Coherence and decay in microtraps on a magnetic film atom chip

With a permanent magnetic-film atom chip we load clouds of ultracold ⁸⁷Rb atoms in a lattice of microtraps. The sites are spaced 10 μm apart and contain tens to hundreds of atoms each with temperatures down to about 1 μK. The goal is to develop this system of magnetically trapped atomic ensembles as a scalable platform for quantum simulation science. To reach this goal we study the imaging sensitivity of our system, the characteristics of the microtraps and the coherence properties we can reach in each microtrap.
We find an effective imaging sensitivity of about 15 atoms per trap per realisation of the experiment. We use RF and audio frequency methods for characterising, for each individual site: the temperature, trap bottom frequency and trap frequencies. Rabi and Ramsey measurements on the two-photon qubit transitions in the ⁸⁷Rb ground state are also performed, using microwave and radio frequency fields, to study the coherence in the atomic ensembles. Here we find coherence times of about 15 ms for clouds of a few tens of atoms at about 1 μK. We find that the main limitation to the coherence times comes from spin-flip induced trap losses, caused by inelastic collisions in the F = 2, m_F = 1 state.
Future goals are to use long-range dipole-dipole interactions between Rydberg atoms to induce interactions between the ensembles in this system.