Spin-squeezing for alkali earth atom interferometers*

Today, matter-wave interferometers as clocks and gravimeters allow for precision measurements of time and gravity at unprecedented levels [1].  In all these sensors, the exquisite control of both internal (electronic) and external (center of mass motion) degrees of freedom of ultra-cold atomic samples, enable us to study interactions at their most basic, quantum level, paving the way for new tests of fundamental physics. 

However, despite all the efforts done so far, highest precision clocks and interferometers have not taken full advantage from the quantum properties of matter waves, yet. Here, we present alternative schemes for the production and the use of metrologically useful entanglement in cold-atom systems, through the coupling of atoms with a high-finesse optical cavity. All these schemes rely on the use of narrow optical intercombination transitions in alkali-earth atoms, recently employed in new generation atom interferometers based on single photon (clock) and two photon (Bragg) interaction [2,3,4].

The presence of high coherence internal states connected with such high relative frequency resolution, makes these atoms very good candidates for the actual implementation of spin-squeezing schemes on their internal and external degrees of freedom, free from decoherence [5,6]. Here, in particular, I’ll show the work we’ve been doing so far towards the realization of an experimental apparatus for the production of a spin squeezed source based on strontium atoms with direct application in Bragg and clock interferometers.

Moreover, the experimental results toward the production of ultra-cold cadmium for atom interferometry and prospects for tests of fundamental physics will also be discussed [7,8].