Larmor Precession and Tunnelling Time of a Non—Relativistic Neutral Spin—1／2 Particle Through an Arbitrary Potential Barrier

We investigate the Larmor precession of a non-relativistic neutral spin-1/2 particle in a uniform constant magnetic field confined to the region of a one-dimensional arbitrary potential barrier.With the help of a general spin coherent state it is explicitly shown that the spin precession time is equal to the dwell time.For the special case of a symmetric rectangular potential barrier,the precession time is also in agreement with the transmission time.We present a numerical estimation of the precession time showing an apparent superluminal tunnelling.     

Quantum spin transport through Aharonov--Bohm ring with a tangent magnetic field

Quantum spin transport in a mesoscopic Aharonov--Bohm ring with two leads subject to a magnetic field with circular configuration is investigated by means of one-dimensional quantum waveguide theory.Within the framework of Landauer--B\"{u}ttiker formalism, the polarization direction of transmitted electrons can be controlled either by the AB magnetic flux or by the tangent magnetic field. In particular, the spin flips can be induced by hopping the AB magnetic flux or the tangent field.     

Entanglement Dynamics of Two Atoms in a Double Damping Jaynes-Cummings System

The entanglement between two stationary qubits is a kind of valuable quantum resources in quantum information or quantum network. This paper investigates the time evolution of the entanglement between two atoms,which are initially prepared in the Bell states and each of which interacts with its own cavity field in the identical and non-identical double damping Jaynes-Cummings(J-C) system. It mainly considers the effect of the atomic spontaneous decay Γ and the decay of cavity field κ on the two-qubit entanglement in such system. While causing the decay of entanglement, Γ and κ can also play a positive role in the entanglement evolution, which may imply a way to better control and maintain the entanglement. What is more, the rules governing the transfer of entanglement between two-qubit subsystems in strong coupling regime are finally studied by taking Γ and κ into consideration.     

逾渗分立时间量子行走的传输及纠缠特性

在一维分立时间量子行走中,通过静态和动态两种方式随机地断开连接边引入无序效应,研究了静态逾渗和动态逾渗对量子行走传输特性以及位置自由度和硬币自由之间纠缠的影响.随着演化时间的增加,静态逾渗会使得量子行走从弹道传输转变为安德森局域化,而动态逾渗则会使之转变为经典扩散.理想情况下,量子纠缠在较短的时间内就达到一个常数值E_0.静态逾渗量子行走的纠缠减小,并随着时间做无规振荡,而动态逾渗量子行走的纠缠则会随着时间光滑地增加,并在某一时间超过理想情况下的常数值,表现出动态逾渗增强量子纠缠的特性.     

Electronic transport through a periodic array of quantum-dot rings

Using the tight-binding approximation and the transfer matrix method, this paper studies the electronic transport properties through a periodic array of quantum-dot (QD) rings threaded by a magnetic flux. It demonstrates that the even--odd parity of the QD number in a single ring and the number of the QD rings in the array play a crucial role in the electron transmission. For a single QD ring, the resonance and antiresonance transmission depend not only on the applied magnetic flux but also on the difference between the number of QDs on the two arms of the ring. For an array of QD rings, the transmission properties are related not only to the even--odd parity of the number $N_{0}$ of QDs in the single ring but also to the even--odd parity of the ring number $N$ in the array. When the incident electron energy is aligned with the site energy, for the array of $N$ rings with $N_{0}={\rm odd}$ the antiresonance transmission cannot occur but the resonance transmission may occur and the transmission spectrum has $N$ resonance peaks ($N-1$ resonance peaks) in a period for $N={\rm odd}$ (for $N={\rm even}$). For the array of $N$ rings with $N_{0}={\rm even}$ the transmission properties depend on the flux threading the ring and the QD number on one arm of the ring. These results may be helpful in designing QD devices.     

殊途同归 择优而行——以“一题多解”为例浅谈数学物理方法课程思政

数学物理方法课程是物理学专业和部分工科专业重要的基础课，在数学物理方法课程中融入课程思政，是新时期落实立德树人教育根本目标的必要之举。基于数学物理方法课程教学内容和知识体系的特点，该课程开展思政建设的重点在于提高学生的科学思维意识、辩证思维能力和创新能力。本文我们以教学内容中经典例题的“一题多解”为引，以“殊途同归择优而行”为切入点，浅谈在数学物理方法课程思政建设中的一些思考和教学实践。     

A Measure of Non-Classicality of Even and Odd Coherent States

A measure of non-classicality of even and odd coherent states is studied. We first calculate the Wigner functions of the even and odd coherent states, which consists of two terms： the positive-definite Gaussian term and the wave term with negativity, and then calculate the integrated value εmax of the wave term of the Wigner functions of the even and odd coherent states in their area with negativity, and use εmax to measure non-classicality of the even and odd coherent states. For the even and odd coherent states with certain photon count, it is very convenient for us to use εmax to measure their non-classicality. The methods of our definition and calculation for εmax have theoretical reference value.     

用半波带法推导单缝夫琅禾费衍射暗纹条件的相关讨论

在大学物理教学中,半波带法是一种处理单缝夫琅禾费衍射的简单方法. 半波带法可以推导出单缝夫 琅禾费衍射的暗纹条件,但是,学生容易对这个推导过程产生误解,从而把暗纹位置判断成明纹位置. 为了让学生 更好地理解半波带法和衍射现象的实质,分析了对暗纹条件产生的两种误解,并得出误解产生的原因,即学生计算 半波带或者波带间的干涉叠加时,未考虑它们之间的相位关系     

“格物致理、慎思笃行”——数学物理方法课程教学改革、创新与实践

山西大学数学物理方法课程团队在教学各环节尝试改革创新.教学理念创新以满足培养创新型拔尖人才的目标,教学内容改革以体现该课程“承上启下”的作用,教学内容重组创新以面向国家开展量子科技研究的重大需求,教学模式创新以实现“以学生为中心”,教学手段创新实现数学、物理相互融合,客观有效的教学评价以保障教学质量、提高教学效果,课程思政与教研融合,实现“春风化雨、润物无声”.     

基于量子Fisher信息的耗散相互作用光-物质耦合常数的估计

量子参数估计在量子度量学中有着重要的应用,量子Cramer-Rao下界表明量子参数估计精度极限与量子Fisher信息是直接相关的.本文利用量子参数估计理论对光场与原子失谐很大(大失谐)的Jaynes-Cummings模型耦合常数进行估计.制备探测初态为Qubit系统与光场的直积态,光场分别为Fock态、热态和相干态,分别计算了这三种探测态经大失谐Jaynes-Cummings模型哈密顿量演化后复合系统以及Qubit和光场系统的量子Fisher信息.通过分析发现,复合系统的量子Fisher信息随平均光子数单调递增,Qubit基态与激发态的等权叠加态为最优探测态,此时量子Fisher信息达到最大值;当探测态的光场为Fock态和热态时,关于被估计参数的信息都包含于Qubit系统;对于大失谐Jaynes-Cummings模型耦合常数的估计,光场为热态或相干态时耦合常数的估计精度高于光场为Fock态时的精度.