Spectroscopy of Sub-Hertz Transtions in excited Yb⁺

Ytterbium atoms and ions provide access to a rich set of metastable states via optical transitions with <10 Hz natural linewidths, enabling optical clocks and precision tests beyond the Standard Model. The exceptionally long-lived ²F^o_7/2 state (τ ≈ 1.5 years) makes Yb⁺ a powerful platform for quantum information processing. We present progress toward coherent laser coupling between ²F^o_7/2 and higher-lying odd-parity states. The rich manifold of metastable high-J states directly accessible from ²F^o_7/2 provides promising pathways to two-qubit gates and expansion of King plot analyses in Yb. We report isotope shifts, hyperfine splittings, and lifetimes of three previously unobserved E2 transitions in Yb⁺. Finally, we outline plans to exploit these states for two-qubit operations and precision studies of King-plot nonlinearities.