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Exceptional points (EPs) has seen substantial advances in both experiment and theory. However, in quantum systems, higher-order exceptional points remain of great interest and possess numerous intriguing properties yet to be fully explored.…

Quantum Gases · Physics 2025-01-22 Yu-Jun Liu , Ka Kwan Pak , Peng Ren , Mengbo Guo , Entong Zhao , Chengdong He , Gyu-Boong Jo

Exceptional points (EPs) are degeneracies in open wave systems with coalescence of at least two energy levels and their corresponding eigenstates. In higher dimensions, more complex EP physics not found in two-state systems is observed. We…

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…

Large single-atom cooperativity in quantum systems is important for quantum information processing. Here, we propose to exponentially enhance the single-atom cooperativity parameter by exploiting the strongly localized effect of modes in…

Quantum Physics · Physics 2025-09-08 Qian Bin , Ying Wu , Jin-Hua Gao , Aixi Chen , Franco Nori , Xin-You Lü

We identify a general connection between the physics of exceptional points in non-Hermitian systems and the few-photon bound states in waveguide quantum electrodynamics (QED) systems. We show that, in waveguide QED systems where the local…

Quantum Physics · Physics 2019-06-12 Shanshan Xu , Shanhui Fan

We study a circuit QED setup where multiple superconducting qubits are ultrastrongly coupled to a single radio-frequency resonator. In this extreme parameter regime of cavity QED the dynamics of the electromagnetic mode is very slow…

Quantum Physics · Physics 2020-02-28 T. Jaako , J. J. Garcia-Ripoll , P. Rabl

In conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, electrons with opposite momenta bind into Cooper pairs due to an attractive interaction mediated by phonons in the material. While superconductivity naturally emerges at…

We investigate the conditions yielding plasmon-exciton strong coupling at the single emitter level in the gap between two metal nanoparticles. A quasi-analytical transformation optics approach is developed that makes possible a thorough…

Mesoscale and Nanoscale Physics · Physics 2016-09-07 Rui-Qi Li , D. Hernangómez-Pérez , F. J. García-Vidal , A. I. Fernández-Domínguez

We propose a quantum simulation of a two-level atom coupled to a single mode of the electromagnetic field in the ultrastrong-coupling regime based upon resonant Raman transitions in an atom interacting with a high finesse optical cavity…

Quantum Physics · Physics 2014-08-27 Arne L. Grimsmo , Scott Parkins

Tailoring the losses of optical systems within the frame of non-Hermitian physics has appeared very fruitful in the last few years. In particular, the description of exceptional points (EPs) with coupled resonators have become widespread.…

Non-Hermitian systems enable advanced control of wave propagation by exploiting engineered losses. This introduces an additional degree of freedom that permits the emergence of exceptional points (EPs). In this letter, we theoretically and…

The nontrivial degeneracies in non-Hermitian systems, exceptional points (EPs), have attracted extensive attention due to intriguing phenomena. Compared with commonly observed second-order EPs, high-order EPs show rich physics due to their…

Quantum Physics · Physics 2024-12-16 Yue Li , Yang Wu , Yuqi Zhou , Mengxiang Zhang , Xingyu Zhao , Yibo Yuan , Xu Cheng , Yi Li , Xi Qin , Xing Rong , Yiheng Lin , Jiangfeng Du

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

To go beyond quantum optics in free-space setups, atom-light interfaces with structured photonic environments are often employed to realize unconventional quantum electrodynamics (QED) phenomena. However, when employed as quantum buses,…

Quantum Physics · Physics 2025-03-03 Xin Wang , Huai-Bing Zhu , Tao Liu , Franco Nori

Exceptional points (EPs) are degeneracy of non-Hermitian Hamiltonians, at which the eigenvalues, along with their eigenvectors, coalesce. Their orders are given by the Jordan decomposition. Here, we focus on higher-order EPs arising in…

Quantum Physics · Physics 2023-04-18 Kang Yang , Ipsita Mandal

Non-Hermiticity has emerged as a new paradigm for controlling coupled-mode systems in ways that cannot be achieved with conventional techniques. One aspect of this control that has received considerable attention recently is the encircling…

We propose an analysis technique for the exceptional points (EPs) occurring in the discrete spectrum of open quantum systems (OQS), using a semi-infinite chain coupled to an endpoint impurity as a prototype. We outline our method to locate…

Quantum Physics · Physics 2012-10-16 Savannah Garmon , Ingrid Rotter , Naomichi Hatano , Dvira Segal

We demonstrate third-order conjugate exceptional points (EPs) in a gain-loss assisted multi-mode 1D complementary photonic bandgap waveguide. Our study reveals the higher-order mode conversion phenomenon facilitated by parametrically…

Optics · Physics 2025-04-02 Sibnath Dey , Harish N S Krishnamoorthy , Somnath Ghosh

Exceptional points (EPs) in non-Hermitian systems offer a remarkably strong response to weak perturbations, but the nonorthogonal nature of the corresponding eigenvectors causes noise to diverge, hindering EPs practical application. Here,…

Understanding physical properties of quantum emitters strongly interacting with quantized electromagnetic modes is one of the primary goals in the emergent field of waveguide quantum electrodynamics (QED). When the light-matter coupling…

Quantum Physics · Physics 2023-05-30 Yuto Ashida , Takeru Yokota , Atac Imamoglu , Eugene Demler