  The quantum coupling of individual superconducting qubits to microwave
photons leads to remarkable experimental opportunities. Here we consider the
phononic case where the qubit is coupled to an electromagnetic surface acoustic
wave antenna that enables supersonic propagation of the qubit oscillations.
This can be considered as a giant atom that is many phonon wavelengths long. We
study an exactly solvable toy model that captures these effects, and find that
this non-Markovian giant atom has a suppressed relaxation, as well as an
effective vacuum coupling between a qubit excitation and a localized wave
packet of sound, even in the absence of a cavity for the sound waves. Finally,
we consider practical implementations of these ideas in current surface
acoustic wave devices.
