A New Approach to Measurement of Heating Rate of Trapped Ions

We propose a new scheme to estimate the heating rate of trapped ions in thermal states. By applying a controlled-U gate between the internal and the motional states of one of the trapped ions, we could obtain the mean phonon number from the population of the internal state of the ion. The imperfection due to fluctuations of the relevant parameters in real experiments is considered and we anaiyze the experimental feasibility of our scheme with sophisticated ion trap techniques.     

Generation and Properties of Two-Mode Circular States

Two-mode circular states, which are superposition states from some two-mode coherent states, are studied theoretically. It is shown that under certain conditions two-mode circular states may exhibit nonclassical effects, such as sub-Poissonian statistics and intermode correlation. We propose schemes to generate two-mode circular states by the interaction of a trapped ion with traveling wave lasers.     

Entanglement and Phase-Covariant Cloning for Multiple Trapped Ions via Adiabatic Passage

We describe a scheme for the generation of W states and implementation of phase-covariant cloning for n trapped ions. The scheme does not use the vibational mode as the memory and works beyond the Lamb-Dicke regime. The procedure is robust against moderate fluctuations of experimental parameters by using adiabatic passage.     

Effects of transverse trapping on the ground state of a cigar-shaped two-component Bose-Einstein condensate

We derive the coupled nonpolynomial nonlinear Schro¨dinger equations for a two-component Bose-Einstein condensate in a quasi-one-dimension geometry and investigate the effects of a tightly transverse trapping on the ground state and the miscibility-immiscibility threshold. We find that the density profile of the matter wavepacket is remarkably dependent on the transverse width and the effective one-dimension nonlinear coupling strengths in miscible and immiscible regimes.     

Multi-ion Mach–Zehnder interferometer with artificial nonlinear interactions

We propose a method to implement a Mach-Zehnder interferometry based upon a string of trapped ions with artificial nonlinear interactions. By manipulating the coupling strength between two involved internal states of the ions, we could achieve the beam splitting/recombination with NOON states. Using current techniques for manipulating trapped ions, we discuss the experimental feasibility of our scheme and analyze some undesired uncertainty under realistic experimental environment.     

Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

In this paper an investigation into dust acoustic solitary waves(DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian(κ) distribution function(DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries(mKdV) equation using Reductive Perturbation Theory(RPT). Two types of solitary waves, fast and slow dust acoustic soliton(DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively(or positively) charged. The properties of DASs are also investigated numerically.     

Preparation of Squeezed State and Entanglement State Between Vibrational Motion of Trapped Ion and Light

Several schemes have been proposed to prepare two-mode squeezed state and entanglement state between motional states of a single trapped ion and light. Preparation of two-mode squeezed state is based on interaction of a trapped ion located in light cavity with cavity field. Preparation of entanglement state is based on interaction of a trapped ion located in light cavity with cavity field and a traveling wave light field.     

Ni2O3掺杂对新固相源顶部籽晶熔渗生长法制备单畴GdBCO超导块材超导性能的影响

本文通过在新固相源中添加Ni₂O₃的方法, 采用顶部籽晶熔渗生长工艺(TSIG)制备出组分为(1-x) (Gd₂O₃+1.2BaCuO₂)+x Ni₂O₃、直径为20 mm的单畴GdBCO 超导块材(其中x = 0, 0.02, 0.06, 0.10, 0.14, 0.18, 0.30, 0.50 wt%), 并研究了Ni₂O₃的掺杂量x对样品的表面生长形貌、微观结构、临界温度T_c、磁悬浮力以及俘获磁通密度的影响. 研究结果表明, 当Ni₂O₃的掺杂量x在0–0.50 wt%的范围内时, 均可制备出单畴性良好的样品, 且Ni₂O₃的掺杂对样品中Gd211粒子的分布和粒径没有明显的影响. 在Ni₂O₃的掺杂量x从0增加到0.50 wt%的过程中, 样品的临界温度T_c呈现下降的趋势, 从x=0时的92.5 K下降到x=0.50 wt%时的86.5 K, 这是由于Ni^{3 +}替代GdBCO晶体中Cu^{2 +}所致; 样品磁悬浮力和俘获磁通密度均呈现先增大后减小的变化规律, x=0.14 wt%时, 磁悬浮力达到最大值34.2 N, x=0.10 wt%时, 俘获磁通密度达到最大值0.354 T. 样品磁悬浮力和俘获磁通密度的变化规律与Ni₂O₃的掺杂量x有密切关系, 只有当掺杂量x合适时, Ni³⁺对Cu^{2 +}的替代既不会造成T_c的明显下降, 但又能产生适量的Ni^{3 +}/Cu²⁺ 晶格畸变, 从而达到提高样品磁通钉扎能力和超导性能的效果.     

An Analytical Approach to the Turbulence-Relaxed State in Tokamak Plasmas

Starting from the continuity, temperature, and motion equations of the trapped electron fluid in generaltokamak magnetic field with positive or reversed shear and the definition of Lagrangian invariant, dL / dt = ( t u. )L =0, where u is convective velocity, the trapped electron dynamics is considered in the following two assumptions: (i) theturbulence is low frequency electrostatic, and (ii) L is a functional only of the density n, temperature T, and magneticfield B, and the effect of perturbation potential φ is included in the convective velocity u, i.e., u is a functional of n,T, B, and φ. The Lagrangian invariant hidden in the trapped electron dynamics is strictly found: L= ln[(n/B)c1(T/B2/3)c2], where c1 and c2 are dimensionless changeable parameters and c1 ∝ c2. From this Lagrangian invariant thewhich, in the limit of large aspect ratio, reduce to n(r)q(r) = const. and T3/2(r)q(r) = const., respectively. The lattertwo scaling laws are compared with existent experimental results, being in good agreement.     

Closed Trapped Surfaces in Cosmology

The existence of closed trapped surfaces need not imply a cosmological singularity when the spatial hypersurfaces are compact. This is illustrated by a variety of examples, in particular de Sitter spacetime admits many closed trapped surfaces and obeys the null convergence condition but is non-singular in the k = +1 frame.     

Loss estimation of electrostatically trapped ND3 molecules

Losses of electrostatically trapped molecules are caused by the Majorana transition or the inelastic collisions between trapped molecules. The loss rate of electrostatically trapped ND₃ molecules in the (J=1,K=1,M=1, A) state was estimated: ND₃ molecules in this state have actually been trapped. When trapping cold molecules, using ¹⁵ND₃ molecules (fermion) with a minimum electric field higher than 10 kV/cm yields high stability.     

An Analytical APproach to the Turbulence—Relaxed State in Tokamak Plasmas

Starting from the continuity, temperature, and motion equations of the trapped electron fluid in general tokamak magnetic field with positive or reversed shear and the definition of Lagrangian invariant, dL/dt≡(\partial_t+ u•▽)L=0, where u is convective velocity, the trapped electron dynamics is considered in the following two assumptions: (i) the turbulence is low frequency electrostatic, and (ii) L is a functional only of the density n, temperature T, and magnetic field B, and the effect of perturbation potential φ is included in the convective velocity u, i.e., u is a functional of n, T, B, and φ. The Lagrangian invariant hidden in the trapped electron dynamics is strictly found: L=ln[(n/B)^c₁(T/B^2/3)^c₂], where c₁ and c₂ are dimensionless changeable parameters and c₁∝c₂. From this Lagrangian invariant the turbulent particle and electron thermal transport scaling laws are derived: 〈n>_ψq(ψ)=const. and 〈T^3/2>_ψq(ψ)=const., which, in the limit of large aspect ratio, reduce to n(r)q(r)=const. and T^3/2(r)q(r)=const., respectively. The latter two scaling laws are compared with existent experimental results, being in good agreement.     

Luminescence of [Be] centre in MgO:Be

Doping of MgO single crystals with Be results in the formation of numerous Be-containing paramagnetic centres, easily detectable by EPR, and creates an intensive luminescence band at 6.2 eV, observable at T<200 K, and gives rise to new thermoluminescence peaks at 147 and 190 K. A paramagnetic centre with a rhombic symmetry that decays at 160 K was identified as a [Be]⁺ (i.e. O⁻–Be²⁺) centre—a hole trapped by O²⁻ lattice ion near a Be²⁺ perturbing defect. The luminescence excitation and isochronal annealing studies led to the conclusion that the 6.2 eV luminescence arises at the radiative decay of electron excitations near Be²⁺. These excitations can be created at the recombination of electrons with the holes localised in the [Be]⁺ centres, at the recombination of holes with the electrons trapped in the Be¹⁺ centre or at a direct excitation of oxygen near the Be²⁺ ion.     

Squeezing Properties of the Ion Traps

With time and space transformation, we first solve the Schrodinger equation of the time-dependent harmonic oscillator (TDHO) system. The properties of the squeezing in the case of ω(t) =√U + VcosΩt, i.e., the Paul trap and ω(t) = ω₀ + ω₁secλt, namely a stable frequency interfered by a single-pulsing-type disturbance, are investigated by using function series expansion. Results in the former case are compared with the numerical calculations carried out before. It is found that the condition related to the most strong squeezing is the direct result of our method, not any approximation is needed. Solutions of the latter one are valuable for the study of the ion trap, where different cases are studied in detail. Finally we made a discussion for the measurement and observation of a trapped ion by using squeezing properties.     

稀土掺杂碱土金属硫化物晶体中的载流子俘获中心

研究了典型红外激励发光材料XS:Ra,Sm(X=Sr,Ca;Ra=Ce,Eu)的激励发光过程中电子与空穴的俘获中心及其转移过程,通过激发前后的红外吸收光谱的差异及吸收差与光激励谱的细微结构说明,电子俘获中心并不是Sm³⁺离子,但与Sm³⁺离子处于相邻的空间位置关系,Sm³⁺离子在载流子俘获与复合的过程中也没有发生价态或数量的变化,进一步的EPR谱研究表明Eu²⁺离子的价态在激发前后也没有发生变化。与共价性强的Ⅲ-Ⅴ族半导体晶体不同的是,在这类离子性较强的晶体中,载流子被杂质所引起的晶格缺陷而非杂质本身俘获。在多种发光中心的情况下,不同的激发波长可以使空穴束缚在不同的发光中心附近,随后产生不同的光激励发光。     

Precision measurement and compensation of optical stark shifts for an ion-trap quantum processor

Using optical Ramsey interferometry, we precisely measure the laser-induced ac-Stark shift on the S(1/2)-D(5/2) "quantum bit" transition near 729 nm in a single trapped 40Ca+ ion. We cancel this shift using an additional laser field. This technique is of particular importance for the implementation of quantum information processing with cold trapped ions. As a simple application we measure the atomic phase evolution during a n x 2 pi rotation of the quantum bit.     

Energy Fluctuation of Ideal Fermi Gas Trapped under Generic Power Law Potential U=Σ_(i=1)~d c_i|x_i/a_i|~(n_i) in d Dimensions

Energy fluctuation of ideal Fermi gas trapped under generic power law potential U=Σ_(i=1)~d c_i|x_i/a_i|~(n_i) has been calculated in arbitrary dimensions.Energy fluctuation is scrutinized further in the degenerate limit μK_B T with the help of Sommerfeld expansion.The dependence of energy fluctuation on dimensionality and power law potential is studied in detail.Most importantly our general result can not only exactly reproduce the recently published result regarding free and harmonically trapped ideal Fermi gas in d =3 but also can describe the outcome for any power law potential in arbitrary dimension.     

Harmonically trapped ideal quantum gases

We solve the problem of a Bose or Fermi gas in d-dimensions trapped by δ ⩽ d mutually perpendicular harmonic oscillator potentials. From the grand potential we derive their thermodynamic functions (internal energy, specific heat, etc.) as well as a generalized density of states. The Bose gas exhibits Bose-Einstein condensation at a nonzero critical temperature T _c if and only if d + δ > 2, along with a jump in the specific heat at T _c if and only if d + δ > 4. Specific heats for both gas types precisely coincide as functions of temperature when d + δ = 2. The trapped system behaves like an ideal free quantum gas in d + δ dimensions. For δ = 0 we recover all known thermodynamic properties of ideal quantum gases in d dimensions, while in 3D for δ = 1, 2 and 3 one simulates behavior reminiscent of quantum wells, wires anddots, respectively. Good agreement is found between experimental critical temperatures for the trapped boson gases ₃₇ ⁸⁷Rb, ₃ ⁷Li, ₃₇ ⁸⁵Rb, ₂ ⁴He, ₁₉ ⁴¹K and the known theoretical expression which is a special case for d = δ = 3, but only moderate agreement for ₁₁ ²⁷Na and ₁ ¹H. Received 17 July 2002 / Received in final form 14 October 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: mdgg@hp.fciencias.unam.mx     

Virial Coefficients from Unified Statistical Thermodynamics of Quantum Gases Trapped under Generic Power Law Potential in d Dimension and Equivalence of Quantum Gases

From the unified statistical thermodynamics of quantum gases, the virial coefficients of ideal Bose and Fermi gases, trapped under generic power law potential are derived systematically. From the general result of virial coefficients, one can produce the known results in d=3 and d=2. But more importantly we found that, the virial coefficients of Bose and Fermi gases become identical (except the second virial coefficient, where the sign is different) when the gases are trapped under harmonic potential in d=1. This result suggests the equivalence between Bose and Fermi gases established in d=1 (J. Stat. Phys. DOI 10.1007/s10955-015-1344-4). Also, it is found that the virial coefficients of two-dimensional free Bose (Fermi) gas are equal to the virial coefficients of one-dimensional harmonically trapped Bose (Fermi) gas.     

Structure and magnetism of iron-sulfur clusters in proteins

Iron-sulfur clusters are mixed-valence systems exhibiting both localized and delocalized valence states. We discuss here spin-coupling models for two types of oxidized [3Fe-4S] clusters with localized Fe³⁺ valence states; a Heisenberg Hamiltonian with isotropic antiferromagnetic exchange fits the data well. Reduced [3Fe-4S] clusters, on the other hand, contain a trapped Fe³⁺ site and a delocalized Fe³⁺-Fe²⁺ pair. The pair has spin S₁₂=9/2 (formally ferromagnetic coupling) and is antiferromagnetically coupled to the Fe³⁺ S₃=5/2 spin to yield a system spin S=2. We discuss also recent results for [4Fe-4S] clusters such as [3Fe-4S]→[4Fe-4S] conversions, incorporation of other metals into the iron-sulfur core, and the observation of novel spin states.