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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

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

arXiv

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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

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Quantum games of asymmetric information

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Physical Review E 2003年第1期68卷 016124-016124页

作者： Jiangfeng Du Hui Li Chenyong Ju Structure Research Laboratory and Department of Modern Physics University of Science and Technology of China Hefei 230027 People’s Republic of China Department of Physics National University of Singapore Lower Kent Ridge Singapore 119260 Singapore Centre for Quantum Computation Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom

We investigate quantum games in which the information is asymmetrically distributed among the players and find that the possibility of the quantum game outperforming its classical counterpart depends strongly on not only the entanglement but also the informational asymmetry. What is more interesting, when the information distribution is asymmetric, is that the contradictive impact of the quantum entanglement on the profits is observed, which is not reported in quantum games of symmetric information.

关键词： Quantum theory

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Joint product numerical range and geometry of reduced density matrices

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science China(physics,Mechanics & Astronomy) 2017年第2期60卷 9-17页

作者： Jianxin Chen Cheng Guo Zhengfeng Ji Yiu-Tung Poon Nengkun YU Bei Zeng Jie Zhou Joint Center for Quantum Information and Computer Science University of Maryland College Park 20740 USA Institute for Advanced Study Tsinghua University Beijing 100084 China Centre for Quantum Computation ＆ Intelligent Systems School of Software Faculty of Engineering and Information Technology University of Technology Sydney Sydney 2007 Australia State Key Laboratory of Computer Science.Institute of Software Chinese Academy of Sciences Beijing 100084 China Department of Mathematics Iowa State University Ames 50011-2140 USA Institute for Quantum Computing University of Waterloo Waterloo N2L 3G1 Canada Department of Mathematics ＆ Statistics University of Guelph Guelph N1G 2 W1 Canada Perimeter Institute for Theoretical Physics Waterloo N2L 2Y5 Canada

The reduced density matrices of a many-body quantum system form a convex set, whose three-dimensional projection is convex in R3. The boundary of may exhibit nontrivial geometry, in particular ruled surfaces. Two physical mechanisms are known for the origins of ruled surfaces： symmetry breaking and gapless. In this work, we study the emergence of ruled surfaces for systems with local Hamiltonians in infinite spatial dimension, where the reduced density matrices are known to be separable as a consequence of the quantum de Finetti＇s theorem. This allows us to identify the reduced density matrix geometry with joint product numerical range II of the Hamiltonian interaction terms. We focus on the case where the interaction terms have certain structures, such that a ruled surface emerges naturally when taking a convex hull of ∏. We show that, a ruled surface on sitting in ∏ has a gapless origin, otherwise it has a symmetry breaking origin. As an example, we demonstrate that a famous ruled surface, known as the oloid, is a possible shape of , with two boundary pieces of symmetry breaking origin separated by two gapless lines.

关键词： reduced density matrices quantum tomography numerical range quantum information oloid ruled surface

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Strain Tunable Semimetal–Topological-Insulator Transition in Monolayer 1T′−WTe2

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Physical Review Letters 2020年第4期125卷 046801-046801页

作者： Chenxiao Zhao Mengli Hu Jin Qin Bing Xia Canhua Liu Shiyong Wang DanDan Guan Yaoyi Li Hao Zheng Junwei Liu Jinfeng Jia Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education) Shenyang National Laboratory for Materials Science School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Department of Physics Hong Kong University of Science and Technology Hong Kong China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai 200240 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

A quantum spin hall insulator is manifested by its conducting edge channels that originate from the nontrivial topology of the insulating bulk states. Monolayer 1T′−WTe2 exhibits this quantized edge conductance in transport measurements, but because of its semimetallic nature, the coherence length is restricted to around 100 nm. To overcome this restriction, we propose a strain engineering technique to tune the electronic structure, where either a compressive strain along the a axis or a tensile strain along the b axis can drive 1T′−WTe2 into an full gap insulating phase. A combined study of molecular beam epitaxy and in situ scanning tunneling microscopy or spectroscopy then confirmed such a phase transition. Meanwhile, the topological edge states were found to be very robust in the presence of strain.

关键词： Topological phase transition Topological phases of matter Monolayer films Topological materials Transition metal dichalcogenides First-principles calculations Scanning tunneling microscopy Scanning tunneling spectroscopy

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Using weak values to experimentally determine “negative probabilities” in a two-photon state with Bell correlations

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Physical Review A 2015年第1期91卷 012113-012113页

作者： B. L. Higgins M. S. Palsson G. Y. Xiang H. M. Wiseman G. J. Pryde Centre for Quantum Dynamics and Centre for Quantum Computation and Communication Technology Griffith University Brisbane 4111 Australia Institute for Quantum Computing and Department of Physics & Astronomy University of Waterloo Waterloo ON N2L 3G1 Canada Key Laboratory of Quantum Information University of Science and Technology of China Hefei 230026 China

Bipartite quantum entangled systems can exhibit measurement correlations that violate Bell inequalities, revealing the profoundly counter-intuitive nature of the physical universe. These correlations reflect the impossibility of constructing a joint probability distribution for all values of all the different properties observed in Bell inequality tests. Physically, the impossibility of measuring such a distribution experimentally, as a set of relative frequencies, is due to the quantum back-action of projective measurements. Weakly coupling to a quantum probe, however, produces minimal back-action, and so enables a weak measurement of the projector of one observable, followed by a projective measurement of a noncommuting observable. By this technique it is possible to empirically measure weak-valued probabilities for all of the values of the observables relevant to a Bell test. The marginals of this joint distribution, which we experimentally determine, reproduces all of the observable quantum statistics including a violation of the Bell inequality, which we independently measure. This is possible because our distribution, like the weak values for projectors on which it is built, is not constrained to the interval [0,1]. It was first pointed out by Feynman that, for explaining singlet-state correlations within “a [local] hidden variable view of nature … everything works fine if we permit negative probabilities.” However, there are infinitely many such theories. Our method, involving “weak-valued probabilities,” singles out a unique set of probabilities, and moreover does so empirically.

关键词： PHONON-phonon interactions BELL'S theorem QUANTUM entanglement QUANTUM information science QUANTUM theory QUANTUM statistics

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Quantum emitters in bilayer hexagonal boron nitride

arXiv

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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

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

arXiv

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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

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In-Situ Single-Photon Detection of Er Sites in Si

In-Situ Single-Photon Detection of Er Sites in Si

引用

Conference on Lasers and Electro-Optics (CLEO)

作者： Ian R. Berkman Alexey Lyasota Gabriele G. de Boo John G. Bartholomew Brett C. Johnson Jeffrey C. McCallum Bin-Bin Xu Shouyi Xie Rose L. Ahlefeldt Matthew J. Sellars Chunming Yin Sven Rogge Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales Sydney New South Wales Australia Centre for Engineered Quantum Systems School of Physics The University of Sydney Sydney New South Wales Australia The University of Sydney Nano Institute The University of Sydney Sydney New South Wales Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne Victoria Australia Centre of Excellence for Quantum Computation and Communication Technology School of Engineering RMIT University Victoria Australia Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics Australian National University Canberra Australian Capital Territory Australia Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China Hefei China

Using sample-on-SSPD and photoluminescence excitation spectroscopy, we demonstrate Er sites in Si with inhomogeneous broadening below 100 MHz, a 350 kHz upper bound on the homogeneous linewidth, and electron T 1 lowe... 详细信息

ISBN: (数字)9781957171050

ISBN: (纸本)9781665466660

关键词： Spectroscopy Upper bound Photoluminescence Lasers and electrooptics Nonhomogeneous media Silicon Laser excitation

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Berry Curvature and Bulk-Boundary Correspondence from Transport Measurement for Photonic Chern Bands

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Physical Review Letters 2023年第13期131卷 133601-133601页

作者： Chao Chen Run-Ze Liu Jizhou Wu Zu-En Su Xing Ding Jian Qin Lin Wang Wei-Wei Zhang Yu He Xi-Lin Wang Chao-Yang Lu Li Li Barry C. Sanders Xiong-Jun Liu Jian-Wei Pan Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 China National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing 210093 China Department of Physics Southern University of Science and Technology Shenzhen 518055 China The Physics Department and the Solid State Institute Technion–Israel Institute of Technology Haifa 3200003 Israel Department of Physics University of Konstanz D-78457 Konstanz Germany School of Computer Science Northwestern Polytechnical University Xi’an 710129 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Institute for Quantum Science and Technology University of Calgary Alberta T2N 1N4 Canada International Center for Quantum Materials School of Physics Peking University Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China International Quantum Academy Shenzhen 518048 China

Berry curvature is a fundamental element to characterize topological quantum physics, while a full measurement of Berry curvature in momentum space was not reported for topological states. Here we achieve two-dimensional Berry curvature reconstruction in a photonic quantum anomalous Hall system via Hall transport measurement of a momentum-resolved wave packet. Integrating measured Berry curvature over the two-dimensional Brillouin zone, we obtain Chern numbers corresponding to −1 and 0. Further, we identify bulk-boundary correspondence by measuring topology-linked chiral edge states at the boundary. The full topological characterization of photonic Chern bands from Berry curvature, Chern number, and edge transport measurements enables our photonic system to serve as a versatile platform for further in-depth study of novel topological physics.

关键词： Quantum simulation Quantum walks Topological effects in photonic systems Topological phase transition Topological phases of matter

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