Increasing measurement sensitivity for the electron's electric dipole moment using trapped molecular ions

Based on our latest measurements of the electron's electric dipole moment (eEDM) using trapped HfF$^+$ ions, after 100 hours of data collection, the statistical error still dominates in our overall uncertainty budget \footnote{Daniel N Gresh's presentation}. Overcoming the bottleneck of limited statistical sensitivity can increase the precision of the eEDM measurement directly. Here, we present the progress of three ongoing experiments: (1) applying STImulated Raman Adiabatic Passage (STIRAP) with rotating linear polarization for increased coherent population transfer from the ground $X^1\Sigma^+$ state to the eEDM-sensitive $^3\Delta_1$ state; (2) implementing a new ion-counting detector toward shot-noise limited sensitivity with significant suppression technical noise; (3) exploring the possibility of using the ground $^3\Delta_1$ state of ThF$^+$ ions to realize a larger effective electric field and a longer coherence time. These experiments provide a route towards an order of magnitude increase in statistical sensitivity in the second generation of measurements.