Surface-electrode ion trap with integrated light source

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 $^{88}$Sr$^+$. Through \emph{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 $0.13\pm0.10$ of the mode center despite an initial offset of $3.30\pm0.10$. Fiber-induced charging at $125 \mu$W is observed to be ${\sim}10$ V/m at an ion height of $670 \mu$m, with charging and discharging time constants of $1.6\pm0.3$ s and $4.7\pm0.6$ 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.Comment: 4 pages, 4 figure

An optical-fiber interface to a trapped-ion quantum computer

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from PDF version of thesis.Includes bibliographical references (p. 163-174).The trapped-ion quantum computer is an atom-based implementation of a quantum computer that has successfully demonstrated numerous quantum algorithms and the potential for scalability. Fundamental to its operation is the short-range Coulombic interaction among its atomic ion registers, which has led to the development of local, single-chip devices. In this work, we demonstrate the integration of an optical-fiber with a planar ion trap, and show the physical interaction between fiber light and the trapped-ion qubit. As the single-mode fiber is well-suited to the transport of single photons, the fiber interface (when augmented by an optical cavity) represents a means to link distantly located quantum computers through a common optical network. Hence, this work represents a step towards the paradigm of distributed quantum computing: self-contained, technically-simple processors may be optically linked together to perform large-scale quantum computation. This thesis is divided into two parts. In the first, we provide a thorough review of ion trap design and a detailed numerical analysis of trapped-ion motion. This theoretical discussion culminates with the development of an electronic technique that permits the arbitrary, in situ positioning of a trapped atom in the ion trap. The positioning ability is an enabling technology for trap-integration as it allows for complete freedom in the alignment of the trapped atom with respect to the integrated element. In the second part, the construction of the experimental setup and the integrated "fibertrap" is described. In our experiment, a single 38Sr+ is trapped 670 [mu]m above the end of an 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 88Sr+. Using in situ translation of the ion, the Gaussian beam profile of the fiber output is imaged, and the fiberion 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 arising from fabrication. We also quantify the perturbative effects of the fiber dielectric on ion trap operation. Light-induced charging by 125 [mu]W of 674 nm fiber light is measured as an induced electric field of ~ 10 V/m at the ion, with charging and discharging time constants of 1.6 ± 0.3 s and 4.7 t 0.6 s. These measurements are of general importance to trapped-ion quantum computing, where the scalability of the platform depends crucially on the feasibility of on-chip optics integration.by Tony Hyun Kim.M.Eng

A surface electrode point Paul trap

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 \emph{in situ}. We demonstrate trapping of single and few Sr+ ions over an ion height range of 200-1000 microns for several hours under Doppler laser cooling, and use these to characterize the trap, finding good agreement with our model.Comment: 10 pages, 11 figures, 1 tabl

Near-Infrared Photometry of the Star Clusters in the Dwarf Irregular Galaxy IC 5152

We present JHK-band near-infrared photometry of star clusters in the dwarf irregular galaxy IC 5152. After excluding possible foreground stars, a number of candidate star clusters are identified in the near-infrared images of IC 5152, which include young populations. Especially, five young star clusters are identified in the (J-H, H-K) two color diagram and the total extinction values toward these clusters are estimated to be A_V =2 - 6 from the comparison with the theoretical values given by the Leitherer et al. (1999)'s theoretical star cluster model.Comment: Accepted by the Journal of the Korean Astronomical Society, 2006 December issue (Vol. 39, No. 4

BOAO Photometric Survey of Galactic Open Clusters. III. Czernik 24 and Czernik 27

We present BV CCD photometry for the open clusters Czernik 24 and Czernik 27. These clusters have never been studied before, and we provide, for the first time, the cluster parameters; reddening, distance, metallicity and age. Czernik 24 is an old open cluster with age 1.8 +/- 0.2 Gyr, metallicity [Fe/H]=-0.41 +/- 0.15 dex, distance modulus (m-M)_0 = 13.1 +/- 0.3 mag (d=4.1 +/- 0.5 kpc), and reddening E(B-V) = 0.54 +/- 0.12 mag. The parameters for Czernik 27 are estimated to be age = 0.63 +/- 0.07 Gyr, [Fe/H]= -0.02 +/- 0.10 dex, (m-M)_0 = 13.8 +/- 0.2 mag (d=5.8 +/- 0.5 kpc), and E(B-V) = 0.15 +/- 0.05 mag. The metallicity and distance values for Czernik 24 are consistent with the relation between the metallicity and the Galactocentric distance of other old open clusters. We find the metallicity gradient of 51 old open clusters including Czernik 24 to be Delta [Fe/H]/Delta R_gc= -0.064 +/- 0.009 dex/kpc.Comment: Accepted by the Journal of the Korean Astronomical Society, 2005 December issu

Real-space imaging of acoustic plasmons in large-area CVD graphene

An acoustic plasmonic mode in a graphene-dielectric-metal heterostructure has recently been spotlighted as a superior platform for strong light-matter interaction. It originates from the coupling of graphene plasmon with its mirror image and exhibits the largest field confinement in the limit of a nm-thick dielectric. Although recently detected in the far-field regime, optical near-fields of this mode are yet to be observed and characterized. Direct optical probing of the plasmonic fields reflected by the edges of graphene via near-field scattering microscope reveals a relatively small damping rate of the mid-IR acoustic plasmons in our devices, which allows for their real-space mapping even with unprotected, chemically grown, large-area graphene at ambient conditions. We show an acoustic mode that is twice as confined - yet 1.4 times less damped - compared to the graphene surface plasmon under similar conditions. We also image the resonant acoustic Bloch state in a 1D array of gold nanoribbons responsible for the high efficiency of the far-field coupling. Our results highlight the importance of acoustic plasmons as an exceptionally promising platform for large-area graphene-based optoelectronic devices operating in mid-IR