  We demonstrate heralded single photon generation in a CMOS-compatible silicon
nanophotonic device. The strong modal confinement and slow group velocity
provided by a coupled resonator optical waveguide (CROW) produced a large
four-wave-mixing nonlinearity coefficient gamma_eff ~4100 W^-1 m^-1 at
telecommunications wavelengths. Spontaneous four-wave-mixing using a degenerate
pump beam at 1549.6 nm created photon pairs at 1529.5 nm and 1570.5 nm with a
coincidence-to-accidental ratio exceeding 20. A photon correlation measurement
of the signal (1529.5 nm) photons heralded by the detection of the idler
(1570.5 nm) photons showed antibunching with g^(2)(0) = 0.19 \pm 0.03. The
demonstration of a single photon source within a silicon platform holds promise
for future integrated quantum photonic circuits.
