Kerr效应对二项式腔场谱量子干涉的影响

研究了含Kerr介质高Q腔内单个二能级原子与双模二项式光场发生双光子共振相互作用系统的腔场谱,给出了Kerr效应与量子干涉项ΔS(ω)关系的数值计算结果,讨论了Kerr效应对二项式腔场谱量子干涉的影响.结果表明:若初始时刻原子处于激发态而双模光场处于二项式态,随Kerr效应的增强,致使量子干涉项引起谱线强度的改变量呈现出"不规则的周期性衰减振荡"特性,震荡幅度与两模光场的频差密切相关.在Kerr系数χ＜g(g为光场与原子的耦合常数)时,Kerr效应对干涉项的影响比     

油藻混合水体遥感反射比光谱分析

辐射传输模式HydroLight是研究水体辐射传输特性的有效工具,同时也是进行石油类水体辐射传输特性的有效模型。本文基于2018年8月在辽宁大连港海域实测的石油类污染水体的表观及固有光学量数据,通过设置不同浓度的配比模拟试验,利用HydroLight对油类物质和藻类物质的单一组分和两者混合水体的遥感反射比（remote sensing reflectance,R_rs）光谱进行了模拟。模拟结果表明：（1）在仅含油类物质单一组分的水体中,R_rs随着油浓度C_oil的变化分为两个特征波段：400~480 nm和480~700 nm。在400~480 nm波段范围内R_rs随C_oil的增加而减小,在480~700 nm随C_oil的增大而增大;（2）在仅含藻类物质的单一成分水体中,叶绿素的光谱特性需要其浓度C_chl达到一定值才能表现出来,在低C_chl时的R_rs光谱特性反映为纯水的光谱特性;（3）在油藻混合水体中,随C_oil的增加会增大叶绿素的R_rs,但不会明显改变叶绿素的R_rs随波长的变化趋势,这说明油藻混合水体的光谱形状主要受叶绿素的影响,油类物质的存在只改变光谱的量值。利用HydroLight对石油类污染水体的R_rs展开研究,有助于丰富水色遥感基础研究,对完善各类水体生物光学模型研究具有重要的理论意义。     

钪原子的自电离里德伯能级3d4s(1 D2)nf2 D3/2,3d4s(1 D2)nf2 F5/2和3d4s(1 D2)np2 D3/2的理论研究

在多通道量子亏损理论框架下,利用相对论多通道理论,分别在冻结实近似和考虑偶极极化下计算钪原子的J^π=(3/2)^-,(5/2)^-的三个收敛于 3d4s(¹D₂)的自电离里德伯系列的能级.对3d4s(¹D₂)np²D_3/2和3d4s(¹     

Cs2NaMF6(M＝Al,Ga):Cr3+ 络合分子体系局域结构和基态分裂的理论研究

采用双自旋轨道耦合系数模型并结合完全能量矩阵的方法对Cs₂NaMF₆(M=Al, Ga):Cr³⁺ 体系中Cr³⁺ 离子的基态分裂和局域结构进行了研究.通过模拟光谱和EPR谱确定了Cr³⁺ 取代 M³⁺ 形成的两种占位结构的畸变角,发现用双自旋轨道耦合系数模型与单自旋轨道耦合系数模型计算出的畸变角Δθ存在较大的差异.这表     

开孔双壁圆形钢吊箱围堰消波效果影响因素分析

跨海大桥桥墩基础施工若采用双壁钢围堰,则在其外壁进行开孔可有效减小波浪力,有利于降低钢围堰的制作造价和提高基础施工的安全性。以某跨海大桥基础施工采用的双壁圆形钢吊箱围堰为研究对象,引入波浪力折减系数K_d对消波效果进行评价,采用数值方法着重分析波浪参数和围堰自身结构设计参数对消波效果的影响规律。结果表明:K_d随波陡增大呈先快后缓的增大趋势,波陡超过0.032后,消波效果基本不再变化;随着相对水深的增大,K_d呈先减小后增大并趋缓的规律,在相对水深d/L约为0.455时取得最小值;K_d随开孔率的增大呈线性减小,开孔率越大,消波效果越好。随着双壁间距s的增大,K_d总体上呈减小趋势,且减小速率先快后慢;双壁间距较小时,开孔的消波作用较弱。开孔率和双壁间距两种因素间存在耦合作用,两者越大,其耦合作用也越强。围堰设计中可适当增大开孔率并选取合适的双壁间距以得到最佳消波效果。     

单层正三角锯齿型石墨烯量子点的电子结构和磁性

采用基于密度泛函理论的广义梯度近似(GGA),对不同尺寸(N=2—11)的单层正三角锯齿型石墨烯量子点(Z _{N -GNDs)的结构进行优化,得到与实验数据较好符合的晶格常数,进一步计算得到不同尺寸下体系的自旋多重度、磁矩、电子态密度以及自旋电子密度.结果表明:所有体系都呈现金属性,在尺寸较小的体系中量子尺寸效应对电子结构的影响比较明显;与单层石墨烯片一样,sp²杂化作用和非键态电子在量子点中仍起到非常重要的作用;费米能级上有自旋向上的电子分布,体系的自旋多重度}     

集成于方箱防波堤的双气室振荡水柱波能装置转换效率研究

为实现建造、运行和维护等方面的资源共享,将振荡水柱(oscillating water column,简称OWC)波能转换装置与现有海工结构集成耦合,已成为目前海洋波浪能转换利用的热点问题。以集成于方箱防波堤的双气室OWC装置为研究对象,借助开源代码平台OpenFOAM和造/消波工具箱waves2Foam,采用流体体积法(VOF)捕捉自由面和6自由度(6DOF)动网格求解器模拟垂荡运动响应,对在不同规则波作用下,中墙相对宽度、中墙相对吃水对装置波能转换效率及水动力特性的影响进行数值研究。结果表明,较大的中墙相对宽度能够增强装置的波能转换效率(ξ_total(max)=73%)、降低结构物的相对垂荡位移并对装置前后气室内水柱的振荡幅度与压强变化产生影响;增加中墙相对吃水能显著提高气室在中高频波段波能提取效率(ξ_total(max)=78%),并显著拓宽气室的高效频率带宽(0.9≤ω²h/g≤2.2)。     

基于核磁共振的子空间量子过程重构

基于三核自旋量子系统实现了内嵌两量子位子空间量子过程重构.通过输入完备态集合对执行的量子过程进行了表征.由于量子过程内嵌于子空间,使得重构实验所需输入次数及时间显著减少,同时实验尽量避免使用时间较长的J偶合演化,有效控制了系统的退相干.     

近壁面柔性圆柱流致振动—拍击耦合特性试验研究

大跨度柔性悬跨海管的振动响应及管床碰撞会加剧管道的疲劳损伤,影响管道油气的安全输运。基于高速摄像非介入测试方法捕捉了近底床柔性悬跨海管的振动响应特征及管床拍击过程,对比分析了间隙比G/D及约化速度U_r对振动—拍击耦合响应的影响,辨识并提出了试验观测的管床拍击模式。研究结果表明：悬跨管的均方根振幅A_z,rms/D在前二阶主导模态下随约化速度U_r的升高先增大后减小;当间隙比减小时,共振区的振动频率减小,且一阶振动向二阶振动的过渡在更高的约化速度时发生,过渡时存在时间上的模态切换现象。振动平衡位置向远离壁面一侧偏移。根据悬跨管振动的主导模态与拍击特性,通过试验辨识了6种管—床拍击模式,包括一阶模态主导的小段拍击、大段拍击,一阶向二阶模态过渡时的Ⅰ、Ⅱ型拍击,以及二阶模态主导的单段拍击、双段交替拍击。     

退火对B掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用热丝化学气相沉积法制备B掺杂纳米金刚石薄膜,并对薄膜进行真空退火处理,系统研究了不同退火温度对B掺杂纳米金刚石薄膜的微结构和电化学性能的影响.结果表明,当退火温度升高到800 ℃后,薄膜的Raman谱图中由未退火时在1157,1346,1470,1555 cm^-1处的4个峰转变为只有D峰和G峰,说明晶界上的氢大量解吸附量减少;并且D峰和G峰的积分强度比I_D/I_G值变为最小,即sp²相团簇     

Coherent spectroscopy of a strongly driven triple quantum dot molecule

Based on a calculation model, we study the interference phenomena of serially coupled V-type and Λ-type triple quantum dots (CTQDs) driven simultaneously by a strong driving field and a weak probe field. Strongly depending on the configuration of the three-level CTQD, the probe absorption spectra, which are shown in the tunneling current, exhibit various quantum coherence properties. In the case where the two pairs of transitions of the CTQD have a small eigenfrequency difference Δω, the double-coupling effect of the driving field results in two Autler-Townes doublets and one weak Mollow triplet in one spectrum. With the value of Δω increasing, only one Autler-Townes splitting remains due to the single-coupling of the field. We also find that the effect of spontaneous emission of phonons may lead to an obvious background current, which can be used to distinguish which transition is driven by the driving field in experiment. The interesting quantum property of a CTQD revealed in our results suggests its potential applications in quantum modulators and quantum logic devices.     

强磁场中Rydberg NO分子的回归谱研究

利用分子的闭合轨道理论和多通道量子亏损理论,考虑核的转动影响,计算了Rydberg NO分子在外磁场中的回归谱. 研究表明,复杂谱的结构可以用包含分子实散射的闭合轨道理论来解释,不管是同一通道内的弹性散射还是不同通道间的非弹性散射都起着非常重要的作用,尤其是较大标度作用量下,散射作用远大于基本轨道和重复轨道的贡献,很大程度上影响着体系的动力学性质.     

Fast generation of cluster states in a linear ion trap

We propose a practical scheme to generate cluster states by simultaneously accomplishing two-qubit conditional gating on an array of equidistant ions by using transverse modes. Our operation is robust to heating and insensitive to Lamb--Dicke parameter. Meanwhile, as it is carried out in a geometric quantum computing fashion, our scheme enables the fast and high-fidelity generation of cluster states. The experimental feasibility is discussed with sophisticated ion trap techniques.     

Two quantum oscillators coupled with a planar radio frequency ion trap

In this scheme, two quantum oscillators in a planar radio frequency ion trap are coupled by the trap electrodes. The ions motional states encode the quantum bits (qubits), and a swap gate could be achieved. Under different conditions of the experiments, the intensity of the coupling between two quantum oscillators and the dissipation of the system are calculated. We compute fidelities for a quantum swap gate and discuss experimental issues.     

一维铁磁链中量子孤波的能级和磁矩

使用Hartree近似和一种简化的准离散多标度方法,研究了具有交换作用和经典磁矩相互作用的一维铁磁链中的量子孤波解. 这种一维铁磁链中不仅存在着运动的量子孤波,也存在着静态的量子孤波(即量子内禀局域模).利用所获得的量子孤波解,进一步研究了量子孤波的能级和由量子孤波所携带的磁矩. 研究表明,量子孤波的能量和磁矩都是量子化的,这些结果为正确理解磁性材料中像磁滞回线的量子台阶等宏观量子特性提供了一条可能的途径.     

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor core-shell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence (PL) measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.     

Scheme for teleportation of unknown single qubit state via continuous variables entangling channel

A new scheme for quantum teleportation of single quantum bit state with using continuous variables entangling channel is presented. In our scheme two entangled light fields are employed. An outstanding characteristic of this scheme is that one atomic state is transmitted directly to another atom without using the third atom as the mediate.     

各向异性光子晶体中二能级原子和自发辐射场间的纠缠

应用 Von Neumann熵 和 Schmidt number K两种纠缠度量讨论了各向异性光子晶体中二能级原子和自发辐射场间纠缠度的演化性质. 研究发现,原子-光场纠缠度的演化与原子上能级和光子晶体能带带边的相对位置有关,当原子上能级处于光子晶体禁带内,原子-光场纠缠度将保持稳定,当原子上能级处于光子晶体能带中,原子-光场纠缠度先增大后衰减到零. 纠缠度的大小还与原子的初态有关. 可以通过控制原子的初态和原子上能级与带边的相对位置来控制原子-光场纠缠度的演化特性.     

Faithful quantum secure direct communication protocol against collective noise

An improved quantum secure direct communication (QSDC) protocol is proposed in this paper. Blocks of entangled photon pairs are transmitted in two steps in which secret messages are transmitted directly. The single logical qubits and unitary operations under decoherence free subspaces are presented and the generalized Bell states are constructed which are immune to the collective noise. Two steps of qubit transmission are used in this protocol to guarantee the security of communication. The security of the protocol against various attacks are discussed.