Quantum algorithm for a set of quantum 2SAT problems

We present a quantum adiabatic algorithm for a set of quantum 2-satisfiability(Q2SAT)problem,which is a generalization of 2-satisfiability(2SAT)problem.For a Q2SAT problem,we construct the Hamiltonian which is similar to that of a Heisenberg chain.All the solutions of the given Q2SAT problem span the subspace of the degenerate ground states.The Hamiltonian is adiabatically evolved so that the system stays in the degenerate subspace.Our numerical results suggest that the time complexity of our algorithm is O(n^3.9)for yielding non-trivial solutions for problems with the number of clauses m=dn(n-1)/2(d■0.1).We discuss the advantages of our algorithm over the known quantum and classical algorithms.     

Polarization-independent silicon photonic grating coupler for large spatial light spots

We design and demonstrate a one-dimensional grating coupler with a low polarization-dependent loss(PDL)for large spatial light spots.Based on current fabrication conditions,we first utilize genetic algorithms to find the optimal grating structure including the distributions of duty and periods,making the effective refractive index of transverse electric mode the same as that of transverse magnetic mode.The designed grating coupler is fabricated on the common silicon-on-insulator platform and the PDL is measured to be within 0.41 d B covering the C-band.     

Nonlocal advantage of quantum coherence in a dephasing channel with memory

We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.     

基于吸聚一体的低散射传输型透镜设计

通过传输型超表面透镜与电路模拟雷达波吸收器的集成设计,提出了一种兼具透射波前变换与带外雷达散射截面减缩特性的微波复合材料设计方法。透镜采用亚波长分布的周期性单元,由梯度相位补偿对透射波进行调节,进而获得平面波前与球面波前之间的互易变换。并且,使用透镜在波前变换频带以外低频端的反射特征,结合单个有耗层设计,构造了电路模拟吸波器。选用一副缝隙耦合馈电的微带贴片天线单元作为初级馈源天线,观察到复合材料的波前变换特性可在宽频带范围内产生主瓣增益增强效果。与透镜相比,电路模拟吸波器的引入使得复合材料针对TE与TM极化分别可在130.68%与155.11%的频率范围内获得雷达散射截面减缩效果。通过全波模拟和实验测量,验证了辐射增益增强与雷达散射截面减缩效果,表明了复合材料吸聚一体设计的有效性。     

BaCuS_2: A Superconductor with Moderate Electron-Electron Correlation

We show that the layered-structure BaCuS₂ is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors.Theoretical calculations reveal that the in-plane d-p σ^*-bonding bands are isolated near the Fermi level.As the energy separation between the d and p orbitals are much smaller than those in cuprates and iron-based superconductors,BaCuS₂ is expected to be moderately correlated.We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms,namely the conventional BCS electron-phonon interaction and the electron-electron correlation,which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.     

First-Principles Study of Intrinsic Point Defects of Monolayer GeS

The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the“transfer to real state”model,based on density functional theory.We find that Ge vacancy is the dominant intrinsic acceptor defect,due to its shallow acceptor transition energy level and lowest formation energy,which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS,and effectively explains the native p-type conductivity of GeS observed in experiment.The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions.Furthermore,with respect to growth conditions,Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions.Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS,as well as expanding the understanding of defect properties in lowdimensional semiconductor materials.     

基于原子操纵技术的人工量子结构研究

扫描隧道显微镜原子操纵技术是指利用扫描探针在特定材料表面以晶格为步长搬运单个原子或分子的技术.它是纳米尺度量子物理与器件研究领域一种独特而有力的研究手段.利用这种手段,人们能够以原子或分子为单元构筑某些常规生长或微加工方法难以制备的人工量子结构,通过对格点原子、晶格尺寸、对称性、周期性的高度控制,实现对局域电子态、自旋序、以及能带拓扑特性等量子效应的设计与调控.原子操纵技术与超快测量及自动控制技术的结合,使得人们能够进一步研究原子级精准的量子器件,因而该技术成为探索未来器件新机理、新工艺的重要工具.本文首先简介原子操纵方法的发展过程和技术要点,然后分别介绍人工电子晶格、半导体表面人工量子点、磁性人工量子结构、人工结构中的信息存储与逻辑运算、单原子精度原型器件等方面的最新研究进展,以及单原子刻蚀和自动原子操纵等方面的技术进展,最后总结并展望原子操纵技术的应用前景和发展趋势.     

双金属/TiO2纳米管复合结构中增强的光电流

将传统半导体材料与金属微纳结构相结合,利用其表面等离激元共振效应,可有效地增强复合结构的光电转换效率,使其广泛地被用于光电化学和光电探测等领域.本文以氧化铝纳米管为模板,采用原子层沉积技术制备出高有序的TiO2纳米管,并通过电子束热蒸发技术在大孔径的纳米管薄膜中分别负载金、铝和双金属金/铝纳米颗粒,形成金属纳米颗粒/T...     

基于接触数引导的迭代多组独立分子动力学模拟实现配体-蛋白质结合与解离过程

配体的结合与解离过程在蛋白质实现其生物学功能方面非常关键,因此对这些高度动态过程的研究变得非常重要. 尽管已有实验方法可以确定蛋白质-配体复合物的三维结构,但一般仅可获得静态图片. 随着计算机算力的快速提高以及算法的优化,分子动力学模拟在探索配体的结合与解离过程方面具有诸多优势. 然而,当系统变得足够大时,分子动力学模拟的时间和空间尺度成为了巨大的挑战. 本工作提出了一种研究配体-蛋白质结合与解离的增强采样工具,它基于配体和蛋白质之间形成的接触数来引导迭代多组独立分子动力学模拟. 在腺苷酸激酶的模拟结果中,观测到配体的结合和解离过程,而使用传统分子动力学模拟在同一时间尺度下则无法实现这一过程.     

大型综合医院室外声景观评价影响因素分析——以长沙市中心医院为例

大型综合医院室外本是医患康复疗养、舒缓身心的场所,但并未引起足够的重视,噪声影响严重,声景观较差.该文以长沙市中心医院为例,通过定点实测结合问卷调查的方式,探究影响大型综合医院室外声景观评价结果的因素.结果表明:长沙市中心医院室外声景观整体满意度一般,语义词调查结果整体偏向贬义负值,受访者身份、调查时间和声源构成对声景...