Journal of Visualized Experiments

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Seokjun Hong, Minjae Lee, Yeong‐Dae Kwon, Dong‐il Cho, Taehyun Kim

Published Aug 17, 2017• 4 citations

Abstract

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 µm-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

DOI: 10.3791/56060-v

Related papers

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Seokjun Hong, Minjae Lee, Yeong-Dae Kwon +2 more

Journal of Visualized ExperimentsAug 17, 201718 citations

The development of microfabricated ion traps towards quantum information and simulation

Marcus Hughes

Trapped ions within Paul traps have shown to be a promising architecture in the realisation of a quantum information processor together with the ability of providing quantum simulations. Linear Paul traps have demonstrated long coherence times with ions being well isolated from the environment, single and multi-qubit gates and the high fidelity detection of states. The scalability to large number of qubits, incorporating all the previous achievements requires an array of linear ion traps. Microfabrication techniques allow for fabrication and micron level accuracy of the trap electrode dimensions through photolithography techniques. The first part of this thesis presents the experiential setup and trapping of Yb+ ions needed to test large ion trap arrays. This include vacuum systems that can host advanced symmetric and asymmetric ion traps with up to 90 static voltage control electrodes. Demonstration of a single trapped Yb+ ion within a two-layer macroscopic ion trap is presented. with an ion-electrode distance of 310(10) µm. The anomalous heating rate and spectral noise density of the trap was measured, a main form of decoherence within ion traps. The second half of this thesis presents the design and fabrication of multi-layer asymmetric ion traps. This allows for isolated electrodes that cannot be accessed via surface pathways, allowing for higher density of electrodes as well as creating novel trap designs that allow for the potential of quantum simulations to be demonstrated. These include two-dimensional lattices and ring trap designs in which the isolated electrodes provide more control in the ion position. For the microfabrication of these traps I present a novel high-aspect ratio electroplated electrode design that provides shielding of the dielectric layer. This provides a means to mitigate stray electric field due to charge build up on the dielectric surfaces. Electrical testing of the trap structures was performed to test bulk breakdown and surface flashover of the ion trap architectures. Results showed sufficient isolation between electrodes for both radio frequency and static breakdown. Surface flashover voltage measurements over the dielectric layer showed an improvement of more than double over previous results using a new fabrication technique. This will allow for more powerful ion trap chips needed for the next generation of microfabricated ion trap arrays for scalable quantum technologies.

Jun 16, 20130 citations

New scalable microfabrication method for surface ion traps and experimental results with trapped ions

Seokjun Hong, M. Lee, H. Cheon +4 more

This paper presents a new microfabrication method for surface ion traps and experimental results with trapped ions. Fabricating ion trap chips is a very formidable task because the top electrodes are vertically spaced more than 10 µm from the bottom electrodes with an indented dielectric layer in the middle. Previous ion traps were fabricated using TEOS timed etch or tungsten sacrificial etch techniques. This paper presents a new microfabrication method, using copper as a sacrificial material for an aluminum-oxide-aluminum ion trap structure. Using the developed method the overhang dimensions of the top aluminum electrodes can be accurately controlled. Fabricated ion trap chips are installed in a 1 × 10−11Torr vacuum environment for ion trapping experiments. Successful results in trapping strings of171Yb+and174Yb+ions as well as manipulating171Yb+ions for qubit operation are demonstrated.

IEEE International Conference on Micro Electro Mechanical Systems (MEMS)Jan 1, 20151 citation

Microfabricated Paul traps for levitating and shuttling of ions and charged particles

Hwanjit Rattanasonti

Trapped ions in Paul traps (radio frequency ion traps) are a promising candidate for the realization of a quantum computer. To date, experimental demonstrations of quantum computing and information processing with trapped ions have been limited to small numbers of quantum bits (qubits). The most prominent challenge to realise ion-trap quantum computation is to scale the system and control a large number of trapped ions coherently. Surface-electrode ion trap designs which are amenable to various microfabrication techniques offer a path to achieve this. In this work, design, fabrication and key operations of two types of surface-electrode ion traps, i.e. a Y-junction trap and a two-dimensional (2D) hexagonal lattice trap developed towards scaling ion-trap architectures, are presented. The steps involved in the fabrication of the ion-trap devices included photolithography, wet etch (hydrofluoric acid etch) and dry etch (deep reactive ion and inductively coupled plasma etching), and metal evaporation. The devices were fabricated on SOI substrates with different buried oxide thicknesses (i.e. 5 µm and 10 µm) and different metals for the trap electrodes (i.e. gold and aluminium). An extremely high-breakdown voltage up to 1 kV was measured in vacuum for the SOI-built test devices with a 10 µm-thick buried oxide formed by oxide film-to-oxide film bonding process. This is attributed to the deep V-shaped undercut profile of the buried oxide layer which resulted in a large breakdown path length, and so mitigating surface breakdown effects. Owing to the V-shaped undercut profile, the surface breakdown voltage was improved by 15% for the devices fabricated on SOI substrates with a 10 µm-thick buried oxide. In the first experiment, the demonstration of ytterbium (174Yb+) ion trapping in the 2D hexagonal lattice trap is achieved with a relatively long lifetime of a laser-cooled ion up to 90 minutes and ≤ 5 minutes without cooling in ultra-high vacuum system. The 2D lattice trap design allows for reliable trapping of 2D ion lattices, rudimentary shuttling between lattice sites and deterministic introducing of defects into the ion lattice. Based on all these abilities, such a 2D lattice trap with the predicted reduction of lattice spacing down to 32 µm can be configured as a versatile architecture for 2D quantum simulations with trapped ions. In the second experiment, microparticle trapping in the 2D lattice trap, performed in air, is achieved with the longest trapping lifetime of 60 minutes. Both gold and aluminium-coated electrodes also lead to comparable trapping performances. Furthermore, the in situ levitation of microparticles is successfully demonstrated at the maximum levitation height of 30 µm. This ability provides additional control on the trapping height which increases the overall functionality of the 2D lattice trap.

Jan 1, 20150 citations

Trapping and cooling of 174Yb+ ions in a microfabricated surface trap

Rachel Noek, Taehyun Kim, Emily Mount +3 more

Trapped atomic ions are the leading candidate to act as individual quantum bits in a large quantum information processing system. Ion traps can be conformed to a two-dimensional surface, which provides a way to increase the number of ions while maintaining the ability to move individual ions in a two-dimensional grid. However, surface traps tend to suffer from shallow trap depths and higher motional heating rates. In this work, we report the design, fabrication, and testing of a simple gold-on-fused-silica ion trap optimized for a deep trapping potential and stable motional modes. The desirable trap characteristics include long lifetime, fully-compensated micromotion, and high secular trap frequencies that were measured using a trapped and cooled 174 Yb + ion. This trap design can be integrated with an optical cavity to enhance the ion-photon coupling.

Journal of the Korean Physical SocietyAug 1, 20135 citations

Yb+ ion trapping and optimum planar trap geometries for scalable quantum technology

Altaf Hussain Nizamani

Trapped ions in linear Paul traps are largely isolated from interaction with the environment. This property of trapped ions make them a primary choice for quantum technology. \nOver the last decade, trapped atomic ions in linear radio frequency Paul traps have shown to be an important tool to implement quantum algorithms. The scalability of linear ion \ntraps is required to handle large numbers of qubits, in order to implement useful quantum computation. Advance micro-fabrication technology allows the realisation of scalable ion traps. Further developments of micro-trap designs, for the purpose of scalable quantum technology, requires inter-disciplinary investigations of ion traps. Micro-scale ion trap designs typically require a versatile experimental setup. The first part of this thesis describes such an experimental setup including a chip bracket that can host macroscopic ion traps as well as advanced symmetric and asymmetric ion trap chips with up to 90 control electrodes. The system provides versatile optical access for both type of traps and the vacuum chamber is designed in a way so the ion traps can be replaced within a short amount of time. To test the working of the setup, a macroscopic ion trap with an ion-electrode distance of 310±10 μm is used to trap ytterbium ions (Yb+). The trap is characterised by measuring the heating rate, (n•), and spectral noise density SE(ω). A \nphotoionisation technique is used to ionise the different isotopes of Yb in our trap. Isotope selective photoionisation requires exact measurements of 1So↔1P1 transition for the different Yb isotopes. A technique to measure these resonant frequencies is described. \nThis technique works by observing and aligning fluorescence spots and by using this technique, the 1So↔1P1 transition frequencies for stable isotopes of Yb were measured with an accuracy of 60 MHz. These new measured transition frequencies for stable Yb isotopes differ from previously published work by 660 MHz. Furthermore, this technique can also be used to obtain the transition frequencies at different laser-atomic beam angles, typical for non-perpendicular laser-atomic beam angles. The second part of this thesis discusses the optimisation of surface trap geometries as they are being used to implement scalable ion trap designs which consist of a large number of trapping zones. The trap depth in surface traps is low compared to symmetric traps of similar dimensions. How to optimise the trap geometry to achieve maximum trap depth for a given ion height above the trap electrodes, is discussed. Fast and adiabatic ion shuttling operations in one dimension as well as ion separation and recombination processes are important for many quantum information implementations. The maximum speed of separation of trapped ions for adiabatic shuttling operations depends on the secular frequencies, the trapped ion experiences in the process. It will be shown how such ion trap structures have to be designed for fast ion separation process and linear shuttling. Numerical results of adiabatic shuttling operations for trapped ions in such trap structures are also presented.

Aug 6, 20111 citation