Strontium optical lattice clocks at JILA recently demonstrated record-high accuracy and stability. These advances were enabled by an ultrastable laser with fractional frequency stability of 1x10^-16 at 1 second. This laser allows us to study systematic shifts of the strontium clock transition with unprecedented precision. Density-dependent frequency shifts represent an unavoidable perturbation for clocks based on many atoms.
Our studies of atomic interactions in an optical lattice clock system uncover the nature of these interactions and reveal important many-body atomic correlation effects. By extending our measurements to all ten nuclear-spin sublevels of the clock states, we observe the first direct evidence of SU(N) symmetric interactions in alkaline earth(-like) atoms. Using the techniques we developed in these studies, we also demonstrate a novel technique for measuring the frequency noise spectrum of an ultrastable laser. We discuss designs for the future direction of our experiment which will place strontium atoms within a high finesse cavity that is resonant on an atomic transition.
We will use this system to study collective effects in cavity quantum electrodynamics. Most notably, the cavity can enhance the spectroscopic sensitivity of our clock by creating spin-squeezed states via quantum non-demolition measurements.