Quantum metrology with molecular ensembles for fundamental physics using cavity quantum electrodynamics

In recent years, the application of well-established atomic physics techniques to molecules has emerged as a vibrant area of research. While molecules introduce additional complexity, their rich internal quantum structure expands the toolbox for a wide range of phenomena, including tests of fundamental physics, precision measurements, and quantum computation [1]. The fundamental limit imposed by quantum noise on a measurement is known as the Standard Quantum Limit (SQL), where the uncertainty scales as the square root of the system size. In atomic systems, cavity quantum electrodynamics (cQED) enables the exploitation of quantum effects such as entanglement to surpass the SQL [2]. Our goal is to generate spin squeezing in a system of hundreds of molecules through light-mediated interactions, coupling the molecules to the single mode of a high-finesse optical resonator. However, achieving substantial metrological gain requires overcoming decoherence mechanisms inherent to molecules, such as multiple decay channels that weaken the effective interaction between the molecules and the cavity field. We will present the conditions necessary to achieve quantum enhancement in these systems and outline the path toward cavity QED with molecules. By leveraging strong light-matter interactions in the cavity to improve precision, we can explore physics beyond the Standard Model, including searches for symmetry-violating moments, measurements of fundamental constants, and even potential dark matter detection.

References:

[1] DeMille, D, et al., “Quantum sensing and metrology for fundamental physics with molecules” https://doi.org/10.1038/s41567-024-02499-9

[2] E. Pedrozo-Peñafiel et al. Entanglement in an Optical Atomic-Clock Transition. Nature 588, 414-418 (2020) (Link: Entanglement on an optical atomic-clock transition | Nature).