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2014, arXiv: Atomic Physics
We describe an ex-situ surface-cleaning procedure that is shown to reduce motional heating from ion-trap electrodes. This precleaning treatment, to be implemented immediately before the final assembly and vacuum processing of ion traps, removes surface contaminants remaining after the electrode-fabrication process. We incorporate a multi-angle ion-bombardment treatment intended to clean the electrode surfaces and interelectrode gaps of microfabricated traps. This procedure helps to minimize redeposition in the gaps between electrodes that can cause electrical shorts. We report heating rates in a stylus-type ion trap prepared in this way that are lower by one order of magnitude compared to a similar untreated stylus-type trap using the same experimental setup.
Review of Scientific Instruments, 2007
A description of the design and microfabrication of arrays of micrometer-scale cylindrical ion traps is offered. Electrical characterization and initial ion trapping experiments with a massively parallel array of 5 m internal radius ͑r 0 ͒ sized cylindrical ion traps ͑CITs͒ are also described. The ion trap, materials, and design are presented and shown to be critical in achieving minimal trapping potential while maintaining minimal power consumption. The ion traps, fabricated with metal electrodes, have inner radii of 1, 2, 5, and 10 m and range from 5 to 24 m in height. The electrical characteristics of packaged ion trap arrays were measured with a vector network analyzer. The testing focused on trapping toluene ͑C 7 H 8 ͒, mass 91, 92, or 93 amu, in the 5 m sized CITs. Ions were formed via electron impact ionization and were ejected by turning off the rf voltage applied to the ring electrode; a current signal was collected at this time. Optimum ionization and trapping conditions, such as a sufficient pseudopotential well and high ionization to ion loss rate ratio ͑as determined by simulation͒, proved to be difficult to establish due to the high device capacitance and the presence of exposed dielectric material in the trapping region. However, evidence was obtained suggesting the trapping of ions in 1%-15% of the traps in the array. These first tests on micrometer-scale CITs indicated the necessary materials and device design modifications for realizing ultrasmall and low power ion traps.
The Review of scientific instruments, 2013
An electroformed, three-dimensional stylus Paul trap was designed to confine a single atomic ion for use as a sensor to probe the electric-field noise of proximate surfaces. The trap was microfabricated with the UV-LIGA technique to reduce the distance of the ion from the surface of interest. We detail the fabrication process used to produce a 150 μm tall stylus trap with feature sizes of 40 μm. We confined single, laser-cooled, 25 Mg + ions with lifetimes greater than 2 h above the stylus trap in an ultra-high-vacuum environment. After cooling a motional mode of the ion at 4 MHz close to its ground state ( n = 0.34 ± 0.07), the heating rate of the trap was measured with Raman sideband spectroscopy to be 387 ± 15 quanta/s at an ion height of 62 μm above the stylus electrodes.
Journal of Analytical Chemistry, 2012
ABSTRACT Linear ion traps exhibit greater space charge capacity compared to conventional 3D Paul traps. Commercial ion traps are made of electrodes of hyperbolic shape. The present work investigates the possibilities of designing linear ion traps from simple electrodes, which are relatively cheap and handy for manufacturing and, at the same time, are comparable to commercial ion traps in resolving power of mass analysis. Using computer simulations and optimization of resonance ejection scan, it is shown linear ion traps can be made of electrodes of triangular cross-section with an ejection slit width of 16% of the trap inradius; the resolving power of the mass spectrum is more than 18000.
Nature Physics, 2006
he electromagnetic manipulation of isolated atoms has led to many advances in physics, from laser cooling 1 and Bose-Einstein condensation of cold gases 2 to the precise quantum control of individual atomic ions 3 . Work on miniaturizing electromagnetic traps to the micrometre scale promises even higher levels of control and reliability 4 . Compared with 'chip traps' for confining neutral atoms 5-7 , ion traps with similar dimensions and power dissipation offer much higher confinement forces and allow unparalleled control at the single-atom level. Moreover, ion microtraps are of great interest in the development of miniature mass-spectrometer arrays 8 , compact atomic clocks 9 and, most notably, large-scale quantum information processors 10,11 . Here we report the operation of a micrometre-scale ion trap, fabricated on a monolithic chip using semiconductor micro-electromechanical systems (MEMS) technology. We confine, laser cool and measure heating of a single 111 Cd + ion in an integrated radiofrequency trap etched from a doped gallium-arsenide heterostructure. Current ion-trap research is largely driven by the quest to build a quantum information processor , where quantum bits (qubits) of information are stored in individual atomic ions and connected through a common interaction with a phonon or photon field. The fundamental experimental requirements for quantum processing have all been met with ion traps, including demonstrations of multi-qubit quantum gates and small algorithms . Effort in this area is now focused on the scaling of ion traps to host much larger numbers of qubits, perhaps by shuttling individual atoms through a complex maze of ion-trap electrodes . The natural host for such a scalable system is an integrated ion-trap chip. We confine single 111 Cd + qubit ions in a radiofrequency linear ion trap 3,19 on a chip by applying a combination of static and oscillating electric potentials to integrated electrodes 20 . The electrodes are lithographically patterned from a monolithic semiconductor substrate, eliminating the need for manual assembly and alignment of individual electrodes. The scaling of this structure to hundreds or thousands of electrodes thus seems possible with existing semiconductor fabrication technology. Candidate linear ion-trap geometries amenable to microfabrication include (i) symmetric high-aspect-ratio multilayer structures with electrodes surrounding the ions 20 , and (ii) asymmetric planar structures with the ions residing above a
Anomalous heating of trapped atomic ions is a major obstacle to their use as quantum bits in a scalable quantum computer. The physical origin of this heating is not fully understood, but experimental evidence suggests that it is caused by electric-field noise emanating from the surface of the trap electrodes. In this study, we have investigated the role that adsorbates on the electrodes play by identifying contaminant overlayers, developing an in situ argon-ion beam cleaning procedure, and measuring ion heating rates before and after cleaning the trap electrodes' surfaces. We find a reduction of two orders of magnitude in heating rate after cleaning.
Physical Review A, 2010
We present a model as well as experimental results for a surface electrode radio-frequency Paul trap that has a circular electrode geometry well-suited for trapping of 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 200-1000µm for several hours under Doppler laser cooling, and use these to characterize the trap, finding good agreement with our model.
2010
Ion traps provide an excellent tool for controlling and observing the state of a single trapped ion. For this reason, ion traps have been proposed as a possible system for large-scale quantum computation. However, many obstacles must be overcome before quantum computing can become a reality. In particular, perturbations in the electric field due to noise and electrode charging must be reduced to increase coherence of the motional quantum state. Gold has been a popular choice in the past due to its inert properties; however, it is undesireable due its incompatibility with CMOS technology. This has led to increased research into alternative CMOS-compatible materials, such as aluminum and copper. This thesis presents measurements of electric field noise and light-induced charging in aluminum, copper, and gold surface electrode traps. In addition, the effect of oxide growth on field noise and electrode charging is explored by controlling the thickness of aluminum oxide on several aluminum traps. The measurements show that electric field noise can be suppressed in aluminum traps to approximately 10-18 V 2 cm-2 Hz-1, matching the noise exhibited in gold traps, and that copper traps exhibit noise within an order of magnitude of that in aluminum and gold. However, the natural oxide of aluminum poses many problems towards high-performance aluminum ion traps. The electric field noise is shown to be strongly dependent on the oxide thickness, increasing the noise by a factor of about 10 until saturation at a thickness of 13 nm. Charging of surface electrodes is shown to be highly dependent upon the material, but the model presented does not match the experimental data and is found to be incomplete. These results indicate that ion traps made out of CMOS-compatible materials can perform as well as more traditional traps fabricated from gold with respect to heating and charging as long as methods are developed for controlling oxide growth.
2013
Recent studies have shown a great potential of application of trapped ions in quantum information processing . Due to the stability of ion oscillation frequencies, ion traps also play a fundamental role in optical frequency standards . In turn, new fabrication methods enable the realization of compact integrated ion traps, which can simultaneously operate with multiple ions. Consequently, in order to effectively use a large number of trapped ions, new scalable and feasible designs are required.
The Review of scientific instruments, 2017
This paper presents the design and implementation of an in situ measurement setup for the capacitance of a five electrode Penning ion trap (PIT) facility at room temperature. For implementing a high Q resonant circuit for the detection of trapped electrons/ions in a PIT, the value of the capacitance of the trap assembly is of prime importance. A tunable Colpitts oscillator followed by a unity gain buffer and a low pass filter is designed and successfully implemented for a two-fold purpose: in situ measurement of the trap capacitance when the electric and magnetic fields are turned off and also providing RF power at the desired frequency to the PIT for exciting the trapped ions and subsequent detection. The setup is tested for the in situ measurement of trap capacitance at room temperature and the results are found to comply with those obtained from measurements using a high Q parallel resonant circuit setup driven by a standard RF signal generator. The Colpitts oscillator is also te...
Journal of Modern Optics, 2007
We present a number of alternative designs for Penning ion traps suitable for quantum information processing (QIP) applications with atomic ions. The first trap design is a simple array of long straight wires which allows easy optical access. A prototype of this trap has been built to trap Ca + and a simple electronic detection scheme has been employed to demonstrate the operation of the trap. Another trap design consists of a conducting plate with a hole in it situated above a continuous conducting plane. The final trap design is based on an array of pad electrodes. Although this trap design lacks the open geometry of the traps described above, the pad design may prove useful in a hybrid scheme in which information processing and qubit storage take place in different types of trap. The behaviour of the pad traps is simulated numerically and techniques for moving ions rapidly between traps are discussed. Future experiments with these various designs are discussed. All of the designs lend themselves to the construction of multiple trap arrays, as required for scalable ion trap QIP.
Hyperfine Interactions, 2019
At Central Michigan University, we are developing a high-precision Penning trap mass spectrometer (CHIP-TRAP) for precise mass measurements with stable and long-lived isotopes. Ions will be produced using external ion sources and then transported to the Penning trap at low energy using electrostatic ion optics. Ion sources that will be utilized with CHIP-TRAP include a laser ablation ion source (LAS) that has already been commissioned, and a low current Penning ion trap (PIT) source that is currently being developed. The LAS enables ion production from solid targets via ablation and ionization with a high-powered laser pulse. The PIT source is a novel Penning ionization gauge (PIG) type source, consisting of a 0.55 T NdFeB ring magnet, cylindrical Penning trap, and low current thermal electron emitter that enables ion production via electron impact ionization of gaseous samples. For both ion sources, small bunches of ∼100-1000 ions can be produced from a minimal sample of source material. The ion bunches are then transported along the CHIP-TRAP beamline, where time-of-flight mass filtering can be performed before they are captured in the CHIP-TRAP Penning traps.
International Journal of Mass Spectrometry, 2011
Reduced power operation of a mass analyzer with minimum loss of spectral resolution and mass range is desirable in portable instruments. Miniaturizing quadrupole-based ion traps can be especially worthwhile since the RF amplitude necessary for mass analysis scales with the square of the analyzer dimensions. The performance of a miniature, stainless steel, rectilinear ion trap (RIT) with dimensions of 1.66 mm × 1.43 mm (x 0 and y 0 respectively) is characterized by sampling externally generated ions and performing mass analysis without benefit of differential pumping to simulate conditions in a miniature system. This system is capable of detecting analyte ions of up to m/z 1250 at operating voltages of 610 V 0-p (drive frequency of 1.105 MHz), and with spectral resolution on the order of 2 Th (FWHM) across the entire mass range. The ability to acquire structural information through tandem MS is also demonstrated.
Review of Scientific Instruments, 2009
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 hours. 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 $^{88}$Sr$^+$ 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 minutes.
Journal of Applied Physics, 2015
We report on the design and experimental characterization of a surface-electrode multipole ion trap. Individual microscopic sugar particles are confined in the trap. The trajectories of driven particle motion are compared with a theoretical model, both to verify qualitative predictions of the model and to measure the charge-to-mass ratio of the confined particle. The generation of harmonics of the driving frequency is observed as a key signature of the nonlinear nature of the trap. We remark on possible applications of our traps, including to mass spectrometry.
International Journal of Mass Spectrometry, 1999
A new ion trap is constructed of a cylindrical ring electrode and hyperbolic end caps. The premise is to determine the effect ring electrode geometry has on the operation of the ion trap. A model for the potential and electric field within the trap is developed. The model is used to show how adjusting the geometric parameters of the cell could be used to reduce the presence of higher order fields or optimize other desired properties. The stability diagram is mapped experimentally and using the standard definition for q z , the q eject was determined to be 0.76. A proposed modification for the definition of q z , which adjusts for the shape of the cylindrical ring electrode, results in a q eject of 0.93. The trap is shown to have a linear scanning relationship, resolved isolation and unit mass resolution. (Int J Mass Spectrom 190/191 (1999) 47-57)
Effective and efficient trapped ion transportation operations are important for many quantum information implementations. This paper presents an efficient shuttling protocol for the linear shuttling of ions in asymmetric surface trap geometries in which outer electrode is segmented to provide control over ion transportation from one trapping region to another trapping region. During the adiabatic shuttling operations, the maximum transportation speed of trapped ions depends on the secular frequencies of trapped ions during the process. This paper further express how adiabatic linear shuttling protocols can be implemented in optimised surface trap geometries. In order to make the shuttling process adiabatic, the important parameters that need to be taken into account, are also discussed.
Nature Physics, 2009
Small, controllable, highly accessible quantum systems can serve as probes at the single-quantum level to study a number of physical effects, for example in quantum optics or for electric-and magnetic-field sensing. The applicability of trapped atomic ions as probes is highly dependent on the measurement situation at hand and thus calls for specialized traps. Previous approaches for ion traps with enhanced optical access included traps consisting of a single ring electrode 1,2 or two opposing endcap electrodes 2,3 . Other possibilities are planar trap geometries, which have been investigated for Penning traps 4,5 and radiofrequency trap arrays 6-8 . By not having the electrodes lie in a common plane, the optical access can be substantially increased. Here, we report the fabrication and experimental characterization of a novel radiofrequency ion trap geometry. It has a relatively simple structure and provides largely unrestricted optical and physical access to the ion, of up to 96% of the total 4π solid angle in one of the three traps tested. The trap might find applications in quantum optics and field sensing. As a force sensor, we estimate sensitivity to forces smaller than 1 yN Hz −1/2 . The basic electrode geometry is shown in and is formed by two concentric cylinders over a ground plane. The design provides straightforward indexing and assembly of the trap electrodes, with large solid angle access to the ion. Four extra electrodes were placed on a circle between the grounded plane and the radiofrequency electrode to break the rotational symmetry of the radiofrequency pseudopotential about the vertical axis and to compensate for stray electric fields to minimize ion radiofrequency micromotion in the trap 9 .
Applied Physics B: Lasers and Optics, 2004
We describe a novel high aspect ratio radiofrequency linear ion trap geometry that is amenable to modern microfabrication techniques. The ion trap electrode structure consists of a pair of stacked conducting cantilevers resulting in confining fields that take the form of fringe fields from parallel plate capacitors. The confining potentials are modeled both analytically and numerically. This ion trap geometry may form the basis for large scale quantum computers or parallel quadrupole mass spectrometers.
Trapped ion transportation operations in the horizontal direction have been already demonstrated successfully by several researchers. In this paper, we propose a novel trap design for fast and adiabatic vertical shuttling of trapped ions. The novel planar surface electrode ion trap consists of a set of independently controlled small strip-electrodes of fixed widths. New trap geometry was modelled to support vertical shuttling protocols. Ion trajectory in the vertical direction from the surface of the trap was simulated for from ~40 height to ~100 . Trap-depth and secular frequencies were investigated during shuttling of ion with slow and fast shuttling protocols.
arXiv (Cornell University), 2022
Despite the progress in building sophisticated microfabricated ion traps, Paul traps employing needle electrodes retain their significance due to the simplicity of fabrication while producing high-quality systems suitable for quantum information processing, atomic clocks etc. For low noise operations such as minimizing 'excess micromotion', needles should be geometrically straight and aligned precisely with respect to each other. Self-terminated electrochemical etching, previously employed for fabricating ion trap needle electrodes employs a sensitive and time-consuming technique resulting in a low success rate of usable electrodes. Here we demonstrate an etching technique for quick fabrication of straight and symmetric needles with a high success rate and a simple apparatus with reduced sensitivity to alignment imperfections. The novelty of our technique comes from using a two-step approach employing turbulent etching for fast shaping and slow etching/polishing for subsequent surface finish and tip cleaning. Using this technique, needle electrodes for an ion-trap can be fabricated within a day, significantly reducing the setup time for a new apparatus. The needles fabricated via this technique have been used in our ion-trap to achieve trapping lifetimes of several months.
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