  We study the generation of Greenberger-Horne-Zeilinger (GHZ) states of three
path-encoded photons. Inspired by the seminal work of Bouwmeester et al. [1] on
polarization-entangled GHZ states, we find a corresponding path representation
for the photon states of an optical circuit, identify the elements required for
the state generation, and propose a possible implementation of our strategy.
Besides the practical advantage of employing an integrated system that can be
fabricated with proven lithographic techniques, our example suggests that it is
possible to enhance the generation efficiency by using microring resonators.
