共查询到20条相似文献,搜索用时 62 毫秒
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一只钢球抛向坚硬的表面,在二者接触之后,钢球将被表面反射,这一图像是人们的经典直觉.然而,如果将钢球换成原子,表面反射过程将有许多新特点.例如,原子可能在尚未接触到表面之前就“掉头”折返,这一现象被称为量子反射.与量子隧穿一样,量子反射也是源于粒子的波粒二象性. 相似文献
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研究了一维时间周期势的量子隧穿,建立了周期势的两种物理模型,并分别在不同情况下对其进行理论研究和推导,证明了一维周期势下的量子隧穿可统一由一种模型处理. 相似文献
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文章介绍了分子磁体中的量子隧穿和宏观量子效应理论和实验研究的新进展.分子磁体既有宏观磁体特性也呈现纯量子行为,例如磁化矢量的量子隧穿.文章作者解释了如何通过量子隧穿实现宏观量子相干(即薛定谔猫态的相干叠加)和量子态位相干涉.对隧穿率计算的瞬子方法,特别是有限温度隧穿理论及其在分子磁体量子隧穿中的应用也做了简要的阐述. 相似文献
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不同维度模型原子隧穿电离研究 总被引:1,自引:0,他引:1
本文数值求解一维和二维模型原子在强激光场作用下含时Schr??dinger方程,研究了在隧穿电离区相同基态能量和相同峰值场强条件下二者的电离速率,发现一维模型计算得到的电离速率比二维的结果大很多.产生该电离速率差别的原因是不同维度下束缚电子所需隧穿的含时势垒的不同. 相似文献
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本文通过严格求解定态薛定谔方程,研究了一维对称三方势垒的量子隧穿特性,解析地给出透射系数的精确表达式,并且数值模拟了势垒高度、势垒间距以及粒子入射能量对透射系数的影响.结果表明:当取不同的势垒宽度,或者不同的粒子入射能量时,透射系数随着势垒间距的增加而呈现出明显的周期式振荡.将一维对称双方势垒和三方势垒进行比较,透射系数随着势垒间距的增大,均呈现周期性振荡,并且振荡周期相同,但三方势垒振荡更剧烈,振幅越大,并且三方对称势垒是双峰曲线,而双方对称势垒是单峰曲线.该特性为设计新型纳米器件以及共振隧穿量子器件等提供理论指导. 相似文献
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量子隧穿效应在实际技术中具有重要应用,本文首先展示了如何求解一维任意边界非对称以及对称双方势垒的透射系数,然后研究了对称双方势垒透射系数对垒宽、垒间距以及微观粒子入射能量与垒高比值(E/U 0)的变化依赖关系.最终得出以下结论,随着双方势垒垒宽的增加,透射系数从最大值1衰减至最小值0.随着垒间距的增加,透射系数呈现周期振荡,本文首次推导得出透射系数最大时对应的垒间距解析表达式,并给出振荡的周期,进一步证明得到它等于微观粒子的德布罗意波长.当垒宽越小时,随着E/U 0的增大,透射系数更容易达到1,并且保持不变,当垒间距越大时,随着E/U 0的增大,透射系数振荡周期变大,而振幅变小,粒子更容易实现共振隧穿. 相似文献
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We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio. 相似文献
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For laser internal therapy in medical applications, optical fibres are required to propagate the laser beam. The far-field pattern of the laser beam at the exit face of the optical fibre is studied using a multimode step-index fibre and a graded index Selfoc fibre. The degree of dispersion, or the output angular distribution, of the beam passing through the Selfoc fibre is much smaller than that passing through the multimode step-index fibre. Consequently, the energy density in the far-field pattern of the beam passing through the Selfoc fibre is very much larger than that for the beam passing through the multimode step-index fibre. It is concluded that the Selfoc fibre is more effective in laser internal therapy. 相似文献
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This paper investigates the squeezing properties of an atom laser
without rotating-wave approximation in the system of a binomial states
field interacting with a two-level atomic Bose--Einstein condensate.
It discusses the influences of atomic eigenfrequency, the interaction
intensity between the optical field and atoms,parameter of the binomial
states field and virtual photon field on the squeezing properties.
The results show that two quadrature components of an atom laser can be
squeezed periodically. The duration and the degree of squeezing an atom
laser have something to do with the atomic eigenfrequency and the parameter
of the binomial states field, respectively. The collapse and revival
frequency of atom laser fluctuation depends on the interaction intensity
between the optical field and atoms. The effect of the virtual photon field
deepens the depth of squeezing an atom laser. 相似文献
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冷原子重力仪的倾斜角会对绝对重力测量产生显著的影响.高精度的绝对重力测量需要对重力仪的倾斜角进行精确的测量、控制及校正.本文从理论上分析了四种不同情况下倾斜对绝对重力测量的影响规律,并在实验上对得到的理论进行了实验验证.基于此,设计了一种基于双倾斜计的绝对重力测量方案,主要是为了解决恶劣测量环境下的冷原子重力仪倾斜漂移问题.此方案利用高精度倾斜计记录放置在被动隔振平台上的拉曼反射镜的倾斜角度,并使用另外一个倾斜计监控真空系统的倾斜,以实现振动噪声的抑制和倾斜的高精度测量.基于自研的小型化冷原子重力仪,对该方案进行了实验验证,并最终实现了车间复杂环境下的高精度绝对重力测量.由于倾斜得到精确测量和补偿,冷原子重力仪的测量精度达到了12.3μGal.本文为复杂环境下的高精度绝对重力测量提供了一种可行的方案,为冷原子重力仪的实用化提供了参考数据. 相似文献
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研究了Kerr介质中对相干态光场与V型三能级原子依赖强度耦合相互作用的量子统计性质.对Cauchy-Schwartz不等式的研究表明:失谐量不为零(Ω1=Ω2≠0)时两模间的非经典相关程度有所增强,当初始场强ξ一定而两模场光子数差q增大时,场的非经典相关程度加强;q一定而ξ增大时,场的非经典相关程度减弱,Kerr效应使两模场的非经典相关性有所减弱.对二阶相干度的研究表明,第一模总呈现反聚束效应且Kerr效应对其影响相对较小,而第二模则聚束与反聚束效应交替出现,Kerr效应对g(222)的振荡幅度影响与q的 相似文献
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Electron tunnelling phase time and dwell time through an associated delta potential barrier 下载免费PDF全文
The electron tunnelling phase time τP and dwell time τD through an associated delta potential barrier U(x) = ξδ(x) are calculated and both are in the order of 10^-17~10^-16s. The results show that the dependence of the phase time on the delta barrier parameter ξ can be described by the characteristic length lc = h^2/meξ and the characteristic energy Ec=meξ^2/h^2 of the delta barrier, where me is the electron mass, lc and Ec are assumed to be the effective width and height of the delta barrier with lcEc=ξ, respectively. It is found that TD reaches its maximum and τD = τp as the energy of the tunnelling electron is equal to Ec/2, i.e. as lc =λDB, λDB is de Broglie wave length of the electron. 相似文献
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We investigated the quantum speed limit time of a non-Hermitian two-level system for which gain and loss of energy or amplitude are present. Our results show that, with respect to two distinguishable states of the non-Hermitian system, the evolutionary time does not have a nonzero lower bound. The quantum evolution of the system can be effectively accelerated by adjusting the non-Hermitian parameter, as well as the quantum speed limit time can be arbitrarily small even be zero. 相似文献