Kerr介质中双模纠缠相干光与Bell态原子相互作用系统的原子偶极压缩

运用全量子理论并结合数值计算方法，研究了Kerr介质腔中处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的原子偶极压缩特性.讨论了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及Kerr介质与双模光场的耦合强度对原子偶极压缩特性的影响.结果表明：双原子体系的初态为|β₁₁>时，不会出现偶极压缩效应；初态为|β₀₀>，|β₀₁>或|β₁₀>时在一定条件下可能出现原子压缩效应，且此时原子压缩的特性与Kerr介质与双模光场的耦合强度、初始光场的平均光子数、双模纠缠相干光场的纠缠程度有关. 关键词： 量子光学 Bell态 双模纠缠相干光场 Kerr介质     

三能级原子与奇偶纠缠相干光作用的光场压缩

采用求解薛定谔方程和数值计算方法,研究了V型三能级原子与双模奇偶纠缠相干光场相互作用过程中的光场压缩效应,讨论了压缩效应与双模奇偶纠缠相干光场的纠缠程度、系统失谐量、双模光场的平均光子数和原子基态概率幅的依赖关系。结果表明：光场压缩效应与双模奇偶纠缠相干光场的纠缠程度、失谐量、平均光子数和原子初态相关联：双模纠缠相干光场处于非纠缠状态时的光场压缩量比光场处于纠缠状态时要大;原子处在单纯的基态或激发态时光场都有明显的压缩现象出现;而原子初态中基态和激发态的概率幅较接近时无光场压缩现象;无论光场是否处于纠缠态,只有两模平均光子数接近时,光场才会出现压缩效应。     

双模纠缠相干光与Bell态原子系统的光子统计

运用全量子理论并结合数值计算方法,研究了处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的光子统计性质.分析了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及双原子体系的原子间耦合强度对双模光场的光子统计性质的影响.结果表明：双原子体系的初态为｜β00〉、｜β10〉时,光场在其演化过程中不出现光子的反聚束效应；而当原子初态为｜β01〉或｜β11〉时,在一定的条件下可出现光子的反聚束效应.并且在光场的演化过程中,光子的反聚束效应出现的次数、时间和深度极其敏感地依赖于初始光场的平均光子数,而受到双模纠缠光场的纠缠程度以及双原子间偶极作用强度的影响很微弱.     

Bell态原子与双模纠缠相干光场相互作用系统的原子布居数演化

运用全量子理论并结合数值计算方法,研究了处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的原子布居数演化特性.讨论了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及双原子体系的原子间耦合强度对原子布居时间演化的影响.结果表明:双原子体系的初态为|β11〉时,原子布居数不随时间变化;初态为|β00〉、|β01〉和|β10〉时,当初始平均光子数增大到一定数值时演化特性呈现出周期性的崩塌和回复效应,随初始光子数的增加时间演化曲线的振荡频率增大振幅减小,且初态为|β00〉或|β10〉时原子布居的回复周期是初态为时|β01〉的两倍;双模纠缠相干光场的纠缠程度以及原子间偶极相互作用的强弱对Rabi振荡频率没有影响但对振幅有着显著的影响.     

Bell态原子与双模纠缠相干光场双光子相互作用系统的量子纠缠

运用全量子理论和数值计算的方法,借助于原子的量子约化熵研究了初始处于Bell态|β00>和| β10>的两原子与双模纠缠相干光场双光子相互作用系统中两原子与双模光场之间纠缠的演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对原子熵演化特性的影响.结果表明:随着双模光场的平均光子数的增大,原子熵的时间演化曲线逐渐变为规则振荡;增大原子间的相互作用强度,原子熵的振荡频率和振幅都减小;改变双模光场的纠缠度,原子熵的振荡频率和振幅都不发生改变.     

Bell态原子与双模纠缠相干光场相互作用的纠缠特性

运用Negativity熵研究了Bell态原子与双模纠缠相干光场相互作用系统中两个全同二能级原子之间的纠缠演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对纠缠的影响.结果表明:原子处于|β11〉时,两原子始终处于最大纠缠态;原子处于|β00〉时,初始纠缠的两原子始终较长时间处于退纠缠状态;原子处在|β10〉时,增大双模光场的平均光子数可以明显增大两原子之间的纠缠度并保持较大的纠缠状态;原子初态处在|β01〉时,原子间的相互作用强度对双原子间纠缠度有较显著的非线性调制作用.     

V型三能级原子与双模奇偶纠缠相干光场相互作用系统的光子统计性质

本文采用求解Schr dinger方程和数值计算方法,研究了V-型三能级原子与双模奇偶纠缠相干光场相互作用系统的光子统计性质,结果表明:此性质与双模奇偶纠缠相干光场的纠缠程度、失谐量、原子的初态以及双模光的平均光子数相关联.     

双模纠缠相干光场与V型三能级原子相互作用系统的光子统计性质

本文采用求解Schrodinger方程和数值计算方法,研究了双模纠缠相干光场与三能级原子相互作用系统的光子统计性质,结果表明:此性质与双模纠缠相干光场的纠缠程度、失谐量、双模光的平均光子数和原子的初态相关联.     

Ⅴ型三能级原子与双模奇偶纠缠相干光场相互作用系统的光子统计性质

本文采用求解Schroedinger方程和数值计算方法，研究了Ⅴ-型三能级原子与双模奇偶纠缠相干光场相互作用系统的光子统计性质，结果表明：此性质与双模奇偶纠缠相干光场的纠缠程度、失谐量、原子的初态以及双模光的平均光子数相关联．     

Bell态原子与双模纠缠相干光场双光子相互作用的原子布居数演化特性

运用全量子理论研究了Bell态原子与双模纠缠相干光场双光子相互作用过程中的原子粒子布居差的时间演化规律.结果表明:原子初始处于|β11＞时,原子粒子布居差恒为零;原子初始处于其他三个Bell态时,随着初始光场平均光子数的增加,原子粒子数布居差时间演化曲线的振荡频率明显增大,振荡幅度明显减小;双模光场纠缠程度的大小对曲线的振荡频率及整体曲线的位置都没有影响.随着原子间偶极相互作用的增强,当原子初态处在|β01＞时,曲线的Rabi振荡频率明显增大;而两原子初始处于|β10＞或|β00＞态时,曲线的崩塌-回复现象逐渐消失.     

Long-lived nuclear spin states in the solution NMR of four-spin systems

The existence of long-lived nuclear spin states in four-spin systems is explored by solution-state NMR experiments. Long-lived states are proved to exist in three different natural product molecules, each containing either a AA'BB' or a AA'XX' proton spin system. The measured state lifetimes are between four and eight times the spin-lattice relaxation time constants.     

The image potential in the weighted-density approximation

Summary We analyse the image potential of a metal surface in the weightede-density approximation and obtain an analytical expression for the position of the image plane which is independent of the surface electronic structure. We conclude that the position of the plane image given by this density functional approximation cannot be accepted as a physical result.     

Particle Creation in the Oscillatory Phase of Inflaton

A thermal squeezed state representation of inflaton is constructed for a flat Friedmann–Robertson–Walker (FRW) background metric and the phenomenon of particle creation is examined during the oscillatory phase of inflaton, in the semiclassical theory of gravity. An approximate solution to the semiclassical Einstein equation is obtained in thermal squeezed state formalism perturbatively and is found obey the same power-law expansion as that of classical Einstein equation. In addition to that the solution shows oscillatory in nature except on a particular condition. It is also noted that, the coherently oscillating nonclassical inflaton, in thermal squeezed vacuum state, thermal squeezed state, and thermal coherent state, suffers particle production and the created particles exhibit oscillatory behavior. The present study can account for the postinflation particle creation due to thermal and quantum effects of inflation in a flat FRW universe.     

利用腔场与可移动镜子的作用制备两种非经典态

描述了在腔场与可移动镜子相互作用系统中,适当选择作用时间,可以制备单模腔场与镜子的纠缠态,或腔场的薛定谔猫态;通过调节腔场的长度、圆频率,以及镜子的质量、振动频率等宏观物理量,可以获得不同的量子态.     

Arithmetic of the Integer Quantum Hall Effect

The integer quantum Hall effect (IQHE) is analysed, considering the degeneracies of localized and extended states separately. Occupied localized and extended states are counted, and their variation is studied as a function of magnetic field. The number of current-carrying electrons is found to have a saw-tooth variation with magnetic field. The analysis addresses certain basic questions in the IQHE, particularly the one about floatation of extended states as the magnetic field tends to zero.     

Localized electronic states in -layer-based superlattices with structural defects

Using an effect-barrier height method, we study the properties of the localized electronic states in an N-layer-based superlattice with structural defects within the framework of effective-mass theory. The coupling effect between normal and lateral degrees of freedom of an electron on the localized electronic states in both symmetric and asymmetric triple layer superlattices with structural defects has been considered numerically. The results show that the localized states display different behaviors in both symmetric and asymmetric structures in spite of the minibands being not influenced by the structural symmetry. Moreover, the coupling effect causes the minibands, minigaps and localized electron levels to depend on the transverse wave number k_xy. A brief physical analysis is given.     

Superpositions of the dual family of nonlinear coherent states and their non-classical properties

Nonlinear coherent states (CSs) and their dual families were introduced recently. In this paper, we want to obtain their superposition and investigate their non-classical properties such as antibunching effect, quadrature squeezing and amplitude squared squeezing. For this purpose two types of superposition are considered. In the first type, we neglect the normalization factors of the two components of the dual pair, superpose them and then we normalize the obtained states, while in the second type we superpose the two normalized components and then again normalize the resultant states. As a physical realization, the formalism will then be applied to a special physical system with known nonlinearity function, i.e., Hydrogen-like spectrum. We continue with the (first type of) superposition of the dual pair of Gazeau-Klauder coherent states (GKCSs) as temporally stable CSs. An application of the proposal will be given by employing the Pöschl-Teller potential system. The numerical results are presented and discussed in detail, showing the effects of this special quantum interference.     

Charge screening in valence band of solids and in the Fermi sea. Origin of weak-boson masses

Summary An attempt is made to explain the masses of Z and W^± bosons by means of a screening mechanism analogous to charge screening in metals. It considers the effect of the electroweak force on the distribution of negativekinetic-energy neutrinos, which fills the whole universe (neutrino Fermi sea). The large weak-boson masses appear to be a direct consequence of the vanishing neutrino mass.     

Positroniumlike system in quartz

Summary The ortho-state of the Ps-like system, which in crystalline quartz lives in Bloch states, has been detected in the time annihilation spectrum. Its lifetime and abundance are τ₃=0.49ns,I ₃=0.13. The magnetic quenching of this system has been measured and compared with that of Ps-like system living in other molecular media. This work was supported by CISM (Centro Interuniversitario di Struttura della Materia) of Ministero della Pubblica Istruzione and by GNSM (Gruppo Nazionale di Struttura della Materia) of CNR.     

Positron polarization in chiral media

Summary The positron spin depolarization, relative to the direction of a static magnetic field, was investigated in some chiral media where Ps formation occurs. The results indicate that helical positrons are able to distinguish one enantiomer from the other: the remaining polarizations—just before Ps is formed—differ by about 20% on passing from one enantiomer to the other of the same chiral species. Moreover the existence of a process—strictly connected with chirality and able to hinder any depolarizing process more efficiently than the field itself—has been made evident at low fields. This work was supported by INFM (Consorzio Nazionale di Fisica della Materia).