Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules (1705.11020v1)

Abstract: Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the Standard Model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool -- optical trapping. However, the types of molecules that have been laser-cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal co-magnetometer states. We show that by utilizing the internal degrees of freedom present only in molecules with at least three atoms, these features can be attained simultaneously with molecules that have simple structure and are amenable to laser cooling and trapping.

Precision Measurement of Time-Reversal Symmetry Violation Using Laser-Cooled Polyatomic Molecules

This paper presents advancements in precision measurement techniques aimed at detecting time-reversal symmetry violating interactions using laser-cooled polyatomic molecules. The work explores the sensitivity of these interactions as a probe for high-energy physics beyond the Standard Model (BSM). To achieve this, the authors have utilized recent developments in optical trapping facilitated by laser cooling of polar molecules. The focus here is on achieving long coherence times and high count rates, essential for BSM physics exploration at the PeV scale.

The primary challenge addressed is the inadequacy of previously laser-cooled diatomic molecules regarding their electronic structure. Such molecules lack features desirable for new physics searches, including full polarization abilities and internal co-magnetometer states. The authors propose that polyatomic molecules, specifically those with at least three atoms, can simultaneously possess these features. This is achieved through utilizing the internal degrees of freedom unique to polyatomic structures in contrast to diatomic molecules.

Numerical Results and Theoretical Contributions

The paper provides a comprehensive theoretical framework for trapping EDM-sensitive polyatomic molecules directly, through cryogenic buffer gas beams. The discussion extends to RaOH and YbOH polyatomic molecules, demonstrating their potential for sensitivity in fundamental physics exploration. Polyatomic molecules have generally degenerate bending modes allowing angular momentum projection on the molecular dipole. These states facilitate full polarization with moderate laboratory fields, analogous to $\Omega$-doublets in diatomic molecules, but are uncoupled to electronic spin which suggests better laser cooling properties without hindering BSM sensitivity.

Simulation results predict that populating bending modes in polyatomic molecules such as YbOH could lead to effective polarization at electric fields around 250 V/cm. Notably, this paper examines the electron EDM shifts in these states, highlighting the modularity provided by vibrational angular momentum ($\ell$), enabling robust sensitivity and internal co-magnetometry via spectroscopic reversal. Additionally, longer vibrational lifetimes estimated from YbOH further imply coherence times beyond 10 seconds, which are crucial for precision measurement.

Practical and Theoretical Implications

The implications of this work are significant, both practically and theoretically. Practically, the experimental techniques could provide a pathway to highly sensitive detection systems capable of probing BSM physics at scales up to PeV. The ability to trap a multitude of neutral molecules more efficiently than ions opens possibilities for extensive experimental setups. Theoretical implications include the expansion of viable molecular candidates for BSM physics research, encompassing symmetrically complex polyatomic configurations which reveal new BSM sensitivity paths through different atomic compositions.

By providing a systematic approach to leveraging these properties of polyatomic molecules, the authors speculate that incorporating laser-coolable atoms with functional groups will widen scope and accuracy in detecting several symmetry violations, including nuclear EDMs and parity violation, addressing various theoretical constructs extending beyond current limits on BSM physics interactions.

Future Directions

The paper concludes with optimistic directions for future research, including enhanced sensitivity through increased molecular trapping counts and longer coherence times, speculating four orders of magnitude improvement extending current limits. Additionally, investigation into the potential applicability for quantum information processing and quantum simulation underlines the transformative potential of these precision measurement developments.

By effectively integrating laser cooling, optical trapping, and exploring vibrational dynamics, this research not only introduces new polyatomic configurations into experimental setups but also enhances the robustness against systematic errors—a crucial prerequisite for practical BSM physics exploration.