A grooved planar ion trap design for scalable quantum information processing

We describe a new electrode design for a grooved surface-electrode ion trap,which is fabricated in printed-circuitboard technology with segmented electrodes.This design allows a laser beam to get through the central groove to avoid optical access blocking and laser scattering from the ion trap surface.The confining potentials are modeled both analytically and numerically.We optimize the radio frequency(rf) electrodes and dc electrodes to achieve the maximum trap depth for a given ion height above the trap electrodes.We also compare our design with the reality ion chip MI I for practical considerations.Comparison results show that our design is superior to MI I.This ion trap design may form the basis for large scale quantum computers or parallel quadrupole mass spectrometers.     

Three-Dimensional Array for 40Ca+ Ion Trapping

We present a three-dimensional scalable linear ion trap scheme for ion trapping and discuss its applications for the optical frequency standard and scalable quantum information processing with its parallel strings of trapped 40Ca＋ ions. The geometry here contains nine equal-distance parallel rods driven by rf, which form trapping potentials for radial confinement and two end ring electrodes biased at a few volts for axial confinement. Its feasibility is calculated by using the finite element analysis method.     

Optimization of a quadrupole ion storage trap as a source for time-of-flight mass spectrometry

Designs of a quadrupole ion trap (QIT) as a source for time-of-flight (TOF) mass spectrometry are evaluated for mass resolution, ion trapping, and laser activation of trapped ions. Comparisons are made with the standard hyperbolic electrode ion trap geometry for TOF mass analysis in both linear and reflectron modes. A parallel-plate design for the QIT is found to give significantly improved TOF mass spectrometer performance. Effects of ion temperature, trapped ion cloud size, mass, and extraction field on mass resolution are investigated in detail by simulation of the TOF peak profiles. Mass resolution (m/Δm) values of several thousand are predicted even at room temperature with moderate extraction fields for the optimized design. The optimized design also allows larger radial ion collection size compared with the hyperbolic ion trap, without compromising the mass resolution. The proposed design of the QIT also improves the ion-laser interaction volume and photon collection efficiency for fluorescence measurements on trapped ions.     

An all-optical ion-loading technique for scalable microtrap architectures

An experimental demonstration of a novel all-optical technique for loading ion traps, which has particular application to microtrap architectures, is presented. The technique is based on photoionisation of an atomic beam created by pulsed laser ablation of a calcium target, and provides improved temporal control compared to traditional trap loading methods. Ion loading rates as high as 125 ions per second have so far been observed. Also described are observations of trap loading where Rydberg state atoms are photoionised by the ion Doppler cooling laser. PACS 32.80.Fb; 32.80.Dz; 39.10.+j; 52.38.Mf     

Characterization of a miniature Paul-Straubel trap

Frequency standard applications and ultra-high resolution spectroscopy of a confined single ion require traps of drastically reduced dimensions (about or below 1 mm). These small dimensions increase the sensitivity of the trapping behavior to imperfections in the trap geometry and to patch potentials. For the aim of the metrological laser interrogation of a single Ca⁺ ion, a miniature cylindrical ring trap was built. In order to optimize the laser cooling process and to reach strong binding conditions, the boundaries of the stability diagram and the zones of low confinement as well as the ion motion properties were characterized. Received 14 November 2000 and Received in final form 1st February 2001     

Microwave control electrodes for scalable,parallel, single-qubit operations in a surface-electrode ion trap

We propose a surface ion trap design incorporating microwave control electrodes for near-field single-qubit control. The electrodes are arranged so as to provide arbitrary frequency, amplitude and polarization control of the microwave field in one trap zone, whilst a similar set of electrodes is used to null the residual microwave field in a neighbouring zone. The geometry is chosen to reduce the residual field to the 0.5 % level without nulling fields; with nulling, the crosstalk may be kept close to the 0.01 % level for realistic microwave amplitude and phase drift. Using standard photolithography and electroplating techniques, we have fabricated a proof-of-principle electrode array with two trapping zones. We discuss requirements for the microwave drive system and prospects for scalability to a large 2-D trap array.     

Formation of ordered structures of charged macroparticles in a photoemission trap

The possibility of confining positively charged macroscopic dust particles in a unique photoemission trap was studied. The spatial distributions of the potentials for a cylindrical geometry of a phototrap were obtained (by the particles in a cell method) and the dynamics of the formation of ordered structures of dust particles in the potential field of the trap was studied (by the molecular-dynamics method). The dependence of the number of dust particles confined by a phototrap on the particle energies and sizes and the buffer-gas pressure were obtained.     

Surface Planar Ion Chip for Linear Radio-Frequency Paul Traps

We propose a surface planar ion chip which forms a linear radio frequency Paul ion trap. The electrodes reside in the two planes of a chip, and the trap axis is located above the chip surface. Its electric field and potential distribution are similar to the standard linear radio frequency Paul ion trap. This ion trap geometry may be greatly meaningful for quantum information processing.     

Dust particles in a thermophoretic trap in a plasma

The feasibility of confining dust particles in a plasma by thermophoretic forces was demonstrated. An extended dust structure in a positive glow discharge column was experimentally obtained at liquid nitrogen temperature. The dust structure was confined in an electrostatic-thermal trap, in which vertical stability was provided by the summed action of longitudinal electrostatic field and thermophoretic forces. Traps of this kind can be analyzed in terms of the general principles developed for confining particles in traps with the use of electric and magnetic multipole fields. We were able to change the shape and volume of the structure and even separate it into parts by varying temperature fields.     

Quantum transport in parallel magnetic fields: a realization of the Berry-Robnik symmetry phenomenon

We analyze the magnetoconductance of two-dimensional electron and hole gases subject to a parallel magnetic field. It is shown that, for confining potential wells which are symmetric with respect to spatial inversion, a temperature-dependent weak localization signal exists even in the presence of a magnetic field. Deviations from this symmetry lead to magnetoconductance profiles that contain information on both the geometry of the confining potential and characteristics of the disorder.     

Spectral characteristics of cold rubidium atoms in a dark magneto-optical trap

Spectral characteristics of rubidium atoms confined in a dark magneto-optical trap (DMOT) are measured, including probe absorption spectra and atom density as a function of the cooling and repumping laser frequencies. The trap can capture and cool more than 2.5 × 10⁸ rubidium atoms, confining them in a hyperfine state weakly perturbed by the laser beams used to form the trap. The optical density of the trapped atomic cloud approaches 9. A qualitative model of the DMOT operation is presented, based on the experimental results obtained.     

Heating rate and electrode charging measurements in a scalable, microfabricated, surface-electrode ion trap

We characterise the performance of a surface-electrode ion “chip” trap fabricated using established semiconductor integrated circuit and micro-electro-mechanical-system (MEMS) microfabrication processes, which are in principle scalable to much larger ion trap arrays, as proposed for implementing ion trap quantum information processing. We measure rf ion micromotion parallel and perpendicular to the plane of the trap electrodes, and find that on-package capacitors reduce this to ?10?nm in amplitude. We also measure ion trapping lifetime, charging effects due to laser light incident on the trap electrodes, and the heating rate for a single trapped ion. The performance of this trap is found to be comparable with others of the same size scale.     

A reciprocal magnetic trap for neutral atoms

A novel magnetic trap for confining ultracold neutral atoms in a ring is proposed. The magnetic trap is generated by a microfabricated ferromagnetic structure integrated on an “atom chip”. The structure is based on previously demonstrated fabrication techniques and is capable of creating tightly confining reciprocal traps with trap frequencies as large as 50 kHz. Also, the trap exhibits significantly smaller magnetic field inhomogeneities compared to other proposals for current-based reciprocal traps. The suitability of this trap for atom interferometry and the study of low dimensional ultracold systems is outlined.     

Dynamical density functional theory with hydrodynamic interactions and colloids in unstable traps

A density functional theory for colloidal dynamics is presented which includes hydrodynamic interactions between the colloidal particles. The theory is applied to the dynamics of colloidal particles in an optical trap which switches periodically in time from a stable to an unstable confining potential. In the absence of hydrodynamic interactions, the resulting density breathing mode exhibits huge single peaked oscillations in the trap center which become double peaked and damped by hydrodynamic interactions. The predicted dynamical density fields are in good agreement with Brownian dynamics computer simulations.     

A comment on the analogous confinement of a neutral particle to a quantum dot via noninertial effects

In this contribution, we discuss the nonrelativistic limit of the Dirac equation for a neutral particle with a permanent electric dipole moment interacting with external fields in a noninertial frame. We show a case where the geometry of the manifold can play the role of a hard-wall confining potential due to noninertial effects, and can yield bound states analogous to a confinement of the spin-half neutral particle interacting with external fields to a quantum dot described by a hard-wall confining potential [33].     

Long-term drifts of stray electric fields in a Paul trap

We investigate the evolution of quasi-static stray electric fields in a linear Paul trap over a period of several months. Depending on how these electric fields are initially induced, we observe very different timescales for the field drifts. Photo-induced electric fields decay on timescales of days. We interpret this as photo-electrically generated charges on insulating materials which decay via discharge currents. In contrast, stray fields due to the exposure of the ion trap to a beam of Ba atoms mainly exhibit slow dynamics on the order of months. We explain this observation as a consequence of a coating of the trap electrodes by the atomic beam. This may lead to contact potentials which can slowly drift over time due to atomic diffusion and chemical processes on the surface. In order not to perturb the field evolutions, we suppress the generation of additional charges and atomic coatings in the Paul trap during the measurements. For this, we shield the ion trap from ambient light and only allow the use of near-infrared lasers. Furthermore, we minimize the flux of atoms into the ion trap chamber. Long-term operation of our shielded trap led us to a regime of very low residual electric field drifts of less than 0.03 V/m per day.     

On noninertial effects inducing a confinement of a neutral particle to a hard-wall confining potential

In this contribution, we discuss the confinement of a nonrelativistic spin-half neutral particle to a hard-wall confining potential induced by noninertial effects. We show that the geometry of the manifold plays the role of a hard-wall confining potential and yields bound state solutions. We also consider a neutral particle with a permanent magnetic dipole moment interacting with a field configuration induced by noninertial effects, and discuss the behaviour of the induced fields and obtain energy levels for bound states.     

An optimized ion trap geometry to measure quadrupole shifts of ~(171)Yb~+ clocks

We propose a new ion-trap geometry to carry out accurate measurements of the quadrupole shifts in the ~(171)Yb ion.This trap will minimize the quadrupole shift due to the harmonic component of the confining potential by an order of magnitude.This will be useful to reduce the uncertainties in the clock frequency measurements of the 6s ~2S_(1/2)→4f~(13)6s~2 ~2F_(7/2)and 6s ~2S_(1/2)→5d~2D_(3/2) transitions,from which we can deduce the precise values of the quadrupole moments(0s) of the 4f~(13)6s~2 ~2F_(7/2) and 5d~2D_(3/2) states.Moreover,it may be able to affirm the validity of the measured 0 value of the4f~(13)6s~2~2F_(7/2) state,for which three independent theoretical studies defer almost by one order of magnitude from the measurement.We also calculate 0s using the relativistic coupled-cluster(RCC) method.We use these 0 values to estimate the quadrupole shift that can be measured in our proposed ion trap experiment.     

Semi-analytical model for quasi-double-layer surface electrode ion traps

To realize scale quantum processors,the surface-electrode ion trap is an effective scaling approach,including singlelayer,double-layer,and quasi-double-layer traps.To calculate critical trap parameters such as the trap center and trap depth,the finite element method(FEM) simulation was widely used,however,it is always time consuming.Moreover,the FEM simulation is also incapable of exhibiting the direct relationship between the geometry dimension and these parameters.To eliminate the problems above,House and Madsen et al.have respectively provided analytic models for single-layer traps and double-layer traps.In this paper,we propose a semi-analytical model for quasi-double-layer traps.This model can be applied to calculate the important parameters above of the ion trap in the trap design process.With this model,we can quickly and precisely find the optimum geometry design for trap electrodes in various cases.     

Surface-electrode Paul trap with optimized near-field microwave control

We describe the design of a microfabricated Paul trap with integrated microwave conductors for quantum simulation and entangling logic gates. We focus on an approach where near-field amplitude gradients of microwave fields from conductors in the trap structure induce the required spin-motional couplings. This necessitates a strong amplitude gradient of the microwave near-field at the position of the ions, while the field itself needs to be suppressed as much as possible. We introduce a single meander-like microwave conductor structure which provides the desired field configuration. We optimize its parameters through full-wave microwave numerical simulations of the near-fields. The microwave conductor is integrated with additional dc and rf electrodes to form the actual Paul trap. We discuss the influence of the additional electrodes on the field configuration. To be able to fine-tune the overlap of the Paul trap rf null with the microwave field minimum, our trap design allows relative tuning of trap rf electrode amplitudes. Our optimized geometry could achieve a ratio of sideband-to-carrier excitations comparable to experiments with focused laser beams.