In situ determination of Zeeman content of collective atomic memories

Knowledge and control of atomic Zeeman populations is necessary for the realization of useful, long-lived quantum memories. We propose and implement a method to determine atomic state population distributions for atomic spin waves. Zeeman composition of single atomic spin waves of a cold atomic gas, confined in a one-dimensional optical lattice, is inferred with high precision by measurements of signal–idler polarization correlations as a function of spin-wave storage time

Entanglement of a photon and an optical lattice spin wave

We propose and implement a scheme to produce long-lived entanglement between a signal field and a magnetically insensitive collective excitation in an atomic cloud cooled in a one-dimensional optical lattice. After a programmable storage time, we convert the spin-wave excitation into an idler field, and demonstrate violation of Bell’s inequality for storage times in excess of 3 ms.<br/

Optical techniques for Rydberg physics in lattice geometries

We address the technical challenges when performing quantum information experiments with ultracold Rydberg atoms in lattice geometries. We discuss the following key aspects: (i) the coherent manipulation of atomic ground states, (ii) the coherent excitation of Rydberg states, and (iii) spatial addressing of individual lattice sites. We briefly review methods and solutions which have been successfully implemented, and give examples based on our experimental apparatus. This includes an optical phase-locked loop, an intensity and frequency stabilization setup for lasers, and a nematic liquid-crystal spatial light modulator