Polarization in D-shaped fiber modulated by magneto-optical dichroism of magnetic fluid

The polarization of a D-shaped fiber is modulated after immersing it in magnetic fluid(MF)and applying a magnetic field.Theoretical analysis predicts that magneto-optical dichroism of MF plays a key role in light polarization modulation.During light polarization modulation,the evanescent wave polarized parallel to the magnetic field has greater loss than its orthogonal component.Light polarization of a D-shaped fiber with a wide polished surface can be modulated easily.High concentration MF and a large magnetic field all have great ability to modulate light polarization.     

非均匀圆柱型正交各向异性圆板的弯曲

研究了非均匀圆柱型正交各向异性圆板在均布横向载荷作用下的弯曲问题，求得了折算刚度随半径按指数规律变化的非均匀圆柱型正交各向异性圆板弯曲问题的渐近解，给出了周边固支和简支条件下的渐近解．通过算例可以看出，这种非均匀性对圆板中心挠度的影响是显著的     

Quantifying coherence with dynamical discord

Quantum coherence and discord are two kinds of manifestations of nonclassicality. By calculating the coherence and discord in the specific bipartite quantum systems, we show quantitative connections between the coherence and the discord in the bipartite quantum systems created from local systems with the help of incoherent operations. We show that the coherence bounds the dynamical discord, and under particular conditions of the initial quantum states, the coherence of single systems is equal to the dynamical discord. We extend these results to the multipartite quantum systems.     

Quantum phase transition and entanglement in Heisenberg XX spin chain with impurity

In this paper,we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field.We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero,the external magnetic field and impurity parameters have a great effect on it.Also,there exists a relation between the quantum phase transition and the entanglement.By modulating the temperature,magnetic field and the impurity parameters,the entanglement between any two lattices can exhibit platform-like behaviour,which can be used to realize entanglement switch.     

Conditions on converting coherence into entanglement

The present studies show that any nonzero amount of coherence of a system can be converted into entanglement between the system and an incoherent ancillary system via incoherent operations. According to this conclusion, we study the process of converting coherence into entanglement via a unitary operation where the initial ancillary system is of different quantum state. We find that some other conditions should be satisfied in converting coherence into entanglement.We also study the conditions of coherence consumption of converting coherence into entanglement.     

利用分束器产生的一类非经典光场

把相干态和任意粒子数态作为分束器的输入态,通过条件测量可以得到被剪切了的输出态,并研究了这些剪切了的输出态的性质.结果显示,当在某一输出端测量到零个光子时,在另一输出端得到的剪切了的输出态呈现较强的压缩和亚泊松分布等非经典效应,并且这种非经典效应受输入粒子数态的粒子数的影响,即输入粒子数态的粒子数较大时其非经典性相对较强.当在其中一个输出端测量到m(m大于零)个光子时,条件测量后的各输出态在光场性质上表现类似,但也都呈现出明显的压缩和亚泊松分布等非经典效应,尤其值得注意的是当输入的是单粒子数态时,条件测量后的输出态中与测量相对应的粒子数态被剪去.     

远程操纵光场的非经典性质

考虑双模纠缠相干光场，在其中一束光场中注入一个二能级原子（处于基态和激发态线性叠加态），参与腔QED演化之后，对原子作选择性的测量，通过操纵参数的变化范围，可实现对光场非经典性质的控制。我们经过研究发现：如果对相互作用的时间t以及参与相互作用的相干光场的参数｜β｜实行一定的操纵，对于未参与相互作用的光场｜α｜，我们可以控制改变它的反聚束效应（光子数的亚泊松分布）、压缩效应等一系列的非经典性质，如果选取合适的参数和一定的演化时间，我们可以使原来的相干态光场变为反聚束光场、压缩光场等一系列非经典光场。也就是说，我们通过利用相干光场之间的纠缠关联实现了远程操纵光场的非经典性质这一目的。这一研究结果对于连续变量的量子控制和量子通信具有一定的实际应用价值。     

两纠缠原子之一与腔场相互作用过程的纠缠研究

使一对纠缠的二能级原子之一与单模真空腔场发生共振相互作用,通过选择不同的演化时间,对这个三体系统的其中之一做选择性测量,可调节另外两体的纠缠状态。在不做测量时,研究了在不同的初始状态下,三体纠缠及三体中两两纠缠的演化特性。结果表明,该体系纠缠都呈现周期性的振荡,特别是,通过选择合适的初始状态和演化时间可生成强壮纠缠态———W纠缠态;在特定演化时刻,可使两纠缠原子的纠缠信息完全转化到腔外原子和腔场中去。     

气体Cerenkov辐射的量子理论

本文采用量子场论的一级微扰论,建立了气体介质中Cerenkov辐射的量子理论,结果表明,它有与固体、液体Cerenkov辐射不同的特点:线状光谱且轮廓不对称和出现小的红移,辐射角与辐射频率无关,并随入射粒子速度的增大而减小,辐射对入射带电粒子的速度没有阈值限制,激发态与基态原子的Cerenkov辐射几率相等,理论结果与实验基本一致。 关键词：