Surface-electrode ion trap with integrated light source

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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 ⁸⁸Sr+. Through 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±0.10 of the mode center despite an initial offset of 3.30±0.10. Fiber-induced charging at 125 μW is observed to be 10 V/m at an ion height of 670 μm, with charging and discharging time constants of 1.6±0.3 s and 4.7±0.6 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.