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Propensity of oxidation of transition metal dichalcogenide monolayers in relation to physical configuration of chalcogen vacancies

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Physical Review B 2025年第9期111卷 094107-094107页

作者： Hiroyo Kawai Fabio Bussolotti Khoong Hong Khoo Kuan Eng Johnson Goh ASTAR Quantum Innovation Centre (Q.InC) Institute of High Performance Computing (IHPC) Agency for Science Technology and Research (ASTAR) 1 Fusionopolis Way 16-16 Connexis Singapore 138632 Republic of Singapore ASTAR Quantum Innovation Centre (Q.InC) Institute of Materials Research and Engineering (IMRE) Agency for Science Technology and Research (ASTAR) 2 Fusionopolis Way 08-03 Innovis Singapore 138634 Republic of Singapore Department of Physics National University of Singapore 2 Science Drive 3 Singapore 117551 Republic of Singapore Department of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Republic of Singapore

Using first-principles calculations, we studied how the physical configuration of chalcogen vacancies impact the initial step of surface oxidation of two-dimensional transition metal dichalcogenides (TMDs) where the O2 molecule is adsorbed and dissociated into two O atoms. The effects of surface defects on oxidation are studied by calculating the adsorption energies of the O2 molecule and O atoms on the surface as a function of defect size. We showed that the adsorption of O2 on the surface with one or more chalcogen vacancies is thermodynamically more favorable compared to the pristine surface. Furthermore, the stability of adsorption of two O atoms increases with the number of chalcogen vacancies. The calculated projected density of states indicates that the dangling bond (in-gap) states created by the chalcogen vacancies are passivated by the adsorption of O atoms. Oxygen adsorption kinetics calculation shows that there exists a significant energy barrier of about 1 eV for the dissociation of O2 on a surface with only single chalcogen vacancy, whereas a substantially reduced barrier is observed for a surface with two or more vacancies. Our findings suggest that even though vacancy-free two-dimensional (2D) TMDs might not be practically available, the 2D TMD crystals with mainly single chalcogen vacancy defects should be resistant against oxidation and thus provide critical guidance to researchers regarding optimizing the density and clustering of chalcogen vacancies during the crystal growth.

关键词： Dangling bonds

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Field-tuned magnetic structure and phase diagram of the honeycomb magnet YbCl_(3)

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Science China(Physics,Mechanics & Astronomy) 2021年第3期64卷 84-89页

作者： YiQing Hao HongLiang Wo YiMeng Gu XiaoWen Zhang YiQing Gu ShiYi Zheng Yang Zhao GuangYong Xu Jeffrey WLynn Kenji Nakajima Naoki Murai WenBin Wang Jun Zhao State Key Laboratory of Surface Physics and Department of Physics Fudan UniversityShanghai 200433China NIST Center for Neutron Research National Institute of Standards and TechnologyGaithersburg 20899USA Department of Materials Science and Engineering University of MarylandCollege Park 20742USA J-PARC Center Japan Atomic Energy Agency(JAEA)Ibaraki 319-1195Japan Institute of Nanoelectronic Devices and Quantum Computing Fudan UniversityShanghai 200433China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093China

We report thermodynamic and neutron diffraction measurements on the magnetic ordering properties of the honeycomb lattice magnet YbCl_(3). We find YbCl_(3) exhibits a Ne′el type long-range magnetic order at the wavevector(0, 0, 0) below TN= 600 *** magnetic order is associated with a small sharp peak in heat capacity and most magnetic entropy release occurs above the magnetic ordering temperature. The magnetic moment lies in-plane, parallel to the monoclinic a-axis, whose magnitude mYb= 0.86(3) μBis considerably smaller than the expected fully ordered moment of 2.24 μBfor the doublet crystal-field ground state. The magnetic ordering moment gradually increases with increasing magnetic field perpendicular to the ab-plane, reaching a maximum value of 1.6(2) μBat 4 T, before it is completely suppressed above ~ 9 T. These results indicate the presence of strong quantum fluctuations in YbCl_(3).

关键词： magnetic order neutron diffraction honeycomb lattice

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Study on many-body phases in Jaynes-Cummings-Hubbard arrays

arXiv

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arXiv 2023年

作者： Ma, Jin-Lou Liu, Bobo Li, Qing Guo, Zexian Tan, Lei Ying, Lei School of Physics Interdisciplinary Center for Quantum Information Zhejiang University Hangzhou310027 China School of Jia Yang Institute for Quantum Technology and Engineering Computing Zhejiang Shuren University Zhejiang Shaoxing312028 China Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Province Lanzhou University Gansu Lanzhou730000 China

Disorder in one-dimensional (1D) many-body systems emerges abundant phases such as many-body localization (MBL), and thermalization. However, it remains unclear regarding their existence and behavior within hybrid quantum systems. Here, based on a simple bosonic-spin hybrid model, as known as the Jaynes-Cummings-Hubbard (JCH) array, we investigate the effect of disorder comparing to the phenomena in the clean system with the variation of atom-photon coupling strength. By using the level-spacing ratio, entanglement entropy, and the properties of observable diagonal and off-diagonal matrix elements, we find that strong disorder results in the appearance of MBL phase in the JCH model that strongly violate eigenstate thermalization hypothesis (ETH), while a conditional prethermal behavior can exist in weak disorder or weak coupling regime. The conditional prethermal dynamics is based on the choice of initial product states. This work systematically reveals abundant many-body phases in the 1D JCH model and clarifies the discrepancies in the thermalization properties of systems with and without disorder. Copyright © 2023, The Authors. All rights reserved.

关键词： quantum entanglement

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Spin-orbit entangled moments and magnetic exchange interactions in cobalt-based honeycomb magnets BaCo2(XO4)2 (X = P, As, Sb)

arXiv

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arXiv 2024年

作者： Samanta, Subhasis Cossu, Fabrizio Kim, Heung-Sik Department of Semiconductor Physics Institute of Quantum Convergence Technology Kangwon National University Chuncheon24341 Korea Republic of Center for Extreme Quantum Matter and Functionality Sungkyunkwan University Suwon16419 Korea Republic of Department of Physics School of Natural and Computing Sciences University of Aberdeen AberdeenAB24 3UE United Kingdom School of Physics Engineering and Technology University of York Heslington YorkYO10 5DD United Kingdom

Co-based honeycomb magnets have been actively studied recently for the potential realization of emergent quantum magnetism therein such as the Kitaev spin liquid. Here we employ density functional and dynamical mean-field theory methods to examine a family of the Kitaev magnet candidates BaCo2(XO4)2 (X = P, As, Sb), where the compound with X = Sb being not synthesized yet. Our study confirms the formation of Mott insulating phase and the Jeff = 1/2 spin moments at Co2+ sites despite the presence of a sizable amount of trigonal crystal field in all three compounds. The pnictogen substitution from phosphorus to antimony significantly changes the in-plane lattice parameters and direct overlap integral between the neighboring Co ions, leading to the suppression of the Heisenberg interaction. More interestingly, the marginal antiferromagnetic nearest-neighbor Kitaev term changes sign into a ferromagnetic one and becomes sizable at the X = Sb limit. Our study suggests that the pnictogen substitution can be a viable route to continuously tune magnetic exchange interactions and to promote magnetic frustration for the realization of potential spin liquid phases in BaCo2(XO4)2 Copyright © 2024, The Authors. All rights reserved.

关键词： Mean field theory

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Atomic excitation delocalization at the clean to disordered interface in a chirally-coupled atomic array

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Physical Review Research 2024年第1期6卷 013159-013159页

作者： C.-C. Wu K.-T. Lin I. G. N. Y. Handayana C.-H. Chien S. Goswami G.-D. Lin Y.-C. Chen H. H. Jen Institute of Atomic and Molecular Sciences Academia Sinica Taipei 10617 Taiwan Department of Physics and Center for Quantum Science and Engineering National Taiwan University Taipei 10617 Taiwan Molecular Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 115201 Taiwan Department of Physics National Central University Taoyuan City 320317 Taiwan Physics Division National Center for Theoretical Sciences Taipei 10617 Taiwan Trapped-Ion Quantum Computing Laboratory Hon Hai Research Institute Taipei 11492 Taiwan

In one-dimensional quantum emitter systems, the dynamics of atomic excitations are influenced by the collective coupling between emitters through photon-mediated dipole-dipole interactions. By introducing positional disorders in a portion of the atomic array, we investigate the delocalization phenomena at the interface between the disordered and clean zones. The excitation is initialized as symmetric Dicke states in the disordered zone, and several measures are used to quantify the excitation localization. We first use population imbalance and half-chain entropy to investigate the excitation dynamics under time evolutions, and further investigate the crossover of excitation localization to delocalization via the gap ratio from the eigenspectrum in the reciprocal coupling case. In particular, we study the participation ratio of the whole chain and the photon loss ratio between both ends of the atomic chain, which can be used to quantify the delocalization crossover in the nonreciprocal coupling cases. Furthermore, by increasing the overall size or the ratio of the disordered zone under a fixed number of the whole chain, we observe that excitation localization occurs at a smaller disorder strength in the former case, while in the latter, facilitation of the delocalization appears when a significant ratio of the clean zone to disordered zone is applied. Our results can reveal the competition between the clean zone and the disordered zone sizes on localization phenomenon, give insights to nonequilibrium dynamics in the emitter-waveguide interface, and provide potential applications in quantum information processing.

关键词： Localization Collective dynamics Disordered systems

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quantum advantage for differential equation analysis

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Physical Review A 2022年第2期105卷 022415-022415页

作者： Bobak Toussi Kiani Giacomo De Palma Dirk Englund William Kaminsky Milad Marvian Seth Lloyd Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Giacomo De Palma Scuola Normale Superiore 56126 Pisa Italy QuEra Computing Boston Massachusetts 02143 USA Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Electrical and Computer Engineering Center for Quantum Information and Control University of New Mexico Albuquerque New Mexico 87131 USA

quantum algorithms for differential equation solving, data processing, and machine learning potentially offer an exponential speedup over all known classical algorithms. However, there also exist obstacles to obtaining this potential speedup in useful problem instances. The essential obstacle for quantum differential equation solving is that outputting useful information may require difficult postprocessing, and the essential obstacle for quantum data processing and machine learning is that inputting the data is a difficult task just by itself. In this study, we demonstrate that, when combined, these difficulties solve one another. We show how the output of quantum differential equation solving can serve as the input for quantum data processing and machine learning, allowing dynamical analysis in terms of principal components, power spectra, and wavelet decompositions. To illustrate this, we consider continuous-time Markov processes on epidemiological and social networks. These quantum algorithms provide an exponential advantage over existing classical Monte Carlo methods.

关键词： Machine learning quantum algorithms quantum computation Markovian processes Numerical techniques

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Error-mitigated fermionic classical shadows on noisy quantum devices

arXiv

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arXiv 2023年

作者： Wu, Bujiao Koh, Dax Enshan Dahlem Center for Complex Quantum Systems Freie Universität Berlin Berlin14195 Germany Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center on Frontiers of Computing Studies Peking University Beijing100871 China 1 Fusionopolis Way #16-16 Connexis Singapore138632 Singapore

Efficiently estimating fermionic Hamiltonian expectation values is vital for simulating various physical systems. Classical shadow (CS) algorithms offer a solution by reducing the number of quantum state copies needed, but noise in quantum devices poses challenges. We propose an error-mitigated CS algorithm assuming gate-independent, time-stationary, and Markovian (GTM) noise. For n-qubit systems, our algorithm, which employs the easily prepared initial state |0n〉〈0n| assumed to be noiseless, efficiently estimates k-RDMs with Oe(knk) state copies and Oe(√n) calibration measurements for GTM noise with constant fidelities. We show that our algorithm is robust against noise types like depolarizing, damping, and X-rotation noise with constant strengths, showing scalings akin to prior CS algorithms for fermions but with better noise resilience. Numerical simulations confirm our algorithm’s efficacy in noisy settings, suggesting its viability for near-term quantum devices. Copyright © 2023, The Authors. All rights reserved.

关键词： Errors

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State-dependent mobility edge in kinetically constrained models

arXiv

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arXiv 2024年

作者： Badbaria, Manthan Pancotti, Nicola Singh, Rajeev Marino, Jamir Valencia-Tortora, Riccardo J. Department of Physics Indian Institute of Technology Banaras Hindu University Varanasi221005 India AWS Center for Quantum Computing PasadenaCA91125 United States California Institute of Technology PasadenaCA United States Institut für Physik Johannes Gutenberg-Universität Mainz MainzD-55099 Germany Pritzker School of Molecular Engineering University of Chicago ChicagoIL60637 United States

In this work, we show that the kinetically constrained quantum East model lies between a quantum scarred and a many-body localized system featuring an unconventional type of mobility edge in the spectrum. We name this scenario state-dependent mobility edge: while the system does not exhibit a sharp separation in energy between thermal and non-thermal eigenstates, the abundance of nonthermal eigenstates results in slow entanglement growth for many initial states, such as product states, below a finite energy density. We characterize the state-dependent mobility edge by looking at the complexity of classically simulating dynamics using tensor network for system sizes well beyond those accessible via exact diagonalization. Focusing on initial product states, we observe a qualitative change in the dynamics of the bond dimension needed as a function of their energy density. Specifically, the bond dimension typically grows polynomially in time up to a certain energy density, where we locate the state-dependent mobility edge, enabling simulations for long times. Above this energy density, the bond dimension typically grows exponentially making the simulation practically unfeasible beyond short times, as generally expected in interacting theories. We correlate the polynomial growth of the bond dimension to the presence of many non-thermal eigenstates around that energy density, a subset of which we compute via tensor network. The outreach of our findings encompasses quantum sampling problems and the efficient simulation of quantum circuits beyond Clifford families. © 2024, CC BY.

关键词： Tensors

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quantum-Inspired Machine Learning for Molecular Docking

arXiv

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arXiv 2024年

作者： Shu, Runqiu Liu, Bowen Xiong, Zhaoping Cui, Xiaopeng Li, Yunting Cui, Wei Yung, Man-Hong Qiao, Nan School of Automation Science and Engineering South China University of Technology Guangzhou510641 China Central Research Institute 2012 Labs Huawei Technologies China Laboratory of AI for Science Huawei Cloud Computing Technologies Co. Ltd Guizhou550025 China State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai200433 China Shenzhen Institute for Quantum Science and Engineering China

Molecular docking is an important tool for structure-based drug design, accelerating the efficiency of drug development. Complex and dynamic binding processes between proteins and small molecules require searching and sampling over a wide spatial range. Traditional docking by searching for possible binding sites and conformations is computationally complex and results poorly under blind docking. quantum-inspired algorithms combining quantum properties and annealing show great advantages in solving combinatorial optimization problems. Inspired by this, we achieve an improved in blind docking by using quantum-inspired combined with gradients learned by deep learning in the encoded molecular space. Numerical simulation shows that our method outperforms traditional docking algorithms and deep learning-based algorithms over 10%. Compared to the current state-of-the-art deep learning-based docking algorithm DiffDock, the success rate of Top-1 (RMSD Copyright © 2024, The Authors. All rights reserved.

关键词： Binding sites

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Intensity correlations in decoy-state BB84 quantum key distribution systems

arXiv

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arXiv 2024年

作者： Trefilov, Daniil Sixto, Xoel Zapatero, Víctor Huang, Anqi Curty, Marcos Makarov, Vadim Vigo Quantum Communication Center University of Vigo VigoE-36310 Spain School of Telecommunication Engineering Department of Signal Theory and Communications University of Vigo VigoE-36310 Spain atlanTTic Research Center University of Vigo VigoE-36310 Spain Russian Quantum Center Skolkovo Moscow121205 Russia National Research University Higher School of Economics Moscow101000 Russia Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow119049 Russia

The decoy-state method is a prominent approach to enhance the performance of quantum key distribution (QKD) systems that operate with weak coherent laser sources. Due to the limited transmissivity of single photons in optical fiber, current experimental decoy-state QKD setups increase their secret key rate by raising the repetition rate of the transmitter. However, this usually leads to correlations between subsequent optical pulses. This phenomenon leaks information about the encoding settings, including the intensities of the generated signals, which invalidates a basic premise of decoy-state QKD. Here we characterize intensity correlations between the emitted optical pulses in two industrial prototypes of decoy-state BB84 QKD systems and show that they significantly reduce the asymptotic key rate. In contrast to what has been conjectured, we experimentally confirm that the impact of higher-order correlations on the intensity of the generated signals can be much higher than that of nearest-neighbour correlations. Copyright © 2024, The Authors. All rights reserved.

关键词： quantum cryptography

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