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Exceptional points (EPs) are degeneracies in open wave systems where at least two energy levels and their corresponding eigenstates coalesce. We report evidence of the existence of EPs in 3D plasmonic nanostructures. The systems are…

Optics · Physics 2017-02-02 Ashok Kodigala , Thomas Lepetit , Boubacar Kanté

The intricate complex eigenvalues of non-Hermitian Hamiltonians manifest as Riemann surfaces in control parameter spaces. At the exceptional points (EPs), the degeneracy of both eigenvalues and eigenvectors introduces noteworthy topological…

Quantum Physics · Physics 2025-09-08 Sen Zhang , Yangyu Huang , Lei Yu , Kaixuan He , Ning Zhou , Dingbang Xiao , Xuezhong Wu , Franco Nori , Hui Jing , Xin Zhou

Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant…

Exceptional points are complex-valued spectral singularities that lead to a host of intriguing features such as loss-induced transparency - a counterintuitive process in which an increase in the system's overall loss can lead to enhanced…

Quantum Physics · Physics 2021-12-13 Konrad Tschernig , Kurt Busch , Demetrios N. Christodoulides , Armando Perez-Leija

The spectral form factor is a dynamical probe for level statistics of quantum systems. The early-time behaviour is commonly interpreted as a characterization of two-point correlations at large separation. We argue that this interpretation…

Disordered Systems and Neural Networks · Physics 2025-10-07 Wouter Buijsman , Vadim Cheianov , Vladimir Gritsev

We study the connection between exceptional points (EPs) and optimal parameter estimation, in a simple system consisting of two counter-propagating traveling wave modes in a microring resonator. The unknown parameter to be estimated is the…

Quantum Physics · Physics 2025-11-18 Robert L. Cook , Liwen Ko , K. Birgitta Whaley

This work presents a theory of the frequency-resolved light emission of active two-dimensional dielectric microresonators, which are characterized by a highly non-paraxial mode structure and frequently feature a position-dependent…

Optics · Physics 2009-06-16 Henning Schomerus

We demonstrate that a circuit comprising two unstable LC resonators coupled via a gyrator supports an exceptional point of degeneracy (EPD) with purely real eigenfrequency. Each of the two resonators includes either a capacitor or an…

Applied Physics · Physics 2021-10-06 Kasra Rouhi , Alireza Nikzamir , Alexander Figotin , Filippo Capolino

Exceptional points are spectral singularities where both eigenvalues and eigenvectors collapse onto a single mode, causing the system behavior to shift abruptly and making it highly responsive to even small perturbations. Although widely…

Electromagnetic rigidity which exists in large-scale optical resonators if pumping frequency is detuned from the eigenfrequency of resonator have sophisticated spectral dependence which allows to obtain sensitivity better than the Standard…

General Relativity and Quantum Cosmology · Physics 2009-11-07 F. Ya. Khalili

One of the most surprising features of effectively non-Hermitian physical systems is their potential to exhibit a striking nonlinear response and fragility to small perturbations. This feature arises from spectral singularities known as…

Mesoscale and Nanoscale Physics · Physics 2026-02-05 Subhajyoti Bid , Henning Schomerus

We study the problem of robust performance of quantum systems under structured uncertainties. A specific feature of closed (Hamiltonian) quantum systems is that their poles lie on the imaginary axis and that neither a coherent controller…

Quantum Physics · Physics 2021-10-12 S G Schirmer , F C Langbein , C A Weidner , E A Jonckheere

The Nernst effect is known to be a sensitive probe of the scattering mechanisms. Large Nernst effects, a decade ago a topic mainly in vortex dynamics in superconductors, have recently attracted interest in correlated systems like cuprate…

Strongly Correlated Electrons · Physics 2010-11-22 Janik Kailasvuori

In this paper, we show a series of abstract results on fixed point regularity with respect to a parameter. They are based on a Taylor development taking into account a loss of regularity phenomenon, typically occurring for composition…

Dynamical Systems · Mathematics 2018-04-04 Julien Sedro

Using a nonperturbative approach we examine the large frequency asymptotics of the two-point level density correlator in weakly disordered metallic grains. This allows us to study the behavior of the two-level structure factor close to the…

Condensed Matter · Physics 2016-08-31 A. V. Andreev , B. L. Altshuler

A special kind of degeneracies known as the exceptional points (EPs), for resonant states on a dielectric periodic slab, are investigated. Due to their unique properties, EPs have found important applications in lasing, sensing,…

Optics · Physics 2018-06-20 Amgad Abdrabou , Ya Yan Lu

Effective field theories have often been applied to systems with deeply inelastic reactions that produce particles with large momenta outside the domain of validity of the effective theory. The effects of the deeply inelastic reactions have…

High Energy Physics - Phenomenology · Physics 2016-09-21 Eric Braaten , H. -W. Hammer , G. Peter Lepage

Exceptional points (EPs) are distinct characteristics of non-Hermitian Hamiltonians that have no counterparts in Hermitian systems. In this study, we focus on EPs in continuous systems rather than discrete non-Hermitian systems, which are…

Quantum Physics · Physics 2025-05-13 Y. T. Wang , R. Wang , X. Z. Zhang

Advancements in physics are often motivated/accompanied by advancements in our precision measurements abilities. The current generation of atomic and optical interferometers is limited by shot noise, a fundamental limit when estimating a…

Quantum Physics · Physics 2014-11-20 Luca Pezze' , Augusto Smerzi

We extend the idea of weak measurements to the general case, provide a complete treatment and obtain results for both the regime when the pre-selected and post-selected states (PPS) are almost orthogonal and the regime when they are exactly…

Quantum Physics · Physics 2015-03-17 Shengjun Wu , Yang Li