Engineering Field-Insensitive Clock Transitions for Symmetry-Violating New Physics Searches

Author: Takahashi, Yuiki

Year: 2026

Degree: Dissertation (Ph.D.)

Advisor: Hutzler, Nicholas R.

Committee Members: Ooguri, Hirosi; Patterson, Ryan B.; Filippone, Bradley W.; Hutzler, Nicholas R.

Option: Physics

Abstract

Heavy polar molecules are powerful quantum sensors for tests of fundamental symmetries and searches for physics beyond the Standard Model. Their internal electromagnetic environment can provide exceptional sensitivity to symmetry-violating effects, but they also create significant challenges for achieving high precision and accuracy in measurement. In addition, their rich internal structure significantly complicates quantum state preparation, coherent control, and readout. This thesis addresses these challenges by devising and demonstrating a general approach for engineering field-insensitive ``clock'' transitions that suppress sensitivity to external fields while preserving strong sensitivity to new physics. This approach is broadly applicable to a wide range of experimental systems, including species with complex, deformed nuclei and systems compatible with state-of-the-art cooling and trapping techniques, offering the potential to significantly improve sensitivity to various new physics while expanding the experimental design space for quantum sensing.

A central result of this work is the conceptualization and demonstration of field-insensitive clock transitions for symmetry-violation searches. Uncontrolled external electromagnetic fields are a major obstacle to precise and accurate measurements. Minimizing sensitivity to such fields is therefore essential and has played a key role in all precision experiments of this kind. Here, we devise and demonstrate clock transitions engineered to enable robust symmetry-violation searches in YbOH. Sensitivities to external electric and magnetic fields are suppressed by orders of magnitude while maintaining strong sensitivity to the electron electric dipole moment (eEDM). Using Ramsey measurements on these clock transitions, we observe suppression of electric- and magnetic-field sensitivities by at least factors of 700 and 200, respectively, and demonstrate robust spin coherence in the presence of large electromagnetic-field fluctuations. We also identify and employ selected quantum states for sensitive measurements of external magnetic and electric fields, another capability that is critical for high-accuracy experiments.

This thesis also establishes and demonstrates the quantum-control toolkit required for symmetry violation searches in the isotopologue 173YbOH, which is of particular interest because of its large nuclear spin (I = 5/2) and quadrupole-deformed nucleus. These features make it a promising candidate for searches for hadronic symmetry-violating effects, including those arising from the nuclear magnetic quadrupole moment (MQM). Realizing an MQM measurement in 173YbOH, however, requires quantum state control within highly complex hyperfine manifolds. Here, we demonstrate state preparation, coherent control, and readout for Ramsey interferometry on MQM-sensitive transitions in 173YbOH with magnetic-field sensitivity suppressed by more than an order of magnitude. We also demonstrate a "co-magnetometer" protocol that disentangles a potential MQM signature from systematic backgrounds.

These results establish the essential quantum-control toolkit for precision measurements in systems with the intricate hyperfine structure commonly encountered in searches for nuclear symmetry violation, and show that it is possible to take advantage of the suppressed field sensitivities in these complicated systems.

Together, these results show that molecular structure can be engineered and controlled to realize robust precision measurements in complex systems and that molecular complexity can be transformed from a challenge into a resource for robust symmetry-violation measurements.