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Zou D, Chen T, Meng H, Ang YS, Zhang X, Lee CH. Experimental observation of exceptional bound states in a classical circuit network. Sci Bull (Beijing) 2024; 69:2194-2204. [PMID: 38853044 DOI: 10.1016/j.scib.2024.05.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/29/2024] [Accepted: 05/13/2024] [Indexed: 06/11/2024]
Abstract
Exceptional bound (EB) states represent a unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points. Conceptually distinct from the more well-known topological states and non-Hermitian skin states, they were recently discovered as a novel source of negative entanglement entropy in the quantum entanglement context. Yet, EB states have been physically elusive, being originally interpreted as negative probability eigenstates of the propagator of non-Hermitian Fermi gases. In this work, we show that EB states are in fact far more ubiquitous, also arising robustly in broad classes of systems whether classical or quantum. This hinges crucially on a newly-discovered spectral flow that rigorously justifies the EB nature of small candidate lattice systems. As a highlight, we present their first experimental realization through an electrical circuit, where they manifest as prominent stable resonant voltage profiles. Our work brings a hitherto elusive but fundamentally distinctive quantum phenomenon into the realm of classical metamaterials, and provides a novel pathway for the engineering of robust modes in otherwise sensitive systems..
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Affiliation(s)
- Deyuan Zou
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education, Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Tian Chen
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education, Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Haiyu Meng
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, China; Department of Physics, National University of Singapore, Singapore 117542, Singapore.
| | - Yee Sin Ang
- Science, Mathematics and Technology Cluster, Singapore University of Technology and Design, Singapore 487372, Singapore.
| | - Xiangdong Zhang
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education, Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China.
| | - Ching Hua Lee
- Department of Physics, National University of Singapore, Singapore 117542, Singapore; Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China.
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Hayashida K, Makihara T, Marquez Peraca N, Fallas Padilla D, Pu H, Kono J, Bamba M. Perfect intrinsic squeezing at the superradiant phase transition critical point. Sci Rep 2023; 13:2526. [PMID: 36781905 PMCID: PMC9925797 DOI: 10.1038/s41598-023-29202-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 01/31/2023] [Indexed: 02/15/2023] Open
Abstract
Some of the most exotic properties of the quantum vacuum are predicted in ultrastrongly coupled photon-atom systems; one such property is quantum squeezing leading to suppressed quantum fluctuations of photons and atoms. This squeezing is unique because (1) it is realized in the ground state of the system and does not require external driving, and (2) the squeezing can be perfect in the sense that quantum fluctuations of certain observables are completely suppressed. Specifically, we investigate the ground state of the Dicke model, which describes atoms collectively coupled to a single photonic mode, and we found that the photon-atom fluctuation vanishes at the onset of the superradiant phase transition in the thermodynamic limit of an infinite number of atoms. Moreover, when a finite number of atoms is considered, the variance of the fluctuation around the critical point asymptotically converges to zero, as the number of atoms is increased. In contrast to the squeezed states of flying photons obtained using standard generation protocols with external driving, the squeezing obtained in the ground state of the ultrastrongly coupled photon-atom systems is resilient against unpredictable noise.
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Affiliation(s)
- Kenji Hayashida
- grid.21940.3e0000 0004 1936 8278Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005 USA ,grid.39158.360000 0001 2173 7691Division of Applied Physics, Graduate School and Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 Japan
| | - Takuma Makihara
- grid.21940.3e0000 0004 1936 8278Department of Physics and Astronomy, Rice University, Houston, TX 77005 USA
| | - Nicolas Marquez Peraca
- grid.21940.3e0000 0004 1936 8278Department of Physics and Astronomy, Rice University, Houston, TX 77005 USA
| | - Diego Fallas Padilla
- grid.21940.3e0000 0004 1936 8278Department of Physics and Astronomy, Rice University, Houston, TX 77005 USA
| | - Han Pu
- grid.21940.3e0000 0004 1936 8278Department of Physics and Astronomy, Rice University, Houston, TX 77005 USA
| | - Junichiro Kono
- grid.21940.3e0000 0004 1936 8278Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005 USA ,grid.21940.3e0000 0004 1936 8278Department of Physics and Astronomy, Rice University, Houston, TX 77005 USA ,grid.21940.3e0000 0004 1936 8278Department of Materials Science and Nano Engineering, Rice University, Houston, TX 77005 USA
| | - Motoaki Bamba
- Department of Physics I, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan. .,The Hakubi Center for Advanced Research, Kyoto University, Kyoto, 606-8501, Japan. .,PRESTO, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan.
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Lu Y, Zhao Y, Li R, Liu J. Anomalous spontaneous emission dynamics at chiral exceptional points. OPTICS EXPRESS 2022; 30:41784-41803. [PMID: 36366646 DOI: 10.1364/oe.473824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
An open quantum system operated at the spectral singularities where dimensionality reduces, known as exceptional points (EPs), demonstrates distinguishing behavior from the Hermitian counterpart. Here, we present an analytical description of local density of states (LDOS) for microcavity featuring chiral EPs, and unveil the anomalous spontaneous emission dynamics from a quantum emitter (QE) due to the non-Lorentzian response of EPs. Specifically, we reveal that a squared Lorentzian term of LDOS contributed by chiral EPs can destructively interfere with the linear Lorentzian profile, resulting in the null Purcell enhancement to a QE with special transition frequency, which we call EP induced transparency. While for the case of constructive interference, the squared Lorentzian term can narrow the linewidth of Rabi splitting even below that of bare components, and thus significantly suppresses the decay of Rabi oscillation. Interestingly, we further find that an open microcavity with chiral EPs supports atom-photon bound states for population trapping and decay suppression in long-time dynamics. As applications, we demonstrate the advantages of microcavity operated at chiral EPs in achieving high-fidelity entanglement generation and high-efficiency single-photon generation. Our work unveils the exotic cavity quantum electrodynamics unique to chiral EPs, which opens the door for controlling light-matter interaction at the quantum level through non-Hermiticity, and holds great potential in building high-performance quantum-optics devices.
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Xiao YF, Vollmer F. Special Issue on the 60 th anniversary of the first laser-Series I: Microcavity Photonics-from fundamentals to applications. LIGHT, SCIENCE & APPLICATIONS 2021; 10:141. [PMID: 34238916 PMCID: PMC8266797 DOI: 10.1038/s41377-021-00583-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 06/21/2021] [Indexed: 05/19/2023]
Affiliation(s)
- Yun-Feng Xiao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing, China.
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China.
| | - Frank Vollmer
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, UK
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Liu W, Chen YL, Tang SJ, Vollmer F, Xiao YF. Nonlinear Sensing with Whispering-Gallery Mode Microcavities: From Label-Free Detection to Spectral Fingerprinting. NANO LETTERS 2021; 21:1566-1575. [PMID: 33356315 DOI: 10.1021/acs.nanolett.0c04090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Optical microresonators have attracted intense interests in highly sensitive molecular detection and optical precision measurement in the past decades. In particular, the combination of a high quality factor with a small mode volume significantly enhances the nonlinear light-matter interaction in whispering-gallery mode (WGM) microresonators, which greatly boost nonlinear optical sensing applications. Nonlinear WGM microsensors not only allow for label-free detection of molecules with an ultrahigh sensitivity but also support new functionalities in sensing such as the specific spectral fingerprinting of molecules with frequency conversion involved. Here, we review the mechanisms, sensing modalities, and recent progresses of nonlinear optical sensors along with a brief outlook on the possible future research directions of this rapidly advancing field.
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Affiliation(s)
- Wenjing Liu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - You-Ling Chen
- State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083, Beijing, China
| | - Shui-Jing Tang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Frank Vollmer
- Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Yun-Feng Xiao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, 030006, Taiyuan China
- Peking University Yangtze Delta Institute of Optoelectronics, 226010, Nantong, China
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Shen ZZ, Tang M, Chen YL, Huang YZ. Unidirectional emission and nanoparticle detection in a deformed circular square resonator. OPTICS EXPRESS 2021; 29:1666-1677. [PMID: 33726376 DOI: 10.1364/oe.412974] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 12/15/2020] [Indexed: 06/12/2023]
Abstract
We propose a novel deformed square resonator which has four asymmetric circular sides. Photons leak out from specific points, depending on the interplay between stable islands and unstable manifolds in phase space. By carefully breaking the mirror reflection symmetry, optical modes with strong chirality approaching 1 and unidirectional emission can be achieved simultaneously. Upon binding of a nanoparticle, the far-field emission pattern of the deformed microcavity changes drastically. Due to the EP point of the degenerate mode pairs in the deformed cavity, chirality-based far-field detection of nanoparticles with ultra-small size can be realized.
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Cao T, Fang L, Cao Y, Li N, Fan Z, Tao Z. Dynamically reconfigurable topological edge state in phase change photonic crystals. Sci Bull (Beijing) 2019; 64:814-822. [PMID: 36659671 DOI: 10.1016/j.scib.2019.02.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/03/2019] [Accepted: 02/12/2019] [Indexed: 01/21/2023]
Abstract
The observation of topological edge states (TESs) revolutionized our understanding of scattering and propagation of electromagnetic (EM) waves. Supported by topological robustness, the TES at the interface between trivial and non-trivial insulators was not reflected from the structural disorders and imperfections. Recently topological photonic crystals (PhCs) were demonstrated to obtain remarkable one-way propagation of the TES, having the advantages of lossless propagation, dense integration, and high fabrication tolerance over conventional PhCs. Nevertheless, the lack of reversible switching of TES possesses significant limitations in helicity/spin filtering and tunable photonic devices. We proposed a topological PhC based on a prototypical phase-change material, Ge2Sb2Te5 (GST225) to solve the problem. We find that at a particular frequency, the TES within the structure can be reversibly switched between "on" and "off" by transiting the GST225 structural state between amorphous and crystalline. Moreover, the topology of the PhC was maintained since the tuning of TES was achieved by varying the refractive index of GST225 instead of the structural geometry. This provides a continuous change of the spectral position of the photonic bandgap and TES by gradually crystallising the GST225. We show that the phase change of GST225 from amorphous to crystalline and vice versa can be engineered in nanoseconds. Our proof of concept may offer a platform for dynamically tuning the TESs that might otherwise be challenging to attain in photonic systems. We expect it to have potential applications for photonic devices in topological optical circuits and scatter-free one-way light propagation.
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Affiliation(s)
- Tun Cao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China.
| | - Linhan Fang
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China
| | - Ying Cao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China
| | - Nan Li
- China North Vehicle Research Institute, Beijing 100072, China
| | - Zhiyou Fan
- China North Vehicle Research Institute, Beijing 100072, China
| | - Zhiguo Tao
- China North Vehicle Research Institute, Beijing 100072, China
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