  We investigate the formation of photon bound states in a system of
interacting photons inside nanoscale wires. The photons interact through the
exchange of vibrational modes induced along the waveguide mainly due to
radiation pressure. The problem of many-body photons is treated in using the
formalism of contour Green's functions under the T-matrix approximation. The
complex pole of the T-matrix is a signature for the appearance of
photon-molecules. The analysis of such singularity provides the critical
temperature at which the T-matrix approximation breaks down and
photon-molecules appear. For strongly interacting slow photons the amplitude of
the photon-molecule wavefunction acquires a significant quantum nonlinear phase
inside the nanowire. Photon bound-states can be implemented for quantum
information processing as quantum logic gates, e.g. for $\pi$ phase shift the
photon-molecule is shown to serve as a Z-controlled gate.
