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The concept of exceptional point (EP) is demonstrated experimentally in the case of a simple mechanical system consisting of two linearized coupled pendulums. Exceptional points correspond to specific values of the system parameters that…

Computational Physics · Physics 2024-02-08 Nicolas Even , Benoit Nennig , Gautier Lefebvre , Emmanuel Perrey-Debain

A main distinguishing feature of non-Hermitian quantum mechanics is the presence of exceptional points (EPs). They correspond to the coalescence of two energy levels and their respective eigenvectors. Here, we use the Lipkin-Meshkov-Glick…

Statistical Mechanics · Physics 2017-10-12 Milan Šindelka , Lea F. Santos , Nimrod Moiseyev

As an important device for detecting rotation, high sensitivity gyroscope is required for practical applications. In recent years, exceptional point (EP) shows its potential in enhancing the sensitivity of sensing in optical cavity. Here we…

Optics · Physics 2020-09-25 Xuan Mao , Guo-qing Qin , Hao Zhang , Hong Yang , Min Wang , Gui-lu Long

Non-Hermitian systems have attracted much interest in recent decades, driven partly by the existence of exotic spectral singularities, known as exceptional points (EPs), where the dimensionality of the system evolution operator is reduced.…

Exceptional points (EP) are non-Hermitian spectral degeneracies where both eigenvalues and their corresponding eigenvectors coalesce. Recently, EPs have attracted a lot of attention as a means to enhance the responsivity of sensors, via the…

Applied Physics · Physics 2022-02-22 Rodion Kononchuk , Jizhe Cai , Fred Ellis , Ramathasan Thevamaran , Tsampikos Kottos

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

A numerical algorithm is proposed to deal with parametric eigenvalue problems involving non-Hermitian matrices and is exploited to find location of defective eigenvalues in the parameter space of non-Hermitian parametric eigenvalue…

Computational Physics · Physics 2026-01-23 Benoit Nennig , Martin Ghienne , Emmanuel Perrey-Debain

We study interacting ultracold atoms in a three-dimensional (3D) harmonic trap with spin-selective dissipations, which can be effectively described by non-Hermitian parity-time ($\mathcal{PT}$) symmetric Hamiltonians. By solving the…

Quantum Gases · Physics 2019-06-21 Lei Pan , Shu Chen , Xiaoling Cui

In this study, we propose the application of non-Hermitian photonic crystals (PCs) with anisotropic emissions. Unlike a ring of exceptional points (EPs) in isotropic non-Hermitian PCs, the EPs of anisotropic non-Hermitian PCs appear as…

Optics · Physics 2023-03-29 Zhifeng Li , Hai Lin , Rongxin Tang , Haitao Chen , Jiaru Tang , Rui Zhou , Jing Jin , Y. Liu

By preparing a sensor system around isolated exceptional points, one can obtain a great enhancement of the sensitivity benefiting from the non-Hermiticity. However, this comes at the cost of reduction of the flexibility of the system, which…

The $\mathcal{PT}$-symmetric non-Hermitian quantum Rabi model (QRM) with imaginary coupling is solved using the Bogoliubov operators approach. A transcendental function responsible for the exact solutions is derived, with its zeros yielding…

Quantum Physics · Physics 2025-07-15 Jiong Li , Yi-Cheng Wang , Li-Wei Duan , Qing-Hu Chen

Exceptional points (EPs) play a vital role in non-Hermitian (NH) systems, driving unique dynamical phenomena and promising innovative applications. However, the NH dynamics at EPs remains obscure due to the incomplete biorthogonal…

Quantum Physics · Physics 2025-08-06 Yan Xing , Xuedong Zhao , Hui Jing , Shi-Lei Su

Non-Hermitian physics has become a fundamental framework for understanding open systems where gain and loss play essential roles, with impact across photonics, quantum science, and condensed matter. While the role of complex eigenvalues is…

Quantum Physics · Physics 2025-12-23 Kyu-Won Park , Soojoon Lee , Kabgyun Jeong

The energy level degeneracies, also known as exceptional points (EPs), are crucial for comprehending emerging phenomena in materials and enabling innovative functionalities for devices. Since EPs were proposed over half a century age, only…

Quantum Physics · Physics 2025-03-12 Yang Wu , Dongfanghao Zhu , Yunhan Wang , Xing Rong , Jiangfeng Du

Exceptional points (EPs) are special parameter values of a non-Hermitian eigenvalue problem where eigenfunctions corresponding to a multiple eigenvalue coalesce. In optics, EPs are associated with a number of counter-intuitive wave…

Optics · Physics 2019-10-08 Amgad Abdrabou , Ya Yan Lu

The occurrence of exceptional points (EPs) is a fascinating non-Hermitian feature of open systems. A level-repulsion phenomenon between two complex states of an open system can be realized by positioning an EP and its time-reversal (T)…

Optics · Physics 2024-05-15 Arnab Laha , Adam Miranowicz , R. K. Varshney , Somnath Ghosh

Non-Hermitian systems exhibit many peculiar dynamic behaviors which never showed up in Hermitian systems. The existence of spectral singularity (SS) for a non-Hermitian scattering center provides a lasing mechanism in the context of quantum…

Quantum Physics · Physics 2019-04-11 K. L. Zhang , P. Wang , Z. Song

The emergence of exceptional points (EPs) in the parameter space of a non-hermitian (2D) eigenvalue problem is studied in a general sense in mathematical physics, and has in the last decade successively reached the scope of experiments. In…

One of the important features of non-Hermitian Hamiltonians is the existence of a unique type of singularities, the so-called exceptional points (EPs). When the corresponding systems operate around such singularities, they exhibit…

Optics · Physics 2025-08-26 Ioannis Kiorpelidis , Konstantinos G. Makris

The past few years have witnessed growing interests in exceptional points (EPs) in various domains, including photonics, acoustics and electronics. However, EPs have mainly been realized based on the degeneracy of resonances of physical…

Optics · Physics 2021-09-20 Changqing Wang , William R. Sweeney , A. Douglas Stone , Lan Yang