Strong coupling in a single quantum dot-semiconductor microcavity system

Cavity quantum electrodynamics, a central research field in optics and solid-state physics, addresses properties of atom-like emitters in cavities and can be divided into a weak and a strong coupling regime. For weak coupling, the spontaneous emission can be enhanced or reduced compared with its vacuum level by tuning discrete cavity modes in and out of resonance with the emitter. However, the most striking change of emission properties occurs when the conditions for strong coupling are fulfilled. In this case there is a change from the usual irreversible spontaneous emission to a reversible exchange of energy between the emitter and the cavity mode. This coherent coupling may provide a basis for future applications in quantum information processing or schemes for coherent control. Until now, strong coupling of individual two-level systems has been observed only for atoms in large cavities. Here we report the observation of strong coupling of a single two-level solid-state system with a photon, as realized by a single quantum dot in a semiconductor microcavity. The strong coupling is manifest in photoluminescence data that display anti-crossings between the quantum dot exciton and cavity-mode dispersion relations, characterized by a vacuum Rabi splitting of about 140 microeV.     

Field-tuned quantum effects in a triangular-lattice Ising magnet

We report thermodynamic and neutron scattering measurements of the triangular-lattice quantum Ising magnet TmMgGaO4 in longitudinal magnetic fields.Our experime...     

Strong coupling of a single photon to a superconducting qubit using circuit quantum electrodynamics

The interaction of matter and light is one of the fundamental processes occurring in nature, and its most elementary form is realized when a single atom interacts with a single photon. Reaching this regime has been a major focus of research in atomic physics and quantum optics for several decades and has generated the field of cavity quantum electrodynamics. Here we perform an experiment in which a superconducting two-level system, playing the role of an artificial atom, is coupled to an on-chip cavity consisting of a superconducting transmission line resonator. We show that the strong coupling regime can be attained in a solid-state system, and we experimentally observe the coherent interaction of a superconducting two-level system with a single microwave photon. The concept of circuit quantum electrodynamics opens many new possibilities for studying the strong interaction of light and matter. This system can also be exploited for quantum information processing and quantum communication and may lead to new approaches for single photon generation and detection.     

两电子量子环的磁场效应

使用矩阵对角化方法,研究了磁场中两电子量子环自旋单态和三重态的电学和光学性质,发现磁场强度对两电子量子环的能谱和光吸收有强烈的影响.计算结果显示两电子量子环的光吸收系数可以达到107/m,这个结果要比两电子量子点高一个数量级.通过引入磁场和改变量子环半径可以获得较大的吸收系数.     

量子效应的分解

研究了Hilbert空间上一个量子效应分解成几个sharp量子效应和almost sharp量子效应之和的问题.得到了一个量子效应是sharp效应与almost sharp效应之和的充要条件及是两个sharp效应之和的充要条件,给出了一个效应是almost sharp效应的充要条件.作为应用,证明了当H的维数是无限的或者维数是偶数时,一个量子效应可以分解成两个almost sharp量子效应之和;当H的维数是奇数时,一个量子效应可以分解成至多三个almost sharp量子效应之和.     

Magnetoresistance from quantum interference effects in ferromagnets

The desire to maximize the sensitivity of read/write heads (and thus the information density) of magnetic storage devices has stimulated interest in the discovery and design of new magnetic materials exhibiting magnetoresistance. Recent discoveries include the 'colossal' magnetoresistance in the manganites and the enhanced magnetoresistance in low-carrier-density ferromagnets. An important feature of these systems is that the electrons involved in electrical conduction are different from those responsible for the magnetism. The latter are localized and act as scattering sites for the mobile electrons, and it is the field tuning of the scattering strength that ultimately gives rise to the observed magnetoresistance. Here we argue that magnetoresistance can arise by a different mechanism in certain ferromagnets--quantum interference effects rather than simple scattering. The ferromagnets in question are disordered, low-carrier-density magnets where the same electrons are responsible for both the magnetic properties and electrical conduction. The resulting magnetoresistance is positive (that is, the resistance increases in response to an applied magnetic field) and only weakly temperature-dependent below the Curie point.     

统计物理中量子效应的层次性

通过对统计物理中量子效应的深入分析,提出了在教学中应当注意区分量子效应的层次性。按照量子力学的基本假设,量子效应可以分为个体效应和集体效应两种不同的层次,分别对应统计物理中的两种不同的特征温度。认识量子效应的这种层次性,可以帮助学生深入准确理解统计物理的基本概念,针对不同情况选择适当的统计物理学方法。     

天网防火墙的应用

本文对防火墙的一些相关概念,分类等方面的介绍。天网防火墙可以帮你抵挡网络入侵和攻击,防止信息泄露,保障用户机器的网络安全。     

基于表面等离激元的量子相干效应的理论研究

起源于金属中自由电子集体振荡的表面等离激元,具有超小的光学模式体积和亚波长局域的近场增益,为纳米尺度上研究光和物质相互作用带来新的机遇．共振的纳米金属结构的近场区域,具有各向异性的珀塞尔系数,并且可以为量子体系提供近场激发．我们理论上演示了基于表面等离激元结构的单分子共振荧光、原子布居数的本征量子拍频及其在表面等离激元结构中的纳米尺度上的实现、表面等离激元诱导的各向异性珀塞尔系数导致的亚波长尺度自发辐射谱线的变化．这些结果在超紧凑的有源量子器件中有潜在应用．     

Vaidya黑洞量子热效应再讨论

指出了用内向Eddington坐标研究蒸发型Vaidya黑洞热效应可能出现的困难．通过引入一个坐标变换,新的坐标系下对应的困难消失,在新的坐标系下分别用Damour-Ruffini方法和辐射反作用法重新计算了Vaidya黑洞的温度,并讨论了熵,所得结果是合理的．     

极性晶体膜中的强耦合磁极化子

应用变分法研究了极性晶体膜中强耦合磁极化子的性质,给出基态和激发态的系统能量,重点研究了系统处于基态和激发态时的电子－表面声子相互作用能．计算结果表明,在磁场强度一定的条件下（Ｂ＝９Ｔ）,电子－表面声子相互作用能随着膜厚的增加而减小;在一定膜厚的条件下（Ｗ＝３ｎｍ）,电子－表面声子相互作用能随着磁场强度的增加先增大而后缓慢减小,当Ｂ＝３０Ｔ时,｜Ｖｅ－ＳＯ（１）｜和｜Ｖｅ－ＳＯ（０）｜之间的差最大．     

介观电路中的量子效应及其研究路径分析

作者从介观物理的视角介绍了介观电路中量子效应及其研究路径,并从两个方面分析了其研究进展和发展趋势,指出现有理论方法和实验手段方面的成功与不足,并对这一领域的进一步发展提出了可行的研究思路。     

量子场反常维度与相对的质量效应

单个强子发射源中π介子的反常维度为-γB(gR)=0.045±0.012,这个物理量控制粒子产生幅的奇异性;由玻色量子场反常维度γB(gR)而确定的质量反常维度γm(gR)=-2πγB(gR)/3与实验吻合,是质量效应存在的强有力证据;扣除相对的质量效应,以xN=(N-αab)/(〈N〉-αab)为自变量拟合的分布曲线,与实验符合较好。     

外磁场中的强耦合极化子性质

运用变分法系统地研究了外磁场下极化子的电声子耦合作用,其中具体考虑了电子和表面光学声子（ＳＯ）的强耦合作用以及与体纵光学声子（ＬＯ）的弱耦合作用,应用Ｈｕｙｂｅｒｔｃｈ提出的变分方法和二次么正变换,给出了电子－声相互作用能,数值结果表明：随着电子和晶体表面距离的增加,电子－表面光学声子相互作用能的数值减小,而电子－体纵光学声子相互作用能的数值增大;磁场增强,电子与两种声子之间的相互作用均增强。     

强磁场条件下的垒D^—中心

采用ＭａｃＤｏｎａｌｄ使用的对角化方法研究了强磁场条件下由位于ｚ轴上距ｘ－ｙ平面一定距离的正离子和位于ｘ－ｙ平面上受正离子束缚的两个电子构成的垒Ｄ－中心，得到了垒Ｄ－中心能级和束缚能随距离ξ的变化曲线．数值计算结果表明：Ｌ＝０的单重态和Ｌ＝－１，－２的三重态在一定区域内是束缚态，而Ｌ＝－１，－２的单重态是非束缚的．     

河南商丘一次罕见强对流天气分析

利用Micaps常规资料、自动气象站资料、探空资料、卫星资料和新一代天气雷达资料等多种气象资料,采用天气学和天气动力诊断方法,分析了2010年7月17日河南商丘发生的历史罕见强对流天气成因,结果表明:受低槽及副热带高压边缘西南气流共同影响,地面弱冷空气侵入,结合辐合线南侧中低空西南暖湿气流,冷暖空气交汇,层结极不稳定,进而中低空急流的爆发和急流内大风中心的传播造成的强烈辐合上升运动,使中尺度涡旋云系中形成多个对流旺盛的对流单体,最终造成强降雨、雷电、局地强风暴等强对流天气.     

热库对原子-场耦合系统中量子非局域性的影响

讨论了光场初态和热库性质对原子场耦合系统中量子非局域性的作用．结果显示，如果腔损耗很弱，热库的平均光子数很小．系统会周期性地展现出量子非局域性．非局域性的消失速度依赖于初始压缩真空态的振幅、热库的平均光子数和腔的衰退系数．场越强、平均光子数和衰退系数越大，非局域性减小得越快。     

拟双曲轨道的强跟踪性

设M是一个紧致n维C^∞黎曼流形，f∈Diff（M），∧是f的闭不变集合，并且∧具有连续不变分解T∧M=E F，则对任意的ε〉o和λ∈（0，1），存在δ〉0，使得对f的任意λ-拟双曲强δ-伪轨{xi,ni}i=-∞^＋∞都存在一点x∈M，强ε-跟踪{xi,ni}i=-∞^＋∞。     

强磁场条件下的spatial separated D-心

采用MacDonld的对角化法研究了强磁场条件下Ds^-心的束缚态和多电子效应。发现Ds^-心有L＝0，－1，－2，－3，－4五个束缚态，且随着电子与D^0心之间距离ζ值的增大，其束缚能存在一极大值，并利用无规相近似讨论了长波极限Ds^-心的多电子效应，发现Ds^-心的本征能量随朗道能级填充因子作周期性振荡，且随着温度的降低振荡加剧；当填充因子为偶数时，其本征能量的绝对值最大，说明此时电子气对库仑势的屏蔽效应最弱。