  The frequency conversion of light has proved to be a crucial technology for
communication, spectroscopy, imaging, and signal processing. In the quantum
regime, it also offers great potential for realizing quantum networks
incorporating disparate physical systems and quantum-enhanced information
processing over a large computational space. The frequency conversion of
quantum light, such as single photons, has been extensively investigated for
the last two decades using all-optical frequency mixing, with the ultimate goal
of realizing lossless and noiseless conversion. I demonstrate another route to
this target using frequency conversion induced by cross-phase modulation in a
dispersion-managed photonic crystal fiber. Owing to the deterministic and
all-optical nature of the process, the lossless and low-noise spectral
reshaping of a single-photon wave packet in the telecommunication band has been
readily achieved with a modulation bandwidth as large as 0.4 THz. I further
demonstrate that the scheme is applicable to manipulations of a nonclassical
frequency correlation, wave packet interference, and entanglement between two
photons. This approach presents a new coherent frequency interface for photons
for quantum information processing.
