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Exceptional points (EPs) are degeneracies of non-Hermitian systems, where both eigenvalues and eigenvectors coalesce. Classical and quantum systems exhibiting high-order EPs have recently been identified as fundamental building blocks for…

We present a new method to diagnose strong coupling in multi-mode open systems. Our method presents a non-trivial extension of exceptional point (EP) analysis employed for such systems; specifically, we show how eigenvectors can not only…

Quantum Physics · Physics 2021-05-12 C. Kow , Z. Xiao , A. Metelmann , A. Kamal

A Dirac point in the Hermitian photonic system will split into a pair of exceptional points (EPs) or even spawn a ring of EPs if non-Hermiticity is involved. Here, we present a new type of non-Hermitian Dirac point which is situated in the…

Optics · Physics 2024-04-29 Jun Wang , Jie Liu , Peng Hu , Qiao Jiang , Dezhuan Han

We engineer mechanical gain (loss) in system formed by two optomechanical cavities (OMCs), that are mechanically coupled. The gain (loss) is controlled by driving the resonator with laser that is blue (red) detuned. We predict analytically…

Mesoscale and Nanoscale Physics · Physics 2019-02-18 P. Djorwe , Y. Pennec , B. Djafari-Rouhani

Exceptional points (EPs) are remarkable spectral degeneracies in a non-Hermitian system's parameter space, where both eigenvalues and eigenstates coalesce. Here, we show that in non-Hermitian molecular chiral systems the position of EPs in…

Quantum Physics · Physics 2025-12-02 Nicola Mayer , Alexander Löhr , Nimrod Moiseyev , Misha Ivanov , Olga Smirnova

Exceptional points (EPs) are singularities that arise in non-Hermitian physics. Current research efforts focus only on systems supporting isolated EPs characterized by increased sensitivity to external perturbations, which makes them…

Rydberg atoms, with their large transition dipole moments and extreme sensitivity to electric fields, have attracted widespread attention as promising candidates for next-generation quantum precision electrometry. Meanwhile, exceptional…

Atomic Physics · Physics 2026-02-10 Chao Liang , Ce Yang , Wei Huang , Li You

We propose two non-Hermitian arrays consisting of $N=2l+1$ waveguides and exhibiting parity-time ($\mathcal{PT}$) or anti-$\mathcal{PT}$ symmetry for investigating light transfer dynamics based on $N$th-order exceptional points (EPs). The…

Optics · Physics 2022-05-23 Chuanxun Du , Gang Wang , Yan Zhang , Jin-Hui Wu

Exceptional points (EPs), intrinsic to non-Hermitian systems, exhibit singular spectral responses with extreme sensitivity to external perturbations, offering new opportunities for precision sensing. In this work, we investigate the sensing…

Optics · Physics 2025-09-29 Neha Ahlawat , Saurabh Mani Tripathi

In this study, we investigated the propagation pattern and the site-to-site correlation function in a PT-symmetric waveguide array with different input quantum states. Recognizing the stark difference in propagation pattern before and after…

Non-Hermitian optics has revealed a series of counterintuitive phenomena with profound implications for sensing, lasing, and light manipulation. While the non-Hermiticity of Hamitonians is well-recognized, recent advancements in…

Optics · Physics 2024-04-19 Jipeng Xu , Yuanhao Mao , Jianfa Zhang , Biao Yang , Ken Liu , Zhihong Zhu

We study the phenomenon of spontaneous symmetry breaking in dissipationless resonant tunneling heterostructures (RTS). To describe the quantum transport in this system we apply both the nonequilibrium Green function formalism based on a…

Mesoscale and Nanoscale Physics · Physics 2016-08-18 A. A. Gorbatsevich , N. M. Shubin

Eigenstate coalescence in non-Hermitian systems is widely observed in diverse scientific domains encompassing optics and open quantum systems. Recent investigations have revealed that adiabatic encircling of exceptional points (EPs) leads…

Quantum Physics · Physics 2023-06-13 Jung-Wan Ryu , Jae-Ho Han , Chang-Hwan Yi , Moon Jip Park , Hee Chul Park

Non-Hermitian systems distinguish themselves from Hermitian systems by exhibiting a phase transition point called an exceptional point (EP), which is the point at which two eigenstates coalesce under a system parameter variation. Many…

Mesoscale and Nanoscale Physics · Physics 2016-04-20 Kun Ding , Guancong Ma , Meng Xiao , Z. Q. Zhang , C. T. Chan

The emergence of exceptional points in non-Hermitian systems represents an intriguing phenomenon characterized by the coalescence of eigenenergies and eigenstates. When a system approaches an exceptional point, it exhibits a heightened…

Mesoscale and Nanoscale Physics · Physics 2025-05-21 Shu-Xuan Wang , Zhongbo Yan

Non-Hermitian physics has found a fertile ground in optics. Recently, the study of mode degeneracies, i.e. exceptional points, has led to the discovery of intriguing and counterintuitive phenomena. Degeneracies are typically modeled through…

Optics · Physics 2022-03-29 Stefano Biasi , Riccardo Franchi , Filippo Mione , Lorenzo Pavesi

In a recent paper entitled "Winding around non-Hermitian singularities" by Zhong et al., published in Nat. Commun. 9, 4808 (2018), a formalism is proposed for calculating the permutations of eigenstates that arise upon encircling (multiple)…

Quantum Physics · Physics 2019-02-21 Eric J. Pap , Daniël Boer , Holger Waalkens

We investigate a scheme for observing the third-order exceptional point (EP3) in an ion-cavity setting. In the lambda-type level configuration, the ion is driven by a pump field, and the resonator is probed with another weak laser field. We…

Quantum Physics · Physics 2023-11-07 Jinuk Kim , Taegyu Ha , Donggeon Kim , Dowon Lee , Ki-Se Lee , Jongcheol Won , Youngil Moon , Moonjoo Lee

The dispersion of a three-way waveguide is engineered to exhibit exceptional modal characteristics. Two coupled waveguides with Parity-Time (PT) symmetry have been previously demonstrated to exhibit second order exceptional points of…

Applied Physics · Physics 2022-06-08 Farshad Yazdi , Tarek Mealy , Alireza Nikzamir , Robert Marosi , Filippo Capolino

Exceptional points (EPs) are complex singularities of parametric linear operators where two or more eigenvalues and eigenvectors coalesce. EPs are attracting increasing interest in mechanical metamaterials due to their strong potentials for…

Applied Physics · Physics 2022-04-05 Weidi Wang , Alireza V. Amirkhizi