranowicz , Somnath Ghosh

Controlling gain and loss of coupled optical cavities can induce non-Hermitian degeneracies of eigenstates, called exceptional points (EPs). Various unconventional phenomena around EPs have been reported, and expected to incorporate extra…

Phase transitions can dramatically alter system dynamics, unlocking new behavior and improving performance. Exceptional points (EPs), where the eigenvalues and corresponding eigenvectors of a coupled linear system coalesce, are particularly…

Quantum Physics · Physics 2025-07-15 Hanfeng Wang , Kurt Jacobs , Donald Fahey , Yong Hu , Dirk R. Englund , Matthew E. Trusheim

Higher-order exceptional points (EPs) in non-Hermitian systems showcase diverse physical phenomena but require more parameter space freedom or symmetries. It leads to a challenge for the exploration of high-order EP geometries in…

Quantum Physics · Physics 2025-10-22 Hao Chen , Xiao Qin , Jian-Jun Dong , Yu-Yu Zhang , Zi-Xiang Hu

We study exceptional points (EPs) of a nonhermitian Hamiltonian $\hat{H}(\lambda,\delta)$ whose parameters $\lambda \in {\mathbb C}$ and $\delta \in {\mathbb R}$. As the real control parameter $\delta$ is varied, the $k$-th EP (or $k$-th…

Quantum Physics · Physics 2023-03-22 Milan Šindelka , Pavel Stránský , Pavel Cejnar

We propose a novel type of exceptional points, dubbed interaction-enabled $n$-fold exceptional points [EP$n$s ($n=2,3$)] -- EP$n$s protected by topology that are prohibited at the non-interacting level. Specifically, we demonstrate that…

Mesoscale and Nanoscale Physics · Physics 2026-02-17 Musashi Kato , Tsuneya Yoshida