  Light-pulse atom interferometers constitute powerful quantum sensors for
inertial forces. They are based on delocalised spatial superpositions and the
combination with internal transitions directly links them to atomic clocks.
Since classical tests of the gravitational redshift are based on a comparison
of two clocks localised at different positions under gravity, it is promising
to explore whether the aforementioned interferometers constitute a competitive
alternative for tests of general relativity. Here we present a specific
geometry which together with state transitions leads to a scheme that is
concurrently sensitive to both violations of the universality of free fall and
gravitational redshift, two premises of general relativity. The proposed
interferometer does not rely on a superposition of internal states, but merely
on transitions between them, and therefore generalises the concept of physical
atomic clocks and quantum-clock interferometry. An experimental realisation
seems feasible with already demonstrated techniques in state-of-the-art
facilities.
