'Designer atoms' for quantum metrology

Entanglement is recognized as a key resource for quantum computation and quantum cryptography. For quantum metrology, the use of entangled states has been discussed and demonstrated as a means of improving the signal-to-noise ratio. In addition, entangled states have been used in experiments for efficient quantum state detection and for the measurement of scattering lengths. In quantum information processing, manipulation of individual quantum bits allows for the tailored design of specific states that are insensitive to the detrimental influences of an environment. Such 'decoherence-free subspaces' (ref. 10) protect quantum information and yield significantly enhanced coherence times. Here we use a decoherence-free subspace with specifically designed entangled states to demonstrate precision spectroscopy of a pair of trapped Ca+ ions; we obtain the electric quadrupole moment, which is of use for frequency standard applications. We find that entangled states are not only useful for enhancing the signal-to-noise ratio in frequency measurements--a suitably designed pair of atoms also allows clock measurements in the presence of strong technical noise. Our technique makes explicit use of non-locality as an entanglement property and provides an approach for 'designed' quantum metrology.     

Embracing the quantum limit in silicon computing

Quantum computers hold the promise of massive performance enhancements across a range of applications, from cryptography and databases to revolutionary scientific simulation tools. Such computers would make use of the same quantum mechanical phenomena that pose limitations on the continued shrinking of conventional information processing devices. Many of the key requirements for quantum computing differ markedly from those of conventional computers. However, silicon, which plays a central part in conventional information processing, has many properties that make it a superb platform around which to build a quantum computer.     

量子统计系统极限判据的讨论

目的对量子统计系统的极限判据进行讨论。方法对不同量子极限进行比较分析。结果推导得到了量子统计系统的极限判据,并进行了讨论。结论对近独立粒子体系的统计分布,小Planck常数极限与高温、低密度极限具有相同的极限效应。     

Inferring the statistical interpretation of quantum mechanics from the classical limit

It is widely believed that the statistical interpretation of quantum mechanics cannot be inferred from the Schrodinger equation itself, and must be stated as an additional independent axiom. Here I propose that the situation is not so stark. For systems that have both continuous and discrete degrees of freedom (such as coordinates and spin respectively), the statistical interpretation for the discrete variables is implied by requiring that the system's gross motion can be classically described under circumstances specified by the Schrodinger equation. However, this is not a full-fledged derivation of the statistical interpretation because it does not apply to the continuous variables of classical mechanics.     

Heisenberg群上的Schroedinger算子

证明了（-△H^n＋V）iγ是Heisenberg群上的Calderon-Zygmund算子。     

海森堡薄膜的临界温度

在相关有效场理论框架内,应用类伊辛模型分析方法,研究了海森堡薄膜的临界行为     

两量子比特海森伯模型的热纠缠

研究两粒子的XYZ海森伯模型的热纠缠态,并讨论了这个系统哈密顿量中的参数和温度对纠缠度的影响.结果表明:对于一定的温度,耦合常数的增加能够增加纠缠度,但是纠缠度却随着温度的增加而减小,直到临界温度时纠缠度为零.     

三角海森堡反铁磁体中的磁激发

利用标准的自旋波理论,研究了二维三角海森堡反铁磁体的色散关系．分别采用了三子格模型和单子格模型来描述同一平面上几何阻挫的三角反铁磁结构,并对两者的结果进行了比较和分析．研究表明无论是基于三子格模型还是基于单子格模型,磁激发展示了一致的机制,色散关系也完全相同．单子格模型的研究为以后计算三维六角密排晶格的磁激发提供了简便的方法．     

海森堡群Hn的Fourier变换

基于欧几里德空间的性质，得到了L^2（R^n）上的Foreries变换以及Plancherel定理，在定义H^n酉表示的基础上得到了海森堡群H^n Fourier变换．     

Nonlinear Liouville Theorem in the Quaternionic Heisenberg Group

This paper deals with the problem of the type △nf f^p=0 in quaternionie Heisenberg group, where △n is the quaternionic Heisenberg Laplacian. It is proved that, un der suitable conditions on p and f. the only solution of △nf f^P=0 is f=0.     

关于Heisenberg群上的等周不等式

证明了在一维Heisenberg群H1上C-C球不是等周集;同时在A类集中有等周集的假设前提下,给出了Heisenberg群H1上等周不等式的最佳常数.     

如何用数列极限定义证明数列极限问题

以数列极限为例,详细阐述了用极限定义证明极限存在的三种常用的方法:基本方法、适当放大法、条件放大法,以及在应用这些方法时应注意的一些主要问题,从而强化对极限概念的理解·     

提高显示速度的方法

简要说明 Visual Basic编程中提高绘图和其它的显示操作速度常用的几种方法。     

有阻尼项的Heisenberg链方程的差分格式

本文研究了具有阻尼项的Heisenberg链方程u t =-α1u × (u ×△u ) α2 (u ×△u )　　　的周期初值的显式差分格式 ,并证明了格式的收敛性和稳定性。