Hyperfine spectroscopy of optical-cycling transitions in singly ionized thulium

arXiv:2512.14885v1 Announce Type: new
Abstract: We present a spectroscopic investigation of $^{169}mathrm{Tm}^+$ that provides two key foundations for its use as a platform for advanced quantum applications. First, we establish the complete spectroscopic road map for optical cycling (including laser cooling) by performing high-resolution spectroscopy on $^{169}mathrm{Tm}^+$ ions in an ion trap. We characterize the primary $313,mathrm{nm}$ and complementary $448/453,mathrm{nm}$ cycling transitions, identify the essential near-infrared repumping frequencies, and determine the magnetic-dipole hyperfine $A$ constants for all relevant levels. Second, we report detailed characterization of a metastable state as a candidate for hosting a robust qubit, performing lifetime measurements and Zeeman-resolved microwave hyperfine spectroscopy with $mathrm{kHz}$ precision.