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Development of 400-μW cryogen-free dilution refrigerators for quantum experiments

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Chinese Physics B 2024年第7期33卷 28-35页

作者：关翔樊洁边勇波程智刚姬忠庆 Institute of Physics Chinese Academy of SciencesBeijing 100190China School of physical sciences University of Chinese Academy of SciencesBeijing 100190China

We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 m K, with a minimum temperature of 7.6 m K and a cooling power of 450 μW at 100 m K. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.

关键词： cryogen-free dilution refrigerator quantum computing low-temperature detector superconducting magnet

ESM Cloud Toolkit: A Copilot for Energy Storage Material Research

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Chinese Physics Letters 2024年第5期41卷 40-46页

作者：许晶肖睿娟李泓 Institute of Physics Chinese Academy of SciencesBeijing 100190China School of physical sciences University of Chinese Academy of SciencesBeijing 100049China

Searching and designing new materials play crucial roles in the development of energy storage devices. In today's world where machine learning technology has shown strong predictive ability for various tasks, the combination with machine learning technology will accelerate the process of material development. Herein, we develop ESM Cloud Toolkit for energy storage materials based on Mat Elab platform, which is designed as a convenient and accurate way to automatically record and save the raw data of scientific research. The ESM Cloud Toolkit includes multiple features such as automatic archiving of computational simulation data, post-processing of experimental data, and machine learning applications. It makes the entire research workflow more automated and reduces the entry barrier for the application of machine learning technology in the domain of energy storage materials. It integrates data archive, traceability, processing, and reutilization, and allows individual research data to play a greater role in the era of AI.

关键词： Toolkit Storage ESM

Rational Solutions of First Order Algebraic Ordinary Differential Equations

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Journal of Systems Science & Complexity 2024年第2期37卷 567-580页

作者： FENG Shuang SHEN Liyong School of physical and Mathematical sciences Nanjing Tech UniversityNanjing 211816China School of Mathematical sciences University of Chinese Academy of SciencesBeijing 100049China

Let f(t,y,y')=∑ _(i=0)^(n )a_(i)(t,y)y'^(i)=0 be an irreducible first order ordinary differential equation with polynomial coefficients.Eremenko in 1998 proved that there exists a constant C such that every rational solution of f(t,y,y')=0 is of degree not greater than C.Examples show that this degree bound C depends not only on the degrees of f in t,y,y' but also on the coefficients of f viewed as the polynomial in t,y,y'.In this paper,the authors show that if f satisfies deg(f,y)0,then the degree bound C only depends on the degrees of f in t,y,y',and furthermore we present an explicit expression for C in terms of the degrees of f in t,y,y'.

关键词： Degree bound first order AODE height rational solution

Investigation and Mitigation of Carbon Deposition over Copper Catalyst during Electrochemical CO_(2)Reduction

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Precision Chemistry

Precision Chemistry 2024年第4期2卷 151-160页

作者： Jing-Wen DuanMu Zhi-Zheng Wu Fei-Yue Gao Peng-Peng Yang Zhuang-Zhuang Niu Yu-Cai Zhang Li-Ping Chi Min-Rui Gao division of Nanomaterials and Chemistry Hefei National Laboratory for Physical Sciences at the MicroscaleUniversity of Science and Technology of ChinaHefei 230026China

Copper(Cu)is considered to be the most effective catalyst for electrochemical conversion of carbon dioxide(CO_(2))into value-added hydrocarbons,but its stability still faces considerable challenge.Here,we report the poisoning effect of carbon deposition during CO_(2)reduction on the active sites of Cu electrodea critical deactivation factor that is often overlooked.We find that,*C,an intermediate toward methane formation,could desorb on the electrode surface to form carbon species.We reveal a strong correlation between the formation of methane and the carbon deposition,and the reaction conditions favoring methane production result in more carbon deposition.The deposited carbon blocks the active sites and consequently causes rapid deterioration of the catalytic performance.We further demonstrate that the carbon deposition can be mitigated by increasing the roughness of the electrode and increasing the pH of the electrolyte.This work offers a new guidance for designing more stable catalysts for CO_(2)reduction.

关键词： carbon deposition roughness in situ spectrum CO_(2)electroreduction copper catalyst

Holevo bound independent of weight matrices for estimating two parameters of a qubit

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Chinese Physics B 2024年第2期33卷 137-143页

作者：牛畅郁司夏 Department of Modern Physics&Hefei National Research Center for physical sciences at the Microscale and School of physical sciences University of Science and Technology of ChinaHefei 230026China Hefei National Laboratory University of Science and Technology of ChinaHefei 230088China

Holevo bound plays an important role in quantum metrology as it sets the ultimate limit for multi-parameter estimations,which can be asymptotically achieved.Except for some trivial cases,the Holevo bound is implicitly defined and formulated with the help of weight matrices.Here we report the first instance of an intrinsic Holevo bound,namely,without any reference to weight matrices,in a nontrivial case.Specifically,we prove that the Holevo bound for estimating two parameters of a qubit is equivalent to the joint constraint imposed by two quantum Cramér–Rao bounds corresponding to symmetric and right logarithmic derivatives.This weightless form of Holevo bound enables us to determine the precise range of independent entries of the mean-square error matrix,i.e.,two variances and one covariance that quantify the precisions of the estimation,as illustrated by different estimation models.Our result sheds some new light on the relations between the Holevo bound and quantum Cramer–Rao bounds.Possible generalizations are discussed.

关键词： quantum metrology quantum Fisher information Holevo bound quantum multi-parameter estimation

Two-dimensional semiconductor heterostructures for photocatalytic CO2 conversion

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Science China Chemistry 2024年第8期67卷 2434-2447页

作者： Yang Wu Mingyu Wu Yongfu Sun Yi Xie Hefei National Research Center for physical sciences at Microscale University of Science and Technology of China

The CO2reduction into carbon-contained fuel via solar energy offers the powerful tools to realize the zero-emission carbon cycle. Owing to the intriguing features of the two-dimensional（2D） heterostructures, it is susceptible to modulate the electronic structure as well as the surface geometry for optimizing the photocatalytic CO2reactivity. From this perspective, we surveyed the fundamental insights of 2D semiconductor heterostructures, involving the fabrication strategies and classification of the 2D semiconductor heterostructure. Also, we have detailly discussed the overview of 2D semiconductor heterostructure for optimizing CO2photocatalytic influenced factors, including the solar energy utilization, photogenerated carriers separation, and redox reaction kinetics. Afterwards, we showed the significant advantages of 2D heterostructures in elevating CO2photoreduction performance, focusing on activity, selectivity and photostability. By analyzing the limitations and developments, we ended by putting forward insights into the further researches about the CO2photocatalysts and reactor design, even industrial applications.

关键词： CO2 conversion photocatalysis two-dimensional semiconductor heterostructures

Spin-based magnetic random-access memory for high-performance computing

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National Science Review 2024年第3期11卷 20-23页

作者： Kaiming Cai Tianli Jin Wen Siang Lew School of Physics Huazhong University of Science and Technology Interuniversity Microelectronics Centre(IMEC) School of physical and Mathematical sciences Nanyang Technological University

Memory serves as a critical component in today's electronic systems for data storage and processing. In traditional computer architectures, the logic and memory units are physically separated, due to the performance gap in operational speed and capacity among memories, resulting in the fundamental limitation of the von Neumann computers.

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Preparing highly entangled states of nanodiamond rotation and NV center spin

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Chinese Physics B 2024年第2期33卷 144-151页

作者：李文亮周端陆 Institute of Physics Beijing National Laboratory for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100190China School of physical sciences University of Chinese Academy of SciencesBeijing 100049China

A nanodiamond with an embedded nitrogen-vacancy(NV)center is one of the experimental systems that can be coherently manipulated within current technologies.Entanglement between NV center electron spin and mechanical rotation of the nanodiamond plays a fundamental role in building a quantum network connecting these microscopic and mesoscopic degrees of motions.Here we present a protocol to asymptotically prepare a highly entangled state of the total quantum angular momentum and electron spin by adiabatically boosting the external magnetic field.

关键词： nanodiamond NV center entanglement

Needs and challenges of optical atmospheric monitoring on the background of carbon neutrality in China

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Frontiers of Environmental Science & Engineering 2024年第6期18卷 49-62页

作者： Wenqing Liu Chengzhi Xing Anhui Institute of Optics and Fine Mechanics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 23001China

The achievement of the targets of coordinated control of PM2.5 and O3 and the carbon peaking and carbon neutrality depend on the development of pollution and greenhouse gas monitoring technologies.Optical monitoring technology,based on its technical characteristics of high scalability,high sensitivity and wide-targets detection,has obvious advantages in pollution/greenhouse gases monitoring and has become an important direction in the development of environmental monitoring technology.At present,a system of environmental optical monitoring technology with differential optical absorption spectroscopy(DOAS),cavity ring-down spectroscopy(CRDS),light detection and ranging(LIDAR),laser heterodyne spectroscopy(LHS),tunable diode laser absorption spectroscopy(TDLAS),fourier transform infrared spectroscopy(FTIR)and fluorescence assay by gas expansion(FAGE)as the main body has been established.However,with the promotion of“reduction of pollution and carbon emissions”strategy,there have been significant changes in the sources of pollution/greenhouse gases,emission components and emission concentrations,which have put forward new and higher requirements for the development of monitoring technologies.In the future,we should pay more attention to the development of new optical monitoring techniques and the construction of stereoscopic monitoring system,the interdisciplinarity(among mathematics,physics,chemistry and biology,etc.),and the monitoring of greenhouse gases and research on atmospheric chemistry.

关键词： Pollution Greenhouse gas Optical atmospheric monitoring Needs and challenges