Slowing and storing light processes without a trapping dark state in a double two-level system. Theoretical study

We present a detailed theoretical study of a method for slowing light based on the oscillations of Zeeman coherences in a double two-level system [Hashmi, F.A.; Bouchene, M.A. Phys. Rev. A 2008, 77, 051803(R)]. This method does not require the presence of any trapping state. We focus on the properties and the limitations of such a method and compare it to previous ones. We also investigate the possibility of obtaining fast light and to store the light with such a method.     

Long-distance teleportation based on a selected receiver in a quantum network

Quantum networks are useful for global communication. A new multi-hop scheme of single unitary transformation method (SUTM) is proposed for long-distance teleportation of an unknown W state in a quantum network. All the measurement outcomes are sent to the selected receiver independently. The initial quantum state can be recovered by a corresponding local operation. The probability of successful teleportation can reach 1 without auxiliary particles. Our scheme is superior to the hop-by-hop method owing to lower delays.     

Sub-Poissonian photon squeezing and entanglement in optical chain second harmonic generation

Nonclassical properties exhibited by a chain of cavity modes second harmonic generation in coupled oscillators system, designed by using multichannel optical waveguides, is explored. The solution for the Hamiltonian of the coupled-modes driven by coherent excitation is obtained via an exact formulation of the normal-ordered Fokker-Planck equation. Nonclassical effects, namely the sub-Poissonian photons, squeezing and entanglement are noticed. Multichannel coupling of the coupled oscillators induces new possibilities for correlation between the modes in different channels, henceforth, provides an effective way towards manipulation of quantum light.     

原子系统的光吸收量子理论

根据电磁辐射场的量子化理论,结合SU(1,1)Lie代数理论和SO(3)Lie代数理论,得到原子系统光吸收的量子论。作为例子,给出氢原子的光吸收截面。     

物理学与计量学—21世纪的计量学

回顾物理学与计量滨发展历史,指出建立在经典物理学基础上的计量单位制存在的问题。分析２１世纪物理学的研究重点及其与计量学密不可分的关系,并讨论了高新技术的发展对量子计量学的需求,以及计量学对地社会安全与安定所起的重要作用。     

System approach to metrology of quantum multiparticle systems

Features of the metrology of quantum multiparticle systems in connection with general system theory and representational theory are considered. Quantitative characteristics of the periodic system of elements (PSE) are introduced and studied, including property correlation, and also system hierarchies are considered leading to its analysis and possible application of nanosystems and quantum computers. __________ Translated from Izmeritel’naya Tekhnika, No. 4. pp. 3–7, April, 2008.     

氢原子的量子力学表征

建立了适合氢原子特性的量子算符代数理论,给出氢原子中电子与原子核绕其质心作圆周运动的旋转角频率及其轨道速度等物理量与时间量子数之间的关系。根据氢原子的量子算符代数理论,得到氢原子的能量及氢原子的光谱常数表示。结果表明,氢原子的光谱常数与实验测定值完全符合。     

Permanently disentangled states of atom–field system via spontaneously generated coherence

Abstract

The effect of spontaneously generated coherence on evolution of the entanglement between a driven four-level Y-type atom and its spontaneous emission field is studied. We have shown that the atom will be entangled to its spontaneous emission field due to spontaneously generated coherence and coherent population trapping at the steady state. It is found that the degree of entanglement strongly depends on the initial atomic state. So, it can be controlled by the pumping laser pulses used for preparing an initial atomic system. More interestingly, the atom–field system can be found in a permanently disentangled state for a properly prepared atom.     

含自旋轨道相互作用的氢原子精确量子论

首次建立超微粒子费密算符理论。利用该理论 ,并结合文献 [1]的工作 ,得到含自旋轨道相互作用的氢原子精确量子论。     

Pre-selection of optical transitions in rare-earth ions in crystals perspective for quantum information processing

A systematic analysis of decoherence rates due to electron–phonon interactions for optical transitions of rare-earth dopant ions in crystals is presented in the frame of the point charge model. For this model, the large value of any one of the matrix elements of the unit tensor operator U ^{( k )} of rank k for transitions within the 4f-electronic configuration, viz. U2, U4 or U6, is enough to ensure the strong optical transition between different levels, while the Stark–Stark transitions within the multiplet can be characterized by the matrix element U2 alone, the influence of elements U4, U6 being of much smaller order of magnitude and neglected. The circumstance that exactly such Stark–Stark transitions within the multiplet define the efficiency of electron–phonon interaction and, consequently, the decoherence rate (except for the case of lowest, less than approximately 2–4?K, temperatures), enables selection of optical transitions which are strong enough and at the same time are characterized by relatively small decoherence rates. Correspondingly, these optical transitions, provided that they lie in an appropriate spectral range and the gap to the nearest neighboring energy level is large enough (>500?cm^?1) to prevent eventual fast phonon-assisted relaxation, should be considered as prospective for subsequent use in quantum informatics processing and communication. The list of such pre-selected transitions is given; the applicability area and limitations of our approach are discussed.