  We experimentally demonstrate phase sensitive amplification (PSA) in a
silicon photonic crystal waveguide based on pump-degenerate four-wave mixing.
An 11 dB phase extinction ratio is obtained in a record compact 196 {\mu}m
nanophotonic device due to broadband slow-light, in spite of the presence of
two-photon absorption and free-carriers. Numerical calculations show good
agreement with the experimental results.
