Chin. Phys. B Vol. 21, No. 6 (2012) 063701 A grooved planar ion trap design for scalable quantum information processing * Ji Wei-Bang(冀炜邦), Wan Jin-Yin(万金银), Cheng Hua-Dong(成华东), and Liu Liang(刘 亮) † Key Laboratory for Quantum Optics and Center for Cold Atom Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China (Received 16 September 2011; revised manuscript received 11 January 2012) We describe a new electrode design for a grooved surface–electrode ion trap, which is fabricated in printed-circuit- board technology with segmented electrodes. This design allows a laser beam to get through the central groove to avoid optical access blocking and laser scattering from the ion trap surface. The confining potentials are modeled both analytically and numerically. We optimize the radio frequency (rf) electrodes and dc electrodes to achieve the maximum trap depth for a given ion height above the trap electrodes. We also compare our design with the reality ion chip MI I for practical considerations. Comparison results show that our design is superior to MI I. This ion trap design may form the basis for large scale quantum computers or parallel quadrupole mass spectrometers. Keywords: ion trapping, microfabrication, quantum information PACS: 37.10.Ty, 85.40.–e, 03.67.–a DOI: 10.1088/1674-1056/21/6/063701 1. Introduction The ion trap is currently a major candidate for quantum information processing (QIP) and other quantum problems. [1-5] A practical challenge is the development of ion traps capable of storing and pre- cisely manipulating a substantial number of ions. [6] Many typical ion traps have demonstrated QIP oper- ations and shuttling of ions. For instance, some two- layer ion traps and three-layer ion traps have been designed for QIP. However, the complex structures of these ion traps are difficult to fabricate for scalable QIP in a large region. The surface–electrode or pla- nar designs [7,8] with arbitrary electrode arrangements can be easily fabricated and more easily integrated with on-chip control electronics and optics. [9] Chiaverini et al. [7] have proposed a planar ion trap geometry which is easy to scale up to many- zone traps and amenable to modern microfabrication techniques. All the electrodes lie in a plane and ions are trapped above the plane of the electrodes. [10] For the five-electrode planar trap design, [7] the center and outermost electrodes are held at radio frequency (rf) ground while the remaining two electrodes are biased with an rf potential for radial confinement. Either the center electrode or the outermost two electrodes can be segmented and dc biased for axial confinement. In a planar ion chip, the laser access cannot be blocked and laser scattering from ion trap surface should be avoided. The trapped ions must leave the surface of chip by some distance, which limits the ion chip’s further miniaturization. One of the methods used is to cut a groove between the rf electrodes. Thus the cooling or manipulating laser beams can get through the groove. For instance, the planar ion trap geom- etry is designed as a Sandia trap. [11] But the San- dia trap has a complicated structure, which is fabri- cated using an established semiconductor integrated circuit and micro-electro-mechanical-system (MEMS) microfabrication processes. The MEMS microfabrica- tion processes have long turn-around times and high costs. In this paper, we design a gold-on-silica planar trap geometry that is suitable for microfabrication. The ion trap design has a similar trap geometry to Chiaverini’s “five wire” design with a center groove, which is used to let laser beams through. The seg- mented planar ion trap is fabricated by using printed- circuit-board (PCB) technology. The advantages of PCB-traps are a fast and reliable fabrication and con- sequently a quick turn-around time, combined with low fabrication costs. [12] This paper is organized as follows: Section 2 pro- * Project supported by the National Natural Science Foundation of China (Grant No. 1097421). † Corresponding author. E-mail: liang.liu@siom.ac.cn © 2012 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn 063701-1