A Single Laser Cooled Trapped ^40Ca^＋ Ion in a Miniature Paul Trap

We have observed the phenomenon of phase transition of a few trapped ions in a miniature Paul trap. Judging from the quantum jump signa/s, a single laser-cooled trapped Ca^ ion has been realized. The ion temperature is estimated to be 22 mK. The result shows that the amplitude of ion micromotion is strongly dependent on the rf voltage.     

Experimental Improvement of Signal of a Single Laser-Cooled Trapped ^40Ca^＋ Ion

A single ^40Ca^＋ ion is loaded in a miniature Paul trap and the probability of directly loading a single ion is above 50%. The signal-to-noise ratio and the storage time for a single ion have been improved by minimizing the ion micromotion and locking a 397nm cooling laser to a Fabry-Perot interferometer and optogalvanic signal. From the fluorescence spectrum, the ion temperature is estimated to be about 5mK.     

Frequency-Shift of a Frequency Stabilized Laser Based on Zeeman Effect

We introduce a new method of frequency-shifting for a diode laser in laser cooling experiments, the method is based on the Zeeman egect of^87 Rb atoms. The laser frequency is stabilized by absorption spectrum line of atoms in magnetic field. We show that a magnetic field can be added up to 10^-2T. The corresponding frequency shift is 10^2 MHz and the response time is about 1ms. The large range of the frequency shift is suffcient for laser-cooling experiments.     

Control Method of Cooling a Charged Particle Pair in a Paul Trap

We propose a simple feedback cooling method, including both the component feedback and the velocity feedback,for cooling a charged particle pair in a Paul trap. It is found that the system can be cooled to periodic orbits;and if control intensity is strong, the system can be cooled to a one-periodic orbit, which is only in a horizontalplane. The result shows that the cooled system is also robust for noise.     

Dynamics of Two-Level Trapped Ion in a Standing Wave Laser in Noncommutative Space

We study the dynamics of a two-level trapped ion in a standing wave electromagnetic field in two-dimensional （2D） noncommutative spaces in the Lamb-Dicke regime under the rotating wave approximation. We obtain the explicit analytical expressions for the energy spectra, energy eigenstates, unitary time evolution operator, atomic inversion, and phonon number operators. The Rabi oscillations, the collapse, and revivals in the average atomic inversion and the average phonon number are explicitly shown to contain the information of the parameter of the space noncommutativity, which sheds light on proposing new schemes based on the dynamics of trapped ion to test the noncommutativity.     

Evaluation of Light Frequency Shift in a Caesium Beam Frequency Standard with Sharp Angle Incident Detecting Laser

Light frequency shift measured in a small optically pumped caesium beam frequency standard is reported and analysed. Two light sources, the diffused laser light scattered from the caesium beam tube parts and the fluorescence light from the beam atoms excited by the laser light, for the light frequency shift are discussed.     

Trapping State in a System of Single Three-level Trapped Ion Driven by External Fields

We investigate the interaction of a single three-level trapped ion with two laser beams. By applying a unitary transformation and a small rotating transformation, an exact solution to this quantum system is obtained without performing the Lamb-Dicke approximation, and the trapping state is observed.     

Optical Guiding of Trapped Atoms by a Blue-Detuned Hollow Laser Beam in the Horizontal Direction

Optical guiding of ^Rb atoms in a magneto-optical trap (MOT) by a blue-detuned horizontal hollow laser beam is demonstrated experimentally. The guiding efficiency and the velocity distribution of the guided atoms are found to have strong dependence on the detuning of the guiding laser. In particular, the optimum guiding occurs when the blue detuning of the hollow laser beam is approximately equal to the hyperfine structure splitting of the ^85Rb ground states, in good agreement with the theoretical analysis based on a three-level model.     

Effect of Incident Intensity on Films Growth in Pulsed Laser Deposition

Incident intensity, defined by the amount of particles deposited per pulse, is an important parameter in the film growth process of pulsed laser deposition （PLD）. Different from previous models, we investigate the irreversible and reversible growth processes by using a kinetic Monte Carlo method and find that island density and film morphology strongly depend on pulse intensity. At higher pulse intensities, lots of adatoms instantaneously diffuse on the substrate surface, and then nucleation easily occurs between the moving adatoms resulting in more smaller-size islands. In contrast, at the lower pulse intensities, nucleation event occurs preferentially between the single adatom and existing islands rather than forming new islands, and therefore the average island size becomes larger in this case. Additionally, our results show that substrate temperature plays an important role in film growth. In particular, it can determine the films shape and weaken the effect of pulse intensity on film growth at the lower temperatures by controlling the mobility rate of atoms. Our results can match the related theoretical and experimental results.     

Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard

A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave dock, like the 5071 Cs clock （from Hp to Agilent, now Symmetricom company）, both in accuracy and stability.     

Formation of High Concentration Cr^4＋ Ion in a PbWO4 Single Crystal

Cr^4＋ ion with tetrahedral symmetry, as found in single crystals of forsterite and YAG, have found application as saturable-absorbors, tunable solid state lasers etc. However, a high concentration of active Cr^4＋ species is difficult to obtain because it is rather unstable in these materials. It is expected that the continuing search for other ahernative hosts will lead to the emergence of new efficient Cr^4＋ -doped lasers.     

A Robust Scheme for Two－Qubit Grover Quantum Search Alogrithm Based on the Motional and Internal States of a Single Cold Trapped Ion

We propose a scheme to implement a two-qubit Grover quantum search algorithm. The novelty in the proposal is that the motional state is introduced into the computation and the internal state within a single cold trapped ion.The motional and internal states of the ion are manipulated as two qubits by the laser pulses to accomplish anexample of a Grover algorithm based on the two qubits. The composite laser pulses that are applied to implementthe Grover algorithm have been designed in detail. The issues concerning measurement and decoherence arediscussed.     

Carrier－Envelop Phase－Dependent Effect on Photoelectron Angular Distribution in Single－Cycle Laser Pulses ＊

Using a nonperturbative scattering theory, We study the photoelectron angular distributions (PADs) of Kr atoms irradiated by an infinite sequence of intense single-cycle pulses of circular polarization. We demonstrate the inversion asymmetry of PADs and the dependence of PADs on the carrier-envelop phase of the single-cycle pulses. The inversion asymmetry is caused by the interference between transition channels where the different channels are characterized by different combinations of absorbed-photon numbers in the ionization process. Our results provide a possible method to determine the value of carrier-envelop phase by the detected PADs.     

Surface Plasmon—Assisted Excitation of Atomic Visible Light Spectral Lines in the Impact of Highly Charged Ions 126Xeq＋ on Solid Surfaces

We measured the visible light spectral lines of sputtering atoms from solid surfaces orAl, Ti, Ni, Ta and Au which are impacted by 150 keV 126Xeq (6 ≤q ≤ 30). It is found that intensities of the light spectral lines are greatly and suddenly enhanced when the charge state of the ion is raised up to a critical value. If assuming that potential energy released from the incident ion due to capturing one electron is enough to excite a surface plasmon, we can estimate the critical charge states and obtain the results very well consistent with the measurements for the above-mentioned target materials. This means that a surface plasmon induced by one electron capture can enhance the excitation of atomic visible light spectral lines in the impact of a highly charged ion on a solid surface.