Dual-Platform Precision Measurement of the $3^2{D}_{5\mathrm{/}2}$ to $4^2{S}_{1\mathrm{/}2}$ $g$-Factor Ratio in ${}^{40}{\text{Ca}}^{+}$

We report precision measurements of the ratio of Landé $g$ factors between the $3^2{D}_{5\mathrm{/}2}$ and $4^2{S}_{1\mathrm{/}2}$ states of a single trapped ${}^{40}{\text{Ca}}^{+}$ ion. The measurements are performed in two distinct ion trap apparatus: a cryogenic surface electrode radiofrequency Paul trap and a room-temperature permanent magnet Penning trap. The Penning trap measurements yield a ratio of $0.5994888133(2)$, which represents a more than 40-fold uncertainty reduction compared to previous work. The radiofrequency trap measurement yields a concurring value of $0.599488813(6)$. We estimate that systematic shifts for each system are well below the respective statistical uncertainty.