Surface-electrode ion trap with integrated light source

Abstract

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

Technologies for trapped-ion quantum information systems

“…The second problem is that dielectric surfaces are susceptible to light-induced charging, which results in strong and difficult-to-control forces on the ions, inducing micromotion, large displacements, or even making the ions untrappable [79][80][81]. Nonetheless, these challenges have started to be addressed in the last several years by a number of groups integrating various optical elements with ion traps, including microfabricated phase Fresnel lenses [82,83], embedded micromirrors [84,85] and fibers [45,86], transparent trap electrodes [44], nanophotonic dielectric waveguides [87], macroscopic optical cavities [46,[88][89][90][91], and microscopic, fiber-based cavities [92].…”

“…Brady et al [95] created an ion trap chip incorporating an array of optical fibers and confirmed ion trapping and preliminary light detection with their system, establishing a proof of concept for a large fiber array trap architecture. Following this work on light collection, Kim et al [45] demonstrated light delivery through an integrated single-mode (SM) fiber.…”

“…To accommodate an optical fiber, Kim et al [45] chose to deviate from the standard, linear Paul trap layout and instead to develop a trap in which the quadrupole potential is generated by a planar RF ring (a concept first explored analytically by Brewer et al [96]). The axial symmetry of this kind of trap is naturally suited to optical fiber Reproduced from Ref.…”

“…So not only should the ion be aligned with the optical fiber, it must also be positioned so that it sits close to the RF null of the trapping field. To achieve this twofold alignment, Kim et al [45] repositioned the ion through RF translation (thereby avoiding micromotion), by adjusting an RF voltage in phase with the trap RF applied to a neighboring triangular electrode (see Fig. 5) [45,86,97,99].…”

“…In attempting to control errors and noise, ion traps incorporating exotic materials such as graphene [42] and superconductors [43] have been created. Toward scalable photonic interfaces, traps integrating devices including photodetectors [44], optical fibers [45], and high finesse cavities [46] have been designed and implemented. Through this trap integration, we seek to move beyond proof-of-principle experiments to machines encompassing thousands of manipulable atoms.…”