Abstract

Superconducting atom chips and Rydberg atoms are promising tools for quantum information processing operations based on the dipole blockade effect. Nevertheless, one has to face the severe problem of stray electric fields in the vicinity of the chip. We demonstrate a simple method circumventing this problem. Microwave spectroscopy reveals extremely long coherence lifetimes (in the millisecond range) for a qubit stored in a Rydberg level superposition close to the chip surface. This is an essential step for the development of quantum simulations with Rydberg atoms and of a hybrid quantum information architecture based on atomic ensembles and superconducting circuits.