1,169 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
Handling robot constraints within a Set-Based Multi-Task Priority Inverse Kinematics Framework
Set-Based Multi-Task Priority is a recent framework to handle inverse
kinematics for redundant structures. Both equality tasks, i.e., control
objectives to be driven to a desired value, and set-bases tasks, i.e., control
objectives to be satisfied with a set/range of values can be addressed in a
rigorous manner within a priority framework. In addition, optimization tasks,
driven by the gradient of a proper function, may be considered as well, usually
as lower priority tasks. In this paper the proper design of the tasks, their
priority and the use of a Set-Based Multi-Task Priority framework is proposed
in order to handle several constraints simultaneously in real-time. It is shown
that safety related tasks such as, e.g., joint limits or kinematic singularity,
may be properly handled by consider them both at an higher priority as
set-based task and at a lower within a proper optimization functional.
Experimental results on a 7DOF Jaco$^2
On the manipulability of dual cooperative robots
The definition of manipulability ellipsoids for dual robot systems is given. A suitable kineto-static formulation for dual cooperative robots is adopted which allows for a global task space description of external and internal forces, and relative velocities. The well known concepts of force and velocity manipulability ellipsoids for a single robot are formally extended and the contributions of the two single robots to the cooperative system ellipsoids are illustrated. Duality properties are discussed. A practical case study is developed
Reduction of trapped ion anomalous heating by in situ surface plasma cleaning
Anomalous motional heating is a major obstacle to scalable quantum
information processing with trapped ions. While the source of this heating is
not yet understood, several previous studies suggest that surface contaminants
may be largely responsible. We demonstrate an improvement by a factor of four
in the room-temperature heating rate of a niobium surface electrode trap by in
situ plasma cleaning of the trap surface. This surface treatment was performed
with a simple homebuilt coil assembly and commercially-available matching
network and is considerably gentler than other treatments, such as ion milling
or laser cleaning, that have previously been shown to improve ion heating
rates. We do not see an improvement in the heating rate when the trap is
operated at cryogenic temperatures, pointing to a role of thermally-activated
surface contaminants in motional heating whose activity may freeze out at low
temperatures.Comment: 5 pages, 4 figure
Safety-related Tasks within the Set-Based Task-Priority Inverse Kinematics Framework
In this paper we present a framework that allows the motion control of a
robotic arm automatically handling different kinds of safety-related tasks. The
developed controller is based on a Task-Priority Inverse Kinematics algorithm
that allows the manipulator's motion while respecting constraints defined
either in the joint or in the operational space in the form of equality-based
or set-based tasks. This gives the possibility to define, among the others,
tasks as joint-limits, obstacle avoidance or limiting the workspace in the
operational space. Additionally, an algorithm for the real-time computation of
the minimum distance between the manipulator and other objects in the
environment using depth measurements has been implemented, effectively allowing
obstacle avoidance tasks. Experiments with a Jaco manipulator, operating in
an environment where an RGB-D sensor is used for the obstacles detection, show
the effectiveness of the developed system
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