  Unitary Fourier transform lies at the core of the multitudinous computational
and metrological algorithms. Here we show experimentally how the unitary
Fourier transform-based phase estimation protocol, used namely in quantum
metrology, can be translated into the classical linear optical framework. The
developed setup made of beam splitters, mirrors and phase shifters demonstrates
how the classical coherence, similarly to the quantum coherence, poses a
resource for obtaining information about the measurable physical quantities.
Our study opens route to the reliable implementation of the small-scale unitary
algorithms on path-encoded qudits, thus establishing an easily accessible
platform for unitary computation.
