Suppression of heating rates in cryogenic surface-electrode ion traps

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.     

Optimization of parameters of a surface-electrode ion trap and experimental study of influences of surface on ion lifetime

In this paper we report the optimal design and fabrication of a gold-on-silica linear segmented surface-electrode ion trap. By optimizing the thickness and width of the electrodes, we improved the trapping ability and trap scalability. By using some practical experimental operation methods, we successfully minimized the trap heating rate. Consequently, we could trap a string of up to 38 ions, and a zigzag structure with 24 ions, and transport two trapped ions to different zones. We also studied the influences of the ion chip surface on the ion lifetime. The excellent trapping ability and flexibility of operation of the planar ion trap shows that it has high feasibility for application in the development a practical quantum information processor or quantum simulator.     

Micro-optical realization of arrays of selectively addressable dipole traps: a scalable configuration for quantum computation with atomic qubits

We experimentally demonstrate novel structures for the realization of registers of atomic qubits: We trap neutral atoms in one- and two-dimensional arrays of far-detuned dipole traps obtained by focusing a red-detuned laser beam with a microfabricated array of microlenses. We are able to selectively address individual trap sites due to their large lateral separation of 125 microm. We initialize and read out different internal states for the individual sites. We also create two interleaved sets of trap arrays with adjustable separation, as required for many proposed implementations of quantum gate operations.     

Optimum electrode configurations for fast ion separation in microfabricated surface ion traps

For many quantum information implementations with trapped ions, effective shuttling operations are important. Here, we discuss the efficient separation and recombination of ions in surface ion trap geometries. The maximum speed of separation and recombination of trapped ions for adiabatic shuttling operations depends on the secular frequencies the trapped ion experiences in the process. Higher secular frequencies during the transportation processes can be achieved by optimising trap geometries. We show how two different arrangements of segmented static potential electrodes in surface ion traps can be optimised for fast ion separation or recombination processes. We also solve the equations of motion for the ion dynamics during the separation process and illustrate important considerations that need to be taken into account to make the process adiabatic.     

Combined ion and atom trap for low-temperature ion–atom physics

We report an experimental apparatus and technique which simultaneously traps ions and cold atoms with spatial overlap. Such an apparatus is motivated by the study of ion–atom processes at temperatures ranging from hot to ultra cold. This area is a largely unexplored domain of physics with cold trapped atoms. In this article we discuss the general design considerations for combining these two traps and present our experimental setup. The ion trap and atom trap are characterized independently of each other. The simultaneous operation of both is then described and experimental signatures of the effect of the ions and cold atoms on each other are presented. In conclusion, the use of such an instrument for several problems in physics and chemistry is briefly discussed.     

Ideal multipole ion traps from planar ring electrodes

We present designs for multipole ion traps based on a set of planar, annular, concentric electrodes which require only rf potentials to confine ions. We illustrate the desirable properties of the traps by considering a few simple cases of confined ions. We predict that mm-scale surface traps may have trap depths as high as tens of electron volts when parameters of a magnitude common in the field are chosen. Under similar conditions, micromotion amplitudes in a 2D ion crystal as low as tens of nanometers could be realized. Several example traps are studied, and the scaling of those properties with voltage, frequency, and trap scale, for small numbers of ions, is derived. Applications of these traps include quantum information science, frequency metrology, and cold ion–atom collisions.     

Ion-trap quantum information processing:experimental status

Atomic ions trapped in ultra-high vacuum form an especially well-understood and useful physical system for quantum information processing. They provide excellent shielding of quantum information from environmental noise, while strong, well-controlled laser interactions readily provide quantum logic gates. A number of basic quantum information protocols have been demonstrated with trapped ions. Much current work aims at the construction of large-scale ion-trap quantum computers using complex microfabricated trap arrays. Several groups are also actively pursuing quantum interfacing of trapped ions with photons.      

Ion-trap quantum information processing: Experimental status

Atomic ions trapped in ultra-high vacuum form an especially well-understood and useful physical system for quantum information processing. They provide excellent shielding of quantum information from environmental noise, while strong, well-controlled laser interactions readily provide quantum logic gates. A number of basic quantum information protocols have been demonstrated with trapped ions. Much current work aims at the construction of large-scale ion-trap quantum computers using complex microfabricated trap arrays. Several groups are also actively pursuing quantum interfacing of trapped ions with photons.     

Surface-electrode Paul trap with optimized near-field microwave control

We describe the design of a microfabricated Paul trap with integrated microwave conductors for quantum simulation and entangling logic gates. We focus on an approach where near-field amplitude gradients of microwave fields from conductors in the trap structure induce the required spin-motional couplings. This necessitates a strong amplitude gradient of the microwave near-field at the position of the ions, while the field itself needs to be suppressed as much as possible. We introduce a single meander-like microwave conductor structure which provides the desired field configuration. We optimize its parameters through full-wave microwave numerical simulations of the near-fields. The microwave conductor is integrated with additional dc and rf electrodes to form the actual Paul trap. We discuss the influence of the additional electrodes on the field configuration. To be able to fine-tune the overlap of the Paul trap rf null with the microwave field minimum, our trap design allows relative tuning of trap rf electrode amplitudes. Our optimized geometry could achieve a ratio of sideband-to-carrier excitations comparable to experiments with focused laser beams.     

基于有限元方法的离子俘获装置模拟计算

利用有限元程序ANSYS,开展潘宁离子俘获装置的电场模拟计算。基于电场数据,结合Runge_Kutta_Fehlberg方法进行潘宁装置在多种模式下的离子俘获过程模拟工作,得到了准确的离子俘获结果。并对实际条件下具有偏离理想情况电极分布的俘获装置进行了优化计算及电场分析,同样实现了离子俘获过程的准确模拟。有限元方法用于离子俘获装置的电场计算以及后续离子俘获过程模拟流程的建立,为类似的电势阱离子俘获装置建造运行提供有效的技术支持。     

Microfabricated surface ion trap on a high-finesse optical mirror

A novel approach to optics integration in ion traps is demonstrated based on a surface electrode ion trap that is microfabricated on top of a dielectric mirror. Additional optical losses due to fabrication are found to be as low as 80 ppm for light at 422 nm. The integrated mirror is used to demonstrate light collection from, and imaging of, a single Sr88(+) ion trapped 169±4 μm above the mirror.     

A reciprocal magnetic trap for neutral atoms

A novel magnetic trap for confining ultracold neutral atoms in a ring is proposed. The magnetic trap is generated by a microfabricated ferromagnetic structure integrated on an “atom chip”. The structure is based on previously demonstrated fabrication techniques and is capable of creating tightly confining reciprocal traps with trap frequencies as large as 50 kHz. Also, the trap exhibits significantly smaller magnetic field inhomogeneities compared to other proposals for current-based reciprocal traps. The suitability of this trap for atom interferometry and the study of low dimensional ultracold systems is outlined.     

Microfabricated surface-electrode ion trap for scalable quantum information processing

Individual laser-cooled 24Mg+ 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 microm 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.     

Imaging of trapped ions with a microfabricated optic for quantum information processing

Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4 μm and the field of view was 140±20 μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures.     

Semi-analytical model for quasi-double-layer surface electrode ion traps

To realize scale quantum processors,the surface-electrode ion trap is an effective scaling approach,including singlelayer,double-layer,and quasi-double-layer traps.To calculate critical trap parameters such as the trap center and trap depth,the finite element method(FEM) simulation was widely used,however,it is always time consuming.Moreover,the FEM simulation is also incapable of exhibiting the direct relationship between the geometry dimension and these parameters.To eliminate the problems above,House and Madsen et al.have respectively provided analytic models for single-layer traps and double-layer traps.In this paper,we propose a semi-analytical model for quasi-double-layer traps.This model can be applied to calculate the important parameters above of the ion trap in the trap design process.With this model,we can quickly and precisely find the optimum geometry design for trap electrodes in various cases.     

Towards the implanting of ions and positioning of nanoparticles with nm spatial resolution

Decreasing structure sizes in both conventional and quantum solid state devices require novel fabrication methods: we present a technology which allows to implant ions through a small hole in the tip of an atomic force microscope. This technique offers a maskless addressing of small structures using different projectiles at kinetic energies between 0.5 and 5.0 keV. Our method aims to implant single atomic ions, molecular ions or charged nanoparticles with nm resolution. We test the method by implanting N⁺ ions into diamond and generating nitrogen-vacancy color centers. The system is operated with a conventional ion gun. However, in future we will employ an ion trap as a deterministic source of cold single ions. PACS 03.67.-a; 29.25.Ni; 61.72.Ji; 81.16.Rf; 85.40.Ry     

Planar ion chip design for scalable quantum information processing

We investigate a planar ion chip design with a two-dimensional array of linear ion traps for scalable quantum information processing. Qubits are formed from the internal electronic states of trapped ^40Ca^＋ ions. The segmented electrodes reside in a single plane on a substrate and a grounded metal plate separately, a combination of appropriate rf and DC potentials is applied to them for stable ion confinement. Every two adjacent electrodes can generate a linear ion trap in and between the electrodes above the chip at a distance dependent on the geometrical scale and other considerations. The potential distributions are calculated by using a static electric field qualitatively. This architecture provides a conceptually simple avenue to achieving the microfabrication and large-scale quantum computation based on the arrays of trapped ions.     

Microfabricated magnetic waveguides for neutral atoms

We describe how tightly confining magnetic waveguides for atoms can be created with microfabricated or nanofabricated wires. Rubidium atoms guided in the devices we have fabricated would have a transverse mode energy spacing of K. We discuss the creation of a single-mode waveguide for atom interferometry whose depth is comparable to magneto-optical trap (MOT) temperatures. We also discuss the application of microfabricated waveguides to low-dimensional systems of quantum degenerate gases, and show that confinement can be strong enough to observe fermionization in a strongly interacting bosonic ensemble. Received 1st December 1998 and Received in final form 23 February 1999     

Employing trapped cold ions to verify the quantum Jarzynski equality

We propose a scheme to investigate the nonequilibrium work distribution of a quantum particle under well controlled transformations of the external potential, exploiting the versatility of a single ion in a segmented linear Paul trap. We describe in detail how the motional quantum state of a single ion can be prepared, manipulated, and finally readout to fully determine the free energy difference in both harmonic and anharmonic potentials. Uniquely to our system, we show how an ion may be immersed in an engineered laser-field reservoir. Trapped ions therefore represent an ideal tool for investigating the Jarzynski equality in open and closed quantum systems.     

A planar ion trap chip with integrated structures for an adjustable magnetic field gradient

We present the design, fabrication, and characterization of a segmented surface ion trap with integrated current-carrying structures. The latter produce a spatially varying magnetic field necessary for magnetic-gradient-induced coupling between ionic effective spins. We demonstrate trapping of strings of ¹⁷²Yb⁺ ions and characterize the performance of the trap and map magnetic fields by radio frequency-optical double-resonance spectroscopy. In addition, we apply and characterize the magnetic gradient and demonstrate individual addressing in a string of three ions using RF radiation.