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Multi-error-correcting amplitude damping codes

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Multi-error-correcting amplitude damping codes

IEEE International Symposium on Information Theory

作者： Runyao Duan Markus Grassl Zhengfeng Ji Bei Zeng State Key Laboratory of Intelligent Technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Computer Science and Technology Tsinghua University Beijing China Centre for Quantum Computation and Intelligent Systems (QCIS) Faculty of Engineering and Information Technology University of Technology Sydney NSW Australia Centre for Quantum Technologies National University of Singapore Singapore Perimeter Institute of Theoretical Physics Waterloo ONT Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy and Sciences Beijing China Institute for Quantum Computing and the Department of Combinatorics and Optimization University of Waterloo Waterloo ONT Canada

ISBN: (纸本)9781424478903

We construct new families of multi-error-correcting quantum codes for the amplitude damping channel. Our key observation is that, with proper encoding, two uses of the amplitude damping channel simulate a quantum erasure channel. This allows us to use concatenated codes with quantum erasure-correcting codes as outer codes for correcting multiple amplitude damping errors. Our new codes are degenerate stabilizer codes and have parameters which are better than the amplitude damping codes obtained by any previously known construction.

关键词： Damping Quantum mechanics Quantum computing Error correction codes Noise level Laboratories Phase noise physics computing Intelligent systems Computer science

Monte Carlo Study of Lattice Compact Quantum Electrodynamics with Fermionic Matter: The Parent State of Quantum Phases

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Physical Review X 2019年第2期9卷 021022-021022页

作者： Xiao Yan Xu Yang Qi Long Zhang Fakher F. Assaad Cenke Xu Zi Yang Meng Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong China Center for Field Theory and Particle Physics Department of Physics Fudan University Shanghai 200433 China State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Institut für Theoretische Physik und Astrophysik Universität Würzburg 97074 Würzburg Germany Department of Physics University of California Santa Barbara California 93106 USA Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics The University of Hong Kong China CAS Center of Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China

The interplay between lattice gauge theories and fermionic matter accounts for fundamental physical phenomena ranging from the deconfinement of quarks in particle physics to quantum spin liquid with fractionalized anyons and emergent gauge structures in condensed matter physics. However, except for certain limits (for instance, a large number of flavors of matter fields), analytical methods can provide few concrete results. Here we show that the problem of compact U(1) lattice gauge theory coupled to fermionic matter in (2+1)D is possible to access via sign-problem-free quantum Monte Carlo simulations. One can hence map out the phase diagram as a function of fermion flavors and the strength of gauge fluctuations. By increasing the coupling constant of the gauge field, gauge confinement in the form of various spontaneous-symmetry-breaking phases such as the valence-bond solid (VBS) and Néel antiferromagnet emerge. Deconfined phases with algebraic spin and VBS correlation functions are also observed. Such deconfined phases are incarnations of exotic states of matter, i.e., the algebraic spin liquid, which is generally viewed as the parent state of various quantum phases. The phase transitions between the deconfined and confined phases, as well as that between the different confined phases provide various manifestations of deconfined quantum criticality. In particular, for four flavors Nf=4, our data suggest a continuous quantum phase transition between the VBS and Néel order. We also provide preliminary theoretical analysis for these quantum phase transitions.

关键词： Critical exponents Lattice gauge theory Quantum electrodynamics Quantum phase transitions Quantum spin liquid Quantum Monte Carlo

Boson-boson pure-dephasing model with non-Markovian properties

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arXiv 2018年

作者： Xiong, Fei-Lei Li, Li Chen, Zeng-Bing Hefei National Laboratory for Physical Sciences at the Microscale Department of Modern Physics University of Science and Technology of China Hefei Anhui230026 China CAS Center for Excellence in QIQP Synergetic Innovation Center for QIQP University of Science and Technology of China Hefei Anhui230026 Centre for Quantum Computation and Communication Technology Australian Research Council Centre for Quantum Dynamics Grith University BrisbaneQLD4111

Understanding decoherence processes is crucial in the study of open quantum systems. In this paper, we discuss the mechanism of pure-dephasing process with a newly proposed boson-boson model, namely, a bosonic field coupled to another bosonic bath in thermal equilibrium. Our model is fully solvable and can reproduce the pure-dephasing process which is usually described by the well-known spin-boson model, therefore ofiering a new perspective to understanding decoherence processes in open quantum systems of high dimension. We also show that this model admits a generically non-Markovian dynamics with respect to various different non-Markovian measures. Copyright © 2018, The Authors. All rights reserved.

关键词： Bosons

Probing the Meissner effect in pressurized bilayer nickelate superconductors using diamond quantum sensors

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arXiv 2024年

作者： Wen, Junyan Xu, Yue Wang, Gang He, Ze-Xu Chen, Yang Wang, Ningning Lu, Tenglong Ma, Xiaoli Jin, Feng Chen, Liucheng Liu, Miao Fan, Jing-Wei Liu, Xiaobing Pan, Xin-Yu Liu, Gang-Qin Cheng, Jinguang Yu, Xiaohui Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Department of Physics Hefei University of Technology Anhui Hefei230009 China Laboratory of High Pressure Physics and Material Science School of Physics and Physical Engineering Qufu Normal University Shandong Province Qufu273165 China CAS Center of Excellence in Topological Quantum Computation Beijing100190 China

Recent reports on the signatures of high-temperature superconductivity with a critical temperature Tc close to 80 K have triggered great research interest and extensive follow-up studies1-8. Although zero-resistance state has been successfully achieved under improved hydrostatic pressure conditions2,3,9, there is no clear evidence of superconducting diamagnetism in pressurized La3Ni2O7-δ due to the low superconducting volume fraction and limited magnetic measurement techniques under high pressure conditions10. Here, using shallow nitrogen-vacancy centers implanted on the culet of diamond anvils as in-situ quantum sensors, we observe convincing evidence for the Meissner effect in polycrystalline samples La3Ni2O7-δ and La2PrNi2O7: the magnetic field expulsion during both field cooling and field warming processes. The correlated measurements of Raman spectra and NV-based magnetic imaging indicate an incomplete structural transformation related to the displacement of oxygen ions emerging in the non-superconducting region. Furthermore, comparative experiments on different pressure transmitting media (silicone oil and KBr) and nickelates (La3Ni2O7-δ and La2PrNi2O7) reveal that an improved hydrostatic pressure conditions and the substitution of La by Pr in La3Ni2O7-δ can dramatically increase the superconductivity. Our work clarifies the controversy about the Meissner effect of bilayer nickelate and contributes to a deeper understanding of the mechanism of nickelate high-temperature superconductors. Copyright © 2024, The Authors. All rights reserved.

关键词： High temperature superconductors

A resource theory of activity for quantum thermodynamics in the absence of heat baths

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arXiv 2023年

作者： Swati Singh, Uttam Chiribella, Giulio QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pokfulam Road Hong Kong Shenzhen518055 China Center for Theoretical Physics Polish Academy of Sciences Aleja Lotników 32/46 Warsaw02-668 Poland Centre of Quantum Science and Technology International Institute of Information Technology Gachibowli Telangana Hyderabad500032 India Department of Computer Science University of Oxford Wolfson Building Parks Road Oxford United Kingdom HKU-Oxford Joint Laboratory for Quantum Information and Computation Perimeter Institute for Theoretical Physics 31 Caroline Street North WaterlooON Canada

Active states, from which work can be extracted by time-dependent perturbations, are an important resource for quantum thermodynamics in the absence of heat baths. Here we characterize this resource, establishing a resource theory that captures the operational scenario where an experimenter manipulates a quantum system by means of energy-preserving operations and resets to non-active states. Our resource theory comes with simple conditions for state convertibility and an experimentally accessible resource quantifier that determines the maximum advantage of active states in the task of producing approximations of the maximally coherent state by means of energy-preserving quantum operations. Copyright © 2023, The Authors. All rights reserved.

关键词： Quantum optics

Robust topological edge states and superconductivity in few-layer stanene

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Research Square

Research Square 2021年

作者： Zhao, Chenxiao Li, Leiqiang Zhang, Liying Qin, Jin Ma, Haiyang Xia, Bing Yang, Bo Zheng, Hao Wang, Shiyong Liu, Canhua Li, Yaoyi Guan, Dandan Cui, Ping Zhang, Zhenyu Jia, Jinfeng Shenyang National Laboratory for Materials Science School of Physics and Astronomy Shanghai Jiao Tong University Shanghai200240 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Anhui Hefei230026 China University of Science and Technology of China China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai200240 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China

Stanene was proposed to be a large-gap quantum spin Hall insulator, yet to date, convincing evidence of topological edge states in stanene remains to be seen, partly due to the fact that the topological property depends on the interplay between substrate, chemical functionalization, and layer thickness. Here we fabricate 1-5 layer high-quality stanene films on the Bi(111) substrate by using hydrogen atoms as surfactants, and demonstrate their strikingly robust nontrivial topology using scanning tunneling microscopy/spectroscopy and first-principles calculations. The observed topological edge states possess a bilateral-penetration depth shorter than 4 nm, allowing the formation of dense and parallel multi-edge-channels. Our calculations further show that surface hydrogenation helps to improve the quality of stanene films, while the Bi substrate endows the films with robust nontrivial topology. These stanene films also exhibit superconductivity, and the coexistence of nontrivial topology and superconductivity renders them distinct potential to become the simplest one-dimensional topological superconductors. © 2021, CC BY.

关键词： Superconducting materials

Induced anomalous Hall effect of massive Dirac fermions in ZrTe5 and HfTe5 thin flakes

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Physical Review B 2021年第20期103卷 L201110-L201110页

作者： Yanzhao Liu Huichao Wang Huixia Fu Jun Ge Yanan Li Chuanying Xi Jinglei Zhang Jiaqiang Yan David Mandrus Binghai Yan Jian Wang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China School of Physics Sun Yat-Sen University Guangzhou 510275 China Department of Condensed Matter Physics Weizmann Institute of Science Rehovot 7610001 Israel High Magnetic Field Laboratory Chinese Academy of Sciences Hefei 230031 Anhui China Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Materials Science and Engineering University of Tennessee Knoxville Tennessee 37996 USA CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Beijing Academy of Quantum Information Sciences Beijing 100193 China

Research on the anomalous Hall effect (AHE) has been lasting for a century to make clear the underlying physical mechanism. Generally, the AHE appears in magnetic materials, in which the extrinsic process related to scattering effects and intrinsic contribution connected with Berry curvature are crucial. Recently, AHE has been counterintuitively observed in nonmagnetic topological materials and attributed to the existence of Weyl points. However, the Weyl point scenario would lead to unsaturated AHE even in large magnetic fields and contradicts the saturation of AHE in several tesla (T) in experiments. In this work, we investigate the Hall effect of ZrTe5 and HfTe5 thin flakes in static ultrahigh magnetic fields up to 33 T. We find the AHE saturates to 55(70)Ω1cm1 for ZrTe5 (HfTe5) thin flakes above ∼10T. Combining detailed magnetotransport experiments and Berry curvature calculations, we clarify that the splitting of massive Dirac bands without Weyl points can be responsible for AHE in nonmagnetic topological materials ZrTe5 and HfTe5 thin flakes. This model can identify our thin flake samples to be weak topological insulators and serve as a tool to probe the band structure topology in topological materials.

关键词： Anomalous Hall effect Electronic structure Magnetotransport Mesoscopics Topological materials Topological insulators GGA Hall bar Pseudopotentials

Deep learning-based variational autoencoder for classification of quantum and classical states of light

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arXiv 2024年

作者： Bhupati, Mahesh Mall, Abhishek Kumar, Anshuman Jha, Pankaj K. Department of Physics Indian Institute of Technology Bombay Powai Mumbai400076 India Max Planck Institute for the Structure and Dynamics of Matter Hamburg22761 Germany Center for Free Electron Laser Science Hamburg22761 Germany Centre of Excellence in Quantum Information Computation Science and Technology Indian Institute of Technology Bombay Powai Mumbai400076 India Quantum Technology Laboratory 〈Q|T|L〉 Department of Electrical Engineering and Computer Science Syracuse University SyracuseNY United States

Advancements in optical quantum technologies have been enabled by the generation, manipulation, and characterization of light, with identification based on its photon statistics. However, characterizing light and its sources through single photon measurements often requires efficient detectors and longer measurement times to obtain high-quality photon statistics. Here we introduce a deep learning-based variational autoencoder (VAE) method for classifying single photon added coherent state (SPACS), single photon added thermal state (SPACS), mixed states between coherent/SPACS and thermal/SPATS of light. Our semi-supervised learning-based VAE efficiently maps the photon statistics features of light to a lower dimension, enabling quasi-instantaneous classification with low average photon counts. The proposed VAE method is robust and maintains classification accuracy in the presence of losses inherent in an experiment, such as finite collection efficiency, non-unity quantum efficiency, finite number of detectors, etc. Additionally, leveraging the transfer learning capabilities of VAE enables successful classification of data of any quality using a single trained model. We envision that such a deep learning methodology will enable better classification of quantum light and light sources even in the presence of poor detection quality. © 2024, CC BY.

关键词： Photons

Adjustable current-induced magnetization switching utilizing interlayer exchange coupling

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arXiv 2018年

作者： Sheng, Yu Edmonds, Kevin William Ma, Xingqiao Zheng, Houzhi Wang, Kaiyou State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing100083 China Department of Physics University of Science and Technology Beijing Beijing100083 China School of Physics and Astronomy University of Nottingham NottinghamNG7 2RD United Kingdom College of Materials Science and Opto-Electronic Technology University of Chinese Academy of Science Beijing100049 China Center for Excellence in Topological Quantum Computation University of Chinese Academy of Science Beijing100049 China

Electrical current-induced deterministic magnetization switching in a magnetic multilayer structure without external magnetic field is realized by utilizing interlayer exchange coupling. Two ferromagnetic Co layers, with in-plane and out-of-plane anisotropy respectively, are separated by a spacer Ta layer, which plays a dual role of inducing antiferromagnetic interlayer coupling, and contributing to the current-induced effective magnetic field through the spin Hall effect. The current-induced magnetization switching behavior can be tuned by pre-magnetizing the in-plane Co layer. The antiferromagnetic exchange coupling field increases with decreasing thickness of the Ta layer, reaching 630 ±5 Oe for a Ta thickness of 1.5nm. The magnitude of the current-induced perpendicular effective magnetic field from spin-orbit torque is 9.2 Oe/(107Acm-2). The large spin Hall angle of Ta, opposite in sign to that of Pt, results in a low critical current density of 9×106A/cm2. This approach is promising for the electrical switching of magnetic memory elements without external magnetic field. Copyright © 2018, The Authors. All rights reserved.

关键词： Switching