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Time reversal of a discrete system coupled to a continuum based on non-Hermitian flip

Science Bulletin 2017年第12期62卷 869-874页

作者： stefano longhi Dipartimento di Fisica Politecnico di Milano and Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle RicerchePiazza L.da Vinci 321-20133 MilanoItaly

Time reversal in quantum or classical systems described by an Hermitian Hamiltonian is a physically allowed process, which requires in principle inverting the sign of the Hamiltonian. Here we consider the problem of time reversal of a subsystem of discrete states coupled to an external environment characterized by a continuum of states, into which they generally decay. It is shown that, by flipping the discrete-continuum coupling from an Hermitian to a non-Hermitian interaction, thus resulting in a non unitary dynamics, time reversal of the subsystem of discrete states can be achieved, while the continuum of states is not reversed. Exact time reversal requires frequency degeneracy of the discrete states,or large frequency mismatch among the discrete states as compared to the strength of indirect coupling mediated by the continuum. Interestingly, periodic and frequent switch of the discrete-continuum coupling results in a frozen dynamics of the subsystem of discrete states.

关键词：时间反转耦合强度离散系统埃尔米特连续介质翻转离散状态量子系统

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通过静电类比设计非厄米实能谱

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Science Bulletin 2022年第18期67卷 1865-1873,M0004页

作者： Russell Yang Jun Wei Tan Tommy Tai Jin Ming Koh 李林虎 stefano longhi Ching Hua Lee Department of Physics National University of SingaporeSingapore 117551Singapore Clarendon Laboratory University of OxfordOxford OX13PUUK Cavendish Laboratory University of CambridgeCambridge CB30HEUK Division of Physics Mathematics and AstronomyCaltechPasadenaCA 91125USA Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing&School of Physics and Astronomy Sun Yat-Sen University(Zhuhai Campus)Zhuhai 519082China Dipartimento di Fisica Politecnico di MilanoPiazza Leonardo da Vinci 32I-20133 MilanItaly IFISC(UIB-CSIC) Instituto de Fisica Interdisciplinary Sistemas ComplejosPalma de Mallorca E-07122Spain

非厄米性的研究蕴涵着诸多新物理机制与现象,在激光与传感等多个方面有着重要的应用价值.在非厄米系统中,实本征能量意味着系统具有稳定性,这一性质可通过奇偶时间(PT)对称性保护,并在不同物理系统中得到广泛的研究.本文利用一种新的动... 详细信息

非厄米性的研究蕴涵着诸多新物理机制与现象,在激光与传感等多个方面有着重要的应用价值.在非厄米系统中,实本征能量意味着系统具有稳定性,这一性质可通过奇偶时间(PT)对称性保护,并在不同物理系统中得到广泛的研究.本文利用一种新的动力学机制保证实能谱,提出了一种普适的方案来设计具有实能谱的哈密顿量.该方案基于对扩展非厄米体边对应的静电类比,其中静电荷对应态密度,电场则对应复能谱流.通过这一方案,可以重构出具有任意能谱及态局域性质的哈密顿量,即便这些性质不具备任何对称性特征.通过用泊松边值问题代替原本的非厄米哈密顿量对角化问题,这一静电类比也避免了传统数值方法中因非厄米耗散/增益引起的浮点误差问题,从而允许对更大尺寸的系统进行计算.

关键词：哈密顿量类比设计静电荷对应态物理系统厄米性动力学机制对角化

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Ultrafast control of fractional orbital angular momentum of microlaser emissions

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Light(Science & Applications) 2020年第1期9卷 286-294页

作者： Zhifeng Zhang Haoqi Zhao Danilo Gomes Pires Xingdu Qiao Zihe Gao Josep *** stefano longhi Natalia M.Litchinitser Liang Feng Department of Electrical and Systems Engineering University of PennsylvaniaPhiladelphiaPA 19104USA Department of Electrical and Computer Engineering Duke UniversityDurhamNC 27708USA Department of Materials Science and Engineering University of PennsylvaniaPhiladelphiaPA 19104USA Department of Electrical and Computer Engineering Northeastern UniversityBostonMA 02115USA Dipartimento di Fisica Politecnico di Milano and Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle RicerchePiazza L.da Vinci 32I-20133 MilanoItaly Instituto de Fisica Interdisciplinar y Sistemas Complejos IFISC(CSIC-UIB) Palma de MallorcaSpain

On-chip integrated laser sources of structured light carrying fractional orbital angular momentum(FOAM)are highly desirable for the forefront development of optical communication and quantum information-processing technologies.While integrated vortex beam generators have been previously demonstrated in different optical settings,ultrafast control and sweep of FOAM light with low-power control,suitable for high-speed optical communication and computing,remains challenging.Here we demonstrate fast control of the FOAM from a vortex semiconductor microlaser based on fast transient mixing of integer laser vorticities induced by a control pulse.A continuous FOAM sweep between charge 0 and charge+2 is demonstrated in a 100 ps time window,with the ultimate speed limit being established by the carrier recombination time in the gain medium.Our results provide a new route to generating vortex microlasers carrying FOAM that are switchable at GHz frequencies by an ultrafast control pulse.

关键词： momentum fractional vortex

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Plasmon hybridization engineering in self-organized anisotropic metasurfaces

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Nano Research 2018年第7期11卷 3943-3956页

作者： Maria C. Giordano stefano longhi Matteo Barelli Andrea Mazzanti Francesco Buatier de Mongeot Giuseppe Della Valle Dipartimento di Fisica Universita di Genova Via Dodecaneso 33 Genova I-16146 Italy Dipartimento di Fisica and IFN-CNR Politecnico di Milano Piazza L. da Vinci 32 Milano 1-20133 Italy

The engineering of self-organized plasmonic metasurfaces is demonstrated using a maskless technique with defocused ion-beam sputtering and kinetically controlled deposition. The proposed reliable, cost-effective, and controllable approach enables large-area （order of square centimeter） sub-wavelength periodic patterning with close-packed gold nanostrips. A multi-level variant of the method leads to high-resolution manufacturing of vertically stacked nanostrip dimer arrays, without resorting to lithographic approaches. The design of these self-organized metasurfaces is optimized by employing plasmon hybridization methods. In particular, preliminary results on the so-called gap-plasmon configuration of the nanostrip dimers, implementing magnetic dipole resonance in the near-infrared range, are reported. This resonance offers a superior sensitivity and field enhancement, compared with the more conventional electric dipole resonance. The translational invariance of the nanostrip configuration leads to a high filling factor of the hot spots. These advanced features make the large-area metasurface based on gap-plasmon nanostrip dimers very attractive for surface-enhanced linear and nonlinear spectroscopy （e.g., surface-enhanced Raman scattering） and plasmon-enhanced photon harvesting in solar and photovoltaic cells.

关键词： metasurfaces self-organization gold nanostructures plasmon hybridization gap plasmon resonances

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Unidirectional lasing in semiconductor microring lasers at an exceptional point [Invited]

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Photonics Research 2017年第6期5卷 11-16页

作者： stefano longhi LIANG FENG Dipartimento di Fisica Politecnico di Milano and Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche Department of Electrical Engineering The State University of New York at Buffalo

Recent experiments demonstrated that chiral symmetry breaking at an exceptional point(EP) is a viable route to achieve unidirectional laser emission in microring lasers. By a detailed semiconductor laser rate equation model,we show here that unidirectional laser emission at an EP is a robust regime. Slight deviations from the EP condition can break preferential unidirectional lasing near threshold via a Hopf instability. However, abovea "second" laser threshold, unidirectional emission is restored.

关键词： Unidirectional lasing in semiconductor microring lasers at an exceptional point

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A high-density, multi-parental SNP genetic map on apple validates a new mapping approach for outcrossing species

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Horticulture Research 2016年第1期3卷 30-42页

作者： Erica A Di Pierro Luca Gianfranceschi Mario Di Guardo Herma JJ Koehorst-van Putten Johannes W Kruisselbrink Sara longhi Michela Troggio Luca Bianco Hélène Muranty Giulia Pagliarani stefano Tartarini Thomas Letschka Lidia Lozano Luis Larisa Garkava-Gustavsson Diego Micheletti Marco CAM Bink Roeland E Voorrips Ebrahimi Aziz Riccardo Velasco François Laurens W Eric van de Weg Department of Biosciences University of MilanMilan20133Italy Plant Breeding Wageningen University and ResearchWageningen6700AJThe Netherlands Research and Innovation Centre Edmund Mach FoundationSan Michele all’Adige38010Italy Biometris Wageningen University and ResearchWageningen6700AAThe Netherlands IRHS INRAAGROCAMPUS-OuestUniversitéd’AngersSFR 4207 QUASAVBeaucouzé49071France Department of Agricultural Sciences University of BolognaBologna40127Italy Department of Molecular Biology Laimburg Research Centre for Agriculture and ForestryOra39040Italy Department of Plant Breeding Swedish University of Agricultural SciencesAlnarp23053Sweden Hendrix Genetics Research Technology&ServicesBoxmeer 5830 ACThe Netherlands

Quantitative trait loci(QTL)mapping approaches rely on the correct ordering of molecular markers along the chromosomes,which can be obtained from genetic linkage maps or a reference genome sequence.For apple(Malus domestica Borkh),the genome sequence v1 and v2 could not meet this need;therefore,a novel approach was devised to develop a dense genetic linkage map,providing the most reliable marker-loci order for the highest possible number of markers.The approach was based on four strategies:(i)the use of multiple full-sib families,(ii)the reduction of missing information through the use of HaploBlocks and alternative calling procedures for single-nucleotide polymorphism(SNP)markers,(iii)the construction of a single backcross-type data set including all families,and(iv)a two-step map generation procedure based on the sequential inclusion of markers.The map comprises 15417 SNP markers,clustered in 3 K HaploBlock markers spanning 1267 cM,with an average distance between adjacent markers of 0.37 cM and a maximum distance of 3.29 cM.Moreover,chromosome 5 was oriented according to its homoeologous chromosome 10.This map was useful to improve the apple genome sequence,design the Axiom Apple 480 K SNP array and perform multifamily-based QTL studies.Its collinearity with the genome sequences v1 and v3 are reported.To our knowledge,this is the shortest published SNP map in apple,while including the largest number of markers,families and individuals.This result validates our methodology,proving its value for the construction of integrated linkage maps for any outbreeding species.

关键词： breeding linkage mapping

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