Recent advancements in superconducting circuits have enabled the experimental
study of collective behavior of precisely controlled intermediate-scale
ensembles of qubits. In this work, we demonstrate an atomic frequency comb
formed by individual artificial atoms strongly coupled to a single resonator
mode. We observe periodic microwave pulses that originate from a single
coherent excitation dynamically interacting with the multi-qubit ensemble. We
show that this revival dynamics emerges as a consequence of the constructive
and periodic rephasing of the five superconducting qubits forming the vacuum
Rabi split comb. In the future, similar devices could be used as a memory with
in-situ tunable storage time or as an on-chip periodic pulse generator with
non-classical photon statistics