Deterministic Secure Direct Communication by Using Swapping Quantum Entanglement and Local Unitary Operations

A deterministic direct quantum communication protocol is proposed by using swapping quantum entanglement and local unitary operations. The present protocol is secure for the proof of the security of the present scheme, the same as that in the two-step protocol [Phys. Rev. A 68(2003)042317]. Additionally, the advantages and disadvantages of the present protocol is also discussed.     

Explicit Analysis of Creating Maximally Entangled State in the Mott Insulator State

We clarify the essence of the method proposed by You (Phys. Rev. Lett. 90 (2004) 030402) to create the maximally entangled atomic N-GHZ state in the Mott insulator state. Based on the time-independent perturbation theory,we find that the validity of the method can be summarized as that the Hamiltonian governing the evolution is approximately equivalent to the type αJx^2 bJx, which is the well known form used to create the maximally entangled state.     

用NMR弛豫研究溶液中聚苯乙烯的缠结特性

详细研究了在θ溶剂环已烷和二氧六环中聚苯乙烯（ＰＳ）链的弛豫特性随分子量、浓度和温度的变化规律，发现在ＰＳ的溶液中同时存在拓扑缠结和凝聚缠结．前者的形成强烈的依赖于分子量、浓度和温度，而后者主要同浓度和温度有关．侧基苯环的层叠作用（即凝聚缠结）对ＰＳ的溶解过程及主链的运动有很大影响，从而对ＰＳ的溶液性质乃至固体性质起着决定性作用．另外还发现在不同分子量范围内，分子量对ＰＳ的弛豫特性的影响明显不同．这被解释为同溶液中ＰＳ链的缠结的形成，单位体积内缠结点数的增加等因素有关．     

Quantum Dialogue Revisited

An entanglement-based quantum dialogue protocol [Phys. Lett. A 328 (2004) 6] is proven to be insecure: that is, in the protocol an eavesdropper can steal the secret messages without being detected provided that he/she adopts the intercept-and-resend attack strategy. We modify the protocol, i.e. in the control mode, by introducing and randomly choosing two sets of measuring basis: the intercept-and-resend attack can be accordingly detected. Hence, within the present version two users can securely and simultaneously exchange their secret messages.     

用NMR弛豫研究溶液中聚苯乙烯的缠结特性

详细研究了在θ溶剂环已烷和二氧六环中聚苯乙烯(PS)链的弛豫特性随分子量、浓度和温度的变化规律,发现在PS的溶液中同时存在拓扑缠结和凝聚缠结.前者的形成强烈的依赖于分子量、浓度和温度,而后者主要同浓度和温度有关.侧基苯环的层叠作用(即凝聚缠结)对PS的溶解过程及主链的运动有很大影响,从而对PS的溶液性质乃至固体性质起着决定性作用.另外还发现在不同分子量范围内,分子量对PS的弛豫特性的影响明显不同.这被解释为同溶液中PS链的缠结的形成,单位体积内缠结点数的增加等因素有关.     

混合离子液体对聚甲基丙烯酸甲酯分子链缠结及松弛行为的影响

首先通过两步法合成了具有双咪唑环阳离子结构的离子液体(DIL),并将其与单咪唑环离子液体(MIL)进行混合以调控黏度变化,混合离子液体(ILs)的黏度符合对数混合规则且随温度变化呈现Arrhenius型流体行为.进一步通过动态流变、示差扫描量热(DSC)、电化学测试等方法研究了混合离子液体中DIL比例对聚甲基丙烯酸甲酯(PMMA)链缠结和松弛行为的影响,并讨论了PMMA/ILs体系热稳定性、玻璃化转变及离子电导率等的变化.结果表明,DIL独特的双咪唑环结构可与PMMA分子形成更多相互作用位点,从而导致凝聚缠结的形成,很大程度上限制了PMMA分子链的运动和松弛.随DIL含量增加,PMMA/ILs体系的松弛时间、热分解温度、玻璃化转变温度等参数均呈增大趋势,但其离子电导率有所损失,这与DIL较大的分子尺寸和运动能力有关.     

Monte Carlo模拟方法研究管道受限对高分子链缠结的影响

采用基于格子模型的Monte Carlo模拟方法,考察了链长分别为30和250的线形高分子在管道内受限状态下的尺寸及扩散性质.结果表明,当线形高分子的链长低于其缠结链长时,其受限条件下高分子的性质随受限程度的变化而单调变化;而当线形高分子的链长大于缠结链长时,高分子的性质表现出非单调性,进而说明受限具有一定程度的解缠结...     

深度冷冻干燥对聚(L-乳酸)结晶性能的影响

采用广角X射线衍射(XRD)和差示扫描量热(DSC)方法研究了深度冷冻干燥对PLLA结晶性能的影响.深度冷冻干燥方法可以改善PLLA的结晶性能.实验结果表明,0.1%、1%、5%和10%PLLA的对二甲苯溶液经过深度冷冻干燥得到PLLA的结晶速度系数(CRC)分别为0.935、0.877、0.826和0.863,高于从0.1%对二甲苯溶液中结晶得到的PLLA的CRC(为0.643).     

链解缠结后聚合物的结晶行为

就近年来关于高分子链解缠结及其对聚合物结晶行为的影响研究作了较为详细的介绍,阐明链解缠结后由于高分子的运动不受或很少受到周围分子的限制,聚合物的结晶能力是增强的,并对可能影响链解缠结程度以及结晶的多种因素(制样溶液浓度、溶剂性能、溶剂尺寸等)进行了讨论.     

Entropy evolvement properties in a system of Schrodinger cat state light field interacting with two entangled atoms

The field entropy can be regarded as a measurement of the degree of entanglement between the light field and the atoms of a system which is composed of two-level atoms initially in an entangled state interacting with the Schr\"{o}dinger cat state. The influences of the strength of light field and the phase angle between the two coherent states on the field entropy are discussed by using numerical calculations. The result shows that when the strength of light field is large enough the field entropy is not zero and the degrees of entanglement between the atoms and the three different states of the light fields are equal. When the strength of the light field is small, the degree of entanglement is maximum in a system of the two entangled atoms interacting with an odd coherent state; it is intermediate for a system of the two entangled atoms interacting with the Yurke--Stoler coherent state, and it is minimum in a system of the two entangled atoms interacting with an even coherent state.