共查询到19条相似文献,搜索用时 125 毫秒
1.
运用全量子理论并结合数值计算方法,研究了Kerr介质腔中处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的原子偶极压缩特性.讨论了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及Kerr介质与双模光场的耦合强度对原子偶极压缩特性的影响.结果表明:双原子体系的初态为|β11>时,不会出现偶极压缩效应;初态为|β00>,|β01>或|β10>时在一定条件下可能出现原子压缩效应,且此时原子压缩的特性与Kerr介质与双模光场的耦合强度、初始光场的平均光子数、双模纠缠相干光场的纠缠程度有关.
关键词:
量子光学
Bell态
双模纠缠相干光场
Kerr介质 相似文献
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三角晶格排列的光子晶体微腔中的偶极模式是简并的,通过改变其晶格的对称性可以消除模式简并.晶格的整体形变破坏了晶格对称性从而影响光场的分布,同时还改变了电磁场的偏振分布.晶格整体形变使得简并的偶极模式分离成x极和y极偶极模式.通过计算分析发现分离后的模式具有良好的偏振特性,从而为实现单偏振光子晶体激光器提供了一种很好的途径.文中针对光子晶体薄板结构的微腔,主要计算了偶极模中x极偶极模式在不同拉伸时以及不同填充因子情况下的Q值,并分别计算了x关键词:
光子晶体
偶极模
品质因子
偏振度 相似文献
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叠加激发相干态的量子特性 总被引:4,自引:0,他引:4
构造了2个强度相同位相不同的激发相干态的叠加态,并通过数值计算研究了该叠加态的反聚束效应和振幅平方压缩效应随激发光子数m、光场强度x和相位差θ的变化,结果表明:随激发光子数m和光场强度x增大,该量子态的振幅平方压缩均会加深;压缩效应与相位差θ有密切的关系;随光场强度x的增大和激发光子数m的增大,其反聚束效应减弱. 相似文献
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本文基于分子束光学Stark减速理论,提出采用调制的红失谐光晶格来减速和囚禁任意脉冲超声分子束方案,并予以理论研究.以CH4超声分子束为例,利用Monte-Carlo方法模拟了调制光晶格中的分子减速与囚禁的动力学过程,给出减速级数、同步分子初始位相角与减速效果的关系.研究结果表明:随着减速级数的增加,被减速的分子波包逐渐从原来的分子速度分布的大波包中分离开来,且减速级数越高,减速后的分子速度越小.在其他条件相同时同步分子初始位相角越大,减速波包内的分子数目越少,同时位相空间被压缩.与未调制的光晶格减速方案相比,本方案中无分子自由飞行过程,在相同的光晶格长度内完成了双倍的减速级数.当光晶格长度取3.71 mm时,模拟结果显示CH4分子从280 m/s减速至172 m/s,而未调制光晶格只能将CH4分子从280 m/s减速至232 m/s,减速效果提高了26%.本方案可以集分子的减速、囚禁于一体,是一种新型的分子光学功能器件,在冷分子光学、量子信息、冷化学等前沿研究领域中有潜在的应用. 相似文献
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推导了多色部分相干偏心光束在non-Kolmogorov 湍流中传输的总光强、轴上光谱、相干度的解析表达式, 研究了光束偏心参数β 、湍流广义指数α和源光谱带宽Ω对激光传输特性的影响. 研究表明: β越大, 则光束重心偏离传输轴越远, 相干度的不对称性越明显, 但是, β对轴上光谱几乎没有影响; 湍流广义指数α对总光强、 轴上光谱和相干长度的影响是非单调的, 当α=3.1时, 湍流对光束传输特性的影响最大. 值得指出的是: 在某些传输距离处, 不同α对应的轴上光谱位移量相同; 在某些传输距离处, 轴上光谱位移量为零, 且该传输距离与Ω无关, 但湍流使得该传输距离缩短. 所得结论对多色部分相干偏心光束在 湍流大气中传输的相关应用具有重要意义.
关键词:
non-Kolmogorov湍流
多色部分相干偏心光束
光谱强度
相干度 相似文献
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采用嵌入原子方法的原子间相互作用势,利用分子动力学模拟,详细研究不同角度入射的载能Ni原子在Pt(111)基体表面的沉积过程.结果表明,随着入射角度θ从0°增加到80°,溅射产额、表面吸附原子产额、空位产额的变化情况均可按入射角度近似地分为θ≤20°,20° < θ < 60°和θ≥60°三个区域.当θ≤20°时,载能沉积对基体表面的影响与垂直入射时的情况类似,表面吸附原子的分布较为集中,入射原子容易达到基体表面第二层及以下,对基体内部晶格产生-定的影响;在20° < θ < 60°的范围内,入射原子的注入深度有所下降,对基体内部晶格的影响减小,表面吸附原子的分布较为均匀,有利于薄膜的均匀成核与层状生长;当θ≥60°时,所有入射原子均直接被基体表面反射,表面吸附原子产额、溅射产额、表面空位产额均接近0,载能沉积作用没有体现. 相似文献
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提出了用相位型错位光栅产生光学双阱的新方案.用平面光波(或TEM00模式高斯光波)照射、正透镜聚焦,在透镜焦平面上产生的适用于冷原子或冷分子囚禁的多对可调光学双阱.计算和推导了双阱的光强分布、强度梯度以及光阱的几何参数与光学系统参数间的解析关系,研究了双阱到单阱三种不同的演化过程.同时还计算了光学双阱囚禁冷原子的光学偶极势和光子散射速率.研究发现,该方案不仅简单可行、操作方便,而且在原子物理、原子光学、分子光学和量子光学领域中有着广阔的应用前景.
关键词:
原子光学
相位光栅
光学双阱
冷原子囚禁 相似文献
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Extending the recent work completed by Fan et al. [Front. Phys. 9(1), 74 (2014)] to a two-mode case, we investigate how a two-mode squeezed vacuum evolves when it undergoes a two-mode amplitude dissipative channel, with the same decay rate κ, using the continuous-variable entangled state approach. Our analytical results show that the initial pure-squeezed vacuum state evolves into a definite mixed state with entanglement and squeezing, decaying over time as a result of amplitude decay. We also investigate the time evolutions of the photon number distribution, the Wigner function, and the optical tomogram in this channel. Our results indicate that the evolved photon number distribution is related to Jacobi polynomials, the Wigner function has a standard Gaussian distribution (corresponding to the vacuum) at long periods, losing its nonclassicality due to amplitude decay, and a larger squeezing leads to a longer decay time. 相似文献
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Long Tian Shao-Ping Shi Yu-Hang Tian Ya-Jun Wang Yao-Hui Zheng Kun-Chi Peng 《Frontiers of Physics》2021,16(2):21502
We demonstrate experimentally the simultaneous generation and detection of two types of continuous variable nonclassical states from one type-0 phase-matching optical parametric amplification (OPA) and subsequent two ring filter cavities (RFCs). The output field of the OPA includes the baseband ω0 and sideband modes ω0±nωfsubjects to the cavity resonance condition, which are separated by two cascaded RFCs. The first RFC resonates with half the pump wavelength ω0 and the transmitted baseband component is a squeezed state. The reflected fields of the first RFC, including the sideband modes ω0±ωf, are separated by the second RFC, construct Einstein–Podolsky–Rosen entangled state. All freedoms, including the filter cavities for sideband separation and relative phases for the measurements of these sidebands, are actively stabilized. The noise variance of squeezed states is 10.2 dB below the shot noise limit (SNL), the correlation variances of both quadrature amplitude-sum and quadrature phase-difference for the entanglement state are 10.0 dB below the corresponding SNL. 相似文献
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晶体表面的扩散和缺陷对晶体振动模式的影响是表面物理学研究的一个重要和基本的课题.晶格振动的频率对应于系统的能带.由于晶格中原子的振动不是孤立的,并且晶格具有周期性,所以在晶体中形成格波.格波代表晶体中所有原子都参与的频率相同的振动,又常称为一种振动模.本文讨论在表面吸附位势系数β_0与晶体内部原子的周期位势系数β不同的情况下,晶体表面吸附一个质量为m_0(与晶格原子质量m不同)的原子以后晶格的振动模.采用不变本征算符方法,严格地导出此振动模为ω=((2β(1-coshα))/(hm))~(1/2),其中α=ln[-(mβ_0+m_0(-2β+β_0)+(β_0)~(1/2)((-4mm_0β+(m+m_0)~2β_0))~(1/2)/2m_0β].此结果表明,ω不但取决于吸附位势与吸附原子的质量,也与晶格原子的质量与内位势有关. 相似文献
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腔内中性原子的长时间控制与俘获一直是腔量子电动力学(QED)中的一个难题,极大地制约了人们相干操控单原子及其与光相互作用的研究.基于传统Fabry-Perot光学腔,设计了一套易于内腔原子操控的强耦合腔QED系统,其典型参数为:腔长3.5 mm精细度约为57000,(g0,κ,γ)=2π×(1.48,0.375,2.61)MHz,临界光子数和原子数分别为1.54和0.89.该系统的特点是:能够在腔内直接实现冷原子磁光阱,并建立腔内光学晶格,实现腔内可控数目的中性原子的长时间俘获.通过合理选择构建光学偶极阱和原子成像系统,可实现对腔内单个原子或原子阵列的操控、探测、成像等.该系统可以克服传统腔QED系统中转移原子的困难,大幅增加腔内原子的寿命,为构建以腔QED系统为基础的量子信息演示平台提供了一种可能. 相似文献
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与关联双模辐射场作用的级联三能级
原子的偶极压缩效应 总被引:16,自引:6,他引:10
研究了与关联双模压缩真空场作用的级联三能级原子的偶极压缩效应。通过数值计算,讨论 了初始压缩光场的压缩参数、单光子失谐量以及原子-光场耦合强度对原子偶极压缩的影响 。 相似文献
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Qian Dong Ariadna J. Torres-Arenas Guo-Hua Sun Wen-Chao Qiang Shi-Hai Dong 《Frontiers of Physics》2019,14(2):21603
In this work we analyze the characteristics of quantum entanglement of the Dirac field in noninertial reference frames in the context of a new type pseudo-pure state, which is composed of the Bell states. This will help us to understand the relationship between the relativity and quantum information theory. Some states will be changed from entangled states into separable ones around the critical value F = 1/4, but there is no such a critical value for the variable y related to acceleration a. We find that the negativity NABI (ρTAABI) increases with F but decreases with the variable y, while the variation of the negativity NBIBII(ρTAABI) is opposite to that of the negativity NABI (ρTAABI). We also study the von Neumann entropies S(ρABI) and S(ρBIBII). We find that the S(ρABI) increases with variable y but S(ρBIBII) is independent of it. However, both S(ρABI) and S(ρBIBII) first decreases with F and then increases with it. The concurrences C(ρABI) and C(ρBIBII) are also discussed. We find that the former decreases with y while the latter increases with y but both of them first increase with F and then decrease with it. 相似文献
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An all-optical phase detector by amplitude modulation of the local field in a Rydberg atom-based mixer 下载免费PDF全文
Xiu-Bin Liu 《中国物理 B》2022,31(9):90703-090703
Recently, a Rydberg atom-based mixer was developed to measure the phase of a radio frequency (RF) field. The phase of the signal RF (SIG RF) field is down-converted directly to the phase of a beat signal created by the presence of a local RF (LO RF) field. In this study, we propose that the Rydberg atom-based mixer can be converted to an all-optical phase detector by amplitude modulation (AM) of the LO RF field; that is, the phase of the SIG RF field is related to both the amplitude and phase of the beat signal. When the AM frequency of the LO RF field is the same as the frequency of the beat signal, the beat signal will further interfere with the AM of the LO RF field inside the atom, and then the amplitude of the beat signal is related to the phase of the SIG RF field. The amplitude of the beat signal and the phase of the SIG RF field show a linear relationship within the range of 0 to π/2 when the phase of the AM is set with a difference π/4 from the phase of the LO RF field. The minimum phase resolution can be as small as 0.6° by optimizing the experimental conditions according to a simple theoretical model. This study will expand and contribute to the development of RF measurement devices based on Rydberg atoms. 相似文献
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Generation of diffraction-free vectorial elliptic hollow beams with space-varying inhomogeneous polarizations 下载免费PDF全文
Hui-Rong Li 《中国物理 B》2021,30(8):84204-084204
Diffraction-free vectorial elliptic hollow beams (vEHBs) are generated by an optical system composed of a short elliptic hollow fiber (EHF) and an axicon. Each beam has a closed elliptic annular intensity profile and space-varying polarization states in its diffraction-free distance of more than 1 m. The generated beams have a counter-clockwise or clockwise periodically-rotated inhomogeneous polarization. And the spin angular momentum (SAM) of the vEHBs is 1ħ or -1ħ which is consistent with the type of dual-mode in the EHF and the periodic polarization rotations of the vEHBs. The vEHBs have potential applications in optically trapping and micromanipulating the micro- or nano-particles, quantum information transmission, and Bose-Einstein condensates, etc. 相似文献
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Andersen MF Ryu C Cladé P Natarajan V Vaziri A Helmerson K Phillips WD 《Physical review letters》2006,97(17):170406
We demonstrate the coherent transfer of the orbital angular momentum of a photon to an atom in quantized units of variant Planck's over 2pi, using a 2-photon stimulated Raman process with Laguerre-Gaussian beams to generate an atomic vortex state in a Bose-Einstein condensate of sodium atoms. We show that the process is coherent by creating superpositions of different vortex states, where the relative phase between the states is determined by the relative phases of the optical fields. Furthermore, we create vortices of charge 2 by transferring to each atom the orbital angular momentum of two photons. 相似文献