The Next-Generation NIST ²⁷Al⁺ Clock

The NIST aluminum ion optical clock operates based on quantum logic spectroscopy of the 1S0 ⟷ 3P0 transition in ²⁷Al⁺, together with a ²⁵Mg⁺ ion for three-dimensional ground-state cooling and state readout. The previous clock achieved a systematic uncertainty below 10^-18 and clock stability of 1.2x10^-15/√(τ) [1]. The leading systematic uncertainty of this clock was due to time dilation from driven micromotion, and the stability was limited by quantum projection noise. The next-generation NIST aluminum-ion clock will improve on both of these limitations. A redesigned ion trap demonstrates significantly reduced residual micromotion, while a new vacuum system and larger usable trap volume will enable operation with multiple ²⁷Al⁺ ions. Simultaneous interrogation of multiple aluminum ions will reduce quantum projection noise below the single-ion limit. Here, we report the design and commisioning of the new trap, including measurements of systematic shifts for a single ion and preparation for multi-ion operation.

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