  We demonstrate the generation of quantum-correlated photon pairs from a Si
photonic-crystal coupled-resonator optical waveguide. A slow-light supermode
realized by the collective resonance of high-Q and small-mode-volume
photonic-crystal cavities successfully enhanced the efficiency of the
spontaneous four-wave mixing process. The generation rate of photon pairs was
improved by two orders of magnitude compared with that of a photonic-crystal
line defect waveguide without a slow-light effect.
