Cryogenic Vacuum Chamber Design Towards High-Fidelity Ion-Trapping Experiments

We describe a new cryogenic vacuum chamber design for ion-trapping experiments with improved beam-pointing stability, shielding from magnetic-field fluctuations, and an in-vacuum imaging objective. In closed-cycle cryostats, vibrations from the He pumping action often couple to the ion trap, despite the use of an exchange buffer gas. These vibrations lead to beam-pointing and amplitude fluctuations at the ion. We mitigate these effects by mechanically referencing our ion trap to the optical table while using flexible copper straps to thermalize the trap to the cold-head. With the ion trap decoupled from cold-head vibrations, beam-pointing becomes more stable and gate errors due to amplitude fluctuations are reduced. To reduce dephasing errors due to magnetic field fluctuations, we add three layers of in-vacuum magnetic shielding to our chamber. We also implement a radio frequency antenna to drive single-qubit gates between Zeeman sub-levels for global dynamical decoupling. Lastly, to reduce detection time and associated measurement error rates, we use a high numerical aperture lens mounted in vacuum to a hexapod for improved collection efficiency. We report initial results from testing this chamber design.