共查询到20条相似文献,搜索用时 46 毫秒
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S.H. XuZ.H. Xiong L.L. GuY. Liu X.M. DingJ. Zi X.Y. Hou 《Solid State Communications》2003,126(3):125-128
Various combinations of periodically assembled nanoporous silicon layers with different refractive indices and thicknesses have been used to fabricate one-dimensional photonic quantum well structures, in which both the well and barrier regions consist of photonic crystals. The structures are operational in the regime of visible light. Quantized states resulting from the photonic confinement effect are observed, consistent with calculations using the transfer-matrix method. Behaviors of the photons in the structures can be well described by the effective wave-vector approach. 相似文献
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Performing fluorescence wide-field microscopy we have imaged single semiconductor quantum dots deep inside a 3-dimensional photonic crystal prepared from colloidal polymer beads. Exploring the emission diffraction patterns in defocused images of quantum dots we demonstrate that the direction-dependent photonic stop band imprints an anisotropy to the angular emission of a single quantum dot. Hence a single, quasi-point-like emitter is manipulated to radiate its photons only to certain well-defined directions by means of the anisotropic light propagation in photonic crystals. The experiments thus provide new routes to evaluate local, frequency selective optical properties in 3-dimensional photonic crystals employing single emitters. 相似文献
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All beams of electromagnetic radiation are made of photons. Therefore, it is important to find a precise relationship between the classical properties of the beam and the quantum characteristics of the photons that make a particular beam. It is shown that this relationship is best expressed in terms of the Riemann-Silberstein vector - a complex combination of the electric and magnetic field vectors - that plays the role of the photon wave function. The Whittaker representation of this vector in terms of a single complex function satisfying the wave equation greatly simplifies the analysis. Bessel beams, exact Laguerre-Gauss beams, and other related beams of electromagnetic radiation can be described in a unified fashion. The appropriate photon quantum numbers for these beams are identified. Special emphasis is put on the angular momentum of a single photon and its connection with the angular momentum of the beam. 相似文献
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With the Schrödinger equations, we investigate the low-intensity light pulse propagation through a semiconductor quantum wells. Through studying the dispersion and absorption properties of the weak probe field, it is shown that slow light propagation is observed in this system. From the view point of practical purpose, it is more advantageous than its corresponding atomic system. Such investigation of slow light propagation may lead to important practical applications in semiconductor quantum information. 相似文献
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Two-Time Intensity Correlations and Multiple Interference Mechanisms in a Driven Cascade Atom 下载免费PDF全文
We examine the intensity correlation functions of the two fluorescent fields that are emitted from the top and middle states of a doubly driven three-level atom in the cascade configuration. Novel interference effects are shown. (i) Both of the fluorescent fields have anticorrelations which can exist for long times when the applied fields are on the two-photon resonance and far off one.photon resonances. (ii) Both of the fluorescent fields have strong correlations when the applied fields are far off one- and two-photon resonances. In particular, the extremely strong correlation occurs for the photons emitted from the top state. The above phenomena are traced to the multiple interference mechanisms. 相似文献
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研究了二维光子晶体量子阱的光谱特性,该量子阱结构由二维正方晶格圆柱晶胞光子晶体通过移去中间位置的介质圆柱层形成。由于光子晶体中的光子禁带充当了光子运动的势垒,类似于半导体量子阱中电子的行为,在光子晶体量子阱结构中会出现量子化的光子能态。文章利用平面波展开法计算了所用光子晶体的能带结构,利用传输矩阵方法计算了量子阱结构的透射光谱。计算结果表明,在光子禁带中出现了离散的透射峰,透射峰的强度随着势垒宽度的增加而减弱,个数随着势阱宽度的增加而增加,通过计算得到了其定量关系,并且讨论了透射峰频率与势阱宽度的关系。 相似文献
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Decoherence is a subject of great importance in quantum mechanics, particularly in the fields of quantum optics, quantum information processing and quantum computing. Quantum computation relies heavily in the unitary character of each step carried out by a quantum computational device and this unitarity is affected by decoherence. An extensive study of master equations is therefore needed for a better understanding on how quantum information is processed when a system interacts with its environment. Master equations are usually studied by using Fokker–Planck and Langevin equations and not much attention has been given to the use of superoperator techniques. In this report we study in detail several approaches that lead to decoherence, for instance a variation of the Schrödinger equation that models decoherence as the system evolves through intrinsic mechanisms beyond conventional quantum mechanics rather than dissipative interaction with an environment. For the study of the dissipative interaction we use a correspondence principle approach. We solve the master equations for different physical systems, namely, Kerr and parametric down conversion. In the case of light-matter interaction we show that although dissipation destroys the quantumness of the field, information of the initial field may be obtained via the reconstruction of quasiprobability distribution functions. 相似文献
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G.A. Barbosa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):433-440
Quantum states of twin photons entangled in angular momentum and polarization provide new degrees of freedom to researchers
in quantum information and imaging. This work discuss these states and also emphasizes differences between two proposed models
for twin photons entangled in angular momentum. Answers to the presented questions would contribute to a better understanding
of this nonlinear process.
Received 30 August 2002 / Received in final form 10 October 2002 Published online 21 January 2003 相似文献
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The unitary equivalence of different bipartite entangled states with continuous variables under unitary transformations are investigated. With the help of the technique of integration within an ordered product of operators, the corresponding unitary operators are also derived. These results may deepen people's understanding to the various bipartite entangled states, and enrich the representations and transformations theory in quantum mechanics. 相似文献
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Orbital angular momentum entangled photons emitted by a down-conversion source are in higher dimensional entangled states. Here we report the experimental confirmation by demonstrating a violation of a generalized Clauser-Horne-Shimony-Holt-type Bell inequality in three dimensions by more than 18 standard deviations. Higher dimensional entangled states allow the realization of new types of quantum communication protocols. They also provide a more secure quantum cryptography scheme. Therefore our experimental results are likely to have applications in future quantum communication technology. 相似文献
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G. Bastard 《Superlattices and Microstructures》1985,1(3):265-273
We present the results of the calculations of some electronic properties of semiconductor quantum wells and superlattices. The review includes the superlattice band structure and the quantum well bound energy levels; the virtual bound states of semiconductor quantum wells and their influence on the energy spectrum of separate confinement heterostructures. Finally the perturbation of quantum well bound states and exciton states by a static electric field applied parallel to the growth axis is considered. 相似文献
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S. Luin I. Dujovne V. Pellegrini A. Pinczuk B.S. DennisA.S. Plaut L.N. PfeifferK.W. West J.H. Xu 《Solid State Communications》2003,127(12):813-820
Strongly correlated two-dimensional electrons in coupled semiconductor bilayers display remarkable broken symmetry many-body states under accessible and controllable experimental conditions. In the case of continuous quantum phase transitions (QPTs), soft collective modes drive the transformations that link distinct ground states of the electron double layers. In this paper we consider results showing that resonant inelastic light scattering methods detect soft collective modes of the double layers and probe their evolution with temperature and magnetic field. The light scattering experiments offer venues of research of fundamental interactions and continuous QPTs in low-dimensional electron liquids. 相似文献
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Bozsoki P Thomas P Kira M Hoyer W Meier T Koch SW Maschke K Varga I Stolz H 《Physical review letters》2006,97(22):227402
The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and numerically evaluated for a model system. The results demonstrate how the proposed experimental method yields direct information about the spatial distribution of the relevant states and thus on the disorder present in the system. 相似文献
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M. Larqué A. Beveratos I. Robert-Philip 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):119-125
We report on a scheme for the creation of time-bin entangled states out of two subsequent single photons. Both photons arrive
on the same input port of a beamsplitter and the situation in which the photons leave the beamsplitter on different output
ports is post-selected. We derive a full quantum mechanical analysis of such time-bin entanglement for emitters subject to
uncorrelated dephasing processes and apply this model to sequential single photons emerging from a single semiconductor quantum
dot. Our results indicate that the visibility of entanglement is degraded by decoherence effects in the quantum dot, but can
be restored by use of CQED effects, namely the Purcell effect. 相似文献
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We report experimental results of two room-temperature single photon sources with definite polarization based on emitters
embedded in either cholesteric or nematic liquid crystal hosts. In the first case, a cholesteric 1-D photonic bandgap microcavity
provides circular polarization of definite handedness of single photons from single colloidal semiconductor quantum dots (nanocrystals).
In these experiments, the spectral position of the quantum dot fluorescence maximum is at the bandedge of a photonic bandgap
structure. The host does not destroy fluorescence antibunching of single emitters. In the second case, photons with definite
linear polarization are obtained from single dye molecules doped in a planar-aligned nematic liquid crystal host. The combination
of sources with definite linear and circular polarization states of single photons can be used in a practical implementation
of the BB84 quantum key distribution protocol. 相似文献
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In this paper, we present a comprehensive analysis of the coherence phenomenon of two coupled dissipative oscillators. The action of a classical driving field on one of the oscillators is also analyzed. Master equations are derived for both regimes of weakly and strongly interacting oscillators from which interesting results arise concerning the coherence properties of the joint and the reduced system states. The strong coupling regime is required to achieve a large frequency shift of the oscillator normal modes, making it possible to explore the whole profile of the spectral density of the reservoirs. We show how the decoherence process may be controlled by shifting the normal mode frequencies to regions of small spectral density of the reservoirs. Different spectral densities of the reservoirs are considered and their effects on the decoherence process are analyzed. For oscillators with different damping rates, we show that the worse-quality system is improved and vice versa, a result which could be useful for quantum state protection. State recurrence and swap dynamics are analyzed as well as their roles in delaying the decoherence process. 相似文献
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Strong correlations in the fluctuations of the intensity of emission from a semiconductor microcavity under resonant laser excitation are observed. The intensity correlation function exhibits an unusual oscillatory behavior with an unexpectedly long oscillation period and decay time. The visibility of the correlation function reaches 0.81. Long oscillation times are attributed to the Rabi frequency characterizing weak coupling between the electromagnetic field of the semiconductor microcavity mode and long-lived exciton states localized by the random potential of the quantum well. For a laser excitation power density of 400 W/cm2, the power density of the radiation emitted by the microcavity is 12 W/cm2, which corresponds to the total flux of nonclassical light of 1.5 × 1015 photons/s from an excited spot 50 μm in diameter. Thus, a microcavity can serve as a bright emitter of nonclassical light. 相似文献