共查询到18条相似文献,搜索用时 390 毫秒
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利用双模近似方法研究了一维双组分玻色-爱因斯坦凝聚体(Bose-Einstein condensates,BECs)的量子隧穿特性.从描述三维双组分BECs系统的Gross-Pitaevskii方程(GPE)出发,得到了描述一维体系的GP方程.把体系波函数写成原子数和相位指数的乘积,得到描述体系隧穿特性的费曼方程.数值求解费曼方程,研究了原子之间相互作用(双组分BECs体系原子之间的相互作用包括组分内部原子之间的相互作用和不同组分原子之间的相互作用)对隧穿特性的影响.结果显示,当原子之间的相互作用较弱时,体系发生量子隧穿现象,表现为原子数在平衡位置附近作周期振荡;随着原子之间相互作用增强,体系经历一个临界状态,进入自俘获状态,即由于原子之间相互作用的存在,在对称双势阱中演化的BECs可以呈现出原子数高度的不对称分布,好像绝大数原子被其中一个势阱俘获.从隧穿到自俘获原子之间的相互作用存在一个临界值,从而体系的能量也对应一个临界值,根据体系的哈密顿函数,就能求出相互作用临界值的表达式. 相似文献
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本文以纠缠轨线分子动力学方法研究对称受驱双势阱系统的量子隧穿动力学过程.驱动力的幅度和频率改变将对量子隧穿动力学过程产生巨大的影响,这为人们自主控制这一重要的过程提供理论基础.当体系的经典动力学呈现混沌状态时,它的量子动力学过程将发生显著的变化.在强驱动力作用下,双势阱系统的量子共振频率隧穿和非共振频率隧穿因为混沌行为的出现明显增强.通过对比相空间中具有相同初始态的纠缠轨线和经典轨线演化,我们给出量子隧穿过程清晰的物理图像.最后,我们讨论量子隧穿动力学过程中体系不确定度的演化和反映波包动力学过程的自关联函数演化. 相似文献
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以非线性Rosen-Zener隧穿理论为基础, 用平均场近似的方法, 通过考虑高阶非线性项的影响, 研究了非线性两能级系统中费米超流气体的Rosen-Zener隧穿现象. 研究发现粒子间的非线性相互作用能够显著地影响量子隧穿. 分别在快扫描极限和绝热极限的条件下, 解释了Rosen-Zener隧穿现象, 并给出了矩形振荡周期与非线性参数之间的依赖关系. 这为更深入认识费米气体的基本属性提供了理论基础. 相似文献
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作为构成量子多体系统的基本单元,一维少体系统的研究不仅可以在理论上为多体系统的量子关联及动力学等性质提供更为基本的理解,也可以为实验上制备多体系统提供更加方便和功能更加全面的方法.本文回顾了冷原子物理中一维少体系统最新的实验和理论进展.首先介绍了少体实验中实现的谐振子势阱中确定原子数的精确制备,亚稳态势阱和双阱系统中原子的隧穿,以及强相互作用下等效自旋链的实验结果.然后深度解析了理论研究方面,特别是基于精确可解模型的一些重要结果,包括亚稳态势阱中相互作用原子的隧穿概率,以及相应实验上常见势阱的能谱分析、密度分布、隧穿动力学以及强相互作用极限下的有效自旋链模型等. 相似文献
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介绍一种新的量子隧穿———非线性朗道-基纳隧穿.这种隧穿一般发生在有相互作用的二能级系统中,比如光晶格中的玻色-爱因斯坦凝聚物和分子磁体.相对于传统的线性朗道-基纳隧穿,非线性朗道-基纳隧穿由排斥相互作用带来的非线性会增强隧穿的概率.特别是当非线性非常强时,系统的绝热性会遭到破坏;一个无穷小的线性驱动都会造成有限的隧穿概率. 相似文献
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耦合双量子点中电子间静电相互作用对电子在系统中隧穿效应具有重要影响.考虑电子隧穿,交换及Hubbard关联作用后,在单态近似下,本文求解了耦合双量子点二电子问题,讨论了铁磁基态及Mott局域化态出现的条件。这里的结果表明电子的隧穿不利于铁磁基态的形成,Hubbard关联越强越有利于Mott局域化态的形成,并且在交换作用下Mott局域化态会转变为铁磁基态. 此外,外场可以诱导磁序相的改变。 相似文献
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Tunneling dynamics of Bose-Einstein condensates with higher-order interactions in optical lattice
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The nonlinear Landau-Zener tunneling and nonlinear Rabi oscillations of Bose-Einstein condensate (BEC) with higher-order atomic interaction between the Bloch bands in an accelerating optical lattice are discussed. Within the two-level model, the tunneling probability of BEC with higher-order atomic interaction between Bloch bands is obtained. We finds that the tunneling rate is closely related to the higher-order atomic interaction. Furthermore, the nonlinear Rabi oscillations of BEC with higher-order atomic interaction between the bands are discussed by imposing a periodic modulation on the level bias. Analytical expressions of the critical higher-order atomic interaction for suppressing/enhancing the Rabi oscillations are obtained. It is shown that the critical value strongly depends on the modulation parameters (i.e., the modulation amplitude and frequency) and the strength of periodic potential. 相似文献
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We study the Landau-Zener tunneling of a nonlinear two-level system
by applying a periodic modulation on its energy bias. We find that
the two levels are splitting at the zero points of the zero order
Bessel function for high-frequency modulation. Moreover, we obtain
the effective coupling constant between two levels at the zero
points of the zero order Bessel function by calculating the final
tunneling probability at these points. It seems that the effective
coupling constant can be regarded as the approximation of the higher
order Bessel function at these points. For the low-frequency
modulation, we find that the final tunneling probability is a
function of the interaction strength. For the weak inter-level
coupling case, we find that the final tunneling probability is more
disordered as the interaction strength becomes larger. 相似文献
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N. Miura J. Hopwood 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(5):1-10
This paper introduces comprehensive large-signal analyses of modulation dynamics and noise of a chaotic semiconductor laser. The chaos is induced by operating the laser under optical feedback (OFB). Control of the chaotic dynamics and possibility of suppressing the associated noise by sinusoidal modulation are investigated. The studies are based on numerical solutions of a time-delay rate equation model. The deterministic modulation dynamics of the laser are classified into seven regular and irregular dynamic types. Variations of chaotic dynamics and noise with sinusoidal modulation are examined in both time and frequency domains over wide ranges of the modulation depth and frequency. The results showed that chaotic dynamics can be converted into five distinct dynamic types; namely, continuous periodic signal (CPS), continuous periodic signal with relaxation oscillations (CPSRO), periodic pulse (PP), periodic pulse with relaxation oscillations (PPRO) and periodic pulse with period doubling (PPPD). The relative intensity noise (RIN) of these types is characterized when the modulation frequencies are much lower, comparable to, and higher than the resonance frequency. Suppression of RIN to a level 8 dB/Hz higher than the quantum limit was predicted under the CPS type when the modulation frequency is 0.9 times the resonance frequency and the modulation depth is 0.14. 相似文献
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Within the mean-field three-site Bose-Hubbard model, the tunneling dynamics of dipolar bosonic gas with a periodically modulation of s-wave scattering is investigated. The system experiences complex and rich coherent tunneling (CT)-coherent destruction of tunneling (CDT) transitions resulting from the correlated effect among the next-neighbor dipole-dipole interaction, the on-site interaction and the modulated s-wave scattering. In particular, The region of the modulated s-wave scattering for generating CT (CDT) is the widest (narrowest) when the on-site interaction and the next-neighbor dipole-dipole interaction have some correlated values, which are closely related to the tunneling energy and the interaction energy of the system. The correlated values for appearing CDT can be theoreticaJly gained from the tunneling energy and the interaction energy of the system. 相似文献
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The influence of parameters such as the strength and
frequency of a periodic driving force on the tunneling dynamics is
investigated in a symmetric triple-well potential. It is shown that
for some special values of the parameters, tunneling could be
enhanced considerably or suppressed completely. Quantum fluctuation
during the tunneling is discussed as well and the numerical results
are presented and analysed by virtue of Floquet formalism. 相似文献
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Zhi-Wei Jia 《中国物理 B》2022,31(10):100505-100505
Dynamic states in mutual-coupled mid-infrared quantum cascade lasers (QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang—Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τinj, 2τinj, and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution. This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser. 相似文献
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The interactions between a two-level atom and a field via two-photon
transition without rotating wave approximation have been
investigated. We emphasize the dynamic behaviors of the atomic
population inversion, the field squeezing, and the atomic dipole
squeezing numerically when the field frequency varies with time in
the forms of sine and rectangle. Some interesting phenomena are
discovered and discussed. The good periodic character of the atomic
population inversion in the standard two-photon Jaynes--Cummings
model is weakened by the influence of the sine field frequency
modulation. The rectangular field frequency modulation can change
the correlation among different oscillations suddenly and induce new
collapse-revival processes of the atomic population inversion. The
field squeezing increases at the beginning of time, but then
decreases and loses as the time increases after it reaches the
maximum due to the sine modulation. The effects of the rectangular
modulation on the field squeezing depend mostly on the appearance
time of the modulation. The atomic dipole squeezing is weakened
under the influence of the sine or rectangular modulation. Our
results indicate that it is possible to perform the dynamic
controlling of the system properties by changing the parameters of
the system with time. This implies that one can dynamically control
a quantum information process by choosing the system modulation
properly. 相似文献