Helium Spectroscopy in high-finesse Cavity – HESCA

Precision measurements are among the most important applications of atomic, molecular and optical science, from atomic frequency standards to exploration of fundamental physics, such as physics beyond the standard model or as a benchmark for the most accurate theoretical calculations. On the one hand, state-of-the-art optical clocks, leveraging the fast-growing techniques of quantum technologies, offer the highest sensitivity to dark matter or time-variations of fundamental constants, but operate on atoms whose complex level structure cannot be accurately calculated ab-initio. On the other hand, simple two and three-body systems, such as hydrogen atoms or molecular ions and helium atoms can be calculated, but their exploration using quantum-enhanced methods is only at its infancy.

Our project aims at developing a novel experimental system for high-precision spectroscopy of helium (He), a prominent testing platform for fundamental physics, as illustrated in the study of the “proton radius puzzle”. Helium is simple enough to allow for high-accuracy calculations, but complex enough to feature an ultra-narrow (8 Hz) clock-transition in the metastable state where it is amenable to laser cooling and optical trapping. We will build a new generation of experimental to prepare metastable He atoms in a tweezer array, and use cavity-quantum electrodynamics (QED) methods to provide non-destructive detection and quantum enhancement of the signal-to-noise ratio for spectroscopic applications. The project builds upon a strong synergy between the extensive expertise in cooling and manipulating helium of the French team of LCF, and in cavity-QED of the Swiss team at EPFL. We will first construct a new generation of apparatus to load the bosonic species 4He* in an optical trap, and then study the loading and lifetime of He* in tweezers. Last, we will manipulate and detect 4He* in a high-finesse cavity, paving the way to a hundredfold improvement in the spectroscopy of Helium.