超冷单原子分子阵列

用光镊形成光阱囚禁单个原子、用激光将单个原子冷却到基态形成超冷原子、将超冷原子相干合成单个超冷分子、将单原子分子重排串成丰富多样的超冷单原子分子阵列,这就构成了精密相干可控的多粒子量子系统,为多种前沿科学研究与技术发展提供难得的量子平台.文章介绍近年来在单原子量子态高保真操控、异核原子量子纠缠、原子一分子耦合态相干控制...     

非旋波作用对费仑克尔激子超辐射的影响

研究表明,在费仑克尔激子的超辐射理论中出现在辐射强度和相干度中的无规颤动是由非旋波作用所引起的。另外,在不考虑非旋波作用项后,超辐射光场是一阶完全相干的,与初始时激子的状态无关。二阶相干度与初始时激子态的二阶相干度相同,不出现更复杂多样的情况。     

原子相干对光缔合形成分子的影响

用量子统计方法,讨论了原子相干对超冷两态原子经光缔合形成超冷分子的影响.结果表明,在原子相干的作用下,光缔合形成的分子数随时间做近周期减幅振荡.原子相干对光缔合过程的暂态阶段影响强烈,而分子始终保持sub-Poisson统计分布.     

超辐射中的亚泊松光子统计

本文利用推广的Jaynes-Cummings模型描述N个二能级原子的超辐射,得到了辐射场的二阶关联函数的一般表达式。并进而用于缓变耦合情况,着重研究了共振情况下由超泊松光场演化成亚泊松光场的初始条件。作为例子,讨论了推广相干态及压缩相干态的演化条件。最后提出了利用相干态光场观察亚泊松光子统计的实验建议。     

超导体中库珀对的SU(2)与Glauber相干态——库珀对与约瑟夫森超流性的量子特性研究

本文利用类自旋算符证明BCS超导基态波函数是单个库珀对SU(2)相干态波函数的直积、且在一定条件下为库珀对体系的SU(2)相干态波函数。若两块处在BCS超导基态的超导体耦合在一起,则体系仍处在SU(2)相干态,且在一定条件下为定态超辐射态。在SU(2)群到谐振子群的收缩下,库珀对的SU(2)相干态变为Glauber相干态。讨论了两种情形下库珀对与约瑟夫森超流性的量子噪声、分布及二阶相关特性。     

在腔QED系统中变换W态到超单态

提出了一步变换三原子W态为三原子超单态的方案。在方案中,三个五能级原子同时与双模腔发生离散相互作用。方案的优点是可以有效抵御原子自发辐射和腔衰变引起的消相干的影响。     

非谐振子Gazeau-Klauder与Klauder-Perelomov相干态

利用Kinani-Daoud方法构造了非谐振子势的Gazeau-Klauder(GK)相干态和Klauder-Perelomov(KP)相干态，表明两种相干态在非线性谐振子势下具有完全不同的形式，并对两种相干态的完备性以及各自构成的Hilbert空间进行了讨论. 对相干态的Mandel Q参数的研究表明：GK相干态服从亚Poisson统计分布，KP相干态服从超Poisson统计分布. 关键词： 非谐振子 Gazeau-Klauder相干态 Klauder-Perelomov相干态     

叠加对相干态的相位概率分布特性

讨论了叠加对相干态的完备性关系,并根据Pegg和Barnett的相位算符和相位态的定义,计算了叠加对相干态的相位概率分布函数,并应用数值计算讨论了其特性.结果表明,叠加对相干态的相位概率分布受到相位参数和叠加参数的调制.     

李超代数B(0,1)的超相干态表示

本文反相干态的概念推广到李超代数的情形.我们具体地构造了李超代数B(0,1)的超相干态,计算了B(0,1)生成元在超相干态表示中的矩阵元,获得了B(0,1)代数的一种非齐次微分实现.这种非齐次微分实现对研究量子力学中的准精确可解问题有用.     

光子计数分布与生物光子辐射特性

本文应用光子计数分布的理论及生物系统超微弱光子辐射的测试数据对生物光子场的辐射特性进行研究,提出生物光子场基本上属于高斯场的观点,并认为它至少是由两个独立部分的光子辐射叠加的结果;其一是纯相干态的相干辐射;另一则为热平衡浑沌态的热光源辐射。文中最后讨论了生物光子辐射的产生机制。     

Gaussian states as minimum uncertainty states

In bosonic fields, Gaussian states, which consist of a rather wide family of states including coherent states, squeezed states, thermal states, etc., have many classical-like features, and are usually defined from the mathematical perspective in terms of characteristic functions. It is well known that some special Gaussian states, such as coherent states, are minimum uncertainty states for the conventional Heisenberg uncertainty relation involving canonical pair of position and momentum observables. A natural question arises as whether all Gaussian states can be characterized as minimum uncertainty states. In this work, we show that indeed Gaussian states coincide with minimum uncertainty states for an information-theoretic refinement of the conventional uncertainty relation established in Luo (2005) [40]. This characterization puts Gaussian states on a novel basis of physical significance.     

Chimera states in bipartite networks of FitzHugh–Nagumo oscillators

Chimera states consisting of spatially coherent and incoherent domains have been observed in different topologies such as rings, spheres, and complex networks. In this paper, we investigate bipartite networks of nonlocally coupled FitzHugh–Nagumo (FHN) oscillators in which the units are allocated evenly to two layers, and FHN units interact with each other only when they are in different layers. We report the existence of chimera states in bipartite networks. Owing to the interplay between chimera states in the two layers, many types of chimera states such as in-phase chimera states, antiphase chimera states, and out-of-phase chimera states are classified. Stability diagrams of several typical chimera states in the coupling strength–coupling radius plane, which show strong multistability of chimera states, are explored.     

Nonclassical properties and algebraic characteristics of negative binomial states in quantized radiation fields

We study the nonclassical properties and algebraic characteristics of the negative binomial states introduced by Barnett recently. The ladder operator formalism and displacement operator formalism of the negative binomial states are found and the algebra involved turns out to be the SU(1,1) Lie algebra via the generalized Holstein-Primarkoff realization. These states are essentially Perelomov's SU(1,1) coherent states. We reveal their connection with the geometric states and find that they are excited geometric states. As intermediate states, they interpolate between the number states and geometric states. We also point out that they can be recognized as the nonlinear coherent states. Their nonclassical properties, such as sub-Poissonian distribution and squeezing effect are discussed. The quasiprobability distributions in phase space, namely the Q and Wigner functions, are studied in detail. We also propose two methods of generation of the negative binomial states. d 32.80.Pj Optical cooling of atoms; trapping Received 8 May 1999 and Received in final form 8 November 1999     

Raman sum rule and the relation to the infrared sum rule in La2-xSrxCuO4

Electronic Raman scattering has no sum rule in no and weak correlation, but the existence of sum rule has been proposed in strong correlation. The present Raman scattering disclosed that the first moment of the Raman susceptibility is proportional to the generalized moment of the optical conductivity in the metallic phase. The present experiment disclosed that a large amount of electronic states are incoherent states. The incoherent states are the relevant states for the superconductivity, because the gap opens in the incoherent states as well as the coherent states.     

Microscopic structure of fundamental excitations in N = Z nuclei

An extended mean-field model is presented that describes states of different isospin in odd-odd and even-even nuclei. Excitation energies of the T = 1 states in even-even as well as T = 0 and T = 1 states in odd-odd N = Z nuclei are calculated. It is shown that the structure of these states can be determined in a consistent manner when both isoscalar and isovector pairing collectivity as well as isospin projection (treated here within the isocranking approximation) are taken into account. In particular, in odd-odd N = Z nuclei, the interplay between quasiparticle excitations (relevant for the case of T = 0 states) and isorotations (relevant for the case of T = 1 states) explains the near degeneracy of these states.     

Coherent and squeezed states on physical basis

A definition of coherent states is proposed as the minimum uncertainty states with equal variance in two hermitian non-commuting generators of the Lie algebra of the hamiltonian. That approach classifies the coherent states into distinct classes. The coherent states of a harmonic oscillator, according to the proposed approach, are shown to fall in two classes. One is the familiar class of Glauber states whereas the other is a new class. The coherent states of spin constitute only one class. The squeezed states are similarly defined on the physical basis as the states that give better precision than the coherent states in a process of measurement of a force coupled to the given system. The condition of squeezing based on that criterion is derived for a system of spins.     

Extension of the Local Approach to excited states of molecules

The Local Approach for the calculation of electronic correlation energies in molecules is generalized to excited states. Within the Local Approach correlated states are obtained by applying a local projection operator on the Hartree-Fock ground state or simple reference states, which are used as zeroth order approximations for the excited states, respectively. In the case of excited states one has in addition to require the correlated states to be orthogonal on the states lower in energy. This is done by using Schmidt's orthogonalization. The method is applied to a simple model of the H₆-ring for which an exact solution is available. The results obtained are of comparable quality as for the ground state.     

Spectral properties of quasiperiodic superlattices and study of wave functions

We report the study of the spectral properties of a quasiperiodic superlattice within a tight binding model. Numerical work is carried out using the transfer matrix method. An approximate analytical scheme is used to obtain expressions for the band gaps which explain all the features obtained numerically. Due to the fact that blocks of atoms are repeated quasiperiodically, the gaps are shown to vanish at specific energies. These states have much the same behaviour as the extended states but the amplitude is a quasiperiodic function of the site index. The total number of such extended states are estimated. Since it is known that other states in quasiperiodic systems are critical, these states are expected to exhibit a cross-over behaviour to the critical states as a function of the energy. Multifractal analysis of the quasiperiodic wave function show that it has the same signature as the extended wave function. We briefly comment on the cross-over behaviour.     

Class of Unlockable Bound Entangled States and Their Applications

A class of unlockable bound entangled states and their applications are presented. They can be considered as quasi generalized Smolin states [Phys. Rev. A 63 （2001） 032306], which are the states of N ＋ N qubits. No pure entanglement can be distilled from this class of states by local quantum operations and classical communications. However, if certain parties group together, they become distillable. Although they are bound entangled states, they could be used to achieve some non-trivial tasks, such as quantum secret sharing shown in the study.     

Quantum Entanglement Swapping in a Non-Markovian Environment

We propose an entanglement swapping scheme for mixed states in a classical non-Markovian noises, which is modelled as the so-called Ornstein-Uhlenbeck processes. The two mixed states before entanglement swapping are two X-type mixed states, which are caused by the environment-induced decoherence on the initially Bell states. This is more practical than the pure state case in quantum information processing. The fidelity and concurrence of the post-swapping states are discussed.