Steady state signal in the limit of weak optical pumping with D1 or D2 line

The simplified rate equations for electronic polarization of alkali atoms in the hyperfine ground states are shown for circularly polarizedD ₁ andD ₂ lines in the limit of weak pumping. The rate equations include effects due to collisional and spin exchange relaxation of atoms in the ground state. Analytical forms of the repopulation pumping terms are shown assuming the standardJ-randomization model for relaxation of alkali atoms in resonant² P _J states and neglecting energy transfer. Analyses of the analytical steady state solutions have been performed to determine the conditions at which the longitudinal electronic orientation of alkali atoms 〈S _z〉 and the orientation of atoms in hyperfine sublevels 〈S _z〉 _f pass through zero.     

Probabilistically perfect quantum cloning and unambiguous state discrimination

We consider the N → M probabilistically perfect quantum cloning machine that perfectly produces M faithful copies from N identical input states, where the input states are selected, with prior probabilities η₁and η₂ = 1 − η₁, from a given set of the two linearly independent states |ψ₁〉^⊗ N = (cosθ|0〉 + sinθ|1〉)^⊗ N and |ψ₂〉^⊗ N = (sinθ|0〉 + cosθ|1〉)^⊗ N (θ∈(0,π/2)). We derive the optimal distribution of the success probabilities. When M approaches infinite, the probabilistically perfect quantum cloning can be regarded as a kind of the unambiguous state discrimination, and theoretically provides the upper bound of the unambiguous state discrimination. By using the optimal distribution of the success probabilities of the optimal asymmetric 1 → M probabilistically perfect quantum cloning, we can derive the maximum average success probability of the unambiguous discrimination of two nonorthogonal quantum states |ψ₁〉and|ψ₂〉. As an example, we give the explicit transformation of the optimal symmetric 1 → M probabilistically perfect quantum cloning to copy the two input states |ψ₁〉 and |ψ₂〉.     

Lifetimes of Excited Alkalilike Atoms Colliding by Van der Waals Forces with Inert Gas Atoms in the Groundstate

The influence of Van der Waals forces on the lifetime of coherently excited hyperfine-states |F_im_Fi〉 and |F_im_Fi〉 of alkalilike atoms i by collissions with inert gas atoms j in the groundstate |F_jm_Fi〉 has been examined. To do this the timedependent Schrödinger equation has been solved on taking into account a static magnetic field, a radiation field and a Van der Waals force. Introducing an impact parameter model for the colliding atoms with small scattering angles which form a quasimolecule |μ〉 = |F_im_FiF_jm_Fi 〉 an expression for the cross section σ_μμ has been derived which determines the halfwidth Γ _μμ of the coherently excited states. On making use of the irreducible tensor representation the calculation of the cross-section has been reduced to the calculation of multipole transitions. The result has been applied e. g. to the coherently excited 3d¹⁰4p²P_3/2-states of Cu I colliding by dipole-dipole interaction with inert gas atoms He I, and Ar I in the ground state. The values agree well with data which have been derived from zero-level-crossing experiments.     

Magnetoreflectance of the Γ6 – Γ8 exciton ground state in cubic ZnSe

Magnetoreflectance measurements on the ground state of the Γ₆ – Γ₈ free exciton in cubic ZnSe in magnetic fields up to 18 T are reported. The splitting between the |1, ±1〉 states was derived from the measured difference spectrum between σ⁺ and σ^--polarized reflectance in Faraday configuration. The splitting between the two states corresponding to |2, 0〉 and |1, 0〉 at B = 0 was determined by means of a lineshape analysis. We derive an electron g-factor g = 1.48 ± 0.25, in reasonable agreement with existing k · p calculations, and obtain an effective hole g-value $\text{K}\text{?}\text{= -0.26±0.06}$. In addition, we find an upper limit for the short range electron-hole spin exchange energy Δ ? 0.1 meV, which is considerably smaller than values, which is considerably smaller than values reported in the literature, but agrees with recent results on ZnTe obtained by uniaxial stress and also magnetoreflectance measurements.     

Bose-Einstein condensation of 87Rb in a levitated crossed dipole trap

We report an apparatus and method capable of producing Bose-Einstein condensates (BECs) of ～1 × 10^{6 87}Rb atoms, and ultimately designed for sympathetic cooling of ¹³³Cs and the creation of ultracold RbCs molecules. The method combines several elements: (i) the large recapture of a magnetic quadrupole trap from a magneto-optical trap; (ii) efficient forced RF evaporation in such a magnetic trap; (iii) the gain in phase-space density obtained when loading the magnetically trapped atoms into a far red-detuned optical dipole trap, and (iv) efficient evaporation to BEC within the dipole trap. We demonstrate that the system is capable of sympathetically cooling the |F = 1, m _F = ?1〉 and |1,0? sublevels with |1, +1〉 atoms. Finally we discuss the applicability of the method to sympathetic cooling of ¹³³Cs with ⁸⁷Rb.     

A new finite-dimensional pair coherent state studied by virtue of the entangled state representation and its statistical behavior

In this paper we construct a new type of finite-dimensional pair coherent states |ξ, q〉 as realizations of SU(2) Lie algebra. Using the technique of integration within an ordered product of operator, the nonorthogonality and completeness properties of the state |ξ, q〉 are investigated. Based on the Wigner operator in the entangled state |τ〉 representation, the Wigner function of |ξ, q〉 is obtained. The properties of |ξ, q〉 are discussed in terms of the negativity of its Wigner function. The tomogram of |ξ, q〉 is calculated with the aid of the Radon transform between the Wigner operator and the projection operator of the entangled state |η, κ₁, κ₂〉. In addition, using the entangled state |τ〉 representation of |ξ, q〉 to show that the states |ξ, q〉 are just a set of energy eigenstates of time-independent two coupled oscillators.     

一种新型的两态叠加多模叠加态光场的广义非线性等阶N次方Y压缩

本文根据量子力学中的线性叠加原理,构造了由多模(即q模)相干态的相反态|{-Z_j}〉_q及多模虚相干态的相反态|{-iZ_j}〉_q这两者的线性叠加所组成的一种新型的两态叠加多模叠加态光场|ψ_msc⁽²⁾〉_q.利用新近建立的多模辐射场的广义非线性等阶高阶压缩理论,研究了态|ψ_msc⁽²⁾〉_q的广义非线性等阶N次方Y压缩特性.结果发现,1)当压缩阶数N=2P且P=2m(m=1,2,3,…,…)时,态|ψ_msc⁽²⁾〉_q恒处于N-Y最小测不准态;2)当N=2P且P=2m’+1(m’=0,1,2,…,…)时,如果各模的初始相位φ_j、态间的初始相位差与各单模相干态光场的平均光子数之和∑_j=1^qR_j²即[(θ_pq^(R)-θ_nq^(I))-∑_j=1^qR_j²]满足一定的量子化条件,态|ψ_msc⁽²⁾〉_q可呈现周期性变化的、任意阶的等阶N次方Y压缩效应;3)当N为奇数时,态|ψ_msc⁽²⁾〉_q在一定条件下恒处于N-Y测不准态;4)态|ψ_msc⁽²⁾〉_q与文献21中的态|ψ⁽²⁾〉_q出现部分压缩简并现象,从而更进一步表明压缩简并现象的存在是有某种客观内在联系的.     

Local transformations of superpositions of entangled states

Suppose that we have two entangled states |?₁〉, |ψ₁〉 that cannot be converted to any of other two states |?₂〉, |ψ₂〉 by local operations and classical communication. We analyze the possibility of locally transforming a superposition of |?₁〉 and |ψ₁〉 into a superposition of |?₂〉 and |ψ₂〉. By using the Nielsen's theorem we find the necessary and sufficient conditions for this conversion to be performed.     

A high phase-space density mixture of 87Rb and 133Cs: towards ultracold heteronuclear molecules

We report the production of a high phase-space density mixture of ⁸⁷Rb and ¹³³Cs atoms in a levitated crossed optical dipole trap as the first step towards the creation of ultracold RbCs molecules via magneto-association. We present a simple and robust experimental setup designed for the sympathetic cooling of ¹³³Cs via interspecies elastic collisions with ⁸⁷Rb. Working with the |F = 1,m _F = +1〉 and the |3, +3〉 states of ⁸⁷Rb and ¹³³Cs respectively, we measure a high interspecies three-body inelastic collision rate ～10^?25?10^?26 cm⁶ ? s^?1 which hinders the sympathetic cooling. Nevertheless by careful tailoring of the evaporation we can produce phase-space densities near quantum degeneracy for both species simultaneously. In addition we report the observation of an interspecies Feshbach resonance at 181.7(5) G and demonstrate the creation of Cs₂ molecules via magneto-association on the 4(g)4 resonance at 19.8 G. These results represent important steps towards the creation of ultracold RbCs molecules in our apparatus.     

The model of the optical switching center and the polarization anomalies in absorption spectra of cupric oxide after fast particles irradiation

We consider the model of the optical switching center—a system with the following properties: it has two (or more) metastable states |1〉, |2〉, separated by a potential barrier U; it can switch from one state to another by absorbing the photons with energy ?ω∼U; the transition |1〉→|2〉 is allowed only for a certain light wave polarization p₁ and the transition |2〉→|1〉—for other polarization p₂; these polarizations p₁, p₂ are orthogonal. The optical properties of this system are studied and are found to exhibit unconventional polarization dependence. In particular, the absorption spectrum observed in natural (unpolarized) light can display new features, that are absent in the spectra, obtained in two independent polarizations. We discuss these results in connection with the (yet unexplained) experimental findings [N.N. Loshkareva, Yu.P. Sukhorukov, B.A. Gizhevskii, A.S. Moskvin, T.A. Belykh, S.V. Naumov, A.A. Samokhvalov, Phys. Solid State 40 (1998) 383], where the similar anomalous polarization dependence of the absorption spectra of cupric monoxide CuO after the fast particle bombardment is reported.     

Theoretical integrated intensities for the 2ν2 and 2ν2-ν2 bands of HCN and DCN

Dipole moment functions, both perpendicular and parallel to the molecular axis, are calculated from the SCF and MRD-CI results of a previous study for the normal ν₂ bending vibrations of HCN and DCN. Vibrationally averaged dipole moments and the infrared transition matrix elements are then obtained from the dipole moment functions and vibrational wave functions. MRD-CI results, with known experimental values in parentheses, for HCN are 〈0|μ|0〉 = ?2.954(?2.985) D, 〈1|μ|1〉 = ?2.915(±2.942) D, 〈0|μ|1〉 = 0.148(0.147) D, 〈0|μ|2〉 = ?0.027 D, 〈1|μ|2〉 = 0.210 D. Calculated absolute intensities at 1 atm and 0°C for the (02⁰0) ← (000), (02⁰0) ← (010), and (02²0) ← (010) bands of HCN are 25 (40 ± 10 as estimated from spectra), 8.5, and 17.0 atm^?1 cm^?2, respectively. Results for DCN are also reported.     

High-spin states in 24Mg and upper limits for particle spectroscopy of high spins by heavy-ion compound reactions

High-spin states in ²⁴Mg have been investigated by the reaction ¹⁰B(¹⁶O, d)²⁴Mg up to $\text{E}{}^1\text{≈ 24}\text{MeV}$. High-spin states with $\text{I ≧ 9}$ have been identified at $\text{E}{}^1\text{= 19.20, 20.26, 20.8, 21.6, 23.1,}\text{and}\text{23.5}\text{MeV}$. The 10⁺ yrast state in ²⁴Mg is probably located at 20.26 MeV. The upper limits with respect to spin and excitation energy of the applicability of heavy-ion compound reactions for particle spectroscopy of high-spin states are discussed. The main limitations result from the increasing continuum and from a decrease of the high-spin selectivity when the final spins approach the critical angular momentum for compound-nucleus formation. It will be shown that the difficulty in the analysis of the experiments arising from the decreasing probability of finding isolated yrast states at high excitation energies, i.e. from the increasing level density, can be overcome in such experiments. The decrease in the high-spin selectivity of the total cross section is compensated for spins up to J_max by the fact that the shape of the angular distributions depends on the final spin for states with I ～ J_max. This is caused by the decreasing alignment of the final nucleus with decreasing values of |I ? J_max| and can be used for high-spin spectroscopy.     

Population Dynamics of Excited Atoms in Dissipative Cavities

Population dynamics of excited atoms in dissipative cavities is investigated in this work. We present a method of controlling populations of excited atoms in dissipative cavities. For the initial state |ee〉_AB|00〉_ab, the repopulation of excited atoms can be obtained by using atom-cavity couplings and non-Markovian effects after the atomic excited energy decays to zero. For the initial state |gg〉_AB|11〉_ab, the two atoms can also be populated to the excited states from the initial ground states by using atom-cavity couplings and non-Markovian effects. And the stronger the atom-cavity coupling or the non-Markovian effect is, the larger the number of repopulation of excited atoms is. Particularly, when the atom-cavity coupling or the non-Markovian effect is very strong, the number of repopulation of excited atoms can be close to one in a short time and will tend to a steady value in a long time.     

Collision dynamics between stretched states of spin-2 87Rb Bose–Einstein condensates

We experimentally observed the time dependence of the spin populations of spin-2 ⁸⁷Rb Bose–Einstein condensates confined in an optical trap. The condensed atoms were initially populated in the stretched states |F=2,m _F =+2〉 and |F=2,m _F =?2〉 with several varieties of population imbalances. No spin-exchange collisions were observed in a weak magnetic field of 45 mG. The atom loss rate depended on the observed relative population of spin-states. We calculated the loss rate due to two-body inelastic collisions with the population imbalance using an experimentally estimated rate of 17.0(±1.9)×10^?14 cm³?s^?1 under the population balance. The calculations were in good agreement with the measurements. Our results show that the dependence of inelastic collisions on spin channels plays an important role in the time-evolution of spin populations.     

q-NONLINEAR CAVITY FIELD STATES GENERATED BY THE EXCITATIONS ON A q-COHERENT STATE

It is shown that photon-excitation state defined by |α,k〉_q=a^{{\dagger k}}_q|α〉_q (k=1,2,3...) up to a normalization constant can be produced in nonlinear processes in q-nonlinear cavities. The mathematical and quantum statistical properties of this state are studied in detail. We show that this state, along with the number states absented in it, forms a complete set. We also show by numerical method that this state exhibits quantum-squeezing for some values of |α| and always reveals quantum-antibunching effect.     

Rotation-inversion spectrum of methylaminoethane

Microwave spectral assignments have been made for the ground and several excited vibrational states of the normal and amino d₁ species of methylaminoethane. The inversion-rotation spectrum is consistent with a trans rotameric form with an amino inversion barrier of ～5.2 kcal mole^?1. The dipole moment of 8.88 ± 0.02 Debye has components |μ_a| = 0.00 ± 0.03, |μ_b| = 0.25 ± 0.03, and $\text{|〈 ± μ}{}_{\mathrm{c}}\text{? 〉| = 0.84 ± 0.01}$ Debye. The normal species N¹⁴ nuclear quadrupole coupling constants are (in MHz) 2.82 ± 0.09, 0.88 ± 0.13, and ?3.70 ± 0.09 for χ_aa, χ_bb, and χ_cc, respectively.     

使用时间切片离子速度成像技术研究CF2Cl2光解动力学

本文使用时间切片离子速度成像技术结合共振增强多光子电离技术研究了CF₂Cl₂分子在235 nm附近的光解动力学. 通过测量CF₂Cl₂分子在235 nm附近单光子解离产生的氯原子影像,直接得到了解离产物的速度分布和角分布. 激发态氯原子的速度分布包含高动能组分和低动能组分,分别对应³Q₀电子态的直接解离和由于内转换引起的基态预解离. 基态氯原子的速度分布也包含高动能组分和低动能组分,分别对应³Q₀与¹Q₁电子态的预解离和由于内转换引起的基态预解离. 自由基解离通道被确认,二次解离通道和三体解离通道被排除.     

两不同奇相干态组成的第Ⅲ种四态叠加多模叠加态光场的等阶N次方H压缩

本文构造了由两不同奇相干态组成的第种四态叠加多模叠加态光场|ψ_o⁽⁴⁾,Ⅲ〉_q.利用新近建立的多模压缩态理论,详细研究了态|ψ_o⁽⁴⁾,Ⅲ〉_q的广义非线性等阶N次方H压缩特性,结果发现由多模奇相干态|ψ,_o〉_q和多模虚奇相干态|ψ_i⁽²⁾,_o〉_q这两者线性叠加所组成的新量子光场态、|ψ_o⁽⁴⁾,Ⅲ〉_q是一种典型的非经典光场.1)当腔模总数q与压缩阶数N的乘积q·N为偶数、且qN=4m(m=1,2,3,…,…)时,态|ψ_o⁽⁴⁾,Ⅲ〉_q恒处于等阶N-H最小测不准态,与其它参量的取值无关;2)当qN为偶数、且qN=4m-2(m=1,2,3,…,…)时,(i)态|ψ_o⁽⁴⁾,Ⅲ〉_q可呈现等阶N次方H压缩效应,其两正交分量的压缩特性呈现周期性变化的、互补对称关系;(ii)态|ψ_o⁽⁴⁾,Ⅲ〉_q可呈现“半相干态”效应.3)当qN为奇数时,态|ψ_o⁽⁴⁾,Ⅲ〉_q始终不呈现等阶N次方H压缩效应,也不处于等阶N-H最小测不准态,但在一定条件下可呈现“半相干态”效应.     

Weitere Messungen zur Anisotropie der intermolekularen Wechselwirkung durch Streuung von Molekülen in definiertem Quantenzustand

Improved measurements of the ratio of scattering cross sections for various molecular rotational states are reported for scattering of TlF in rotational states ¦J, M〉=¦1, 0〉 and ¦1, 1〉, and CsF in rotational states ¦2, 0〉 and ¦2, 2〉 by rare gases. The results are interpreted in terms of an angle dependent attractive potentialV=?2ε(r _m /r) ⁶(1+q ₆ P ₂(cosΘ) in which the repulsive part of the interaction is neglected. The “high energy” approximation is used to calculate the cross section, which contains the velocity dependence and the state dependence as factors. The experiments show for all scattering partners with the exception of He and Ne, that the state dependence is velocity independent. In those cases this result provides a justification for the neglect of the repulsive potential term. The results for the anisotropy parameterq ₆, which to a good approximation depends only on properties of the moleculus, are:q ₆=0.23±0.01 for TlF,q ₆=0.28±0.02 for CsF.     

一种新型的两态叠加MSCS光场的广义非线性等阶N次方H压缩

本文利用新近建立的多模压缩态理论,详细研究了一种新型的两态叠加多模薛定谔猫态(即MSCS)光场|ψ⁽²⁾〉_q的广义非线性等阶N次方H压缩效应.结果发现:1态|ψ⁽²⁾〉_q是一种典型的非经典光场;当压缩阶数N与腔模总数q这两者之积为偶数,即qN=2p,并且p为奇数亦即p=2m’+1(m’=0,1,2,3,…,…)时,如果各模的初始相位和∑_j=1^qψ_j态间的初始相位差(θ_pq^(I)-θ_nq^(R))、各多模相干态光场的总的平均光子数∑_j=1^qR_j²等满足一定的量子化条件(或者当∑_j=1^qR_j²在总的平均光子数∑_j=1^qR_j²的一系列压缩区内连续取值时),态|ψ(2)〉q总可呈现出周期性变化的、任意阶的广义非线性等阶N次方H压缩效应.2态|ψ⁽²⁾〉_q的第一及第二两个正交分量,其压缩结果(亦即压缩程度和压缩深度)完全相同,但压缩条件不同;两者的等阶N次方H压缩效应呈现出周期性的互补关系.3与文献16相比,本文所研究的态|ψ⁽²⁾〉_q的等阶N次方H压缩效应是比其等阶N次方Y压缩效应更高阶的广义非线性等阶高阶压缩效应.