  We propose an interferometric method to measure Z2 topological invariants of
time-reversal invariant topological insulators realized with optical lattices
in two and three dimensions. We suggest two schemes which both rely on a
combination of Bloch oscillations with Ramsey interferometry and can be
implemented using standard tools of atomic physics. In contrast to topological
Zak phase and Chern number, defined for individual 1D and 2D Bloch bands, the
formulation of the Z2 invariant involves at least two Bloch bands related by
time- reversal symmetry which one has keep track of in measurements. In one of
our schemes this can be achieved by the measurement of Wilson loops, which are
non-Abelian generalizations of Zak phases. The winding of their eigenvalues is
related to the Z2 invariant. We thereby demonstrate that Wilson loops are not
just theoretical concepts but can be measured experimentally. For the second
scheme we introduce a generalization of time-reversal polarization which is
continuous throughout the Brillouin zone. We show that its winding over half
the Brillouin zone yields the Z2 invariant. To measure this winding, our
protocol only requires Bloch oscillations within a single band, supplemented by
coherent transitions to a second band which can be realized by lattice-shaking.
