  We propose a generic protocol to experimentally measure the quantum metric
tensor, a fundamental geometric property of quantum states. Our method is based
on the observation that the excitation rate of a quantum state directly relates
to components of the quantum metric upon applying a proper time-periodic
modulation. We discuss the applicability of this scheme to generic two-level
systems, where the Hamiltonian's parameters can be externally tuned, and also
to the context of Bloch bands associated with lattice systems. As an
illustration, we extract the quantum metric of the multi-band Hofstadter model.
Moreover, we demonstrate how this method can be used to directly probe the
spread functional, a quantity which sets the lower bound on the spread of
Wannier functions and signals phase transitions. Our proposal offers a
universal probe for quantum geometry, which could be readily applied in a wide
range of physical settings, ranging from circuit-QED systems to ultracold
atomic gases.
