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%.
@article{arxiv.0802.0136,
title = {Silica-on-Silicon Waveguide Quantum Circuits},
author = {Alberto Politi and Martin J. Cryan and John G. Rarity and Siyuan Yu and Jeremy L. O'Brien},
journal= {arXiv preprint arXiv:0802.0136},
year = {2008}
}