  We propose a new method to measure Casimir-Polder force in an optical cavity
by means of atomic excitations. We utilize a framework in which Unruh-DeWitt
Hamiltonian mimics the full matter-field interaction and find a connection
between the excitation rate of the two-level atom and the Casimir-Polder
energy, allowing to map one onto the other. We argue that such a realization
opens a route to study Casimir-Polder potentials through measurement of excited
state's population in large, spatially compact ensembles of atoms.
