198 research outputs found
Loading of a surface-electrode ion trap from a remote, precooled source
We demonstrate loading of ions into a surface-electrode trap (SET) from a
remote, laser-cooled source of neutral atoms. We first cool and load
neutral Sr atoms into a magneto-optical trap from an oven that
has no line of sight with the SET. The cold atoms are then pushed with a
resonant laser into the trap region where they are subsequently photoionized
and trapped in an SET operated at a cryogenic temperature of 4.6 K. We present
studies of the loading process and show that our technique achieves ion loading
into a shallow (15 meV depth) trap at rates as high as 125 ions/s while
drastically reducing the amount of metal deposition on the trap surface as
compared with direct loading from a hot vapor. Furthermore, we note that due to
multiple stages of isotopic filtering in our loading process, this technique
has the potential for enhanced isotopic selectivity over other loading methods.
Rapid loading from a clean, isotopically pure, and precooled source may enable
scalable quantum information processing with trapped ions in large, low-depth
surface trap arrays that are not amenable to loading from a hot atomic beam
Bright Source of Cold Ions for Surface-Electrode Traps
We produce large numbers of low-energy ions by photoionization of
laser-cooled atoms inside a surface-electrode-based Paul trap. The
isotope-selective trap loading rate of Yb ions/s exceeds
that attained by photoionization (electron impact ionization) of an atomic beam
by four (six) orders of magnitude. Traps as shallow as 0.13 eV are easily
loaded with this technique. The ions are confined in the same spatial region as
the laser-cooled atoms, which will allow the experimental investigation of
interactions between cold ions and cold atoms or Bose-Einstein condensates.Comment: Paper submitted to PRL for review on 2/1/0
IK-FA, a new heuristic inverse kinematics solver using firefly algorithm
In this paper, a heuristic method based on Firefly Algorithm is proposed for inverse kinematics problems in articulated robotics. The proposal is called, IK-FA. Solving inverse kinematics, IK, consists in finding a set of joint-positions allowing a specific point of the system to achieve a target position. In IK-FA, the Fireflies positions are assumed to be a possible solution for joints elementary motions. For a robotic system with a known forward kinematic model, IK-Fireflies, is used to generate iteratively a set of joint motions, then the forward kinematic model of the system is used to compute the relative Cartesian positions of a specific end-segment, and to compare it to the needed target position. This is a heuristic approach for solving inverse kinematics without computing the inverse model. IK-FA tends to minimize the distance to a target position, the fitness function could be established as the distance between the obtained forward positions and the desired one, it is subject to minimization. In this paper IK-FA is tested over a 3 links articulated planar system, the evaluation is based on statistical analysis of the convergence and the solution quality for 100 tests. The impact of key FA parameters is also investigated with a focus on the impact of the number of fireflies, the impact of the maximum iteration number and also the impact of (a, ß, ¿, d) parameters. For a given set of valuable parameters, the heuristic converges to a static fitness value within a fix maximum number of iterations. IK-FA has a fair convergence time, for the tested configuration, the average was about 2.3394 × 10-3 seconds with a position error fitness around 3.116 × 10-8 for 100 tests. The algorithm showed also evidence of robustness over the target position, since for all conducted tests with a random target position IK-FA achieved a solution with a position error lower or equal to 5.4722 × 10-9.Peer ReviewedPostprint (author's final draft
A microfabricated surface-electrode ion trap for scalable quantum information processing
We demonstrate confinement of individual atomic ions in a radio-frequency
Paul trap with a novel geometry where the electrodes are located in a single
plane and the ions confined above this plane. This device is realized with a
relatively simple fabrication procedure and has important implications for
quantum state manipulation and quantum information processing using large
numbers of ions. We confine laser-cooled Mg-24 ions approximately 40 micrometer
above planar gold electrodes. We measure the ions' motional frequencies and
compare them to simulations. From measurements of the escape time of ions from
the trap, we also determine a heating rate of approximately five motional
quanta per millisecond for a trap frequency of 5.3 MHz.Comment: 4 pages, 4 figure
Laser ablation loading of a surface-electrode ion trap
We demonstrate loading by laser ablation of Sr ions into a
mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed,
frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5
ns. An additional laser is not required to photoionize the ablated material.
The efficiency and lifetime of several candidate materials for the laser
ablation target are characterized by measuring the trapped ion fluorescence
signal for a number of consecutive loads. Additionally, laser ablation is used
to load traps with a trap depth (40 meV) below where electron impact ionization
loading is typically successful ( 500 meV).Comment: 4 pages, 4 figure
Long-lived qubit memory using atomic ions
We demonstrate experimentally a robust quantum memory using a
magnetic-field-independent hyperfine transition in 9Be+ atomic ion qubits at a
magnetic field B ~= 0.01194 T. We observe that the single physical qubit memory
coherence time is greater than 10 seconds, an improvement of approximately five
orders of magnitude from previous experiments with 9Be+. We also observe long
coherence times of decoherence-free subspace logical qubits comprising two
entangled physical qubits and discuss the merits of each type of qubit.Comment: 5 pages, 4 figure
Extra Dimensions at the Weak Scale and Deviations from Newtonian Gravity
We consider theories in which the Standard Model gauge fields propagate in
extra dimensions whose size is around the electroweak scale. The Standard Model
quarks and leptons may either be localized to a brane or propagate in the bulk.
This class of theories includes models of Scherk-Schwarz supersymmetry
breaking and universal extra dimensions. We consider the problem of stabilizing
the volume of the extra dimensions. We find that for a large class of
stabilization mechanisms the field which corresponds to fluctuations of the
volume remains light even after stabilization, and has a mass in the
eV range. In particular this is the case if stabilization does not involve
dynamics at scales larger than the cutoff of the higher dimensional Standard
Model, and if the effective theory below the compactification scale is four
dimensional. The mass of this field is protected against large radiative
corrections by the general covariance of the higher dimensional theory and by
the weakness of its couplings, which are Planck suppressed. Its couplings to
matter mediate forces whose strength is comparable to that of gravity and which
can give rise to potentially observable deviations from Newton's Law at
sub-millimeter distances. Current experiments investigating short distance
gravity can probe extra dimensions too small to be accessible to current
collider experiments. In particular for a single extra dimension stabilized by
the Casimir energy of the Standard Model fields compactification radii as small
as 5 inverse TeV are accessible to current sub-millimeter gravity experiments.Comment: Minor corrections, conclusions unchanged. References adde
Designing spin-spin interactions with one and two dimensional ion crystals in planar micro traps
We discuss the experimental feasibility of quantum simulation with trapped
ion crystals, using magnetic field gradients. We describe a micro structured
planar ion trap, which contains a central wire loop generating a strong
magnetic gradient of about 20 T/m in an ion crystal held about 160 \mu m above
the surface. On the theoretical side, we extend a proposal about spin-spin
interactions via magnetic gradient induced coupling (MAGIC) [Johanning, et al,
J. Phys. B: At. Mol. Opt. Phys. 42 (2009) 154009]. We describe aspects where
planar ion traps promise novel physics: Spin-spin coupling strengths of
transversal eigenmodes exhibit significant advantages over the coupling schemes
in longitudinal direction that have been previously investigated. With a chip
device and a magnetic field coil with small inductance, a resonant enhancement
of magnetic spin forces through the application of alternating magnetic field
gradients is proposed. Such resonantly enhanced spin-spin coupling may be used,
for instance, to create Schr\"odinger cat states. Finally we investigate
magnetic gradient interactions in two-dimensional ion crystals, and discuss
frustration effects in such two-dimensional arrangements.Comment: 20 pages, 13 figure
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