  Two-dimensional arrays of periodically driven qubits can host inherently
dynamical topological phases with anomalous chiral edge dynamics. These chiral
Floquet phases are formally characterized by a dynamical topological invariant,
the chiral unitary index. Introducing a quantity called the chiral mutual
information, we show that this invariant can be precisely interpreted in terms
of a quantized chiral transfer of quantum information along the edge of the
system, and devise a physical setup to measure it.
