  We experimentally demonstrate that the bandwidth of single photons laser
pulse is compressed by a factor of 58 in a periodically poled lithium niobate
(PPLN) waveguide chip. A chirped single photons laser pulse and an oppositely
chirped classical laser pulse are employed to produce a narrowband single
photon pulse with new frequency through sum-frequency generation. In our
experiment, the frequency and bandwidth of single photons at 1550 nm are
simultaneously converted. Our results mark a critical step towards the
realization of coherent photonic interface between quantum communication at
1550 nm and quantum memory in the near-visible window.
