Towards state preparation and measurements in trapped ¹⁶⁹Tm⁺

We investigate the realization of state preparation and measurement (SPAM) protocols for ¹⁶⁹Tm⁺ ions confined in a linear quadrupole trap. As a spin-1/2 rare-earth species, thulium offers a unique combination of a simple nuclear structure and a complex electronic Hilbert space. We focus on the characterization of a metastable state with a measured lifetime of 5.2(3) min as a candidate for optical, metastable, and ground-state qubit encoding. We identify several transitions for SPAM as well as different optical-cycling schemes suitable for laser cooling. The high angular momentum of the metastable state enables the implementation of non-trivial codewords that are inherently robust against first-order quantum errors. We present Zeeman-resolved microwave spectroscopy of these manifolds with kHz-level precision and demonstrate a procedure for initializing the qubit between specific magnetic sublevels via microwave-assisted optical pumping. These results establish the foundational toolbox for using thulium as a scalable platform for high-dimensional quantum information processing