Optical and spin properties of alkali atoms in cryogenic solids

We have studied alkali-metal atoms trapped in solid matrices of neon and parahydrogen. While the optical transitions of the alkali atoms suffer from significant broadening, it is possible to optically pump and measure the spin states of the trapped atoms. Using optically detected magnetic resonance spectroscopy, we have measured the ensemble spin transverse relaxation time (T₂^*). T₂^* varies significantly between different species and spin superposition states; T₂^* times on the order of 10^-4 s have been observed. Using dynamical decoupling techniques, spin coherence times (T₂) as long as 0.1 s have been observed in the matrix, which is promising for quantum sensing. Towards that goal, NMR detection of co-trapped nuclear spins has been demonstrated using ensembles of atoms. If these same measurements can be performed with single atoms, it would enable NMR measurements of single molecules co-trapped in the matrix. We have performed state-selective detection of single atoms in the solid; progress towards single-molecule NMR will be discussed.