  We predict the existence of a novel interaction-induced spatial localization
in a periodic array of qubits coupled to a waveguide. This localization can be
described as a quantum analogue of a self-induced optical lattice between two
indistinguishable photons, where one photon creates a standing wave that traps
the other photon. The localization is caused by the interplay between on-site
repulsion due to the photon blockade and the waveguide-mediated long-range
coupling between the qubits.
