The Experts below are selected from a list of 17289 Experts worldwide ranked by ideXlab platform
D Leibfried - One of the best experts on this subject based on the ideXlab platform.
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optimal Surface Electrode trap lattices for quantum simulation with trapped ions
Physical Review Letters, 2009Co-Authors: Roman Schmied, J.h. Wesenberg, D LeibfriedAbstract:Trapped ions offer long internal state (spin) coherence times and strong interparticle interactions mediated by the Coulomb force. This makes them interesting candidates for quantum simulation of coupled lattices. To this end, it is desirable to be able to trap ions in arbitrary conformations with precisely controlled local potentials. We provide a general method for optimizing periodic planar radio-frequency Electrodes for generating ion trapping potentials with specified trap locations and curvatures above the Electrode plane. A linear-programming algorithm guarantees globally optimal Electrode shapes that require only a single radio-frequency voltage source for operation. The optimization method produces final Electrode shapes that are smooth and exhibit low fragmentation. Such characteristics are desirable for practical fabrication of Surface-Electrode trap lattices.
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microfabricated Surface Electrode ion trap for scalable quantum information processing
Physical Review Letters, 2006Co-Authors: S Seidelin, J.h. Wesenberg, D Leibfried, J Chiaverini, R B Blakestad, J Britton, R Reichle, J J Bollinger, R J Epstein, D B HumeAbstract:Individual laser-cooled {sup 24}Mg{sup +} ions are confined in a linear Paul trap with a novel geometry where gold Electrodes are located in a single plane and the ions are trapped 40 {mu}m above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.
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Surface Electrode architecture for ion trap quantum information processing
Quantum Information & Computation, 2005Co-Authors: J Chiaverini, D Leibfried, R B Blakestad, J Britton, J D Jost, C Langer, Roee Ozeri, D J WinelandAbstract:We investigate a Surface-mounted Electrode geometry for miniature linear radio frequencyPaul ion traps. The Electrodes reside in a single plane on a substrate, and the pseudopotentialminimum of the trap is located above the substrate at a distance on the orderof the Electrodes' lateral extent or separation. This architecture provides the possibilityto apply standard microfabrication principles to the construction of multiplexed iontraps, which may be of particular importance in light of recent proposals for large-scalequantum computation based on individual trapped ions.
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Surface Electrode architecture for ion trap quantum information processing
arXiv: Quantum Physics, 2005Co-Authors: J Chiaverini, D Leibfried, R B Blakestad, J Britton, J D Jost, C Langer, Roee Ozeri, D J WinelandAbstract:We investigate a Surface-mounted Electrode geometry for miniature linear radio frequency Paul ion traps. The Electrodes reside in a single plane on a substrate, and the pseudopotential minimum of the trap is located above the substrate at a distance on order of the Electrodes' lateral extent or separation. This architecture provides the possibility to apply standard microfabrication principles to the construction of multiplexed ion traps, which may be of particular importance in light of recent proposals for large-scale quantum computation based on individual trapped ions.
Dejan B Popovic - One of the best experts on this subject based on the ideXlab platform.
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automatic determination of the optimal shape of a Surface Electrode selective stimulation
Journal of Neuroscience Methods, 2009Co-Authors: Dejan B Popovic, Mirjana PopovicAbstract:Abstract We present a method for automatic determination of the shape and position of the Surface Electrode for selective control of fingers extension and flexion by means of electrical stimulation. The multi-pad Electrodes used in the experiments comprised 24 pads (1 cm diameter) distributed over an area (7 cm × 10 cm) positioned over dorsal and volar aspects of the forearm. The four-channel stimulation system for grasping comprised also an oval reference Electrode over the carpal tunnel, and two oval Electrodes over the thenar and thumb extensor muscles. We measured seven angles: proximal inter-phalangeal and metacarpal phalangeal index and ring finger joint rotations, wrist extension/flexion and ulnar/radial rotation, and pronation/supination of the forearm. The optimal Electrode was determined as the combination of pads that led to fingers, wrist and forearm rotations being similar to the trajectories of healthy individuals when grasping. The similarity of trajectories was assessed by analyzing the aggregate error defined as the sum of squares of differences between the angles measured when stimulating the forearm in tetraplegics and the angles measured in healthy individuals. The aggregate errors were determined from measurements during sequential stimulation of each of the 24 pads. The analysis comprised hand opening and closing for palmar and lateral grasps. The time for determining the optimal Electrode was about 10 min. The optimal Electrodes had different branched shapes in each of the six tetraplegics; however, once determined they remained unchanged when tested on different days.
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multi field Surface Electrode for selective electrical stimulation
Artificial Organs, 2005Co-Authors: Ana Popovicbijelic, Dejan B Popovic, Mirjana Popovic, Goran Bijelic, Nikola Jorgovanovic, Dubravka BojanicAbstract:We designed a 24-field array and an on-line control box that selects which and how many of 24 fields will conduct electrical charge during functional electrical stimulation. The array was made using a conductive microfiber textile, silver two-component adhesive, and the conductive ink imprint on the polycarbonate. The control box comprised 24 switches that corresponded one-to-one to the fields on the array. Each field could be made con- ductive or nonconductive by simple pressing of the corre- sponding push-button type switch on the control box. We present here representative results of the selectivity of the new Electrode measured in three tetraplegic patients dur- ing functional electrical stimulation of the forearm. The task was to generate finger flexion and extension with min- imal interference of the wrist movement during lateral and palmar grasps. Therapists determined the appropriate pat- tern that lead to effective grasping, lasting on average 5 min per stimulation channel in the first session. This opti- mal conductive pattern (size and shape) provided effective finger flexion and extension with minimal wrist flexion/ extension and ulnar/radial deviations ( < 10 degrees). The optimal size and shape of the Electrode in all cases had a branched pattern. The selection of the optimal stimulation site was achieved without moving the Electrode. The size and shape were reproducible in the same subject from session to session, yet were different from subject to sub- ject. The optimal Electrode size and shape changed when subjects pronated and supinated their forearm. The control box includes a program that can dynamically change the number and sites of the conductive fields; hence, it is fea- sible to use this during functional movements. Subjects learned how to determine the optimal Electrode pattern; hence, these Electrodes could be effective for home usage. Key Words: Electrical stimulation—Electrode— Selective—Surface—Conductive fields.
Isaac L. Chuang - One of the best experts on this subject based on the ideXlab platform.
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Surface-Electrode ion trap with integrated light source
Applied Physics Letters, 2011Co-Authors: Peter F. Herskind, Isaac L. ChuangAbstract:An atomic ion is trapped at the tip of a single-mode optical fiber in a cryogenic (8 K) Surface-Electrode ion trap. The fiber serves as an integrated source of laser light, which drives the quadrupole qubit transition of S88r+. Through in situ translation of the nodal point of the trapping field, the Gaussian beam profile of the fiber output is imaged, and the fiber-ion displacement, in units of the mode waist at the ion, is optimized to within 0.13±0.10 of the mode center despite an initial offset of 3.30±0.10. Fiber-induced charging by 125 μW of 674 nm light is observed to be ∼10 V/m at an ion height of 670 μm, with charging and discharging time constants of 1.6±0.3 s and 4.7±0.6 s, respectively. This work is of importance to large-scale, ion-based quantum information processing, where optics integration in Surface-Electrode designs may be a crucial enabling technology.
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Microfabricated Surface trap for scalable ion-photon interfaces
CLEO: 2011 - Laser Science to Photonic Applications, 2011Co-Authors: Peter F. Herskind, Yufei Ge, Marko Cetina, Shannon X. Wang, Isaac L. ChuangAbstract:We demonstrate a Surface Electrode ion trap microfabricated on top of a dielectric mirror, with the ion 169 μm above the trap Surface. This represents a scalable approach to trapped ion quantum computing with photonic interconnects.
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Surface-Electrode point Paul trap
Physical Review A, 2010Co-Authors: Peter F. Herskind, Isaac L. ChuangAbstract:We present a model as well as experimental results for a Surface Electrode radiofrequency Paul trap that has a circular Electrode geometry well suited for trapping single ions and two-dimensional planar ion crystals. The trap design is compatible with microfabrication and offers a simple method by which the height of the trapped ions above the Surface may be changed in situ. We demonstrate trapping of single 88 Sr + ions over an ion height range of 200–1000 µm for several hours under Doppler laser cooling and use these to characterize the trap, finding good agreement with our model.
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Cryogenic ion trapping systems with Surface-Electrode traps
Review of Scientific Instruments, 2009Co-Authors: Paul Antohi, David Schuster, Gleb M. Akselrod, Jaroslaw Labaziewicz, Yufei Ge, Waseem Bakr, Isaac L. ChuangAbstract:We present two simple cryogenic rf ion trap systems in which cryogenic temperatures and ultra high vacuum pressures can be reached in as little as 12 h. The ion traps are operated either in a liquid helium bath cryostat or in a low vibration closed cycle cryostat. The fast turn around time and availability of buffer gas cooling made the systems ideal for testing Surface-Electrode ion traps. The vibration amplitude of the closed cycled cryostat was found to be below 106 nm. We evaluated the systems by loading Surface-Electrode ion traps with S88r+ ions using laser ablation, which is compatible with the cryogenic environment. Using Doppler cooling we observed small ion crystals in which optically resolved ions have a trapped lifetime over 2500 min.
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suppression of heating rates in cryogenic Surface Electrode ion traps
Physical Review Letters, 2008Co-Authors: Jaroslaw Labaziewicz, Paul Antohi, Yufei Ge, David R. Leibrandt, Kenneth R. Brown, Isaac L. ChuangAbstract:: Dense arrays of trapped ions provide one way of scaling up ion trap quantum information processing. However, miniaturization of ion traps is currently limited by sharply increasing motional state decoherence at sub-100 mum ion-Electrode distances. We characterize heating rates in cryogenically cooled Surface-Electrode traps, with characteristic sizes in the 75 to 150 mum range. Upon cooling to 6 K, the measured rates are suppressed by 7 orders of magnitude, 2 orders of magnitude below previously published data of similarly sized traps operated at room temperature. The observed noise depends strongly on the fabrication process, which suggests further improvements are possible.
Mirjana Popovic - One of the best experts on this subject based on the ideXlab platform.
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automatic determination of the optimal shape of a Surface Electrode selective stimulation
Journal of Neuroscience Methods, 2009Co-Authors: Dejan B Popovic, Mirjana PopovicAbstract:Abstract We present a method for automatic determination of the shape and position of the Surface Electrode for selective control of fingers extension and flexion by means of electrical stimulation. The multi-pad Electrodes used in the experiments comprised 24 pads (1 cm diameter) distributed over an area (7 cm × 10 cm) positioned over dorsal and volar aspects of the forearm. The four-channel stimulation system for grasping comprised also an oval reference Electrode over the carpal tunnel, and two oval Electrodes over the thenar and thumb extensor muscles. We measured seven angles: proximal inter-phalangeal and metacarpal phalangeal index and ring finger joint rotations, wrist extension/flexion and ulnar/radial rotation, and pronation/supination of the forearm. The optimal Electrode was determined as the combination of pads that led to fingers, wrist and forearm rotations being similar to the trajectories of healthy individuals when grasping. The similarity of trajectories was assessed by analyzing the aggregate error defined as the sum of squares of differences between the angles measured when stimulating the forearm in tetraplegics and the angles measured in healthy individuals. The aggregate errors were determined from measurements during sequential stimulation of each of the 24 pads. The analysis comprised hand opening and closing for palmar and lateral grasps. The time for determining the optimal Electrode was about 10 min. The optimal Electrodes had different branched shapes in each of the six tetraplegics; however, once determined they remained unchanged when tested on different days.
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multi field Surface Electrode for selective electrical stimulation
Artificial Organs, 2005Co-Authors: Ana Popovicbijelic, Dejan B Popovic, Mirjana Popovic, Goran Bijelic, Nikola Jorgovanovic, Dubravka BojanicAbstract:We designed a 24-field array and an on-line control box that selects which and how many of 24 fields will conduct electrical charge during functional electrical stimulation. The array was made using a conductive microfiber textile, silver two-component adhesive, and the conductive ink imprint on the polycarbonate. The control box comprised 24 switches that corresponded one-to-one to the fields on the array. Each field could be made con- ductive or nonconductive by simple pressing of the corre- sponding push-button type switch on the control box. We present here representative results of the selectivity of the new Electrode measured in three tetraplegic patients dur- ing functional electrical stimulation of the forearm. The task was to generate finger flexion and extension with min- imal interference of the wrist movement during lateral and palmar grasps. Therapists determined the appropriate pat- tern that lead to effective grasping, lasting on average 5 min per stimulation channel in the first session. This opti- mal conductive pattern (size and shape) provided effective finger flexion and extension with minimal wrist flexion/ extension and ulnar/radial deviations ( < 10 degrees). The optimal size and shape of the Electrode in all cases had a branched pattern. The selection of the optimal stimulation site was achieved without moving the Electrode. The size and shape were reproducible in the same subject from session to session, yet were different from subject to sub- ject. The optimal Electrode size and shape changed when subjects pronated and supinated their forearm. The control box includes a program that can dynamically change the number and sites of the conductive fields; hence, it is fea- sible to use this during functional movements. Subjects learned how to determine the optimal Electrode pattern; hence, these Electrodes could be effective for home usage. Key Words: Electrical stimulation—Electrode— Selective—Surface—Conductive fields.
Kenneth R. Brown - One of the best experts on this subject based on the ideXlab platform.
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demonstration of integrated microscale optics in Surface Electrode ion traps
New Journal of Physics, 2011Co-Authors: True J Merrill, Curtis Volin, David W Landgren, Jason M Amini, Kenneth Wright, Charles S Doret, Harley Hayden, Tyler N Killian, Daniel L Faircloth, Kenneth R. BrownAbstract:In ion trap quantum information processing, efficient fluorescence collection is critical for fast, high-fidelity qubit detection and ion–photon entanglement. The expected size of future many-ion processors requires scalable light collection systems. We report on the development and testing of a microfabricated Surface-Electrode ion trap with an integrated high-numerical aperture (NA) micromirror for fluorescence collection. When coupled to a low-NA lens, the optical system is inherently scalable to large arrays of mirrors in a single device. We demonstrate the stable trapping and transport of 40Ca+ ions over a 0.63 NA micromirror and observe a factor of 1.9 enhancement of photon collection compared to the planar region of the trap.
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suppression of heating rates in cryogenic Surface Electrode ion traps
Physical Review Letters, 2008Co-Authors: Jaroslaw Labaziewicz, Paul Antohi, Yufei Ge, David R. Leibrandt, Kenneth R. Brown, Isaac L. ChuangAbstract:: Dense arrays of trapped ions provide one way of scaling up ion trap quantum information processing. However, miniaturization of ion traps is currently limited by sharply increasing motional state decoherence at sub-100 mum ion-Electrode distances. We characterize heating rates in cryogenically cooled Surface-Electrode traps, with characteristic sizes in the 75 to 150 mum range. Upon cooling to 6 K, the measured rates are suppressed by 7 orders of magnitude, 2 orders of magnitude below previously published data of similarly sized traps operated at room temperature. The observed noise depends strongly on the fabrication process, which suggests further improvements are possible.
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Laser ablation loading of a Surface-Electrode ion trap
Physical Review A, 2007Co-Authors: David R. Leibrandt, Paul Antohi, Jaroslaw Labaziewicz, Waseem Bakr, Robert Clark, Kenneth R. Brown, Isaac L. ChuangAbstract:We demonstrate loading of {sup 88}Sr{sup +} ions by laser ablation 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 4 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 (> or approx. 500 meV)
