A New Generation ²⁷Al+ Optical Clock

The ¹S₀-³P₀ transition in ²⁷Al+ is a precise frequency standard thanks to its narrow linewidth and insensitivity to environmental perturbations, yet ion clocks have limited stability due to quantum projection noise. NIST’s Al+ ion clock reached a systematic uncertainty below 10^-18 and a stability of 1.2^-15/√τ with a single ion [1]. A multi-Al+ ion operation would improve clock stability by probing the clock transition for multiple trapped ions simultaneously.

This poster reports on progress toward a multi-ion clock. Such an experiment requires improved apparatus and new experimental techniques for loading and cooling multiple ions simultaneously. In the newest generation of NIST’s Al+ ion clock experiment, the measured two-ion crystal reordering rate of ~1 event/hour is a 30-fold improvement over previous Al+ clocks, indicating a much improved vacuum pressure. This low rate will mitigate shifts and broadening of the clock transition due to collisions with background gas particles. The redesigned trap features more homogeneous fields over a larger volume, allowing for precision spectroscopy of multiple ions. In addition to the improved apparatus, we also discuss ongoing development of methods for ground-state cooling of ion chains.



[1] Brewer et al., PRL 123, 033201 (2019)