Hyperfine spectroscopy of optical-cycling transitions in singly ionized thulium

Abstract

Abstract We present a spectroscopic investigation of $$^{169}\text {Tm}^+$$ 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 $$^{169}\text {Tm}^+$$ ions in an ion trap. We characterize the primary 313 nm and complementary 448/453 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 a detailed characterization of a metastable state as a candidate for hosting a robust qubit, performing lifetime measurements and Zeeman-resolved microwave hyperfine spectroscopy with $$\textrm{kHz}$$ precision.