Photon vacuum renormalization and spontaneous decay of an excited atom near a carbon nanotube

A theory of the spontaneous decay process of an excited atom placed inside or outside (near the surface) of a carbon nanotube has been developed. Numerical calculations of the atomic spontaneous decay enhancement factor have been performed for various achiral nanotubes. The effect of the nanotube surface has been demonstrated to dramatically increase the spontaneous decay rate—by 6–7 orders of magnitude—compared with that of the same atom in a vacuum. Such an increase is associated with nonradiative decay via surface excitations in the nanotube. Possible applications of the predicted effect are discussed.     

Spontaneous decay of an excited atom placed near a rectangular plate

Using the Born expansion of the Green tensor, we consider the spontaneous decay rate of an excited atom placed in the vicinity of a rectangular plate. We discuss the limitations of the commonly used simplifying assumption that the plate extends to infinity in the lateral directions and examine the effects of the atomic dipole moment orientation, atomic position, and plate boundary and thickness on the atomic decay rate. In particular, it is shown that due to the plate finite size, the spontaneous decay may be inhibited even when the atom is situated very close to the surface, and that in the boundary region, the spontaneous decay rate can be strongly modified.     

Lateral shift dependence of spontaneous emission in a planar cavity with perfect conducting cladding

We consider the effect of lateral shift of the “beams" resulting from the atom emissions on spontaneous decay of an excited atom embedded in a planar cavity with perfect conducting cladding. It is found that the spontaneous decay could be enhanced or suppressed owing to the positive and negative lateral shift at the interfaces of the cavity mirror. Compared with the emission between two perfect conducting plates, the surface guided modes could exist and for very thin planar cavity, the density of surface guided modes may be obviously larger than those of the propagating guided modes.     

Casimir-Polder力对左手材料板附近的原子的动力学作用

本文研究了初始处于激发态的两能级原子在左手材料附近运动时Casimir-Polder力对原子动力学的影响. 左手材料有两个的作用: 一是在距离界面波长区域内提供了较强的Casimir-Polder共振力, 二是在这一范围原子的自发辐射受到抑制, 延长了作用时间. 这两种效应使得依靠原子自发辐射这一过程中的Casimir-Polder力能对原子的运动学产生影响, 并将一定初速度的原子排斥远离界面. 由于原子偶极矩的取向会影响Casimir-Polder力的性质, 因此对于某些初始条件(初速度和初始位置), 不同偶极矩取向的原子有不同的运动学结果, 会被吸引到界面或反射出去, 从而对具有不同偶极矩方向的原子进行筛选. 当然由于Casimir-Polder力很小, 能够反射的初速度也很小, 但是已经可以反抗极低温的热涨落, 我们的理论预估值约为15 μupK. 如果和其他约束手段同时作用, 便能对原子的动力学产生更为有利的控制.     

量子关联与原子间相互作用距离关系的研究

本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况。结果表明：原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态。     

量子关联与原子间相互作用距离关系的研究

本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况.结果表明:原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态.     

Spontaneous emission of an atom placed near the aperture of a scanning microscope

Analytic expressions in the quasi-static approximation are obtained for the spontaneous decay rates of an atom placed near the circular aperture of a scanning microscope. The results obtained show not only that the spontaneous decay rates increase substantially near the aperture edge but also that the atomic decay appreciably slows down near the aperture center if the vector of dipole transition moment lies in the aperture plane.     

量子关联与原子间相互作用距离关系的研究

本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况。结果表明：原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态。     

Decay distribution of spontaneous emission from atoms in one-dimensional photonic crystal

Spontaneous emission behavior from atoms (or molecules) in one-dimensional photonic crystal with a defect is investigated. Taken all the TE and TM modes into account, the normalized spontaneous emission rate of the atom is calculated as a function of the position of the atom in the crystal. Results for both nonabsorbing dielectric structure and absorbing dielectric structure are presented. With the increase of the thickness of the defect in which the atoms are embedded, the oscillations of the spontaneous emission rate versus the position of the atom become dense and the lifetime distribution becomes narrow and sharp. The PC effect may lead to the coexistence of both accelerated and inhibited decay processes.     

The Electromagnetically Induced Transparency of Quasi-A-type Four-level Atom System at Low Light Levels

The probe gain and the population in high level in the Quasi-A-type four-level atom system interacting with two fields at low light levels are investigated in this paper： The system always displays three gain peaks with probe detuning. At the same time, the electromagnetically induced transparency （EIT） can be observed in two windows which only relate to coupling detuning. When the system displays EIT, the population in the high level is zero. If the phase of the probe field is changed, the probe gain would be changed and absorption occurs but the population in the high level is a constant. It is worth noting that all results are got on the condition that the fields are as weak as the spontaneous emission fields and without any approximation.     

周期或准周期超晶格薄膜表面吸附原子的自发辐射性质

本文把由库理论和耗散系统量子化方法所求得的表面修饰的光学布洛赫方程,同麦克斯韦方程自洽地相结合,求得周期或准周期超晶格薄膜表面吸附原子的自发辐射寿命和频移,讨论了构成该薄膜各层的厚度和介电性质及总层数对上述自发辐射性质的影响。同时,把周期性情况和准周期情况分别求得的结果进行了比较。 关键词：     

Spontaneous emission of an atom in a cavity with nonorthogonal eigenmodes

The spontaneous emission of an excited atom in a lossy cavity with nonorthogonal eigenmodes is analyzed. The quantum Langevin formalism is used to describe the dynamics of the spontaneous decay. The analysis shows that the spontaneous decay is modified by the Q value and the effective mode volume factor of each cavity eigenmode. The effective mode volume is generalized for cavities with nonorthogonal modes, which can be a very significant modification in the microcavity regime. It is shown that the spontaneous decay is not enhanced by the excess noise factor as claimed by other analyses.     

Nonperturbative analysis of spontaneous emission in one dimensional special photonic crystals

The retarded spontaneous emission (SpE) process of a two-level atom embedded in realistic one dimensional photonic crystals (1DPC) is investigated with the quantum nonperturbative theory. The atomic transient decay is divided into two processes: the first comes from the natural decay to free space and the second is induced by the reflected field emitted from the atom itself. Due to the multi-reflection in the multi-layer structure, the correct delay time of the induced decay process is hard to calculate in the usual ways. However with the special but practical 1DPC provided, we give the analytic result of the atomic dynamic decay in 1DPC. Our result gives a clear picture to show the process which the atom feels the surrounding.     

Models of the Dynamics of Spatially Separated Broadband Electromagnetic Fields Interacting with Resonant Atoms

The Markov model of spontaneous emission of an atom localized in a spatial region with a broadband electromagnetic field with zero photon density is considered in the conditions of coupling of the electromagnetic field with the broadband field of a neighboring space. The evolution operator of the system and the kinetic equation for the atom are obtained. It is shown that the field coupling constant affects the rate of spontaneous emission of the atom, but is not manifested in the atomic frequency shift. The analytic expression for the radiative decay constant for the atom is found to be analogous in a certain sense to the expression for the decay constant for a singly excited localized ensemble of identical atoms in the conditions when the effect of stabilization of its excited state by the Stark interaction with the vacuum broadband electromagnetic field is manifested. The model is formulated based on quantum stochastic differential equations of the non- Wiener type and the generalized algebra of the Ito differential of quantum random processes.     

Fluorescence spectrum due to surface plasmon polariton emission in a three level atom

The dynamics of a V-type three level atom positioned inside a metallic slab sandwiched between two asymmetric infinite dielectrics is studied. The surface plasmon polaritons supported by this structure are calculated, quantized and their dispersions are found to exhibit plasmonic band gaps which in turn modify the spontaneous transition rates and the fluorescence spectrum. Interesting features arise from the variations of the decay rate and spectrum with the mode frequency and electron density including local field effects.     

介质腔中自发辐射原子的寿命分布

在本文中,我们研究了半无限大介质板夹层对空腔中激发态原子的自发辐射率的影响,并利用寿命分布函数来描述原子衰变动力学的性质,在对称和非对称的结构中,分别计算了以原子在板中的相对位置为自变量的原子自发辐射率的函数,计算结果表明,原子的自发辐射率与介质腔的宽度以及外层半无限大介质板的折射率有关,介质腔可以增强或抑制激发态原子的激发,当介质腔的宽度足够大时,原子的寿命分布呈现指数衰减的形势,这些理论结果和实验值相符合的非常好.     

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

<正>We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission.A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal.Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency.It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels.For a zero initial phase,destructive property is presented in the spectra.With the increase of initial phase difference,quantum interference between the two decay channels from upper levels to ground level turns to be constructive.Furthermore, we give an interpretation for the property of these spectra.     

Entanglement generation in trapped atoms

The two atoms in the ion trap are entangled by the interaction with an external excited atom. The evolution of the entanglement is analytically derived without the decoherence. Considering the spontaneous decay from the environment, the evolution of the entanglement is similar to the damping Rabi oscillation. The generation of entanglement is induced by the dipole-dipole type interaction of atoms. It is found that the entanglement of two trapped atoms is robust with the uniform interaction with the external atom. The collective spontaneous emission from the coupling between the atoms may enhance the entanglement.     

Dynamics of spontaneous radiation of atoms scattered by a resonance standing light wave

The scattering of atoms by a resonance standing light wave is considered under conditions when the lower of two resonance levels is metastable, while the upper level rapidly decays due to mainly spontaneous radiative transitions to the nonresonance levels of an atom. The diffraction scattering regime is studied, when the Rabi frequency is sufficiently high and many diffraction maxima are formed due to scattering. The dynamics of spontaneous radiation of an atom is investigated. It is shown that scattering slows down substantially the radiative decay of the atom. The regions and characteristics of the power and exponential decay are determined. The adiabatic and nonadiabatic scattering regimes are studied. It is shown that the wave packets of atoms in the metastable and resonance excited states narrow down during scattering. A limiting (minimal) size of the wave packets is found, which is achieved upon nonadiabatic scattering in the case of a sufficiently long interaction time.     

Scheme for Concentration of Unknown Greeberger-Horne-Zeilinger Entangled States via Cavity Decay

We present a scheme for entanglement concentration of an unknown atomic non-maximally entangled GHZ state via cavity decay. In the scheme, the atom trapped in a cavity is manipulated by laser field, so the maximally entangled GHZ state can be obtained by performing certain operation, which can be realized by illuminating the atom in a cavity. Our method is robust against spontaneous atomic decay.