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Spectral Broadening of a Single Er3+ Ion in a Si Nanotransistor

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Physical Review Applied 2022年第3期18卷 034018-034018页

作者： Jiliang Yang Jian Wang Wenda Fan Yangbo Zhang Changkui Duan Guangchong Hu Gabriele G. de Boo Brett C. Johnson Jeffrey C. McCallum Sven Rogge Chunming Yin Jiangfeng Du CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales NSW 2052 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Engineering RMIT University Victoria 3001 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne Victoria 3010 Australia Hefei National Laboratory University of Science and Technology of China Hefei 230088 China

Single rare-earth ions in solids show great potential for quantum applications, including single-photon emission, quantum computing, and high-precision sensing. However, the linewidths of single rare-earth ions are often broadened due to perturbations associated with the detection methods. Identifying the dominant broadening sources is key to reduce the linewidths for practical applications. We report a spectral broadening study on a single Er3+ ion in a Si nanotransistor. The single ion spectra display a Lorentzian lineshape at all light intensities considered. The linewidth remains nearly constant at 32±2 MHz in the low-intensity regime, and shows a monotonic increase with the intensity in the high-intensity regime. The power broadening does not persist over the microsecond time scales considered after resonant excitation. Nor does it depend on the resonant excitation intensity or the Zeeman shift. These observations and temperature-dependent measurements suggest that charge fluctuations are likely to be a dominant broadening source. Laser heating may also contribute to the power broadening. Charge suppression in the Er3+-doped region and coupling Er3+ ions to a confined optical mode could be implemented to reduce the spectral linewidth and to enhance the sensing precision of single Er3+ ions in Si.

关键词： Quantum sensing Quantum dots Rare-earth doped crystals Optical spectroscopy

Emission engineering in monolithically integrated silicon nitride microring resonators

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arXiv 2024年

作者： Mandal, Kishor Kumar Singh, Anuj Kumar Kumar, Brijesh Shah, Amit P. Vij, Rishabh Majumder, Amrita Khunte, Janhavi Jayawant Achanta, Venu Gopal Kumar, Anshuman Laboratory of Optics of Quantum Materials Department of Physics Indian Institute of Technology Bombay Mumbai400076 India Department of Condensed Matter Physics and Material Science Tata Institute of Fundamental Research Homi Bhabha Road Mumbai400005 India Centre of Excellence in Quantum Information Computation Science and Technology Indian Institute of Technology Bombay Powai Mumbai400076 India

Monolithic integration of solid-state emitters with photonic elements of the same material is a promising approach to overcome the constraints of fabrication complexity and coupling losses in traditional hybrid integration approaches. A wide band-gap, low-loss silicon nitride (SiN) platform is a mature technology, having CMOS compatibility, widely used in hybrid integrated photonics and optoelectronics. However, it has been shown that certain growth conditions enable the SiN material to host color centers, whose origin is currently under investigation. In this work, we have engineered a novel technique for the efficient coupling of these intrinsic emitters into the whispering gallery modes (WGMs) of the SiN microring cavity – which has not been explored previously. We have engineered a subwavelength-sized notch into the rim of the SiN microring structure, to optimize the collection efficiency of the cavity-coupled enhanced photoluminescence (PL) spectra at room temperature. The platform presented in this work will enable the development of monolithic integration of color centers with nanophotonic elements for application to quantum photonic technologies. Copyright © 2024, The Authors. All rights reserved.

关键词： Silicon nitride

Strong decays of the isovector-scalar D∗D¯∗ hadronic molecule

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arXiv 2024年

作者： Deng, Jin-Cheng Wang, Bo College of Physics Science and Technology Hebei University Baoding071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding071002 China

We adopt the effective Lagrangian approach to study the strong decays of the 1−(0++) D∗D¯∗ molecular state [denoted as Tψa0(4010) according to the LHCb naming convention] through triangle diagrams. The decay channels include the open-charm DD¯, and the hidden-charm ηcπ, J/ψρ, and χc1π. The coupling between the Tψa0(4010) and its constituents D∗D¯∗ is obtained by solving for the residue of the scattering T-matrix at the pole. Our calculations yield a total width of few tens MeV for the Tψa0(4010) state using three different form factors, with its main decay channels being ηcπ and χc1π. The X(4100) and X(4050) have similar masses and widths, with both masses being close to the D∗D¯∗ threshold. Additionally, their decay final states are consistent with those of the Tψa0(4010). Therefore, it is likely that they represent the same state and both potentially correspond to the Tψa0(4010). We suggest that future experiments focus on searching for the Tψa0(4010) signal in the final states ηcπ−, χc1π− and D0D− of the B0 → ηcπ−K+, χc1π−K+ and D0D−K+ processes, respectively, as well as further investigating its resonance parameters with Flatté-like formula. © 2024, CC BY.

关键词： Lagrange multipliers

Quantum emitters in bilayer hexagonal boron nitride

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arXiv 2024年

作者： Mehta, Reyhan Kumar, Anshuman Department of Condensed Matter Physics and Materials Science Tata Institute of Fundamental Research Homi Bhabha Road Mumbai400005 India Laboratory of Optics of Quantum Materials Department of Physics Indian Institute of Technology Bombay Mumbai400076 India Centre of Excellence in Quantum Information Computation Science and Technology Indian Institute of Technology Bombay Powai Mumbai400076 India

Hexagonal boron nitride has been experimentally shown to exhibit room-temperature single-photon emission. This emission is attributed to defect states in the wide band-gap of hBN, which allow new optical transitions between these dispersion-less defect levels. In this work, we study the new spectral features introduced by interacting atomic defects in consecutive layers of bilayer hBN. Density Functional theory simulations have been carried out to calculate the energy band structure, frequency-dependent complex dielectric functions, and Kohn-Sham states to demonstrate and understand the cause of the emission enhancements. We found that placing colour centres in the vicinity of each other in bilayer hBN introduces new polarization dependent spectral features, with strong dependence on the distance and relative orientation between atomic defects. Our results provide a pathway to engineering single photon emission in hBN via inter-defect interaction. Copyright © 2024, The Authors. All rights reserved.

关键词： Boron nitride

QuantFactor REINFORCE: Mining Steady Formulaic Alpha Factors with Variance-bounded REINFORCE

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arXiv 2024年

作者： Zhao, Junjie Zhang, Chengxi Qin, Min Yang, Peng Guangdong Provincial Key Laboratory of Brain-Inspired Intelligent Computation Department of Computer Science and Engineering Southern University of Science and Technology Shenzhen518055 China Shenzhen Yujin Hedge Fund Company Limited Shenzhen518033 China Department of Modern Physics University of Science and Technology of China Hefei230026 China

The goal of alpha factor mining is to discover indicative signals of investment opportunities from the historical financial market data of assets, which can be used to predict asset returns and gain excess profits. Deep learning based alpha factor mining methods have shown to be powerful, which, however, lack of the interpretability, making them unacceptable in the risk-sensitive real markets. Alpha factors in formulaic forms are more interpretable and therefore favored by market participants, while the search space is complex and powerful explorative methods are urged. Recently, a promising framework is proposed for generating formulaic alpha factors using deep reinforcement learning, and quickly gained research focuses from both academia and industries. This paper first argues that the originally employed policy training method, i.e., Proximal Policy Optimization (PPO), faces several important issues in the context of alpha factors mining, making it ineffective to explore the search space of the formula. Herein, a novel reinforcement learning based on the well-known REINFORCE algorithm is proposed. Given that the underlying state transition function adheres to the Dirac distribution, the Markov Decision Process within this framework exhibit minimal environmental variability, making REINFORCE algorithm more appropriate than PPO. A new dedicated baseline is designed to theoretically reduce the commonly suffered high variance of REINFORCE. Moreover, the information ratio is introduced as a reward shaping mechanism to encourage the generation of steady alpha factors that can better adapt to changes in market volatility. Experimental evaluations on various real assets data show that the proposed algorithm can increase the correlation with asset returns by 3.83%, and a stronger ability to obtain excess returns compared to the latest alpha factors mining methods, which meets the theoretical results well. © 2024, CC BY.

关键词： Deep reinforcement learning

Switching between topological edge states using phase-change materials

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Switching between topological edge states using phase-change...

2023 Active Photonic Platforms, APP 2023

作者： Veronis, Georgios Huang, Yin Shen, Yuecheng School of Electrical Engineering and Computer Science Louisiana State University Baton RougeLA70803 United States Center for Computation and Technology Louisiana State University Baton RougeLA70803 United States Department of Optoelectrics Information Science and Engineering School of Physics and Electronics Central South University Hunan Changsha410012 China State Key Laboratory of Optoelectronic Materials and Technologies School of Electronics and Information Technology Sun Yat-Sen University Guangdong Guangzhou510275 China

ISBN: (纸本)9781510665088

We introduce non-Hermitian plasmonic waveguide-cavity structures based on the Aubry-Andre-Harper model to realize switching between right and left topological edge states using the phase-change material germanium-antimony-tellurium (GST). The structure unit cells consist of a metal-dielectric-metal (MDM) waveguide side-coupled to MDM stub resonators with modulated distances between adjacent stubs. In such structures the modulated distances introduce an effective gauge magnetic field. We show that switching between the crystalline and amorphous phases of GST leads to a shift of the dispersion relation of the optimized structure so that a right topological edge state for the crystalline phase, and a left topological edge state for the amorphous phase occur at the same frequency. Thus, we realize switching between right and left topological edge states at that frequency by switching between the crystalline and amorphous phases of GST. Our results could be potentially important for developing compact reconfigurable topological photonic devices. © 2023 SPIE.

关键词： Gages

Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter

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Physical Review C 2025年第1期111卷 014320-014320页

作者： K. D. Duan H. B. Zhang X. L. Shang Department of Physics Hebei University Baoding 071002 China CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China School of Nuclear Science and Technology University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of High-Precision Computation and Application of Quantum Field Theory of Hebei Province Baoding 071002 China

The finite-temperature phase structures for neutron-proton superfluidity in asymmetric nuclear matter are investigated, with a particular focus on the angular dependence of the pairing gap induced by the SD13 nucleon-nucleon interaction. This angular dependence of the pairing gap results in the Cooper pair momentum in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state exhibiting exactly two distinct stable orientations: one orthogonal (FFLO-ADG-O) and the other parallel (FFLO-ADG-P) to the symmetry axis of the pairing gap. The FFLO-ADG-O state dominates at low asymmetries, while the FFLO-ADG-P state prevails at high asymmetries. Additionally, this analysis of normal-superfluid phase separation reveals that the angular dependence of the pairing gap eliminates phase separation in the low-asymmetry regime, whereas the Cooper pair momentum effectively suppresses phase separation at high asymmetries. These two mechanisms act in concert to significantly prevent the occurrence of normal-superfluid phase separation across the entire phase diagram, ensuring the stability of the homogeneous superfluid state over a broad range of asymmetries. These results provide new insights into the interplay between the angular dependence of the pairing gap and the stability of superfluidity in asymmetric nuclear matter.

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Orientation-dependent Josephson effect in spin-singlet superconductor/altermagnet/spin-triplet superconductor junctions

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Physical Review B 2024年第2期109卷 024517-024517页

作者： Qiang Cheng Qing-Feng Sun School of Science Qingdao University of Technology Qingdao Shandong 266520 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Hefei National Laboratory Hefei 230088 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

We study the Josephson effect in the spin-singlet superconductor/altermagnet/spin-triplet superconductor junctions using the Green's function method. The current-phase difference relationships in the junctions strongly depend on the orientation of altermagnet and the types of the Cooper pairs. For the orientation angle equal to odd multiples of π/4, the current-phase difference relationships are of the sin2ϕ type, which are irrespective of the pairing wave functions in superconductors. For the other orientation angles, the emergence of the lowest order current becomes possible and its form, sinϕ or cosϕ, depends on the pairing wave functions in superconductors. The ϕ0 phase and the 0−π transition can be realized in our junctions due to the appearance of the lowest order current. The selection rules for the lowest order current are presented. The symmetric relations satisfied by the current-phase difference relationships are analyzed through considering the transformations of the junctions under the mirror reflection, the time-reversal and the spin-rotation operations. Our results not only provide a method to detect the intrinsic spin-triplet superconductivity but also possess application values in the design of the field-free quantum devices.

关键词： Josephson effect Spin-singlet pairing Spin-triplet pairing

Exploring the lifetime frontier with a beam-dump experiment at CiADS

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arXiv 2024年

作者： Chen, Liangwen Du, Mingxuan Sun, Zhiyu Wang, Zeren Simon Xie, Fang Xie, Ju-Jun Yang, Lei Yu, Pei Zhang, Yu Heavy Ion Science and Technology Key Laboratory Institute of Modern Physics Chinese Academy of Sciences Lanzhou730000 China Advanced Energy Science and Technology Guangdong Laboratory Huizhou516000 China School of Nuclear Science and Technology University of Chinese Academy of Sciences Beijing101408 China School of Physics State Key Laboratory of Nuclear Physics and Technology Peking University Beijing100871 China Center for High Energy Physics Peking University Beijing100871 China Department of Physics National Tsing Hua University Hsinchu300 Taiwan Center for Theory and Computation National Tsing Hua University Hsinchu300 Taiwan Institute of Modern Physics Fudan University Shanghai200433 China Institute of Modern Physics Chinese Academy of Sciences Guangdong Huizhou516000 China School of Physics Hefei University of Technology Hefei230601 China

We propose a beam-dump experiment (BDE) at the upcoming facility of China initiative Accelerator Driven System (CiADS), called CiADS-BDE, in order to search for long-lived particles (LLPs) predicted in various beyond-the-Standard-Model (BSM) theories. The experiment is to be located in the forward direction of the incoming low-energy proton beam at CiADS, leveraging the strong forward boost of the produced particles at the beam dump in general. The space between the dump and the detector is largely available, allowing for installation of veto materials and hence low levels of background events. We elaborate on the detector setup, and choose dark photon as a benchmark model for sensitivity study. We restrict ourselves to the signature of an electron-positron pair, and find that with 5 years’ operation, unique, currently unexcluded parts of the parameter space for O(100) MeV dark-photon masses and O(10−9–10−8) kinetic mixing can be probed at the CiADS-BDE. Furthermore, considering that there is no need to set up a proton beam specifically for this experiment and that the detector system requires minimal instrumentation, the experiment is supposed to be relatively cost-effective. Therefore, we intend this work to promote studies on the sensitivity reach of the proposed experiment to additional LLP scenarios, and in the end, the realization of the experiment. Incidentally, we study the sensitivity of the same BDE setups at the High Intensity Heavy-ion Accelerator Facility (HIAF), presently under construction near the CiADS program site, and conclude that HIAF-BDE could probe new parameter regions, too. © 2024, CC BY.

关键词： Heavy ions