Stray Fields and The Electron’s Electric Dipole Moment

The universe is full of matter, and we cannot explain how it got there. According to our most accurate theory of particle physics, the Standard Model, the big bang created equal parts matter and antimatter. In the billions of years since, matter and antimatter should have collided and annihilated, leaving (almost) nothing behind. This obviously is not what happened; we live inside of an entire universe made of matter. Despite this serious shortcoming, the Standard Model is outrageously successful in predicting how particles will behave in experiments here on Earth. To salvage the Standard Model, new theories tack on as-of-yet undiscovered particles and interactions that violate the symmetry between matter and antimatter. A side effect of breaking this symmetry is that electrons should have a non-zero electric dipole moment (EDM). In this thesis, I present the world’s most precise measurement of the electron EDM to date using electrons confined inside hafnium fluoride molecular ions (HfF+). We trap HfF+ in corotating electric and magnetic fields and measure the electron EDM signal by performing Ramsey spectroscopy with coherence times up to 3 seconds. Our result is consistent with an electron EDM of zero and improves on the previous best upper limit by a factor of ∼ 2.4, further constraining proposed theories of particle physics. I also worked towards a future measurement, hopefully 10× more precise, of the electron EDM using thorium fluoride molecular ions. I discuss the systematic errors we uncovered in our HfF+ measurement that require our future experiment to be magnetically shielded.