Manipulation and coherence of ultra-cold atoms on a superconducting atom chip

The coherence of quantum systems is crucial to quantum information processing. Although superconducting qubits can process quantum information at microelectronics rates, it remains a challenge to preserve the coherence and therefore the quantum character of the information in these systems. An alternative is to share the tasks between different quantum platforms, for example, cold atoms storing the quantum information processed by superconducting circuits. Here we characterize the coherence of superposition states of 87Rb atoms magnetically trapped on a superconducting atom chip. We load atoms into a persistent-current trap engineered next to a coplanar microwave resonator structure, and observe that the coherence of hyperfine ground states is preserved for several seconds. We show that large ensembles of a million of thermal atoms below 350 nK temperature and pure Bose–Einstein condensates with 3.5 × 105 atoms can be prepared and manipulated at the superconducting interface. This opens the path towards the rich dynamics of strong collective coupling regimes. Superconducting qubits are promising for quantum information processing, yet maintaining their coherence for long periods is hard. Bernon et al.characterize the coherence of cold atom superposition states trapped on superconducting atom chips and show that such long-lived ensembles are a viable alternative.