  Quantum technologies based on photons are anticipated in the areas of
information processing, communication, metrology, and lithography. While there
have been impressive proof-of-principle demonstrations in all of these areas,
future technologies will likely require an integrated optics architecture for
improved performance, miniaturization and scalability. We demonstrated high-
fidelity silica-on-silicon integrated optical realizations of key quantum
photonic circuits, including two-photon quantum interference with a visibility
of 94.8(5)%; a controlled-NOT gate with logical basis fidelity of 94.3(2)%; and
a path entangled state of two photons with fidelity >92%.
