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Directional quantum random walk induced by coherence

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Frontiers of physics 2020年第2期15卷 13-25页

作者： Jin-Fu Chen Yu-Han Ma chang-pu sun Beijing Computational Science Research Center Beijing 100193China Graduate School of China Academy of Engineering Physics No.10 Xibeiwang East RoadHaidian DistrictBeijing 100193China

Quantum walk (QW), which is considered as the quantum counterpart of the classical random walk (CRW), is actually the quantum extension of CRW from the single-coin interpretation. The sequential unitary evolution engenders correlation between different steps in QW and leads to a non-binomial position distribution. In this paper, we propose an alternative quantum extension of CRW from the ensemble interpretation, named quantum random walk (QRW), where the walker has many unrelated coins, modeled as two-level systems, initially prepared in the same state. We calculate the walker's position distribution in QRW for different initial coin states with the coin operator chosen as Hadamard matrix. In one-dimensional case, the walker's position is the asymmetric binomial distribution. We further demonstrate that in QRW, coherence leads the walker to perform directional movement. For an initially decoherenced coin state, the walker's position distribution is exactly the same as that of CRW. Moreover, we study QRW in 2D lattice, where the coherence plays a more diversified role in the walker's position distribution.

关键词： quantum walk random walk ensemble interpretation directional walking coherence

Coherent excitation transfer via the dark-state channel in a bionic system

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Light(Science & Applications) 2012年第1期1卷 128-133页

作者： Hui Dong Da-Zhi Xu Jin-Feng Huang chang-pu sun State Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

Light absorption and energy transfer were studied in a bionic system with donors and an *** the optimal case of uniform couplings,this seemingly complicated system was reduced to a three-level L-type *** this observation,we showed that the efficiency of energy transfer through a dark-state channel,which is free of the spontaneous decay of the donors,was dramatically *** the overall average transfer time was evaluated,it was revealed that the time required for transfer through this channel was not *** find the optimal parameters for the present system,we defined a new quantity,output power,which characterizes the average mean output of the whole transfer *** estimated the optimal parameters of the system to achieve the maximum output *** splitting behaviour of the maximum power may be used to explain the phenomenon of photosynthetic systems primarily absorbing two colours of light.

关键词： dark state excitation transfer light harvesting quantum coherence

Optimal squeezed cooling of a mechanical oscillator using measurement-based vector feedback

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Science China(Physics,Mechanics & Astronomy) 2023年第7期66卷 55-61页

作者： Zhi-Cheng Gong Cheng-Yu Shen Tian-Hua Mao chang-pu sun Yong Li Hao Fu School of Science Hainan UniversityHaikou 570228China Innovation Academy for Precision Measurement Science and Technology Chinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100190China Graduate School of China Academy of Engineering Physics Beijing 100193China Beijing Computational Science Research Center Beijing 100193China Center for Theoretical Physics Hainan UniversityHaikou 570228China

Measurement-based feedback has been adopted as an efficient cooling scheme capable of suppressing the thermal fluctuation of a mechanical resonator to a level limited by measurement *** present a scheme of squeezed cooling in which the limit of feedback cooling imposed by the measurement imprecision is surpassed by parametrically squeezing the mechanical resonator in a periodically oscillating optical *** stabilize the parametrically amplified quadrature and simultaneously optimize the cooling for the squeezed quadrature,a measurement-based vector feedback capable of independently controlling the orthogonal motional quadrature is *** experiment demonstrates that the optimal condition for the squeezed cooling closely depends on the strength of *** the ability to keep the orthogonal quadrature well decoupled,optimal squeezed cooling of the mechanical resonator under strong squeezing is achieved with the squeezed variance becoming 8.1 dB below the limit of feedback cooling and the creation of a 31.7 dB thermomechanical squeezed *** this research is conducted in the classical regime,the scheme of squeezed cooling can be naturally extended to quantum systems with the prospects of creating quantum squeezing of a room-temperature mechanical resonator and enabling displacement measurement beyond the standard quantum limit.

关键词： squeezed cooling measurement-based feedback parametric squeezing optimal control optomechanics

Decoherence of macroscopic objects from relativistic effect

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Chinese Physics B 2018年第10期27卷 148-158页

作者： Guo-Hui Dong Yu-Han Ma Jing-Fu Chen Xin Wang chang-pu sun Beijing Computational Science Research Center Beijing 100193 China Graduate School of China Academy of Engineering Physics Beijing 100193 China

We study how the decoherence of macroscopic objects originates intrinsically from the relativistic effect. With the degree of freedom of the center of mass（CM） characterizing the collective quantum state of a macroscopic object（MO）,it is found that an MO consisting of N particles can decohere with a time scale of no more than p （√N）^-1. Here, the special relativity can induce the coupling of the collective motion mode and the relative motion modes in an order of 1/c^2, which intrinsically results in the above minimum decoherence.

关键词： decoherence macroscopic object special relativistic effect

The uniqueness of the integration factor associated with the exchanged heat in thermodynamics

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Fundamental Research 2021年第1期1卷 6-9页

作者： Yu-Han Ma Hui Dong Hai-Tao Quan chang-pu sun Beijing Computational Science Research Center Beijing 100193China Graduate School of China Academy of Engineering Physics No.10 Xibeiwang East RoadHaidian DistrictBeijing 100193China School of Physics Peking UniversityBeijing 100871China

State functions play important roles in *** from the process function,such as the exchanged heatδQ and the applied workδW,the change of the state function can be expressed as an exact *** prove here that,for a generic thermodynamic system,only the inverse of the temperature,namely 1/T,can serve as the integration factor for the exchanged heatδ*** uniqueness of the integration factor invalidates any attempt to define other state functions associated with the exchanged heat,and in turn,reveals the incorrectness of defining the entransy E_(vh)=CVT^(2)/2 as a state function by treating T as an integration *** further show the errors in the derivation of entransy by treating the heat capacity C_(V)as a temperature-independent constant.

关键词： Integration factor Process function Exchanged heat Thermodynamic entropy Uniqueness theorem

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基于最大熵原理可靠性分析的病毒传播模型

科学通报 2020年第22期65卷 2356-2362页

作者：杜亦牧孙昌璞中国工程物理研究院研究生院北京100193 北京计算科学研究中心北京100193

应用基于最大熵原理的复杂系统可靠性分析方法对病毒在宿主、易感染者和移除者等共存系统中的传播问题进行了系统的动力学理论分析.在本研究中,我们将病毒传播问题中的病死速率、发病速率和治愈速率等实际统计参量映射成可靠性理论中描... 详细信息

应用基于最大熵原理的复杂系统可靠性分析方法对病毒在宿主、易感染者和移除者等共存系统中的传播问题进行了系统的动力学理论分析.在本研究中,我们将病毒传播问题中的病死速率、发病速率和治愈速率等实际统计参量映射成可靠性理论中描述个体行为的风险(退化)函数:个体宿主的病死速率和治愈速率对应于可修复系统的失效率和修复率;潜伏期阶段患者发病速率对应于可靠性理论中的失效率.通过最大熵原理,本文研究融合了病死时间、治愈周期和潜伏期等统计量的各阶矩信息,从而推断出最概然的病死速率、发病速率和治愈速率.最后,以包含易感、感染(确诊与潜伏期)和移除四类人群的传播模型(SEIR模型)为例,结合基于最大熵原理的退化函数推断,分析了新型冠状病毒肺炎(Corona Virus Disease 2019, COVID-19)传播的一些理论问题.

关键词：最大熵原理可靠性理论病毒传播模型新型冠状病毒肺炎

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Preface

Communications in Theoretical Physics 2022年第9期74卷 5-5页

作者： chang-pu sun 不详

In 1982,as the founding director of the Institute of Theoretical Physics,Chinese Academy of Sciences(ITP-CAS),Professor Huan-Wu Peng created a peer-reviewed scientific journal—Communications in Theoretical Physics(CTP)together with some *** devoted it to the mission in promoting academic exchange of theoretical ideas in all aspects of physics between researchers in China and those from the rest of the *** Peng had served as the Editor-in-Chief for seven years before this job was handed over to ***-Hsiu Ho in 1989,who was also one of the proposers of the journal’s creation.I received the relay baton from the hand of *** in 2013.

关键词： journal devoted founding

Potassium ions and cyano group modified g-C3N4 for effective generation of H2O2 through two-electron oxygen reduction

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Science China Chemistry 2025年第1期 192-200页

作者： Dongying Wang Shulan pu Yongmin Chen Ke Lei Yujie Duan Linjiao Mao Xuhui Zeng Xi Luo Yuntao Zhang Yuqin Dong Jin Zhong Zhang Yan sun School of Mechanical Engineering Chengdu University Department of Chemistry and Biochemistry University of California

Potassium ions （K+） doped graphitic carbon nitride （g-C3N4） was prepared by a thermal etching method using potassium hydroxide （KOH） as an ion *** transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）results showed that the generation of the cyano group was detected while introducing K+.Under simulated sunlight irradiation,the sample with a K+doping amount of 10%showed the highest hydrogen peroxide （H2O2） generation rate of2,140.2μmol *** apparent quantum yield （AQY） at 400 nm and the solar-to-chemical conversion （SCC） are 4.35%and1.23%,respectively.K+acted as a bridge between g-C3N4layers,which enhanced charge transfer ***,the cyano group enhanced the adsorption capacity of protons （H+） and promoted the yield of *** catalyst exhibited excellent photocatalytic stability based on four-cycle *** addition,a mechanism study showed that superoxide radicals （·O2-）were the most important active species in the reaction *** production of H2O2was achieved through consecutive single-electron *** study deepens the understanding of the oxygen reduction reaction process and opens up a new venue for improving H2O2generation.

关键词：

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Progress of crystalline carbon nitride in synthesis,atomic structure characterization and photocatalysis

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Nano Research 2025年第1期18卷 455-476页

作者： Yueyang Tan Zhongyan Zhang Yayun pu Zongzhao sun Limin Huang School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Department of Chemistry Southern University of Science and TechnologyShenzhen 518055China School of Traffic and Environment Shenzhen Institute of Information TechnologyShenzhen 518172China College of Chemistry and Chemical Engineering Linyi UniversityLinyi 276000China School of Optoelectronic Engineering Chongqing University of Posts and TelecommunicationsChongqing 400065China

Crystalline carbon nitride(CCN)has emerged as a highly promising semiconductor photocatalyst with unique properties,such as enhanced charge migration rate,reduced carrier recombination probability,narrow band gap and improved light-harvesting efficiency,which are suitable for a wide range of applications in solar-to-chemical conversion,energy storage,therapeutic and environmental pollution *** the past few years,there has been an increasing number of reviews on CCN ***,most of these reviews mainly focus on synthesis methods,modification and applications,with less emphasis on the relationship between structures and properties,as well as on indepth exploration of the crystalline *** electronic instability of CCN presents challenges for conventional characterization techniques to directly and thoroughly investigate the relationship between its intrinsic atom structure and photocatalytic *** mini-review not only highlights the progress in CCN-based photocatalysts,with a focus on molten-salt synthesis(including solid-salt-induced crystallization),but also emphasizes the atomic structure characterization by specifically introducing the differential phase contrast(DPC)scanning transmission electron microscopy(STEM)technique,which is essential for enhancing our understanding of the crystal structure and photocatalytic mechanisms of ***,the review outlines the photocatalytic performance and puts forward potential challenges on CCN *** review will provide a clearer understanding of the relationship in developing precise customization strategies for CCN materials and ultimately explain the regularity and specificity of the enhanced performance in targeted photocatalytic systems.

关键词： crystalline carbon nitride synthesis characterization photocatalysis