  Future quantum information networks operated on telecom channels require
qubit transfer between different wavelengths while preserving quantum coherence
and entanglement. Qubit transfer is a nonlinear optical process, but currently
the types of atoms used for quantum information processing and storage are
limited by the narrow bandwidth of up-conversion available. Here we present the
first experimental demonstration of broadband and high-efficiency quasi-phase
matching second harmonic generation (SHG) in a chip-scale periodically poled
lithium niobate thin film. We achieve large bandwidth of up to 2 THz for SHG by
satisfying quasi-phase matching and group-velocity matching simultaneously.
Furthermore, by changing film thickness, the central wavelength of quasi-phase
matching SHG bandwidth can be modulated from 2.70 um to 1.44 um. The
reconfigurable quasi-phase matching lithium niobate thin film provides a
significant on-chip integrated platform for photonics and quantum optics.
